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Jarrard CP, McKenna ZJ, Atkins WC, Foster J, Hendrix JM, Jouett NP, Oldham ZR, LeBlanc BJ, Watso JC, Crandall CG. Low-dose sufentanil does not affect tolerance to LBNP-induced central hypovolemia or blood pressure responses during a cold pressor test. Am J Physiol Regul Integr Comp Physiol 2024; 327:R497-R507. [PMID: 39155710 DOI: 10.1152/ajpregu.00003.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 07/24/2024] [Accepted: 08/12/2024] [Indexed: 08/20/2024]
Abstract
Hemorrhage is a leading cause of death in the prehospital setting. Since trauma-induced pain often accompanies a hemorrhagic insult, the administered pain medication must not interfere with critical autonomic regulation of arterial blood pressure and vital organ perfusion. The purpose of this study was to test two unrelated hypotheses: 1) sublingual sufentanil (Dsuvia) impairs tolerance to progressive central hypovolemia and 2) sublingual sufentanil attenuates pain sensation and the accompanying cardiovascular responses to a noxious stimulus. Twenty-nine adults participated in this double-blinded, randomized, crossover, placebo-controlled trial. After sublingual administration of sufentanil (30 μg) or placebo, participants completed a progressive lower-body negative pressure (LBNP) challenge to tolerance (aim 1). After a recovery period, participants completed a cold pressor test (CPT; aim 2). Addressing the first aim, tolerance to LBNP was not different between trials (P = 0.495). Decreases in systolic blood pressure from baseline to the end of LBNP also did not differ between trials (time P < 0.001, trial P = 0.477, interaction P = 0.587). Finally, increases in heart rate from baseline to the end of LBNP did not differ between trials (time P < 0.001, trial P = 0.626, interaction P = 0.424). Addressing the second aim, sufentanil attenuated perceived pain (P < 0.001) in response to the CPT, though the magnitude of the change in mean blood pressure during the CPT (P = 0.078) was not different between trials. These data demonstrate that sublingual sufentanil does not impair tolerance to progressive central hypovolemia. Additionally, sublingual sufentanil attenuates perceived pain, but not the accompanying mean blood pressure responses to the CPT.NEW & NOTEWORTHY Addressing two unique aims, we observed that sublingual sufentanil administration does not impair tolerance or cardiovascular responses to lower-body negative pressure (LBNP)-induced progressive central hypovolemia. Second, despite pain perception being reduced, sublingual sufentanil did not attenuate mean blood pressure responses to a cold pressor test (CPT).
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Affiliation(s)
- Caitlin P Jarrard
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Applied Clinical Research Department, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Zachary J McKenna
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Whitley C Atkins
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Josh Foster
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Centre for Human and Applied Physiological Sciences, King's College London, London, United Kingdom
| | - Joseph M Hendrix
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Noah P Jouett
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Zachary R Oldham
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Applied Physiology and Sport Management, Southern Methodist University, Dallas, Texas, United States
| | - Benjamin J LeBlanc
- University of Texas Southwestern Medical School, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Joseph C Watso
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Applied Clinical Research Department, University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Department of Health, Nutrition, and Food Sciences, Florida State University, Tallahassee, Florida, United States
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, United States
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, United States
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Foster J, Gagnon D, Jarrard CP, Atkins WC, McKenna Z, Romero SA, Crandall CG. Compensatory reserve index during central hypovolemia and volume loading in healthy young and older hyperthermic adults: A pilot study. Physiol Rep 2024; 12:e16177. [PMID: 39107243 PMCID: PMC11303067 DOI: 10.14814/phy2.16177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2024] [Revised: 07/25/2024] [Accepted: 07/25/2024] [Indexed: 08/09/2024] Open
Abstract
The compensatory reserve index (CRI), derived from machine learning algorithms from peripherally obtained photoplethysmography signals, provides a non-invasive assessment of cardiovascular stability, that may be useful clinically. Briefly, the CRI device provides a value between 0 and 1, with 1 reflecting full compensable capabilities and 0 reflecting little to no compensable capabilities. However, the CRI algorithm was developed in younger to middle aged adults, such that it is unknown if older age modulates CRI responses to cardiovascular challenges. In young and older subjects, we compared CRI responses to normothermic and hyperthermic progressive lower body negative pressure (LBNP), and volume loading with saline infusion. Eleven younger (20-36 years) and 10 older (61-75 years) healthy participants underwent (1) graded normothermic LBNP up to 30 mmHg, (2) graded hyperthermic (1.5°C increase in blood temperature) LBNP up to 30 mmHg, and (3) infusion of 15 mL/kg saline (volume loading) with hyperthermia maintained. CRI was obtained throughout each procedure. CRI at 30 mmHg LBNP was 0.18 and 0.24 units greater in the older group during normothermic and hyperthermic LBNP, respectively. However, CRI was not different between age groups at any other LBNP stage, nor did CRI change with volume loading regardless of age. In response to passive hyperthermia alone, regression analyses showed that heart rate was the strongest predictor of CRI. Blood temperature, rate pressure product, and stroke volume were also predictive of CRI but to a lesser extent. In conclusion, age attenuates the reduction in CRI during progressive normothermic and hyperthermic LBNP, but only at 30 mmHg. Second, the CRI was unchanged during volume loading in all subjects. Future studies should determine whether the age differences in CRI reflect age differences in LBNP tolerance.
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Affiliation(s)
- Josh Foster
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
- Centre for Human and Applied Physiological Sciences, Faculty of Life Sciences and MedicineKing's College LondonLondonUK
| | - Daniel Gagnon
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
- Montreal Heart Institute and School of Kinesiology and Exercise ScienceUniversité de MontréalMontrealQuebecCanada
| | - Caitlin P. Jarrard
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Whitley C. Atkins
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Zachary McKenna
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
| | - Steven A. Romero
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
- Department of Physiology and AnatomyUniversity of North Texas Health Science CenterFort WorthTexasUSA
| | - Craig G. Crandall
- Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital Dallas, University of Texas Southwestern Medical CenterDallasTexasUSA
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Rosenberg AJ, Anderson GK, McKeefer HJ, Bird J, Pentz B, Byman BRM, Jendzjowsky N, Wilson RJ, Day TA, Rickards CA. Hemorrhage at high altitude: impact of sustained hypobaric hypoxia on cerebral blood flow, tissue oxygenation, and tolerance to simulated hemorrhage in humans. Eur J Appl Physiol 2024; 124:2365-2378. [PMID: 38489034 PMCID: PMC11321930 DOI: 10.1007/s00421-024-05450-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 02/22/2024] [Indexed: 03/17/2024]
Abstract
With ascent to high altitude (HA), compensatory increases in cerebral blood flow and oxygen delivery must occur to preserve cerebral metabolism and consciousness. We hypothesized that this compensation in cerebral blood flow and oxygen delivery preserves tolerance to simulated hemorrhage (via lower body negative pressure, LBNP), such that tolerance is similar during sustained exposure to HA vs. low altitude (LA). Healthy humans (4F/4 M) participated in LBNP protocols to presyncope at LA (1130 m) and 5-7 days following ascent to HA (3800 m). Internal carotid artery (ICA) blood flow, cerebral delivery of oxygen (CDO2) through the ICA, and cerebral tissue oxygen saturation (ScO2) were determined. LBNP tolerance was similar between conditions (LA: 1276 ± 304 s vs. HA: 1208 ± 306 s; P = 0.58). Overall, ICA blood flow and CDO2 were elevated at HA vs. LA (P ≤ 0.01) and decreased with LBNP under both conditions (P < 0.0001), but there was no effect of altitude on ScO2 responses (P = 0.59). Thus, sustained exposure to hypobaric hypoxia did not negatively impact tolerance to simulated hemorrhage. These data demonstrate the robustness of compensatory physiological mechanisms that preserve human cerebral blood flow and oxygen delivery during sustained hypoxia, ensuring cerebral tissue metabolism and neuronal function is maintained.
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Affiliation(s)
- Alexander J Rosenberg
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
- Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL, USA
- Physiology Department, Midwestern University, Downers Grove, IL, USA
| | - Garen K Anderson
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Haley J McKeefer
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | | | | | | | - Nicholas Jendzjowsky
- University of Calgary, Calgary, AB, Canada
- Institute of Respiratory Medicine & Exercise Physiology, The Lundquist Institute at UCLA Harbor Medical, Torrance, CA, USA
| | | | | | - Caroline A Rickards
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA.
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Morton WJ, Hauge A, Opdahl H, Rein EB, Søvik S, Hisdal J. Nine treatments of 1000 mL therapeutic phlebotomy in a subject with polycythemia: A case report. Physiol Rep 2024; 12:e16035. [PMID: 38844733 PMCID: PMC11156522 DOI: 10.14814/phy2.16035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 04/17/2024] [Accepted: 04/17/2024] [Indexed: 06/10/2024] Open
Abstract
Large-volume therapeutic phlebotomy is the mainstay of hemochromatosis treatment and offers an opportunity to investigate the hemodynamic changes during acute hypovolemia. An otherwise healthy 64-year-old male with hemochromatosis participated. On nine separate visits, 1000 mL therapeutic phlebotomy was performed. On one occasion, pre- and post-phlebotomy orthostatic challenge with 27° reverse Trendelenburg position was administered. Mean arterial pressure, heart rate, and stroke volume were measured continuously during the procedures. The patient's tolerance to the interventions was continuously evaluated. The procedures were well tolerated by the patient. Mean arterial pressure was maintained during hemorrhage and following phlebotomy in both supine and reverse Trendelenburg positions, primarily through an increase in heart rate and systemic vascular resistance. The present study found that 1000 mL therapeutic phlebotomy in a patient with hemochromatosis may be acceptably and safely used to model hemorrhage. The approach demonstrates high clinical applicability and ethically robustness in comparison with volunteer studies.
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Affiliation(s)
- William J. Morton
- Department of AnaesthesiaAkershus University HospitalLørenskogNorway
- Institute of Clinical MedicineFaculty of MedicineUniversity of OsloOsloNorway
- Department of Vascular SurgeryOslo University HospitalOsloNorway
| | - Anton Hauge
- Institute of Clinical MedicineFaculty of MedicineUniversity of OsloOsloNorway
| | - Helge Opdahl
- Department of Acute Medicine, The Norwegian National CBRNE Medical and Advisory CentreOslo University HospitalOsloNorway
| | | | - Signe Søvik
- Department of AnaesthesiaAkershus University HospitalLørenskogNorway
- Institute of Clinical MedicineFaculty of MedicineUniversity of OsloOsloNorway
| | - Jonny Hisdal
- Institute of Clinical MedicineFaculty of MedicineUniversity of OsloOsloNorway
- Department of Vascular SurgeryOslo University HospitalOsloNorway
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5
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Murphy EK, Bertsch SR, Klein SB, Rashedi N, Sun Y, Joyner MJ, Curry TB, Johnson CP, Regimbal RJ, Wiggins CC, Senefeld JW, Shepherd JRA, Elliott JT, Halter RJ, Vaze VS, Paradis NA. Non-invasive biomarkers for detecting progression toward hypovolemic cardiovascular instability in a lower body negative pressure model. Sci Rep 2024; 14:8719. [PMID: 38622207 PMCID: PMC11018605 DOI: 10.1038/s41598-024-59139-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 04/08/2024] [Indexed: 04/17/2024] Open
Abstract
Occult hemorrhages after trauma can be present insidiously, and if not detected early enough can result in patient death. This study evaluated a hemorrhage model on 18 human subjects, comparing the performance of traditional vital signs to multiple off-the-shelf non-invasive biomarkers. A validated lower body negative pressure (LBNP) model was used to induce progression towards hypovolemic cardiovascular instability. Traditional vital signs included mean arterial pressure (MAP), electrocardiography (ECG), plethysmography (Pleth), and the test systems utilized electrical impedance via commercial electrical impedance tomography (EIT) and multifrequency electrical impedance spectroscopy (EIS) devices. Absolute and relative metrics were used to evaluate the performance in addition to machine learning-based modeling. Relative EIT-based metrics measured on the thorax outperformed vital sign metrics (MAP, ECG, and Pleth) achieving an area-under-the-curve (AUC) of 0.99 (CI 0.95-1.00, 100% sensitivity, 87.5% specificity) at the smallest LBNP change (0-15 mmHg). The best vital sign metric (MAP) at this LBNP change yielded an AUC of 0.6 (CI 0.38-0.79, 100% sensitivity, 25% specificity). Out-of-sample predictive performance from machine learning models were strong, especially when combining signals from multiple technologies simultaneously. EIT, alone or in machine learning-based combination, appears promising as a technology for early detection of progression toward hemodynamic instability.
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Affiliation(s)
- Ethan K Murphy
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA.
| | - Spencer R Bertsch
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
| | - Samuel B Klein
- Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA
- Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA
| | - Navid Rashedi
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
| | - Yifei Sun
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - Timothy B Curry
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - Christopher P Johnson
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - Riley J Regimbal
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - Jonathon W Senefeld
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - John R A Shepherd
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, 55902, USA
| | - Jonathan Thomas Elliott
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
- Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA
- Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA
| | - Ryan J Halter
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
- Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA
| | - Vikrant S Vaze
- Thayer School of Engineering, Dartmouth College, Hanover, NH, 03755, USA
| | - Norman A Paradis
- Geisel School of Medicine, Dartmouth College, Hanover, NH, 03755, USA
- Dartmouth-Hitchcock Medical Center, Lebanon, NH, 03756, USA
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6
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Anderson GK, Davis KA, Bhuiyan N, Rusy R, Rosenberg AJ, Rickards CA. The effect of oscillatory hemodynamics on the cardiovascular responses to simulated hemorrhage during isocapnia. J Appl Physiol (1985) 2023; 135:1312-1322. [PMID: 37881852 PMCID: PMC10911761 DOI: 10.1152/japplphysiol.00241.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 10/17/2023] [Accepted: 10/20/2023] [Indexed: 10/27/2023] Open
Abstract
During cerebral hypoperfusion induced by lower body negative pressure (LBNP), cerebral tissue oxygenation is protected with oscillatory arterial pressure and cerebral blood flow at low frequencies (0.1 Hz and 0.05 Hz), despite no protection of cerebral blood flow or oxygen delivery. However, hypocapnia induced by LBNP contributes to cerebral blood flow reductions, and may mask potential protective effects of hemodynamic oscillations on cerebral blood flow. We hypothesized that under isocapnic conditions, forced oscillations of arterial pressure and blood flow at 0.1 Hz and 0.05 Hz would attenuate reductions in extra- and intracranial blood flow during simulated hemorrhage using LBNP. Eleven human participants underwent three LBNP profiles: a nonoscillatory condition (0 Hz) and two oscillatory conditions (0.1 Hz and 0.05 Hz). End-tidal (et) CO2 and etO2 were clamped at baseline values using dynamic end-tidal forcing. Cerebral tissue oxygenation (ScO2), internal carotid artery (ICA) blood flow, and middle cerebral artery velocity (MCAv) were measured. With clamped etCO2, neither ICA blood flow (ANOVA P = 0.93) nor MCAv (ANOVA P = 0.36) decreased with LBNP, and these responses did not differ between the three profiles (ICA blood flow: 0 Hz: 2.2 ± 5.4%, 0.1 Hz: -0.4 ± 6.6%, 0.05 Hz: 0.2 ± 4.8%; P = 0.56; MCAv: 0 Hz: -2.3 ± 7.8%, 0.1 Hz: -1.3 ± 6.1%, 0.05 Hz: -3.1 ± 5.0%; P = 0.87). Similarly, ScO2 did not decrease with LBNP (ANOVA P = 0.21) nor differ between the three profiles (0 Hz: -2.6 ± 3.3%, 0.1 Hz: -1.6 ± 1.5%, 0.05 Hz: -0.2 ± 2.8%; P = 0.13). Contrary to our hypothesis, cerebral blood flow and tissue oxygenation were protected during LBNP with isocapnia, regardless of whether hemodynamic oscillations were induced.NEW & NOTEWORTHY We examined the role of forcing oscillations in arterial pressure and blood flow at 0.1 Hz and 0.05 Hz on extra- and intracranial blood flow and cerebral tissue oxygenation during simulated hemorrhage (using lower body negative pressure, LBNP) under isocapnic conditions. Contrary to our hypothesis, both cerebral blood flow and cerebral tissue oxygenation were completely protected during simulated hemorrhage with isocapnia, regardless of whether oscillations in arterial pressure and cerebral blood flow were induced. These findings highlight the protective effect of preventing hypocapnia on cerebral blood flow under simulated hemorrhage conditions.
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Affiliation(s)
- Garen K Anderson
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - K Austin Davis
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Nasrul Bhuiyan
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Ryan Rusy
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Alexander J Rosenberg
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
- Physiology Department, Midwestern University, Downers Grove, Illinois, United States
- Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Caroline A Rickards
- Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, Texas, United States
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Jain M, Chitturi V, Chandran DS, Jaryal AK, Deepak KK. Vasoconstriction during non-hypotensive hypovolemia is not associated with activation of baroreflex: A causality-based approach. Pflugers Arch 2023; 475:747-755. [PMID: 37076560 DOI: 10.1007/s00424-023-02811-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 02/23/2023] [Accepted: 04/02/2023] [Indexed: 04/21/2023]
Abstract
Non-hypotensive hypovolemia simulated with oscillatory lower body negative pressure in the range of -10 to -20 mmHg is associated with vasoconstriction {increase in total peripheral vascular resistance (TPVR)}. Due to the mechanical stiffening of vessels, there is a disjuncture of mechano-neural coupling at the level of arterial baroreceptors which has not been investigated. The study was designed to quantify both the cardiac and vascular arms of the baroreflex using an approach based on Wiener-Granger causality (WGC) - partial directed coherence (PDC). Thirty-three healthy human volunteers were recruited and continuous heart rate and blood pressure {systolic (SBP), diastolic (DBP), and mean (MBP)} were recorded. The measurements were taken in resting state, at -10 mmHg (level 1) and -15 mmHg (level 2). Spectral causality - PDC was estimated from the MVAR model in the low-frequency band using the GMAC MatLab toolbox. PDC from SBP and MBP to RR interval and TPVR was calculated. The PDC from MBP to RR interval showed no significant change at -10 mmHg and -15 mmHg. No significant change in PDC from MBP to TPVR at -10 mmHg and -15 mmHg was observed. Similar results were obtained for PDC estimation using SBP as input. However, a significant increase in TPVR from baseline at both levels of oscillatory LBNP (p-value <0.001). No statistically significant change in PDC from blood pressure to RR interval and blood pressure to TPVR implies that vasoconstriction is not associated with activation of the arterial baroreflex in ≤-15 mmHg LBNP. Thereby, indicating the role of cardiopulmonary reflexes during the low level of LBNP simulated non-hypotensive hypovolemia.
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Affiliation(s)
- Mansi Jain
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, 110029, India
| | - Vinay Chitturi
- Department of Physiology, All India Institute of Medical Sciences, Rajkot, India
| | - Dinu S Chandran
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, 110029, India
| | - Ashok Kumar Jaryal
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, 110029, India
| | - K K Deepak
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, 110029, India.
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Watso JC, Huang M, Hendrix JM, Belval LN, Moralez G, Cramer MN, Foster J, Hinojosa-Laborde C, Crandall CG. Comparing the Effects of Low-Dose Ketamine, Fentanyl, and Morphine on Hemorrhagic Tolerance and Analgesia in Humans. PREHOSP EMERG CARE 2023; 27:600-612. [PMID: 36689353 PMCID: PMC10329983 DOI: 10.1080/10903127.2023.2172493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 01/09/2023] [Accepted: 01/19/2023] [Indexed: 01/24/2023]
Abstract
Hemorrhage is a leading cause of preventable battlefield and civilian trauma deaths. Ketamine, fentanyl, and morphine are recommended analgesics for use in the prehospital (i.e., field) setting to reduce pain. However, it is unknown whether any of these analgesics reduce hemorrhagic tolerance in humans. We tested the hypothesis that fentanyl (75 µg) and morphine (5 mg), but not ketamine (20 mg), would reduce tolerance to simulated hemorrhage in conscious humans. Each of the three analgesics was evaluated independently among different cohorts of healthy adults in a randomized, crossover (within drug/placebo comparison), placebo-controlled fashion using doses derived from the Tactical Combat Casualty Care Guidelines for Medical Personnel. One minute after an intravenous infusion of the analgesic or placebo (saline), we employed a pre-syncopal limited progressive lower-body negative pressure (LBNP) protocol to determine hemorrhagic tolerance. Hemorrhagic tolerance was quantified as a cumulative stress index (CSI), which is the sum of products of the LBNP and the duration (e.g., [40 mmHg x 3 min] + [50 mmHg x 3 min] …). Compared with ketamine (p = 0.002 post hoc result) and fentanyl (p = 0.02 post hoc result), morphine reduced the CSI (ketamine (n = 30): 99 [73-139], fentanyl (n = 28): 95 [68-130], morphine (n = 30): 62 [35-85]; values expressed as a % of the respective placebo trial's CSI; median [IQR]; Kruskal-Wallis test p = 0.002). Morphine-induced reductions in tolerance to central hypovolemia were not well explained by a prediction model including biological sex, body mass, and age (R2=0.05, p = 0.74). These experimental data demonstrate that morphine reduces tolerance to simulated hemorrhage while fentanyl and ketamine do not affect tolerance. Thus, these laboratory-based data, captured via simulated hemorrhage, suggest that morphine should not be used for a hemorrhaging individual in the prehospital setting.
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Affiliation(s)
- Joseph Charles Watso
- Department of Nutrition & Integrative Physiology, Florida State University, Tallahassee, Florida, USA
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Mu Huang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Office of Science, Medicine, and Health, American Heart Association, Dallas, Texas, USA
| | - Joseph Maxwell Hendrix
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Anesthesiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Luke Norman Belval
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Gilbert Moralez
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Matthew Nathaniel Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Josh Foster
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | | | - Craig Gerald Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Watso JC, Belval LN, Cimino FA, Orth BD, Hendrix JM, Huang M, Johnson E, Foster J, Hinojosa-Laborde C, Crandall CG. Low-dose morphine reduces tolerance to central hypovolemia in healthy adults without affecting muscle sympathetic outflow. Am J Physiol Heart Circ Physiol 2022; 323:H89-H99. [PMID: 35452317 PMCID: PMC9190738 DOI: 10.1152/ajpheart.00091.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 04/19/2022] [Accepted: 04/20/2022] [Indexed: 11/22/2022]
Abstract
Hemorrhage is a leading cause of preventable battlefield and civilian trauma deaths. Low-dose (i.e., an analgesic dose) morphine is recommended for use in the prehospital (i.e., field) setting. Morphine administration reduces hemorrhagic tolerance in rodents. However, it is unknown whether morphine impairs autonomic cardiovascular regulation and consequently reduces hemorrhagic tolerance in humans. Thus, the purpose of this study was to test the hypothesis that low-dose morphine reduces hemorrhagic tolerance in conscious humans. Thirty adults (15 women/15 men; 29 ± 6 yr; 26 ± 4 kg·m-2, means ± SD) completed this randomized, crossover, double-blinded, placebo-controlled trial. One minute after intravenous administration of morphine (5 mg) or placebo (saline), we used a presyncopal limited progressive lower-body negative pressure (LBNP) protocol to determine hemorrhagic tolerance. Hemorrhagic tolerance was quantified as a cumulative stress index (mmHg·min), which was compared between trials using a Wilcoxon matched-pairs signed-rank test. We also compared muscle sympathetic nerve activity (MSNA; microneurography) and beat-to-beat blood pressure (photoplethysmography) during the LBNP test using mixed-effects analyses [time (LBNP stage) × trial]. Median LBNP tolerance was lower during morphine trials (placebo: 692 [473-997] vs. morphine: 385 [251-728] mmHg·min, P < 0.001, CI: -394 to -128). Systolic blood pressure was 8 mmHg lower during moderate central hypovolemia during morphine trials (post hoc P = 0.02; time: P < 0.001, trial: P = 0.13, interaction: P = 0.006). MSNA burst frequency responses were not different between trials (time: P < 0.001, trial: P = 0.80, interaction: P = 0.51). These data demonstrate that low-dose morphine reduces hemorrhagic tolerance in conscious humans. Thus, morphine is not an ideal analgesic for a hemorrhaging individual in the prehospital setting.NEW & NOTEWORTHY In this randomized, crossover, placebo-controlled trial, we found that tolerance to simulated hemorrhage was lower after low-dose morphine administration. Such reductions in hemorrhagic tolerance were observed without differences in MSNA burst frequency responses between morphine and placebo trials. These data, the first to be obtained in conscious humans, demonstrate that low-dose morphine reduces hemorrhagic tolerance. Thus, morphine is not an ideal analgesic for a hemorrhaging individual in the prehospital setting.
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Affiliation(s)
- Joseph C Watso
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Luke N Belval
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Frank A Cimino
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Bonnie D Orth
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Joseph M Hendrix
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Anesthesiology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Mu Huang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Elias Johnson
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Josh Foster
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Carmen Hinojosa-Laborde
- United States Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, Houston, Texas
| | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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10
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Koons NJ, Moses CD, Thompson P, Strandenes G, Convertino VA. Identifying critical DO 2 with compensatory reserve during simulated hemorrhage in humans. Transfusion 2022; 62 Suppl 1:S122-S129. [PMID: 35733031 DOI: 10.1111/trf.16958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 03/09/2022] [Accepted: 03/18/2022] [Indexed: 12/01/2022]
Abstract
BACKGROUND Based on previous experiments in nonhuman primates, we hypothesized that DO2 crit in humans is 5-6 ml O2 ·kg-1 min-1 . STUDY DESIGN AND METHODS We measured the compensatory reserve (CRM) and calculated oxygen delivery (DO2 ) in 166 healthy, normotensive, nonsmoking subjects (97 males, 69 females) during progressive central hypovolemia induced by lower body negative pressure as a model of ongoing hemorrhage. Subjects were classified as having either high tolerance (HT; N = 111) or low tolerance (LT; N = 55) to central hypovolemia. RESULTS HT and LT groups were matched for age, weight, BMI, and vital signs, DO2 and CRM at baseline. The CRM-DO2 relationship was best fitted to a logarithmic model in HT subjects (amalgamated R2 = 0.971) and a second-order polynomial model in the LT group (amalgamated R2 = 0.991). Average DO2 crit for the entire subject cohort was estimated at 5.3 ml O2 ·kg-1 min-1 , but was ~14% lower in HT compared with LT subjects. The reduction in DO2 from 40% CRM to 20% CRM was 2-fold greater in the LT compared with the HT group. CONCLUSIONS Average DO2 crit in humans is 5.3 ml O2 ·kg-1 min-1 , but is ~14% lower in HT compared with LT subjects. The CRM-DO2 relationship is curvilinear in humans, and different when comparing HT and LT individuals. The threshold for an emergent monitoring signal should be recalibrated from 30% to 40% CRM given that the decline in DO2 from 40% CRM to 20% CRM for LT subjects is located on the steepest part of the CRM-DO2 relationship.
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Affiliation(s)
- Natalie J Koons
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, San Antonio, Texas, USA
| | - Catherine D Moses
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, San Antonio, Texas, USA
| | | | - Geir Strandenes
- Norwegian Armed Forces, Haukeland University Hospital, Bergen, Norway
| | - Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, San Antonio, Texas, USA
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11
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Yadav K, Singh A, Jaryal AK, Coshic P, Deepak KK. Temporal Analysis of Sequential Changes in Heart Rate Variability During Non-hypotensive Hypovolemia. High Blood Press Cardiovasc Prev 2022; 29:385-391. [PMID: 35670948 DOI: 10.1007/s40292-022-00525-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 05/10/2022] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION Haemorrhage is associated with changes in the cardiac autonomic drive which begins during early stages of mild haemorrhage. The knowledge of chronology of the autonomic changes at smaller timescale during the period of haemorrhage can help identify the primary autonomic parameter which signals the institution of cardiovascular reflex mechanisms. AIM To evaluate the heart rate variability in 2-min sequential segments with one minute overlap during and after the period of mild haemorrhage (450 ml) using blood donation as a model of acute blood loss. METHODS 47 male blood donors who had volunteered for blood donation were recruited for the study. Continuous lead II ECG was recorded before the start of the blood donation (5 min), during the period of the blood donation (~ 5-7 min) and after blood donation (5 min). The parasympathetic and sympathetic drive to heart was estimated by measures of heart rate variability in time and frequency domain. RESULTS A significant decrease in the parameters assessing parasympathetic drive i.e., normalised High frequency (HFn) and NN50 (Number of pairs of adjacent NN intervals differing by more than 50 ms) and pNN50 (NN50 divided by the total number of all NN Intervals) was observed during blood donation at 3-5 min, as compared to baseline. An increase in parameters associated with sympathetic drive i.e., normalised low frequency (LFn) was observed only in the post donation period at 2-3 min. A significant rise in LF/HF ratio which is a marker of sympatho vagal balance was observed at 4-5 min during blood donation when compared to baseline. CONCLUSION The initial cardiac autonomic change during mild haemorrhage is withdrawal of parasympathetic drive, followed by an increase in sympathetic tone which occurs much later.
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Affiliation(s)
- Kavita Yadav
- Department of Physiology, Pt. BD Sharma Post graduate Institute of Medical Sciences, 1st Floor, Rohtak, India
| | - Akanksha Singh
- Department of Physiology, All India Institute of Medical Sciences, Room no. 2017, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
| | - Ashok Kumar Jaryal
- Department of Physiology, All India Institute of Medical Sciences, Room no. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India.
| | - Poonam Coshic
- Department of Transfusion Medicine (Blood Bank), All India Institute of Medical Sciences, Ground Floor, Main Blood Bank Unit 1, Ansari Nagar, New Delhi, India
| | - K K Deepak
- Department of Physiology, All India Institute of Medical Sciences, Room no. 2009, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India
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12
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AI-Enabled Advanced Development for Assessing Low Circulating Blood Volume for Emergency Medical Care: Comparison of Compensatory Reserve Machine-Learning Algorithms. SENSORS 2022; 22:s22072642. [PMID: 35408255 PMCID: PMC9003258 DOI: 10.3390/s22072642] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 03/22/2022] [Accepted: 03/24/2022] [Indexed: 11/21/2022]
Abstract
The application of artificial intelligence (AI) has provided new capabilities to develop advanced medical monitoring sensors for detection of clinical conditions of low circulating blood volume such as hemorrhage. The purpose of this study was to compare for the first time the discriminative ability of two machine learning (ML) algorithms based on real-time feature analysis of arterial waveforms obtained from a non-invasive continuous blood pressure system (Finometer®) signal to predict the onset of decompensated shock: the compensatory reserve index (CRI) and the compensatory reserve metric (CRM). One hundred ninety-one healthy volunteers underwent progressive simulated hemorrhage using lower body negative pressure (LBNP). The least squares means and standard deviations for each measure were assessed by LBNP level and stratified by tolerance status (high vs. low tolerance to central hypovolemia). Generalized Linear Mixed Models were used to perform repeated measures logistic regression analysis by regressing the onset of decompensated shock on CRI and CRM. Sensitivity and specificity were assessed by calculation of receiver-operating characteristic (ROC) area under the curve (AUC) for CRI and CRM. Values for CRI and CRM were not distinguishable across levels of LBNP independent of LBNP tolerance classification, with CRM ROC AUC (0.9268) being statistically similar (p = 0.134) to CRI ROC AUC (0.9164). Both CRI and CRM ML algorithms displayed discriminative ability to predict decompensated shock to include individual subjects with varying levels of tolerance to central hypovolemia. Arterial waveform feature analysis provides a highly sensitive and specific monitoring approach for the detection of ongoing hemorrhage, particularly for those patients at greatest risk for early onset of decompensated shock and requirement for implementation of life-saving interventions.
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13
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van der Ster BJP, Kim YS, Westerhof BE, van Lieshout JJ. Central Hypovolemia Detection During Environmental Stress-A Role for Artificial Intelligence? Front Physiol 2021; 12:784413. [PMID: 34975538 PMCID: PMC8715014 DOI: 10.3389/fphys.2021.784413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/18/2021] [Indexed: 11/19/2022] Open
Abstract
The first step to exercise is preceded by the required assumption of the upright body position, which itself involves physical activity. The gravitational displacement of blood from the chest to the lower parts of the body elicits a fall in central blood volume (CBV), which corresponds to the fraction of thoracic blood volume directly available to the left ventricle. The reduction in CBV and stroke volume (SV) in response to postural stress, post-exercise, or to blood loss results in reduced left ventricular filling, which may manifest as orthostatic intolerance. When termination of exercise removes the leg muscle pump function, CBV is no longer maintained. The resulting imbalance between a reduced cardiac output (CO) and a still enhanced peripheral vascular conductance may provoke post-exercise hypotension (PEH). Instruments that quantify CBV are not readily available and to express which magnitude of the CBV in a healthy subject should remains difficult. In the physiological laboratory, the CBV can be modified by making use of postural stressors, such as lower body "negative" or sub-atmospheric pressure (LBNP) or passive head-up tilt (HUT), while quantifying relevant biomedical parameters of blood flow and oxygenation. Several approaches, such as wearable sensors and advanced machine-learning techniques, have been followed in an attempt to improve methodologies for better prediction of outcomes and to guide treatment in civil patients and on the battlefield. In the recent decade, efforts have been made to develop algorithms and apply artificial intelligence (AI) in the field of hemodynamic monitoring. Advances in quantifying and monitoring CBV during environmental stress from exercise to hemorrhage and understanding the analogy between postural stress and central hypovolemia during anesthesia offer great relevance for healthy subjects and clinical populations.
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Affiliation(s)
- Björn J. P. van der Ster
- Department of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Anesthesiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Yu-Sok Kim
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Internal Medicine, Medisch Centrum Leeuwarden, Leeuwarden, Netherlands
| | - Berend E. Westerhof
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Pulmonary Medicine, Amsterdam University Medical Center, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Johannes J. van Lieshout
- Department of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Medical Research Council Versus Arthritis Centre for Musculoskeletal Ageing Research, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, The Medical School, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, United Kingdom
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14
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Proczka M, Przybylski J, Cudnoch-Jędrzejewska A, Szczepańska-Sadowska E, Żera T. Vasopressin and Breathing: Review of Evidence for Respiratory Effects of the Antidiuretic Hormone. Front Physiol 2021; 12:744177. [PMID: 34867449 PMCID: PMC8637824 DOI: 10.3389/fphys.2021.744177] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/27/2021] [Indexed: 12/17/2022] Open
Abstract
Vasopressin (AVP) is a key neurohormone involved in the regulation of body functions. Due to its urine-concentrating effect in the kidneys, it is often referred to as antidiuretic hormone. Besides its antidiuretic renal effects, AVP is a potent neurohormone involved in the regulation of arterial blood pressure, sympathetic activity, baroreflex sensitivity, glucose homeostasis, release of glucocorticoids and catecholamines, stress response, anxiety, memory, and behavior. Vasopressin is synthesized in the paraventricular (PVN) and supraoptic nuclei (SON) of the hypothalamus and released into the circulation from the posterior lobe of the pituitary gland together with a C-terminal fragment of pro-vasopressin, known as copeptin. Additionally, vasopressinergic neurons project from the hypothalamus to the brainstem nuclei. Increased release of AVP into the circulation and elevated levels of its surrogate marker copeptin are found in pulmonary diseases, arterial hypertension, heart failure, obstructive sleep apnoea, severe infections, COVID-19 due to SARS-CoV-2 infection, and brain injuries. All these conditions are usually accompanied by respiratory disturbances. The main stimuli that trigger AVP release include hyperosmolality, hypovolemia, hypotension, hypoxia, hypoglycemia, strenuous exercise, and angiotensin II (Ang II) and the same stimuli are known to affect pulmonary ventilation. In this light, we hypothesize that increased AVP release and changes in ventilation are not coincidental, but that the neurohormone contributes to the regulation of the respiratory system by fine-tuning of breathing in order to restore homeostasis. We discuss evidence in support of this presumption. Specifically, vasopressinergic neurons innervate the brainstem nuclei involved in the control of respiration. Moreover, vasopressin V1a receptors (V1aRs) are expressed on neurons in the respiratory centers of the brainstem, in the circumventricular organs (CVOs) that lack a blood-brain barrier, and on the chemosensitive type I cells in the carotid bodies. Finally, peripheral and central administrations of AVP or antagonists of V1aRs increase/decrease phrenic nerve activity and pulmonary ventilation in a site-specific manner. Altogether, the findings discussed in this review strongly argue for the hypothesis that vasopressin affects ventilation both as a blood-borne neurohormone and as a neurotransmitter within the central nervous system.
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Affiliation(s)
- Michał Proczka
- Department of Experimental and Clinical Physiology, Doctoral School, Medical University of Warsaw, Warsaw, Poland
| | - Jacek Przybylski
- Department of Biophysics, Physiology, and Pathophysiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Agnieszka Cudnoch-Jędrzejewska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Ewa Szczepańska-Sadowska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Tymoteusz Żera
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
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15
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Clemency BM, Bola A, Schlader ZJ, Hostler D, Lin H, St James E, Lema PC, Johnson BD. Ultrasonographic Inferior Vena Cava Measurement is More Sensitive Than Vital Sign Abnormalities for Identifying Moderate and Severe Hemorrhage. J Emerg Med 2021; 62:64-71. [PMID: 34544622 DOI: 10.1016/j.jemermed.2021.07.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 06/02/2021] [Accepted: 07/25/2021] [Indexed: 11/19/2022]
Abstract
BACKGROUND Ultrasound inferior vena cava (IVC) diameter has been shown to decrease in response to hemorrhage. IVC diameter cut points to identify moderate and severe blood loss have not been established. OBJECTIVES This study sought to find ultrasound IVC diameter cut points to identify moderate and severe hemorrhage and assess the performance of these cut points vs. vital sign abnormalities. METHODS This is a secondary analysis of data from a study that described changes in vital signs and sonographic measurements of the IVC during a lower body negative pressure model of hemorrhage. Using receiver operator curve analyses, optimal cut points for identifying moderate and severe hemorrhage were identified. The ability of these cut points to identify hemorrhage in patients with no vital sign abnormalities was then assessed. RESULTS In both long- and short-axis views, maximum and minimum IVC diameters (IVCmax and IVCmin) were significantly lower than baseline in severe blood loss. The optimal cut point for IVCmax in both axes was found to be ≤ 0.8 cm. This cut point is able to distinguish between no blood loss vs. moderate blood loss, and no blood loss vs. severe blood loss. The optimal cut point for IVCmin was variable between axes and blood loss severity. IVC diameter cut points obtained were able to identify hemorrhage in patients with no vital sign abnormalities. CONCLUSION An ultrasound IVCmax of ≤ 0.8 cm may be useful in identifying moderate and severe hemorrhage before vital sign abnormalities are evident.
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Affiliation(s)
- Brian M Clemency
- Department of Emergency Medicine, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York; Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Aaron Bola
- Department of Emergency Medicine, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York
| | - Zachary J Schlader
- Department of Kinesiology, School of Public Health - Bloomington, Indiana University, Bloomington, Indiana
| | - David Hostler
- Department of Emergency Medicine, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York; Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Howard Lin
- Department of Emergency Medicine, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York
| | - Erika St James
- Department of Emergency Medicine, University at Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York; Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Penelope C Lema
- Department of Emergency Medicine, Columbia University Vagelos College of Physicians and Surgeons, New York, New York
| | - Blair D Johnson
- Department of Kinesiology, School of Public Health - Bloomington, Indiana University, Bloomington, Indiana
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16
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Worley ML, O'Leary MC, Sackett JR, Schlader ZJ, Willer B, Leddy JJ, Johnson BD. Preliminary Evidence of Orthostatic Intolerance and Altered Cerebral Vascular Control Following Sport-Related Concussion. Front Neurol 2021; 12:620757. [PMID: 33897587 PMCID: PMC8062862 DOI: 10.3389/fneur.2021.620757] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 03/08/2021] [Indexed: 11/13/2022] Open
Abstract
Concussions have been shown to result in autonomic dysfunction and altered cerebral vascular function. We tested the hypothesis that concussed athletes (CA) would have altered cerebral vascular function during acute decreases and increases in blood pressure compared to healthy controls (HC). Ten CA (age: 20 ± 2 y, 7 females) and 10 HC (age: 21 ± 2 y, 6 females) completed 5 min of lower body negative pressure (LBNP; −40 mmHg) and 5 min of lower body positive pressure (LBPP; 20 mmHg). Protocols were randomized and separated by 10 min. Mean arterial pressure (MAP) and middle cerebral artery blood velocity (MCAv) were continuously recorded. Cerebral vascular resistance (CVR) was calculated as MAP/MCAv. Values are reported as change from baseline to the last minute achieved (LBNP) or 5 min (LBPP). There were no differences in baseline values between groups. During LBNP, there were no differences in the change for MAP (CA: −23 ± 18 vs. HC: −21 ± 17 cm/s; P = 0.80) or MCAv (CA: −13 ± 8 vs. HC: −18 ± 9 cm/s; P = 0.19). The change in CVR was different between groups (CA: −0.08 ± 0.26 vs. HC: 0.18 ± 0.24 mmHg/cm/s; P = 0.04). Total LBNP time was lower for CA (204 ± 92 s) vs. HC (297 ± 64 s; P = 0.04). During LBPP, the change in MAP was not different between groups (CA: 13 ± 6 vs. HC: 10 ± 7 mmHg; P = 0.32). The change in MCAv (CA: 7 ± 6 vs. HC: −4 ± 13 cm/s; P = 0.04) and CVR (CA: −0.06 ± 0.27 vs. HC: 0.38 ± 0.41 mmHg/cm/s; P = 0.03) were different between groups. CA exhibited impaired tolerance to LBNP and had a different cerebral vascular response to LBPP compared to HC.
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Affiliation(s)
- Morgan L Worley
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
| | - Morgan C O'Leary
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
| | - James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States
| | - Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States.,Human Integrative Physiology Laboratory, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, IN, United States
| | - Barry Willer
- Department of Psychiatry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - John J Leddy
- UBMD Department of Orthopaedics and Sports Medicine, University at Buffalo, Buffalo, NY, United States
| | - Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, United States.,Human Integrative Physiology Laboratory, Department of Kinesiology, School of Public Health, Indiana University, Bloomington, IN, United States
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17
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Shibata S, Hirabuki K, Hata N, Suzuki R, Suda T, Uechi T, Hirasawa A. Pivotal Role of Heart for Orthostasis: Left Ventricular Untwisting Mechanics and Physical Fitness. Exerc Sport Sci Rev 2021; 49:88-98. [PMID: 33720910 DOI: 10.1249/jes.0000000000000247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Augmentation of left ventricular (LV) untwisting due to central hypovolemia is likely to be a compensatory mechanism for maintaining stroke volume, which is reduced by a decrease in cardiac filling during orthostatic stress. Orthostatic intolerance observed in both high and low fitness levels may be explained by the impaired response of LV untwisting due to central hypovolemia.
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Affiliation(s)
| | | | | | - Rina Suzuki
- Emergency Department, Kyorin University Hospital
| | - Tomoya Suda
- Emergency Department, Kyorin University Hospital
| | | | - Ai Hirasawa
- Department of Health and Welfare, Faculty of Health Sciences, Kyorin University, Tokyo, Japan
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18
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Convertino VA, Koons NJ, Suresh MR. Physiology of Human Hemorrhage and Compensation. Compr Physiol 2021; 11:1531-1574. [PMID: 33577122 DOI: 10.1002/cphy.c200016] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hemorrhage is a leading cause of death following traumatic injuries in the United States. Much of the previous work in assessing the physiology and pathophysiology underlying blood loss has focused on descriptive measures of hemodynamic responses such as blood pressure, cardiac output, stroke volume, heart rate, and vascular resistance as indicators of changes in organ perfusion. More recent work has shifted the focus toward understanding mechanisms of compensation for reduced systemic delivery and cellular utilization of oxygen as a more comprehensive approach to understanding the complex physiologic changes that occur following and during blood loss. In this article, we begin with applying dimensional analysis for comparison of animal models, and progress to descriptions of various physiological consequences of hemorrhage. We then introduce the complementary side of compensation by detailing the complexity and integration of various compensatory mechanisms that are activated from the initiation of hemorrhage and serve to maintain adequate vital organ perfusion and hemodynamic stability in the scenario of reduced systemic delivery of oxygen until the onset of hemodynamic decompensation. New data are introduced that challenge legacy concepts related to mechanisms that underlie baroreflex functions and provide novel insights into the measurement of the integrated response of compensation to central hypovolemia known as the compensatory reserve. The impact of demographic and environmental factors on tolerance to hemorrhage is also reviewed. Finally, we describe how understanding the physiology of compensation can be translated to applications for early assessment of the clinical status and accurate triage of hypovolemic and hypotensive patients. © 2021 American Physiological Society. Compr Physiol 11:1531-1574, 2021.
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Affiliation(s)
- Victor A Convertino
- Battlefield Healthy & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA San Antonio, Texas, USA
| | - Natalie J Koons
- Battlefield Healthy & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA San Antonio, Texas, USA
| | - Mithun R Suresh
- Battlefield Healthy & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA San Antonio, Texas, USA
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19
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Rosenberg AJ, Kay VL, Anderson GK, Sprick JD, Rickards CA. A comparison of protocols for simulating hemorrhage in humans: step versus ramp lower body negative pressure. J Appl Physiol (1985) 2021; 130:380-389. [PMID: 33211600 DOI: 10.1152/japplphysiol.00230.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lower body negative pressure (LBNP) elicits central hypovolemia, and it has been used to simulate the cardiovascular and cerebrovascular responses to hemorrhage in humans. LBNP protocols commonly use progressive stepwise reductions in chamber pressure for specific time periods. However, continuous ramp LBNP protocols have also been utilized to simulate the continuous nature of most bleeding injuries. The aim of this study was to compare tolerance and hemodynamic responses between these two LBNP profiles. Healthy human subjects (N = 19; age, 27 ± 4 y; 7 female/12 male) completed a 1) step LBNP protocol (5-min steps) and 2) continuous ramp LBNP protocol (3 mmHg/min), both to presyncope. Heart rate (HR), mean arterial pressure (MAP), stroke volume (SV), middle and posterior cerebral artery velocity (MCAv and PCAv), cerebral oxygen saturation (ScO2), and end-tidal CO2 (etCO2) were measured. LBNP tolerance, via the cumulative stress index (CSI, summation of chamber pressure × time at each pressure), and hemodynamic responses were compared between the two protocols. The CSI (step: 911 ± 97 mmHg/min vs. ramp: 823 ± 83 mmHg/min; P = 0.12) and the magnitude of central hypovolemia (%Δ SV, step: -54.6% ± 2.6% vs. ramp: -52.1% ± 2.8%; P = 0.32) were similar between protocols. Although there were no differences between protocols for the maximal %Δ HR (P = 0.88), the %Δ MAP during the step protocol was attenuated (P = 0.05), and the reductions in MCAv, PCAv, ScO2, and etCO2 were greater (P ≤ 0.08) when compared with the ramp protocol at presyncope. These results indicate that when comparing cardiovascular responses to LBNP across different laboratories, the specific pressure profile must be considered as a potential confounding factor.NEW & NOTEWORTHY Ramp lower body negative pressure (LBNP) protocols have been utilized to simulate the continuous nature of bleeding injuries. However, it unknown if tolerance or the physiological responses to ramp LBNP are similar to the more common stepwise LBNP protocol. We report similar tolerance between the two protocols, but the step protocol elicited a greater increase in cerebral oxygen extraction in the presence of reduced blood flow, presumably facilitating the matching of metabolic supply and demand.
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Affiliation(s)
- Alexander J Rosenberg
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Victoria L Kay
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Garen K Anderson
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
| | - Justin D Sprick
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas.,Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
| | - Caroline A Rickards
- Cerebral and Cardiovascular Physiology Laboratory, Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, Texas
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20
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Berthelsen LF. Ketamine: yay or neigh? Implications for cardiovascular regulation and considerations for field use. J Physiol 2021; 599:1949-1950. [PMID: 33450043 DOI: 10.1113/jp281254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 01/12/2021] [Indexed: 11/08/2022] Open
Affiliation(s)
- Lindsey F Berthelsen
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Canada
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21
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Combat medic testing of a novel monitoring capability for early detection of hemorrhage. J Trauma Acute Care Surg 2021; 89:S146-S152. [PMID: 32118826 DOI: 10.1097/ta.0000000000002649] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Current out-of-hospital protocols to determine hemorrhagic shock in civilian trauma systems rely on standard vital signs with military guidelines relying on heart rate and strength of the radial pulse on palpation, all of which have proven to provide little forewarning for the need to implement early intervention prior to decompensation. We tested the hypothesis that addition of a real-time decision-assist machine-learning algorithm, the compensatory reserve measurement (CRM), used by combat medics could shorten the time required to identify the need for intervention in an unstable patient during a hemorrhage profile as compared with vital signs alone. METHODS We randomized combat medics from the Army Medical Department Center and School Health Readiness Center of Excellence into three groups: group 1 viewed a display of no simulated hemorrhage and unchanging vital signs as a control (n = 24), group 2 viewed a display of simulated hemorrhage and changing vital signs alone (hemorrhage; n = 31), and group 3 viewed a display of changing vital signs with the addition of the CRM (hemorrhage + CRM; n = 22). Participants were asked to push a computer key when they believed the patient was becoming unstable and needed medical intervention. RESULTS The average time of 11.0 minutes (95% confidence interval, 8.7-13.3 minutes) required by the hemorrhage + CRM group to identify an unstable patient (i.e., stop the video sequence) was less by more than 40% (p < 0.01) compared with 18.9 minutes (95% confidence interval, 17.2-20.5 minutes) in the hemorrhage group. CONCLUSION The use of a machine-learning monitoring technology designed to measure the capacity to compensate for central blood volume loss resulted in reduced time required by combat medics to identify impending hemodynamic instability. LEVEL OF EVIDENCE Diagnostic, level IV.
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22
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Lawley JS, Babu G, Janssen SLJE, Petersen LG, Hearon CM, Dias KA, Sarma S, Williams MA, Whitworth LA, Levine BD. Daily generation of a footward fluid shift attenuates ocular changes associated with head-down tilt bed rest. J Appl Physiol (1985) 2020; 129:1220-1231. [PMID: 32940563 DOI: 10.1152/japplphysiol.00250.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Astronauts have presented with a constellation of visual changes referred to as spaceflight-associated neuro-ocular syndrome (SANS). However, neither have early markers of microgravity-induced optic remodeling been fully identified nor have countermeasures been developed. To identify early markers of SANS, we studied 10 subjects with optical coherence tomography and ultrasonography when upright and supine and again after 24 h of 6° head-down tilt (HDT) bed rest. Upon acute transition from the upright to the supine position, choroid area (2.24 ± 0.53 to 2.28 ± 0.52 mm2, P = 0.001) and volume (9.51 ± 2.08 to 9.73 ± 2.08 mm3, P = 0.002) increased. After 24 h of HDT bed rest, subfoveal choroidal thickness (372 ± 93 to 381 ± 95 µm, P = 0.02), choroid area (2.25 ± 0.52 to 2.33 ± 0.54 mm2, P = 0.08), and volume (9.64 ± 2.03 to 9.82 ± 2.08 mm3, P = 0.08) increased relative to the supine position. Subsequently, seven subjects spent 3 days in -6°HDT bed rest to assess whether low-level lower body negative pressure (LBNP) could prevent the observed choroidal engorgement during bed rest. Maintaining the -6° HDT position for 3 days caused choroid area (Δ0.11 mm2, P = 0.05) and volume (Δ0.45 mm3, P = 0.003) to increase. When participants also spent 8 h daily under -20 mmHg LBNP, choroid volume still increased, but substantially (40%) less than in the control trial (Δ0.27 mm3, P = 0.05). Moreover, the increase in choroid area was diminished (Δ0.03 mm2, P = 0.13), indicating that low-level LBNP attenuates the choroid expansion associated with 3 days of -6° HDT bed rest. These data suggest that low-level LBNP may be an effective countermeasure for SANS.NEW & NOTEWORTHY Choroid measurements appear to be sensitive to changes in gravitational gradients, as well as periods of head-down tilt (HDT) bed rest, suggesting that they are potential indicators of early ocular remodeling and could serve to evaluate the efficacy of countermeasures for SANS. Eight hours of lower body negative pressure (LBNP) daily attenuates the choroid expansion associated with 3 days of strict -6° HDT bed rest, indicating that LBNP may be an effective countermeasure for SANS.
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Affiliation(s)
- Justin S Lawley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas.,Division of Physiology, Department of Sports Science, University of Innsbruck, Innsbruck, Austria
| | - Gautam Babu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | | | - Lonnie G Petersen
- Department of Orthopedic Surgery, University of California San Diego, California
| | - Christopher M Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Katrin A Dias
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
| | - Michael A Williams
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington.,Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington
| | | | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas.,University of Texas Southwestern Medical Center, Dallas, Texas
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23
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Cui J, Blaha C, Herr MD, Sinoway LI. Lower-limb venous distension reflex and orthostatic tolerance in young healthy humans. Am J Physiol Regul Integr Comp Physiol 2020; 319:R142-R147. [PMID: 32663039 DOI: 10.1152/ajpregu.00269.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Earlier reports suggest that limb venous distension evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) (i.e., venous distension reflex). Our recent report also shows that suction of arterially occluded limb evokes venous distension reflex. We postulate that the venous distension reflex contributes to autonomic responses to orthostatic stress. In this study, we hypothesized that orthostatic tolerance would be linked to the MSNA response seen with lower limb suction. Fifteen healthy subjects were tested in the supine position. Negative pressure (-100 mmHg) was applied on an arterially occluded lower limb for 2 min. MSNA from the peroneal nerve in the limb not exposed to suction, ECG, and BP (Finometer) was recorded throughout the study. Limb occlusion without suction was used as a control trial. In a separate visit, the individual's orthostatic tolerance was assessed using a graded lower body negative pressure (LBNP) tolerance test. Mean arterial BP and MSNA (18.6 ± 1.9 to 23.6 ± 2.0 bursts/min) significantly (both P < 0.05) increased during limb suction. Orthostatic tolerance index positively correlated (R = 0.636, P = 0.011) with the MSNA response seen with suction during occlusion. Since the venous distension reflex strength correlates with the level of orthostatic tolerance, we speculate that lower-limb venous distension reflex engagement increases the sympathetic responses during orthostatic challenge and serves to maintain BP with postural stress.
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Affiliation(s)
- Jian Cui
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Cheryl Blaha
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Michael D Herr
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
| | - Lawrence I Sinoway
- Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Milton S. Hershey Medical Center, Hershey, Pennsylvania
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24
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Johnson BD, Schlader ZJ, Schaake MW, O'Leary MC, Hostler D, Lin H, St James E, Lema PC, Bola A, Clemency BM. Inferior Vena Cava Diameter is an Early Marker of Central Hypovolemia during Simulated Blood Loss. PREHOSP EMERG CARE 2020; 25:341-346. [PMID: 32628063 DOI: 10.1080/10903127.2020.1778823] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
INTRODUCTION Inferior vena cava (IVC) diameter decreases under conditions of hypovolemia. Point-of-care ultrasound (POCUS) may be useful to emergently assess IVC diameter. This study tested the hypothesis that ultrasound measurements of IVC diameter decreases during severe simulated blood loss. METHODS Blood loss was simulated in 14 healthy men (22 ± 2 years) using lower body negative pressure (LBNP). Pressure within the LBNP chamber was reduced 10 mmHg of LBNP every four minutes until participants experienced pre-syncopal symptoms or until 80 mmHg of LBNP was completed. IVC diameter was imaged with POCUS using B-mode in the long and short axis views between minutes two and four of each stage. RESULTS Maximum IVC diameter in the long axis view was lower than baseline (1.5 ± 0.4 cm) starting at -20 mmHg of LBNP (1.0 ± 0.3 cm; p < 0.01) and throughout LBNP (p < 0.01). The minimum IVC diameter in the long axis view was lower than baseline (0.9 ± 0.3 cm) at -20 mmHg of LBNP (0.5 ± 0.3 cm; p < 0.01) and throughout LBNP (p < 0.01). Maximum IVC diameter in the short axis view was lower than baseline (0.9 ± 0.2 cm) at 40 mmHg of LBNP (0.6 ± 0.2; p = 0.01) and the final LBNP stage (0.6 ± 0.2 cm; p < 0.01). IVC minimum diameter in the short axis view was lower than baseline (0.5 ± 0.2 cm) at the final LBNP stage (0.3 ± 0.2 cm; p = 0.01). CONCLUSION These data demonstrate that IVC diameter decreases prior to changes in traditional vital signs during simulated blood loss. Further study is needed to determine the view and diameter threshold that most accurate for identifying hemorrhage requiring emergent intervention.
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25
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Zaar M, Herzig MC, Fedyk CG, Montgomery RK, Prat N, Parida BK, Hinojosa-Laborde C, Muniz GW, Shade RE, Bauer C, Delacruz W, Bynum JA, Convertino VA, Cap AP, Pidcoke HF. Similar hemostatic responses to hypovolemia induced by hemorrhage and lower body negative pressure reveal a hyperfibrinolytic subset of non-human primates. PLoS One 2020; 15:e0234844. [PMID: 32579572 PMCID: PMC7314422 DOI: 10.1371/journal.pone.0234844] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 05/18/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND To study central hypovolemia in humans, lower body negative pressure (LBNP) is a recognized alternative to blood removal (HEM). While LBNP mimics the cardiovascular responses of HEM in baboons, similarities in hemostatic responses to LBNP and HEM remain unknown in this species. METHODS Thirteen anesthetized baboons were exposed to progressive hypovolemia by HEM and, four weeks later, by LBNP. Hemostatic activity was evaluated by plasma markers, thromboelastography (TEG), flow cytometry, and platelet aggregometry at baseline (BL), during and after hypovolemia. RESULTS BL values were indistinguishable for most parameters although platelet count, maximal clot strength (MA), protein C, thrombin anti-thrombin complex (TAT), thrombin activatable fibrinolysis inhibitor (TAFI) activity significantly differed between HEM and LBNP. Central hypovolemia induced by either method activated coagulation; TEG R-time decreased and MA increased during and after hypovolemia compared to BL. Platelets displayed activation by flow cytometry; platelet count and functional aggregometry were unchanged. TAFI activity and protein, Factors V and VIII, vWF, Proteins C and S all demonstrated hemodilution during HEM and hemoconcentration during LBNP, whereas tissue plasminogen activator (tPA), plasmin/anti-plasmin complex, and plasminogen activator inhibitor-1 did not. Fibrinolysis (TEG LY30) was unchanged by either method; however, at BL, fibrinolysis varied greatly. Post-hoc analysis separated baboons into low-lysis (LY30 <2%) or high-lysis (LY30 >2%) whose fibrinolytic state matched at both HEM and LBNP BL. In high-lysis, BL tPA and LY30 correlated strongly (r = 0.95; P<0.001), but this was absent in low-lysis. In low-lysis, BL TAFI activity and tPA correlated (r = 0.88; P<0.050), but this was absent in high-lysis. CONCLUSIONS Central hypovolemia induced by either LBNP or HEM resulted in activation of coagulation; thus, LBNP is an adjunct to study hemorrhage-induced pro-coagulation in baboons. Furthermore, this study revealed a subset of baboons with baseline hyperfibrinolysis, which was strongly coupled to tPA and uncoupled from TAFI activity.
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Affiliation(s)
- Morten Zaar
- Center for Human Integrative Physiology, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Maryanne C. Herzig
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
- * E-mail:
| | - Chriselda G. Fedyk
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Robbie K. Montgomery
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Nicolas Prat
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
- French Armed Forces Biomedical Research Institute (IRBA), Brétigny-sur-Orge, France
| | - Bijaya K. Parida
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Carmen Hinojosa-Laborde
- Center for Human Integrative Physiology, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Gary W. Muniz
- Center for Human Integrative Physiology, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Robert E. Shade
- Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Cassondra Bauer
- Southwest National Primate Research Center, Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Wilfred Delacruz
- Center for Human Integrative Physiology, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - James A. Bynum
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Victor A. Convertino
- Center for Human Integrative Physiology, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Andrew P. Cap
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
| | - Heather F. Pidcoke
- Coagulation and Blood Research, United States Army Institute of Surgical Research, Fort Sam Houston, Texas, United States of America
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26
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Trotter CE, Tourula E, Pizzey FK, Batterson PM, Jacobs RA, Pearson J. High‐intensity interval exercise reduces tolerance to a simulated haemorrhagic challenge in heat‐stressed individuals. Exp Physiol 2020; 106:212-221. [DOI: 10.1113/ep088377] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 01/28/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Claire E. Trotter
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
- Department of Applied Physiology and Wellness Southern Methodist University Dallas TX USA
| | - Erica Tourula
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
| | - Faith K. Pizzey
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
- School of Human Movement and Nutrition Sciences The University of Queensland Brisbane Australia
| | - Philip M. Batterson
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
- College of Biological and Population Health Sciences Oregon State University Corvallis OR USA
| | - Robert A. Jacobs
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
| | - James Pearson
- Department of Human Physiology and Nutrition University of Colorado at Colorado Springs Colorado Springs CO USA
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27
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Schlotman TE, Lehnhardt KR, Abercromby AF, Easter BD, Downs ME, Akers LTCKS, Convertino VA. Bridging the gap between military prolonged field care monitoring and exploration spaceflight: the compensatory reserve. NPJ Microgravity 2019; 5:29. [PMID: 31815179 PMCID: PMC6893012 DOI: 10.1038/s41526-019-0089-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 10/31/2019] [Indexed: 01/03/2023] Open
Abstract
The concept of prolonged field care (PFC), or medical care applied beyond doctrinal planning timelines, is the top priority capability gap across the US Army. PFC is the idea that combat medics must be prepared to provide medical care to serious casualties in the field without the support of robust medical infrastructure or resources in the event of delayed medical evacuation. With limited resources, significant distances to travel before definitive care, and an inability to evacuate in a timely fashion, medical care during exploration spaceflight constitutes the ultimate example PFC. One of the main capability gaps for PFC in both military and spaceflight settings is the need for technologies for individualized monitoring of a patient's physiological status. A monitoring capability known as the compensatory reserve measurement (CRM) meets such a requirement. CRM is a small, portable, wearable technology that uses a machine learning and feature extraction-based algorithm to assess real-time changes in hundreds of specific features of arterial waveforms. Future development and advancement of CRM still faces engineering challenges to develop ruggedized wearable sensors that can measure waveforms for determining CRM from multiple sites on the body and account for less than optimal conditions (sweat, water, dirt, blood, movement, etc.). We show here the utility of a military wearable technology, CRM, which can be translated to space exploration.
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Affiliation(s)
- Taylor E. Schlotman
- United States Army Institute of Surgical Research 3698 Chambers Pass, Bldg. 3611 JBSA Fort Sam, Houston, TX 78234 USA
| | | | | | | | - Meghan E. Downs
- NASA Johnson Space Center, 2101 E NASA Pkwy, Houston, TX 77058 USA
| | - L. T. C. Kevin S. Akers
- United States Army Institute of Surgical Research 3698 Chambers Pass, Bldg. 3611 JBSA Fort Sam, Houston, TX 78234 USA
| | - Victor A. Convertino
- United States Army Institute of Surgical Research 3698 Chambers Pass, Bldg. 3611 JBSA Fort Sam, Houston, TX 78234 USA
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28
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van der Ster BJP, Westerhof BE, Stok WJ, van Lieshout JJ. Detecting central hypovolemia in simulated hypovolemic shock by automated feature extraction with principal component analysis. Physiol Rep 2019; 6:e13895. [PMID: 30488597 PMCID: PMC6429974 DOI: 10.14814/phy2.13895] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/10/2018] [Accepted: 09/11/2018] [Indexed: 11/24/2022] Open
Abstract
Assessment of the volume status by blood pressure (BP) monitoring is difficult, since baroreflex control of BP makes it insensitive to blood loss up to about one liter. We hypothesized that a machine learning model recognizes the progression of central hypovolemia toward presyncope by extracting information of the noninvasive blood pressure waveform parametrized through principal component analysis. This was tested in healthy volunteers exposed to simulated hemorrhage by lower body negative pressure (LBNP). Fifty‐six healthy volunteers were subjected to progressive central hypovolemia. A support vector machine was trained on the blood pressure waveform. Three classes of progressive stages of hypovolemia were defined. The model was optimized for the number of principal components and regularization parameter for penalizing misclassification (cost): C. Model performance was expressed as accuracy, mean squared error (MSE), and kappa statistic (inter‐rater agreement). Forty‐six subjects developed presyncope of which 41 showed an increase in model classification severity from baseline to presyncope. In five of the remaining nine subjects (1 was excluded) it stagnated. Classification of samples during baseline and end‐stage LBNP had the highest accuracy (95% and 50%, respectively). Baseline and first stage of LBNP demonstrated the lowest MSE (0.01 respectively 0.32). Model MSE and accuracy did not improve for C values exceeding 0.01. Adding more than five principal components did not further improve accuracy or MSE. Increment in kappa halted after 10 principal components had been added. Automated feature extraction of the blood pressure waveform allows modeling of progressive hypovolemia with a support vector machine. The model distinguishes classes between baseline and presyncope.
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Affiliation(s)
- Björn J P van der Ster
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, Amsterdam, the Netherlands
| | - Berend E Westerhof
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, Amsterdam, the Netherlands.,Department of Pulmonary Diseases, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, the Netherlands
| | - Wim J Stok
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, Amsterdam, the Netherlands
| | - Johannes J van Lieshout
- Department of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.,Laboratory for Clinical Cardiovascular Physiology, Center for Heart Failure Research, Academic Medical Center, Amsterdam, the Netherlands.,MRC/Arthritis Research, UK Centre for Musculoskeletal Ageing Research, School of Life Sciences, the Medical School, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, United Kingdom
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Measurement of compensatory reserve predicts racial differences in tolerance to simulated hemorrhage in women. J Trauma Acute Care Surg 2019; 85:S77-S83. [PMID: 29443858 DOI: 10.1097/ta.0000000000001837] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND The compensatory reserve measurement (CRM) has been established to accurately measure the body's total integrated capacity to compensate for physiologic states of reduced central blood volume and predict hemodynamic decompensation associated with inadequate tissue oxygenation. We previously demonstrated that African American (AA) women have a higher tolerance to reductions in central blood volume. Therefore, we tested the hypothesis that the CRM would identify racial differences during simulated hemorrhage, before the onset of traditional signs/symptoms. METHODS We performed a retrospective analysis during simulated hemorrhage using lower-body negative pressure (LBNP) in 23 AA (22 ± 1 years; 24 ± 1 kg/m) and 31 white women (WW) (20 ± 1 years; 23 ± 1 kg/m). Beat-by-beat blood pressure (BP) and heart rate (HR) were recorded during progressive lower body negative pressure to presyncope. The BP waveforms were analyzed using a machine-learning algorithm to derive the CRM at each lower body negative pressure stage. RESULTS Resting mean arterial BP (AA, 78 ± 3 mm Hg vs. WW, 74 ± 2 mm Hg) and HR (AA, 68 ± 2 bpm vs. WW, 65 ± 2 bpm) were similar between groups. The CRM progressively decreased during LBNP in both groups; however, the rate of decline in the CRM was less (p < 0.05) in AA. The CRM was 4% higher in AA at -15 mm Hg LBNP and progressively increased to 21% higher at -50 mm Hg LBNP (p < 0.05). However, changes in BP and HR were not different between groups. CONCLUSION These data support the notion that the greater tolerance to simulated hemorrhage induced by LBNP in AA women can be explained by their greater capacity to protect the reserve to compensate for progressive central hypovolemia compared with WW, independent of standard vital signs. LEVEL OF EVIDENCE Diagnostic test, level II.
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30
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Anderson GK, Sprick JD, Park FS, Rosenberg AJ, Rickards CA. Responses of cerebral blood velocity and tissue oxygenation to low-frequency oscillations during simulated haemorrhagic stress in humans. Exp Physiol 2019; 104:1190-1201. [PMID: 31090115 PMCID: PMC11022286 DOI: 10.1113/ep087358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 05/14/2019] [Indexed: 04/19/2024]
Abstract
NEW FINDINGS What is the central question of this study? Do low-frequency oscillations in arterial pressure and cerebral blood velocity protect cerebral blood velocity and oxygenation during central hypovolaemia? What is the main finding and its importance? Low-frequency oscillations in arterial pressure and cerebral blood velocity attenuate reductions in cerebral oxygen saturation but do not protect absolute cerebral blood velocity during central hypovolaemia. This finding indicates the potential importance of haemodynamic oscillations in maintaining cerebral oxygenation and therefore viability of tissues during challenges to cerebral blood flow and oxygen delivery. ABSTRACT Tolerance to both real and simulated haemorrhage varies between individuals. Exaggerated low-frequency (∼0.1 Hz) oscillations in mean arterial pressure and brain blood flow [indexed via middle cerebral artery velocity (MCAv)] have been associated with improved tolerance to reduced central blood volume. The mechanism for this association has not been explored. We hypothesized that inducing low-frequency oscillations in arterial pressure and cerebral blood velocity would attenuate reductions in cerebral blood velocity and oxygenation during simulated haemorrhage. Fourteen subjects (11 men and three women) were exposed to oscillatory (0.1 and 0.05 Hz) and non-oscillatory (0 Hz) lower-body negative pressure profiles with an average chamber pressure of -60 mmHg (randomized and counterbalanced order). Measurements included arterial pressure and stroke volume via finger photoplethysmography, MCAv via transcranial Doppler ultrasound, and cerebral oxygenation of the frontal lobe via near-infrared spectroscopy. Tolerance was higher during the two oscillatory profiles compared with the 0 Hz profile (0.05 Hz, P = 0.04; 0.1 Hz, P = 0.09), accompanied by attenuated reductions in stroke volume (P < 0.001) and cerebral oxygenation of the frontal lobe (P ≤ 0.02). No differences were observed between profiles for reductions in mean arterial pressure (P = 0.17) and MCAv (P = 0.30). In partial support of our hypothesis, cerebral oxygenation, but not cerebral blood velocity, was protected during the oscillatory profiles. Interestingly, more subjects tolerated the oscillatory profiles compared with the static 0 Hz profile, despite similar arterial pressure responses. These findings emphasize the potential importance of haemodynamic oscillations in maintaining perfusion and oxygenation of cerebral tissues during haemorrhagic stress.
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Affiliation(s)
- Garen K. Anderson
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Justin D. Sprick
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
| | - Flora S. Park
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Alexander J. Rosenberg
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Caroline A. Rickards
- Cerebral & Cardiovascular Physiology Laboratory, Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort Worth, TX, USA
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Rickards CA. Vive la résistance! The role of inspiratory resistance breathing on cerebral blood flow. Respir Physiol Neurobiol 2019; 265:76-82. [DOI: 10.1016/j.resp.2018.10.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 08/22/2018] [Accepted: 10/03/2018] [Indexed: 10/28/2022]
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Hisdal J, Landsverk SA, Hoff IE, Hagen OA, Kirkebøen KA, Høiseth LØ. Associations between changes in precerebral blood flow and cerebral oximetry in the lower body negative pressure model of hypovolemia in healthy volunteers. PLoS One 2019; 14:e0219154. [PMID: 31251778 PMCID: PMC6599124 DOI: 10.1371/journal.pone.0219154] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Accepted: 06/17/2019] [Indexed: 11/19/2022] Open
Abstract
Reductions in cerebral oxygen saturation (ScO2) measured by near infra-red spectroscopy have been found during compensated hypovolemia in the lower body negative pressure (LBNP)-model, which may reflect reduced cerebral blood flow. However, ScO2 may also be contaminated from extracranial (scalp) tissues, mainly supplied by the external carotid artery (ECA), and it is possible that a ScO2 reduction during hypovolemia is caused by reduced scalp, and not cerebral, blood flow. The aim of the present study was to explore the associations between blood flow in precerebral arteries and ScO2 during LBNP-induced hypovolemia. Twenty healthy volunteers were exposed to LBNP 20, 40, 60 and 80 mmHg. Blood flow in the internal carotid artery (ICA), ECA and vertebral artery (VA) was measured by Doppler ultrasound. Stroke volume for calculating cardiac output was measured by suprasternal Doppler. Associations of changes within subjects were examined using linear mixed-effects regression models. LBNP reduced cardiac output, ScO2 and ICA and ECA blood flow. Changes in flow in both ICA and ECA were associated with changes in ScO2 and cardiac output. Flow in the VA did not change during LBNP and changes in VA flow were not associated with changes in ScO2 or cardiac output. During experimental compensated hypovolemia in healthy, conscious subjects, a reduced ScO2 may thus reflect a reduction in both cerebral and extracranial blood flow.
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Affiliation(s)
- Jonny Hisdal
- Section of Vascular Investigations, Department of Vascular Surgery, Division of Cardiovascular and Pulmonary Diseases, Oslo University Hospital, Oslo, Norway
- Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Svein Aslak Landsverk
- Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
| | - Ingrid Elise Hoff
- Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
- Norwegian Air Ambulance Foundation, Oslo, Norway
| | - Ove Andreas Hagen
- Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
| | - Knut Arvid Kirkebøen
- Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
| | - Lars Øivind Høiseth
- Section of Vascular Investigations, Department of Vascular Surgery, Division of Cardiovascular and Pulmonary Diseases, Oslo University Hospital, Oslo, Norway
- Department of Anesthesiology, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway
- * E-mail:
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Cvirn G, Waha JE, Brix B, Rössler A, Jantscher A, Schlagenhauf A, Koestenberger M, Wonisch W, Wagner T, Goswami N. Coagulation changes induced by lower-body negative pressure in men and women. J Appl Physiol (1985) 2019; 126:1214-1222. [DOI: 10.1152/japplphysiol.00940.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We investigated whether lower-body negative pressure (LBNP) application leads to coagulation activation in whole blood (WB) samples in healthy men and women. Twenty-four women and 21 men, all healthy young participants, with no histories of thrombotic disorders and not on medications, were included. LBNP was commenced at −10 mmHg and increased by −10 mmHg every 5 min until a maximum of −40 mmHg. Recovery up to 10 min was also monitored. Blood samples were collected at baseline, at end of LBNP, and end of recovery. Hemostatic profiling included comparing the effects of LBNP on coagulation values in both men and women using standard coagulation tests, calibrated automated thrombogram, thrombelastometry, impedance aggregometry, and markers of thrombin formation. LBNP led to coagulation activation determined in both plasma and WB samples. At baseline, women were hypercoagulable compared with men, as evidenced by their shorter “lag times” and higher thrombin peaks and by shorter “coagulation times” and “clot formation times.” Moreover, men were more susceptible to LBNP, as reflected in their elevated factor VIII levels and decreased lag times following LBNP. LBNP-induced coagulation activation was not accompanied by endothelial activation. Women appear to be relatively hypercoagulable compared with men, but men are more susceptible to coagulation changes during LBNP. The application of LBNP might be a useful future tool to identify individuals with an elevated risk for thrombosis, in subjects with or without history of thrombosis.NEW & NOTEWORTHY LBNP led to coagulation activation determined in both plasma and whole blood samples. At baseline, women were hypercoagulable compared with men. Men were, however, more susceptible to coagulation changes during LBNP. LBNP-induced coagulation activation was not accompanied by endothelial activation. The application of LBNP might be a useful future tool to identify individuals with an elevated risk for thrombosis, in subjects with or without history of thrombosis.
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Affiliation(s)
- Gerhard Cvirn
- Physiological Chemistry Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - James E. Waha
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Bianca Brix
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Andreas Rössler
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Andreas Jantscher
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Axel Schlagenhauf
- Department of Pediatric Cardiology, Medical University of Graz, Graz, Austria
| | | | - Willibald Wonisch
- Physiological Chemistry Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
| | - Thomas Wagner
- Department of Blood Group Serology and Transfusion Medicine, Medical University of Graz, Graz, Austria
| | - Nandu Goswami
- Physiology Division, Otto Loewi Research Center, Medical University of Graz, Graz, Austria
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Park FS, Kay VL, Sprick JD, Rosenberg AJ, Anderson GK, Mallet RT, Rickards CA. Hemorrhage simulated by lower body negative pressure provokes an oxidative stress response in healthy young adults. Exp Biol Med (Maywood) 2019; 244:272-278. [PMID: 30727766 DOI: 10.1177/1535370219828706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
IMPACT STATEMENT We characterize the systemic oxidative stress response in young, healthy human subjects with exposure to simulated hemorrhage via application of lower body negative pressure (LBNP). Prior work has demonstrated that LBNP and actual blood loss evoke similar hemodynamic and immune responses (i.e. white blood cell count), but it is unknown whether LBNP elicits oxidative stress resembling that produced by blood loss. We show that LBNP induces a 29% increase in F2-isoprostanes, a systemic marker of oxidative stress. The findings of this investigation may have important implications for the study of hemorrhage using LBNP, including future assessments of targeted interventions that may reduce oxidative stress, such as novel fluid resuscitation approaches.
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Affiliation(s)
- Flora S Park
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA
| | - Victoria L Kay
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA
| | - Justin D Sprick
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA.,2 Division of Renal Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Alexander J Rosenberg
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA
| | - Garen K Anderson
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA
| | - Robert T Mallet
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA
| | - Caroline A Rickards
- 1 Department of Physiology & Anatomy, University of North Texas Health Science Center, Fort, TX 76107, USA
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35
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Goswami N, Blaber AP, Hinghofer-Szalkay H, Convertino VA. Lower Body Negative Pressure: Physiological Effects, Applications, and Implementation. Physiol Rev 2019; 99:807-851. [PMID: 30540225 DOI: 10.1152/physrev.00006.2018] [Citation(s) in RCA: 120] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This review presents lower body negative pressure (LBNP) as a unique tool to investigate the physiology of integrated systemic compensatory responses to altered hemodynamic patterns during conditions of central hypovolemia in humans. An early review published in Physiological Reviews over 40 yr ago (Wolthuis et al. Physiol Rev 54: 566-595, 1974) focused on the use of LBNP as a tool to study effects of central hypovolemia, while more than a decade ago a review appeared that focused on LBNP as a model of hemorrhagic shock (Cooke et al. J Appl Physiol (1985) 96: 1249-1261, 2004). Since then there has been a great deal of new research that has applied LBNP to investigate complex physiological responses to a variety of challenges including orthostasis, hemorrhage, and other important stressors seen in humans such as microgravity encountered during spaceflight. The LBNP stimulus has provided novel insights into the physiology underlying areas such as intolerance to reduced central blood volume, sex differences concerning blood pressure regulation, autonomic dysfunctions, adaptations to exercise training, and effects of space flight. Furthermore, approaching cardiovascular assessment using prediction models for orthostatic capacity in healthy populations, derived from LBNP tolerance protocols, has provided important insights into the mechanisms of orthostatic hypotension and central hypovolemia, especially in some patient populations as well as in healthy subjects. This review also presents a concise discussion of mathematical modeling regarding compensatory responses induced by LBNP. Given the diverse applications of LBNP, it is to be expected that new and innovative applications of LBNP will be developed to explore the complex physiological mechanisms that underline health and disease.
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Affiliation(s)
- Nandu Goswami
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Andrew Philip Blaber
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Helmut Hinghofer-Szalkay
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Victor A Convertino
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
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Crandall CG, Rickards CA, Johnson BD. Impact of environmental stressors on tolerance to hemorrhage in humans. Am J Physiol Regul Integr Comp Physiol 2018; 316:R88-R100. [PMID: 30517019 DOI: 10.1152/ajpregu.00235.2018] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hemorrhage is a leading cause of death in military and civilian settings, and ~85% of potentially survivable battlefield deaths are hemorrhage-related. Soldiers and civilians are exposed to a number of environmental and physiological conditions that have the potential to alter tolerance to a hemorrhagic insult. The objective of this review is to summarize the known impact of commonly encountered environmental and physiological conditions on tolerance to hemorrhagic insult, primarily in humans. The majority of the studies used lower body negative pressure (LBNP) to simulate a hemorrhagic insult, although some studies employed incremental blood withdrawal. This review addresses, first, the use of LBNP as a model of hemorrhage-induced central hypovolemia and, then, the effects of the following conditions on tolerance to LBNP: passive and exercise-induced heat stress with and without hypohydration/dehydration, exposure to hypothermia, and exposure to altitude/hypoxia. An understanding of the effects of these environmental and physiological conditions on responses to a hemorrhagic challenge, including tolerance, can enable development and implementation of targeted strategies and interventions to reduce the impact of such conditions on tolerance to a hemorrhagic insult and, ultimately, improve survival from blood loss injuries.
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Affiliation(s)
- Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas and University of Texas Southwestern Medical Center , Dallas, Texas
| | - Caroline A Rickards
- Department of Physiology and Anatomy, University of North Texas Health Science Center , Fort Worth, Texas
| | - Blair D Johnson
- Department of Exercise and Nutrition Sciences, University at Buffalo , Buffalo, New York
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Petersen LG, Lawley JS, Lilja-Cyron A, Petersen JCG, Howden EJ, Sarma S, Cornwell WK, Zhang R, Whitworth LA, Williams MA, Juhler M, Levine BD. Lower body negative pressure to safely reduce intracranial pressure. J Physiol 2018; 597:237-248. [PMID: 30286250 DOI: 10.1113/jp276557] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 10/01/2018] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS During long-term missions, some astronauts experience structural and functional changes of the eyes and brain which resemble signs/symptoms experienced by patients with intracranial hypertension. Weightlessness prevents the normal cerebral volume and pressure 'unloading' associated with upright postures on Earth, which may be part of the cerebral and ocular pathophysiology. By placing the lower body in a negative pressure device (LBNP) that pulls fluid away from cranial compartments, we simulated effects of gravity and significantly lowered pressure within the brain parenchyma and ventricle compartments. Application of incremental LBNP demonstrated a non-linear dose-response curve, suggesting 20 mmHg LBNP as the optimal level for reducing pressure in the brain without impairing cerebral perfusion pressure. This non-invasive method of reducing pressure in the brain holds potential as a countermeasure in space as well as having treatment potential for patients on Earth with traumatic brain injury or other pathology leading to intracranial hypertension. ABSTRACT Patients with elevated intracranial pressure (ICP) exhibit neuro-ocular symptoms including headache, papilloedema and loss of vision. Some of these symptoms are also present in astronauts during and after prolonged space-flight where lack of gravitational stress prevents daily lowering of ICP associated with upright posture. Lower body negative pressure (LBNP) simulates the effects of gravity by displacing fluid caudally and we hypothesized that LBNP would lower ICP without compromising cerebral perfusion. Ten cerebrally intact volunteers were included: six ambulatory neurosurgical patients with parenchymal ICP-sensors and four former cancer patients with Ommaya-reservoirs to the frontal horn of a lateral ventricle. We applied LBNP while recording ICP and blood pressure while supine, and during simulated intracranial hypertension by 15° head-down tilt. LBNP from 0 to 50 mmHg at increments of 10 mmHg lowered ICP in a non-linear dose-dependent fashion; when supine (n = 10), ICP was decreased from 15 ± 2 mmHg to 14 ± 4, 12 ± 5, 11 ± 4, 10 ± 3 and 9 ± 4 mmHg, respectively (P < 0.0001). Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure at midbrain level minus ICP, was unchanged (from 70 ± 12 mmHg to 67 ± 9, 69 ± 10, 70 ± 12, 72 ± 13 and 74 ± 15 mmHg; P = 0.02). A 15° head-down tilt (n = 6) increased ICP to 26 ± 4 mmHg, while application of LBNP lowered ICP (to 21 ± 4, 20 ± 4, 18 ± 4, 17 ± 4 and 17 ± 4 mmHg; P < 0.0001) and increased CPP (P < 0.01). An LBNP of 20 mmHg may be the optimal level to lower ICP without impairing CPP to counteract spaceflight-associated neuro-ocular syndrome in astronauts. Furthermore, LBNP holds clinical potential as a safe, non-invasive method for lowering ICP and improving CPP for patients with pathologically elevated ICP on Earth.
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Affiliation(s)
- Lonnie G Petersen
- Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Denmark.,Department of Orthopedic Surgery, University of California, San Diego, CA, USA
| | - Justin S Lawley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA.,Institut für Sportwissenschaft, Universität Innsbruck, Innsbruck, Austria
| | | | - Johan C G Petersen
- Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Denmark.,Department of Orthopedic Surgery, University of California, San Diego, CA, USA
| | - Erin J Howden
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,Baker Heart and Diabetes Institute, Melbourne, Australia
| | - Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - William K Cornwell
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,Department of Internal Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
| | | | - Michael A Williams
- University of Washington School of Medicine, Departments of Neurology and Neurological Surgery, Seattle, WA, USA
| | - Marianne Juhler
- Department of Neurosurgery, Rigshospitalet, Copenhagen, Denmark
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,University of Texas Southwestern Medical Center, Dallas, TX, USA
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Trotter CE, Pizzey FK, Batterson PM, Jacobs RA, Pearson J. Small reductions in skin temperature after onset of a simulated hemorrhagic challenge improve tolerance in exercise heat-stressed individuals. Am J Physiol Regul Integr Comp Physiol 2018; 315:R539-R546. [DOI: 10.1152/ajpregu.00182.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated whether small reductions in skin temperature 60 s after the onset of a simulated hemorrhagic challenge would improve tolerance to lower body negative pressure (LBNP) after exercise heat stress. Eleven healthy subjects completed two trials (High and Reduced). Subjects cycled at ~55% maximal oxygen uptake wearing a warm water-perfused suit until core temperatures increased by ~1.2°C before lying supine and undergoing LBNP to presyncope. LBNP tolerance was quantified as cumulative stress index (CSI; product of each LBNP level multiplied by time; mmHg·min). Skin temperature was similarly elevated from baseline before LBNP and remained elevated 60 s after the onset of LBNP in both High (37.72 ± 0.52°C) and Reduced (37.95 ± 0.54°C) trials (both P < 0.0001). At 60%CSI skin temperature remained elevated in the High trial (37.51 ± 0.56°C) but was reduced to 34.97 ± 0.72°C by the water-perfused suit in the Reduced trial ( P < 0.0001 between trials). Cutaneous vascular conductance was not different between trials [High: 1.57 ± 0.43 vs. Reduced: 1.39 ± 0.38 arbitrary units (AU)/mmHg; P = 0.367] before LBNP but decreased to 0.67 ± 0.19 AU/mmHg at 60%CSI in the Reduced trial while remaining unchanged in the High trial ( P = 0.002 between trials). CSI was higher in the Reduced (695 ± 386 mmHg·min) relative to the High (441 ± 290 mmHg·min; P = 0.023) trial. Mean arterial pressure was not different between trials at presyncope (High: 62 ± 10 vs. Reduced: 62 ± 9 mmHg; P = 0.958). Small reductions in skin temperature after the onset of a simulated hemorrhagic challenge improve LBNP tolerance after exercise heat stress. This may have important implications regarding treatment of an exercise heat-stressed individual (e.g., soldier) who has experienced a hemorrhagic injury.
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Affiliation(s)
- Claire E. Trotter
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Faith K. Pizzey
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Philip M. Batterson
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - Robert A. Jacobs
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
| | - James Pearson
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, Colorado
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Skytioti M, Søvik S, Elstad M. Respiratory pump maintains cardiac stroke volume during hypovolemia in young, healthy volunteers. J Appl Physiol (1985) 2018; 124:1319-1325. [DOI: 10.1152/japplphysiol.01009.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Spontaneous breathing has beneficial effects on the circulation, since negative intrathoracic pressure enhances venous return and increases cardiac stroke volume. We quantified the contribution of the respiratory pump to preserve stroke volume during hypovolemia in awake, young, healthy subjects. Noninvasive stroke volume, cardiac output, heart rate, and mean arterial pressure (Finometer) were recorded in 31 volunteers (19 women), 19–30 yr old, during normovolemia and hypovolemia (approximating 450- to 500-ml reduction in central blood volume) induced by lower-body negative pressure. Control-mode noninvasive positive-pressure ventilation was employed to reduce the effect of the respiratory pump. The ventilator settings were matched to each subject’s spontaneous respiratory pattern. Stroke volume estimates during positive-pressure ventilation and spontaneous breathing were compared with Wilcoxon matched-pairs signed-rank test. Values are overall medians. During normovolemia, positive-pressure ventilation did not affect stroke volume or cardiac output. Hypovolemia resulted in an 18% decrease in stroke volume and a 9% decrease in cardiac output ( P < 0.001). Employing positive-pressure ventilation during hypovolemia decreased stroke volume further by 8% ( P < 0.001). Overall, hypovolemia and positive-pressure ventilation resulted in a reduction of 26% in stroke volume ( P < 0.001) and 13% in cardiac output ( P < 0.001) compared with baseline. Compared with the situation with control-mode positive-pressure ventilation, spontaneous breathing attenuated the reduction in stroke volume induced by moderate hypovolemia by 30% (i.e., −26 vs. −18%). In the patient who is critically ill with hypovolemia or uncontrolled hemorrhage, spontaneous breathing may contribute to hemodynamic stability, whereas controlled positive-pressure ventilation may result in circulatory decompensation. NEW & NOTEWORTHY Maintaining spontaneous respiration has beneficial effects on hemodynamic compensation, which is clinically relevant for patients in intensive care. We have quantified the contribution of the respiratory pump to cardiac stroke volume and cardiac output in healthy volunteers during normovolemia and central hypovolemia. The positive hemodynamic effect of the respiratory pump was abolished by noninvasive, low-level positive-pressure ventilation. Compared with control-mode positive-pressure ventilation, spontaneous negative-pressure ventilation attenuated the fall in stroke volume by 30%.
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Affiliation(s)
- Maria Skytioti
- Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Signe Søvik
- Department of Anaesthesia and Intensive Care, Akershus University Hospital, Lørenskog, Norway
- Institute of Clinical Medicine, University of Oslo, Oslo, Norway
| | - Maja Elstad
- Division of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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Xiang L, Hinojosa-Laborde C, Ryan KL, Rickards CA, Convertino VA. Time course of compensatory physiological responses to central hypovolemia in high- and low-tolerant human subjects. Am J Physiol Regul Integr Comp Physiol 2018; 315:R408-R416. [PMID: 29668322 DOI: 10.1152/ajpregu.00361.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lower body negative pressure (LBNP) simulates hemorrhage in human subjects. Most subjects (67%) exhibited high tolerance (HT) to hypovolemia, while the remainder (33%) had low tolerance (LT). To investigate the mechanisms for decompensation to central hypovolemia in HT and LT subjects, we characterized the time course of total peripheral resistance (TPR), heart rate (HR), and muscle sympathetic nerve activity (MSNA) during LBNP to tolerance determined by the onset of decompensation (presyncope, PS). We hypothesized that 1) maximum (Max) TPR, HR, and MSNA would coincide, and 2) PS would result from simultaneous decreases in TPR, HR, and MSNA in LT and HT subjects but occur earlier in LT than in HT subjects. Max TPR was lower and occurred earlier in LT ( n = 59) than in HT ( n = 113) subjects (LT: 24 ± 1 mmHg·min·1-1 at 756 ± 31 s; HT: 28 ± 1 mmHg·min·1-1 at 1,265 ± 37 s, P < 0.01). Max TPR occurred several minutes before PS. During subsequent decrease in TPR, HR and MSNA continued to increase. Max HR (LT: 111 ± 2 beat/min at 923 ± 27 s; HT: 130 ± 2 beats/min at 1489 ± 23 s, P < 0.01) occurred several seconds before PS. Higher MSNA ( P < 0.01) was attained in HT ( n = 10; 51 ± 5 bursts/min at max TPR; 54 ± 5 bursts/min at max HR) than LT subjects ( n = 4; 41 ± 8 bursts/min at max TPR; 39 ± 8 bursts/min at max HR). The onset of cardiovascular decompensation is a biphasic process in which vasodilation occurs before bradycardia and sympathetic withdrawal. This pattern was similar in LT and HT but occurred earlier in LT subjects. We conclude that sudden bradycardia plays a critical role in the determination of tolerance to central hypovolemia.
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Affiliation(s)
- Lusha Xiang
- United States Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, San Antonio, Texas
| | - Carmen Hinojosa-Laborde
- United States Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, San Antonio, Texas
| | - Kathy L Ryan
- United States Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, San Antonio, Texas
| | - Caroline A Rickards
- Institute for Cardiovascular and Metabolic Disease, University of North Texas Health Science Center , Fort Worth, Texas
| | - Victor A Convertino
- United States Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, San Antonio, Texas.,United States Army Medical Research and Materiel Command, Fort Detrick, Frederick, Maryland
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Żera T, Przybylski J, Grygorowicz T, Kasarełło K, Podobińska M, Mirowska-Guzel D, Cudnoch-Jędrzejewska A. Vasopressin V1a receptors are present in the carotid body and contribute to the control of breathing in male Sprague-Dawley rats. Peptides 2018. [PMID: 29524562 DOI: 10.1016/j.peptides.2018.03.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Vasopressin (AVP) maintains body homeostasis by regulating water balance, cardiovascular system and stress response. AVP inhibits breathing through central vasopressin 1a receptors (V1aRs). Chemoreceptors within carotid bodies (CBs) detect chemical and hormonal signals in the bloodstream and provide sensory input to respiratory and cardiovascular centers of the brainstem. In the study we investigated if CBs contain V1aRs and how the receptors are involved in the regulation of ventilation by AVP. We first immunostained CBs for V1aRs and tyrosine hydroxylase, a marker of chemoreceptor type I (glomus) cells. In urethane-anesthetized adult Sprague-Dawley male rats, we then measured hemodynamic and respiratory responses to systemic (intravenous) or local (carotid artery) administration of AVP prior and after systemic blockade of V1aRs. Immunostaining of CBs showed colocalization of V1aRs and tyrosine hydroxylase within glomus cells. Systemic administration of AVP increased mean arterial blood pressure (MABP) and decreased respiratory rate (RR) and minute ventilation (MV). Local administration of AVP increased MV and RR without significant changes in MABP or heart rate. Pretreatment with V1aR antagonist abolished responses to local and intravenous AVP administration. Our findings show that chemosensory cells within CBs express V1aRs and that local stimulation of the CB with AVP increases ventilation, which is contrary to systemic effects of AVP manifested by decreased ventilation. The responses are mediated by V1aRs, as blockade of the receptors prevents changes in ventilation. We hypothesize that excitatory effects of AVP within the CB provide a counterbalancing mechanism for the inhibitory effects of systemically acting AVP on the respiration.
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Affiliation(s)
- Tymoteusz Żera
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, the Medical University of Warsaw, Banacha 1B, 02-097 Warsaw, Poland.
| | - Jacek Przybylski
- Department of Biophysics and Physiology, the Medical University of Warsaw, Chałubińskiego 5, 02-004 Warsaw, Poland
| | - Tomasz Grygorowicz
- Chair and Department of Experimental and Clinical Pharmacology, Laboratory of Centre for Preclinical Research, the Medical University of Warsaw, Banacha 1B, 02-097 Warsaw, Poland
| | - Kaja Kasarełło
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, the Medical University of Warsaw, Banacha 1B, 02-097 Warsaw, Poland
| | - Martyna Podobińska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, the Medical University of Warsaw, Banacha 1B, 02-097 Warsaw, Poland
| | - Dagmara Mirowska-Guzel
- Chair and Department of Experimental and Clinical Pharmacology, Laboratory of Centre for Preclinical Research, the Medical University of Warsaw, Banacha 1B, 02-097 Warsaw, Poland
| | - Agnieszka Cudnoch-Jędrzejewska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, the Medical University of Warsaw, Banacha 1B, 02-097 Warsaw, Poland
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The Compensatory Reserve For Early and Accurate Prediction Of Hemodynamic Compromise: A Review of the Underlying Physiology. Shock 2018; 45:580-90. [PMID: 26950588 DOI: 10.1097/shk.0000000000000559] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Shock is deadly and unpredictable if it is not recognized and treated in early stages of hemorrhage. Unfortunately, measurements of standard vital signs that are displayed on current medical monitors fail to provide accurate or early indicators of shock because of physiological mechanisms that effectively compensate for blood loss. As a result of new insights provided by the latest research on the physiology of shock using human experimental models of controlled hemorrhage, it is now recognized that measurement of the body's reserve to compensate for reduced circulating blood volume is the single most important indicator for early and accurate assessment of shock. We have called this function the "compensatory reserve," which can be accurately assessed by real-time measurements of changes in the features of the arterial waveform. In this paper, the physiology underlying the development and evaluation of a new noninvasive technology that allows for real-time measurement of the compensatory reserve will be reviewed, with its clinical implications for earlier and more accurate prediction of shock.
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Lord R, MacLeod D, George K, Oxborough D, Shave R, Stembridge M. Reduced left ventricular filling following blood volume extraction does not result in compensatory augmentation of cardiac mechanics. Exp Physiol 2018; 103:495-501. [DOI: 10.1113/ep086761] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 01/15/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Rachel Lord
- Cardiff Centre for Exercise and Health; Cardiff Metropolitan University; Cardiff UK
| | - David MacLeod
- Duke University School of Medicine; Duke University; Durham NC USA
| | - Keith George
- Research Institute for Sport and Exercise Sciences; Liverpool John Moores University; Liverpool UK
| | - David Oxborough
- Research Institute for Sport and Exercise Sciences; Liverpool John Moores University; Liverpool UK
| | - Rob Shave
- Cardiff Centre for Exercise and Health; Cardiff Metropolitan University; Cardiff UK
| | - Mike Stembridge
- Cardiff Centre for Exercise and Health; Cardiff Metropolitan University; Cardiff UK
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van Helmond N, Johnson BD, Holbein WW, Petersen‐Jones HG, Harvey RE, Ranadive SM, Barnes JN, Curry TB, Convertino VA, Joyner MJ. Effect of acute hypoxemia on cerebral blood flow velocity control during lower body negative pressure. Physiol Rep 2018; 6:e13594. [PMID: 29464923 PMCID: PMC5820424 DOI: 10.14814/phy2.13594] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/03/2018] [Accepted: 01/05/2018] [Indexed: 11/24/2022] Open
Abstract
The ability to maintain adequate cerebral blood flow and oxygenation determines tolerance to central hypovolemia. We tested the hypothesis that acute hypoxemia during simulated blood loss in humans would cause impairments in cerebral blood flow control. Ten healthy subjects (32 ± 6 years, BMI 27 ± 2 kg·m-2 ) were exposed to stepwise lower body negative pressure (LBNP, 5 min at 0, -15, -30, and -45 mmHg) during both normoxia and hypoxia (Fi O2 = 0.12-0.15 O2 titrated to an SaO2 of ~85%). Physiological responses during both protocols were expressed as absolute changes from baseline, one subject was excluded from analysis due to presyncope during the first stage of LBNP during hypoxia. LBNP induced greater reductions in mean arterial pressure during hypoxia versus normoxia (MAP, at -45 mmHg: -20 ± 3 vs. -5 ± 3 mmHg, P < 0.01). Despite differences in MAP, middle cerebral artery velocity responses (MCAv) were similar between protocols (P = 0.41) due to increased cerebrovascular conductance index (CVCi) during hypoxia (main effect, P = 0.04). Low frequency MAP (at -45 mmHg: 17 ± 5 vs. 0 ± 5 mmHg2 , P = 0.01) and MCAv (at -45 mmHg: 4 ± 2 vs. -1 ± 1 cm·s-2 , P = 0.04) spectral power density, as well as low frequency MAP-mean MCAv transfer function gain (at -30 mmHg: 0.09 ± 0.06 vs. -0.07 ± 0.06 cm·s-1 ·mmHg-1 , P = 0.04) increased more during hypoxia versus normoxia. Contrary to our hypothesis, these findings support the notion that cerebral blood flow control is not impaired during exposure to acute hypoxia and progressive central hypovolemia despite lower MAP as a result of compensated increases in cerebral conductance and flow variability.
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Affiliation(s)
| | - Blair D. Johnson
- Center for Research and Education in Special EnvironmentsDepartment of Exercise and Nutrition SciencesUniversity at BuffaloBuffaloNew York
| | | | | | - Ronée E. Harvey
- Mayo Clinic School of Medicine and ScienceMayo ClinicRochesterMinnesota
| | | | - Jill N. Barnes
- Department of KinesiologyUniversity of Wisconsin‐MadisonMadisonWisconsin
| | | | - Victor A. Convertino
- US Army Battlefield Health & Trauma Center for Human Integrative PhysiologyFort Sam HoustonTexas
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The Effect of Passive Heat Stress and Exercise-Induced Dehydration on the Compensatory Reserve During Simulated Hemorrhage. Shock 2018; 46:74-82. [PMID: 27183303 DOI: 10.1097/shk.0000000000000653] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Compensatory reserve represents the proportion of physiological responses engaged to compensate for reductions in central blood volume before the onset of decompensation. We hypothesized that compensatory reserve would be reduced by hyperthermia and exercise-induced dehydration, conditions often encountered on the battlefield. Twenty healthy males volunteered for two separate protocols during which they underwent lower-body negative pressure (LBNP) to hemodynamic decompensation (systolic blood pressure <80 mm Hg). During protocol #1, LBNP was performed following a passive increase in core temperature of ∼1.2°C (HT) or a normothermic time-control period (NT). During protocol #2, LBNP was performed following exercise during which: fluid losses were replaced (hydrated), fluid intake was restricted and exercise ended at the same increase in core temperature as hydrated (isothermic dehydrated), or fluid intake was restricted and exercise duration was the same as hydrated (time-match dehydrated). Compensatory reserve was estimated with the compensatory reserve index (CRI), a machine-learning algorithm that extracts features from continuous photoplethysmograph signals. Prior to LBNP, CRI was reduced by passive heating [NT: 0.87 (SD 0.09) vs. HT: 0.42 (SD 0.19) units, P <0.01] and exercise-induced dehydration [hydrated: 0.67 (SD 0.19) vs. isothermic dehydrated: 0.52 (SD 0.21) vs. time-match dehydrated: 0.47 (SD 0.25) units; P <0.01 vs. hydrated]. During subsequent LBNP, CRI decreased further and its rate of change was similar between conditions. CRI values at decompensation did not differ between conditions. These results suggest that passive heating and exercise-induced dehydration limit the body's physiological reserve to compensate for further reductions in central blood volume.
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46
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Abstract
The microvasculature plays a central role in the pathophysiology of hemorrhagic shock and is also involved in arguably all therapeutic attempts to reverse or minimize the adverse consequences of shock. Microvascular studies specific to hemorrhagic shock were reviewed and broadly grouped depending on whether data were obtained on animal or human subjects. Dedicated sections were assigned to microcirculatory changes in specific organs, and major categories of pathophysiological alterations and mechanisms such as oxygen distribution, ischemia, inflammation, glycocalyx changes, vasomotion, endothelial dysfunction, and coagulopathy as well as biomarkers and some therapeutic strategies. Innovative experimental methods were also reviewed for quantitative microcirculatory assessment as it pertains to changes during hemorrhagic shock. The text and figures include representative quantitative microvascular data obtained in various organs and tissues such as skin, muscle, lung, liver, brain, heart, kidney, pancreas, intestines, and mesentery from various species including mice, rats, hamsters, sheep, swine, bats, and humans. Based on reviewed findings, a new integrative conceptual model is presented that includes about 100 systemic and local factors linked to microvessels in hemorrhagic shock. The combination of systemic measures with the understanding of these processes at the microvascular level is fundamental to further develop targeted and personalized interventions that will reduce tissue injury, organ dysfunction, and ultimately mortality due to hemorrhagic shock. Published 2018. Compr Physiol 8:61-101, 2018.
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Affiliation(s)
- Ivo Torres Filho
- US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas, USA
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47
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Verma AK, Xu D, Garg A, Cote AT, Goswami N, Blaber AP, Tavakolian K. Non-linear Heart Rate and Blood Pressure Interaction in Response to Lower-Body Negative Pressure. Front Physiol 2017; 8:767. [PMID: 29114227 PMCID: PMC5660688 DOI: 10.3389/fphys.2017.00767] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 09/20/2017] [Indexed: 12/14/2022] Open
Abstract
Early detection of hemorrhage remains an open problem. In this regard, blood pressure has been an ineffective measure of blood loss due to numerous compensatory mechanisms sustaining arterial blood pressure homeostasis. Here, we investigate the feasibility of causality detection in the heart rate and blood pressure interaction, a closed-loop control system, for early detection of hemorrhage. The hemorrhage was simulated via graded lower-body negative pressure (LBNP) from 0 to -40 mmHg. The research hypothesis was that a significant elevation of causal control in the direction of blood pressure to heart rate (i.e., baroreflex response) is an early indicator of central hypovolemia. Five minutes of continuous blood pressure and electrocardiogram (ECG) signals were acquired simultaneously from young, healthy participants (27 ± 1 years, N = 27) during each LBNP stage, from which heart rate (represented by RR interval), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were derived. The heart rate and blood pressure causal interaction (RR↔SBP and RR↔MAP) was studied during the last 3 min of each LBNP stage. At supine rest, the non-baroreflex arm (RR→SBP and RR→MAP) showed a significantly (p < 0.001) higher causal drive toward blood pressure regulation compared to the baroreflex arm (SBP→RR and MAP→RR). In response to moderate category hemorrhage (-30 mmHg LBNP), no change was observed in the traditional marker of blood loss i.e., pulse pressure (p = 0.10) along with the RR→SBP (p = 0.76), RR→MAP (p = 0.60), and SBP→RR (p = 0.07) causality compared to the resting stage. Contrarily, a significant elevation in the MAP→RR (p = 0.004) causality was observed. In accordance with our hypothesis, the outcomes of the research underscored the potential of compensatory baroreflex arm (MAP→RR) of the heart rate and blood pressure interaction toward differentiating a simulated moderate category hemorrhage from the resting stage. Therefore, monitoring baroreflex causality can have a clinical utility in making triage decisions to impede hemorrhage progression.
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Affiliation(s)
- Ajay K Verma
- Department of Electrical Engineering, University of North Dakota, Grand Forks, ND, United States
| | - Da Xu
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Amanmeet Garg
- Department of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
| | - Anita T Cote
- School of Human Kinetics, Trinity Western University, Langley, BC, Canada
| | - Nandu Goswami
- Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Andrew P Blaber
- Department of Electrical Engineering, University of North Dakota, Grand Forks, ND, United States.,Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Kouhyar Tavakolian
- Department of Electrical Engineering, University of North Dakota, Grand Forks, ND, United States.,Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
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48
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Johnson BD, Sackett JR, Sarker S, Schlader ZJ. Face cooling increases blood pressure during central hypovolemia. Am J Physiol Regul Integr Comp Physiol 2017; 313:R594-R600. [PMID: 28855179 DOI: 10.1152/ajpregu.00253.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/24/2017] [Accepted: 08/24/2017] [Indexed: 12/24/2022]
Abstract
A reduction in central blood volume can lead to cardiovascular decompensation (i.e., failure to maintain blood pressure). Cooling the forehead and cheeks using ice water raises blood pressure. Therefore, face cooling (FC) could be used to mitigate decreases in blood pressure during central hypovolemia. We tested the hypothesis that FC during central hypovolemia induced by lower-body negative pressure (LBNP) would increase blood pressure. Ten healthy participants (22 ± 2 yr, three women, seven men) completed two randomized LBNP trials on separate days. Trials began with 30 mmHg of LBNP for 6 min. Then, a 2.5-liter plastic bag of ice water (0 ± 0°C) (LBNP+FC) or thermoneutral water (34 ± 1°C) (LBNP+Sham) was placed on the forehead, eyes, and cheeks during 15 min of LBNP at 30 mmHg. Forehead temperature was lower during LBNP+FC than LBNP+Sham, with the greatest difference at 21 min of LBNP (11.1 ± 1.6 vs. 33.9 ± 1.4°C, P < 0.001). Mean arterial pressure was greater during LBNP+FC than LBNP+Sham, with the greatest difference at 8 min of LBNP (98 ± 15 vs. 80 ± 8 mmHg, P < 0.001). Cardiac output was higher during LBNP+FC than LBNP+Sham with the greatest difference at 18 min of LBNP (5.9 ± 1.4 vs. 4.9 ± 1.0 liter/min, P = 0.005). Forearm cutaneous vascular resistance was greater during LBNP+FC than LBNP+Sham, with the greatest difference at 15 min of LBNP (7.2 ± 3.4 vs. 4.9 ± 2.7 mmHg/perfusion units (PU), P < 0.001). Face cooling during LBNP increases blood pressure through increases in cardiac output and vascular resistance.
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Affiliation(s)
- Blair D Johnson
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - James R Sackett
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Suman Sarker
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
| | - Zachary J Schlader
- Center for Research and Education in Special Environments, Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York
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49
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Marshall-Goebel K, Terlević R, Gerlach DA, Kuehn S, Mulder E, Rittweger J. Lower body negative pressure reduces optic nerve sheath diameter during head-down tilt. J Appl Physiol (1985) 2017; 123:1139-1144. [PMID: 28818998 DOI: 10.1152/japplphysiol.00256.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 08/14/2017] [Accepted: 08/14/2017] [Indexed: 01/06/2023] Open
Abstract
The microgravity ocular syndrome (MOS) results in significant structural and functional ophthalmic changes during 6-mo spaceflight missions consistent with an increase in cerebrospinal fluid (CSF) pressure compared with the preflight upright position. A ground-based study was performed to assess two of the major hypothesized contributors to MOS, headward fluid shifting and increased ambient CO2, on intracranial and periorbital CSF. In addition, lower body negative pressure (LBNP) was assessed as a countermeasure to headward fluid shifting. Nine healthy male subjects participated in a crossover design study with five head-down tilt (HDT) conditions: -6, -12, and -18° HDT, -12° HDT with -20 mmHg LBNP, and -12° HDT with a 1% CO2 environment, each for 5 h total. A three-dimensional volumetric scan of the cranium and transverse slices of the orbita were collected with MRI, and intracranial CSF volume and optic nerve sheath diameter (ONSD) were measured after 4.5 h HDT. ONSD increased during -6° (P < 0.001), -12° (P < 0.001), and -18° HDT (P < 0.001) and intracranial CSF increased during -12° HDT (P = 0.01) compared with supine baseline. Notably, LBNP was able to reduce the increases in ONSD and intracranial CSF during HDT. The addition of 1% CO2 during HDT, however, had no further effect on ONSD, but rather ONSD increased from baseline in a similar magnitude to -12° HDT with ambient air (P = 0.001). These findings demonstrate the ability of LBNP, a technique that targets fluid distribution in the lower limbs, to directly influence CSF and may be a promising countermeasure to help reduce increases in CSF.NEW & NOTEWORTHY This is the first study to demonstrate the ability of lower body negative pressure to directly influence cerebrospinal fluid surrounding the optic nerve, indicating potential use as a countermeasure for increased cerebrospinal fluid on Earth or in space.
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Affiliation(s)
- Karina Marshall-Goebel
- Neural Systems Group, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; .,Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Robert Terlević
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.,International Space University, Illkirch-Graffenstaden, France; and
| | - Darius A Gerlach
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Simone Kuehn
- University Clinic Hamburg-Eppendorf, Clinic for Psychiatry and Psychotherapy, Hamburg, Germany
| | - Edwin Mulder
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Jörn Rittweger
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
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50
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Convertino VA, Sawka MN. Wearable technology for compensatory reserve to sense hypovolemia. J Appl Physiol (1985) 2017; 124:442-451. [PMID: 28751369 DOI: 10.1152/japplphysiol.00264.2017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Traditional monitoring technologies fail to provide accurate or early indications of hypovolemia-mediated extremis because physiological systems (as measured by vital signs) effectively compensate until circulatory failure occurs. Hypovolemia is the most life-threatening physiological condition associated with circulatory shock in hemorrhage or sepsis, and it impairs one's ability to sustain physical exertion during heat stress. This review focuses on the physiology underlying the development of a novel noninvasive wearable technology that allows for real-time evaluation of the cardiovascular system's ability to compensate to hypovolemia, or its compensatory reserve, which provides an individualized estimate of impending circulatory collapse. Compensatory reserve is assessed by real-time changes (sampled millions of times per second) in specific features (hundreds of features) of arterial waveform analog signals that can be obtained from photoplethysmography using machine learning and feature extraction techniques. Extensive experimental evidence employing acute reductions in central blood volume (using lower-body negative pressure, blood withdrawal, heat stress, dehydration) demonstrate that compensatory reserve provides the best indicator for early and accurate assessment for compromises in blood pressure, tissue perfusion, and oxygenation in resting human subjects. Engineering challenges exist for the development of a ruggedized wearable system that can measure signals from multiple sites, improve signal-to-noise ratios, be customized for use in austere conditions (e.g., battlefield, patient transport), and be worn during strenuous physical activity.
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Affiliation(s)
- Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, Joint Base San Antonio-Fort Sam Houston, San Antonio, Texas
| | - Michael N Sawka
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia
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