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Webb KL, Pruter WW, Poole RJ, Techentin RW, Johnson CP, Regimbal RJ, Berndt KJ, Holmes DR, Haider CR, Joyner MJ, Convertino VA, Wiggins CC, Curry TB. Comparing the compensatory reserve metric obtained from invasive arterial measurements and photoplethysmographic volume-clamp during simulated hemorrhage. J Clin Monit Comput 2024:10.1007/s10877-024-01166-x. [PMID: 38733507 DOI: 10.1007/s10877-024-01166-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 04/16/2024] [Indexed: 05/13/2024]
Abstract
PURPOSE The compensatory reserve metric (CRM) is a novel tool to predict cardiovascular decompensation during hemorrhage. The CRM is traditionally computed using waveforms obtained from photoplethysmographic volume-clamp (PPGVC), yet invasive arterial pressures may be uniquely available. We aimed to examine the level of agreement of CRM values computed from invasive arterial-derived waveforms and values computed from PPGVC-derived waveforms. METHODS Sixty-nine participants underwent graded lower body negative pressure to simulate hemorrhage. Waveform measurements from a brachial arterial catheter and PPGVC finger-cuff were collected. A PPGVC brachial waveform was reconstructed from the PPGVC finger waveform. Thereafter, CRM values were computed using a deep one-dimensional convolutional neural network for each of the following source waveforms; (1) invasive arterial, (2) PPGVC brachial, and (3) PPGVC finger. Bland-Altman analyses were used to determine the level of agreement between invasive arterial CRM values and PPGVC CRM values, with results presented as the Mean Bias [95% Limits of Agreement]. RESULTS The mean bias between invasive arterial- and PPGVC brachial CRM values at rest, an applied pressure of -45mmHg, and at tolerance was 6% [-17%, 29%], 1% [-28%, 30%], and 0% [-25%, 25%], respectively. Additionally, the mean bias between invasive arterial- and PPGVC finger CRM values at rest, applied pressure of -45mmHg, and tolerance was 2% [-22%, 26%], 8% [-19%, 35%], and 5% [-15%, 25%], respectively. CONCLUSION There is generally good agreement between CRM values obtained from invasive arterial waveforms and values obtained from PPGVC waveforms. Invasive arterial waveforms may serve as an alternative for computation of the CRM.
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Affiliation(s)
- Kevin L Webb
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Wyatt W Pruter
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA
| | - Ruth J Poole
- Special Purpose Processor Development Group, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Robert W Techentin
- Special Purpose Processor Development Group, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Christopher P Johnson
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA
| | - Riley J Regimbal
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA
| | - Kaylah J Berndt
- Special Purpose Processor Development Group, Mayo Clinic, Rochester, Minnesota, United States of America
| | - David R Holmes
- Biomedical Analytics and Computational Engineering Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Clifton R Haider
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Michael J Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA
| | - Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, TX, United States of America
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA
- Department of Kinesiology, Michigan State University, East Lansing, Michigan, United States of America
| | - Timothy B Curry
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, 200 First St. SW, 55905, Rochester, Minnesota, MN, USA.
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Magnin M, Oriel J, Combet-curt J, Salama J, Allaouchiche B, Bonnet-Garin JM, Junot S, Pouzot-Nevoret C. Evaluation of the impact of blood donation on tissue perfusion and sublingual microcirculation in dogs: A pilot study. Res Vet Sci 2022; 152:707-716. [DOI: 10.1016/j.rvsc.2022.09.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/13/2022] [Accepted: 09/26/2022] [Indexed: 11/25/2022]
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Suresh MR. The Early Detection of Hypovolemic Shock and Shifting the Focus to Compensation. J Intensive Care Med 2022; 37:1673-1675. [PMID: 35850608 DOI: 10.1177/08850666221114267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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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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Hutchings SD, Watchorn J, McDonald R, Jeffreys S, Bates M, Watts S, Kirkman E. Quantification of stroke volume in a simulated healthy volunteer model of traumatic haemorrhage; a comparison of two non-invasive monitoring devices using error grid analysis alongside traditional measures of agreement. PLoS One 2021; 16:e0261546. [PMID: 34941918 PMCID: PMC8699736 DOI: 10.1371/journal.pone.0261546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 12/03/2021] [Indexed: 11/19/2022] Open
Abstract
Introduction Haemorrhage is a leading cause of death following traumatic injury and the early detection of hypovolaemia is critical to effective management. However, accurate assessment of circulating blood volume is challenging when using traditional vital signs such as blood pressure. We conducted a study to compare the stroke volume (SV) recorded using two devices, trans-thoracic electrical bioimpedance (TEB) and supra-sternal Doppler (SSD), against a reference standard using trans- thoracic echocardiography (TTE). Methods A lower body negative pressure (LBNP) model was used to simulate hypovolaemia and in half of the study sessions lower limb tourniquets were applied as these are common in military practice and can potentially affect some haemodynamic monitoring systems. In order to provide a clinically relevant comparison we constructed an error grid alongside more traditional measures of agreement. Results 21 healthy volunteers aged 18–40 were enrolled and underwent 2 sessions of LBNP, with and without lower limb tourniquets. With respect to absolute SV values Bland Altman analysis showed significant bias in both non-tourniquet and tourniquet strands for TEB (-42.5 / -49.6 ml), rendering further analysis impossible. For SSD bias was minimal but percentage error was unacceptably high (35% / 48%). Degree of agreement for dynamic change in SV, assessed using 4 quadrant plots showed a seemingly acceptable concordance rate for both TEB (86% / 93%) and SSD (90% / 91%). However, when results were plotted on an error grid, constructed based on expert clinical opinion, a significant minority of measurement errors were identified that had potential to lead to moderate or severe patient harm. Conclusion Thoracic bioimpedance and suprasternal Doppler both demonstrated measurement errors that had the potential to lead to clinical harm and caution should be applied in interpreting the results in the detection of early hypovolaemia following traumatic injury.
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Affiliation(s)
- Sam D. Hutchings
- Department of Inflammation Biology, School of Immunology and Microbial Sciences, King’s College London, London, United Kingdom
- Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, Birmingham, United Kingdom
- * E-mail:
| | - Jim Watchorn
- Department of Inflammation Biology, School of Immunology and Microbial Sciences, King’s College London, London, United Kingdom
| | - Rory McDonald
- Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, Birmingham, United Kingdom
| | - Su Jeffreys
- Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, Birmingham, United Kingdom
| | - Mark Bates
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, United Kingdom
| | - Sarah Watts
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, United Kingdom
| | - Emrys Kirkman
- Defence Science and Technology Laboratory, Porton Down, Wiltshire, United Kingdom
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Convertino VA, Johnson MC, Alarhayem A, Nicholson SE, Chung KK, DeRosa M, Eastridge BJ. Compensatory reserve detects subclinical shock with more expeditious prediction for need of life-saving interventions compared to systolic blood pressure and blood lactate. Transfusion 2021; 61 Suppl 1:S167-S173. [PMID: 34269439 DOI: 10.1111/trf.16494] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 02/11/2021] [Accepted: 02/11/2021] [Indexed: 12/27/2022]
Abstract
INTRODUCTION We conducted a prospective observational study on 205 trauma patients at a level I trauma facility to test the hypothesis that a compensatory reserve measurement (CRM) would identify higher risk for progression to shock and/or need a life-saving interventions (LSIs) earlier than systolic blood pressure (SBP) and blood lactate (LAC). METHODS A composite outcome metric included blood transfusion, procedural LSI, and mortality. Discrete measures assessed as abnormal (ab) were SBP <90 mmHg, CRM <60%, and LAC >2.0. A graded categorization of shock was defined as: no shock (normal [n] SBP [n-SBP], n-CRM, n-LAC); sub-clinical shock (ab-CRM, n-SBP, n-LAC); occult shock (n-SBP, ab-CRM, ab-LAC); or overt shock (ab-SBP, ab-CRM, ab-LAC). RESULTS Three patients displayed overt shock, 53 displayed sub-clinical shock, and 149 displayed no shock. After incorporating lactate into the analysis, 86 patients demonstrated no shock, 25 were classified as sub-clinical shock, 91 were classified as occult shock, and 3 were characterized as overt shock. Each shock subcategory revealed a graded increase requiring LSI and transfusion. Initial CRM was associated with progression to shock (odds ratio = 0.97; p < .001) at an earlier time than SBP or LAC. CONCLUSIONS Initial CRM uncovers a clinically relevant subset of patients who are not detected by SBP and LAC. Our results suggest CRM could be used to more expeditiously identify injured patients likely to deteriorate to shock, with requirements for blood transfusion or procedural LSI.
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Affiliation(s)
- Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, San Antonio, Texas, USA.,Department of Medicine and Surgery, Uniformed Services University, Bethesda, Maryland, USA
| | - Michael C Johnson
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
| | - Abdul Alarhayem
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
| | - Susannah E Nicholson
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
| | - Kevin K Chung
- Department of Medicine and Surgery, Uniformed Services University, Bethesda, Maryland, USA
| | - Mark DeRosa
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
| | - Brian J Eastridge
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
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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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9
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Bonanno FG. The Need for a Physiological Classification of Hemorrhagic Shock. J Emerg Trauma Shock 2020; 13:177-182. [PMID: 33304066 PMCID: PMC7717460 DOI: 10.4103/jets.jets_153_19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 05/23/2020] [Accepted: 08/03/2020] [Indexed: 11/04/2022] Open
Abstract
Classifications mean to conceptualize in a cluster and rapidly summarize the assessment and management of a clinical scenario. In the specific case of a hemorrhagic shock (HS), a classification should serve the purpose of allowing a rapid clinical assessment of the shock level and the earliest or right timing of source control, possibly also on whether to apply damage control surgery (DCS) strategy or not. ATLS® classification of HS is not sensitive and specific enough to help decision-making in reference to the timing of management, based only on the amount of blood loss that may be or may not rightly estimated, for example, blood loss on the floor in penetrating injuries before theatre. Moreover, it focuses also on other parameters, which are taken singularly, instead of the individual generalized physiological response to hemorrhage, which is the core by definition of the derangement we call "shock." It is unhelpful, difficult, and impractical to apply as well. A new classification, which may well be called as the "physiological HS classification" or "therapeutic HS classification," was proposed since 2010, following the new developments on microcirculation and an already going-on sensible praxis among some trauma surgeons. It bases on some physiological considerations such as the significance of fluid-blood resistant hypotension, body natural hemostatic mechanisms, the right definition of shock, and the relevance that hemorrhage-triggered ischemia-reperfusion toxemia and systemic inflammatory response have in critical illness scenarios as secondary insults from ischemia, which is what we mean to prevented with DCS. The key factor remains the persistence of hypotension, following fluid challenge.
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Affiliation(s)
- Fabrizio Giuseppe Bonanno
- Department of Surgery, Polokwane-Mankweng Hospitals Complex, UNILIM, Polokwane, Limpopo, South Africa
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10
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Convertino VA, Koons NJ. The compensatory reserve: potential for accurate individualized goal-directed whole blood resuscitation. Transfusion 2020; 60 Suppl 3:S150-S157. [PMID: 32478902 DOI: 10.1111/trf.15632] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/25/2019] [Accepted: 11/26/2019] [Indexed: 11/29/2022]
Abstract
Hemorrhagic shock can be mitigated by timely and accurate resuscitation designed to restore adequate delivery of oxygen (DO2 ). Current doctrine of using systolic blood pressure (SBP) as a guide for resuscitation can be associated with increased morbidity. The compensatory reserve measurement (CRM) is a novel vital sign based on the recognition that the sum of all mechanisms that contribute to the compensatory response to hemorrhage reside in features of the arterial pulse waveform. CRM can be assessed continuously and non-invasively in real time. Compared to standard vital signs, CRM provides an early, as well as more sensitive and specific, indicator of patient hemorrhagic status since the activation of compensatory mechanisms occurs immediately at the onset of blood loss. Recent data obtained from our laboratory experiments on non-human primates have demonstrated that CRM is linearly related to DO2 during controlled progressive hemorrhage and subsequent whole blood resuscitation. We used this relationship to determine that the time of hemodynamic decompensation (i.e., CRM = 0%) is defined by a critical DO2 at approximately 5.3 mL O2 ∙kg-1 ∙min-1 . We also demonstrated that a target CRM of 35% during whole blood resuscitation only required replacement of 40% of the total blood volume loss to adequately sustain a DO2 more than 50% (i.e., 8.1 mL O2 ∙kg-1 ∙min-1 ) above critical DO2 (i.e., threshold for decompensated shock) while maintaining hypotensive resuscitation (i.e., SBP at ~90 mmHg). Consistent with our hypothesis, specific values of CRM can be used to accurately maintain DO2 thresholds above critical DO2 , avoiding the onset of hemorrhagic shock with whole blood resuscitation.
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Affiliation(s)
- Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Natalie J Koons
- Battlefield Health & Trauma Center for Human Integrative Physiology, United States Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
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Schlotman TE, Akers KS, Cardin S, Morris MJ, Le T, Convertino VA. Evidence for misleading decision support in characterizing differences in tolerance to reduced central blood volume using measurements of tissue oxygenation. Transfusion 2020; 60 Suppl 3:S62-S69. [PMID: 32478865 DOI: 10.1111/trf.15648] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 12/09/2019] [Accepted: 12/09/2019] [Indexed: 02/06/2023]
Abstract
BACKGROUND The physiological response to hemorrhage includes vasoconstriction in an effort to shunt blood to the heart and brain. Hemorrhaging patients can be classified as "good" compensators who demonstrate high tolerance (HT) or "poor" compensators who manifest low tolerance (LT) to central hypovolemia. Compensatory vasoconstriction is manifested by lower tissue oxygen saturation (StO2 ), which has propelled this measure as a possible early marker of shock. The compensatory reserve measurement (CRM) has also shown promise as an early indicator of decompensation. METHODS Fifty-one healthy volunteers (37% LT) were subjected to progressive lower body negative pressure (LBNP) as a model of controlled hemorrhage designed to induce an onset of decompensation. During LBNP, CRM was determined by arterial waveform feature analysis. StO2 , muscle pH, and muscle H+ concentration were calculated from spectrum using near-infrared spectroscopy (NIRS) on the forearm. RESULTS These values were statistically indistinguishable between HT and LT participants at baseline (p ≥ 0.25). HT participants exhibited lower (p = 0.01) StO2 at decompensation compared to LT participants. CONCLUSIONS Lower StO2 measured in patients during low flow states associated with significant hemorrhage does not necessarily translate to a more compromised physiological state, but may reflect a greater resistance to the onset of shock. Only the CRM was able to distinguish between HT and LT participants early in the course of hemorrhage, supported by a significantly greater ROC AUC (0.90) compared with STO2 (0.68). These results support the notion that measures of StO2 could be misleading for triage and resuscitation decision support.
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Affiliation(s)
- Taylor E Schlotman
- Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Kevin S Akers
- Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Sylvain Cardin
- Naval Medical Research Unit, JBSA Fort Sam Houston, Texas
| | | | - Tuan Le
- Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
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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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Comparisons of Traditional Metabolic Markers and Compensatory Reserve as Early Predictors of Tolerance to Central Hypovolemia in Humans. Shock 2019; 50:71-77. [PMID: 29049136 DOI: 10.1097/shk.0000000000001034] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Circulatory shock remains a leading cause of death in both military and civilian trauma. Early, accurate and reliable prediction of decompensation is necessary for the most efficient interventions and clinical outcomes. Individual tolerance to reduced central blood volume can serve as a model to assess the sensitivity and specificity of vital sign measurements. The compensatory reserve (CRM) is the measurement of this capacity. Measurements of muscle oxygen saturation (SmO2), blood lactate, and end tidal CO2 (EtCO2) have recently gained attention as prognostic tools for early assessment of the status of patients with progressive hemorrhage, but lack the ability to adequately differentiate individual tolerance to hypovolemia. We hypothesized that the CRM would better predict hemodynamic decompensation and provide greater specificity and sensitivity than metabolic measures. To test this hypothesis, we employed lower body negative pressure on healthy human subjects until symptoms of presyncope were evident. Receiver operating characteristic area under the curve (ROC AUC), sensitivity, and specificity were used to evaluate the ability of CRM, partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2), SmO2, lactate, EtCO2, potential of hydrogen (pH), base excess and hematocrit (Hct) to predict hemodynamic decompensation. The ROC AUC for CRM (0.94) had a superior ability to predict decompensation compared with pO2 (0.85), pCO2 (0.62), SmO2 (0.72), lactate (0.57), EtCO2 (0.74), pH (0.55), base excess (0.59), and Hct (0.67). Similarly, CRM also exhibited the greatest sensitivity and specificity. These findings support the notion that CRM provides superior detection of hemodynamic compensation compared with commonly used clinical metabolic measures.
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Walters TJ, Kottke MA, Hargens AR, Ryan KL. Noninvasive diagnostics for extremity compartment syndrome following traumatic injury: A state-of-the-art review. J Trauma Acute Care Surg 2019; 87:S59-S66. [PMID: 31246908 DOI: 10.1097/ta.0000000000002284] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Acute compartment syndrome (ACS) is a serious medical condition that can occur following traumatic injury to an extremity. If left undiagnosed, ACS can eventuate in amputation of the limb or even death. Because of this, fasciotomy to release the pressure within the muscle and restore tissue perfusion is often performed upon suspicion of ACS, as the sequelae to fasciotomy are less severe than those associated with not performing the fasciotomy. Currently, the "gold standard" of diagnosis is based on clinical assessment of such symptoms as pain out of proportion to the injury, obvious high pressure and swelling, pain on passive stretch of the muscles in the affected compartment, and deficits in sensory and/ormotor functions. Diagnosis is often confirmed using invasive measurements of intramuscular pressure (IMP); however, controversy exists as to how direct IMP measurement should be accomplished and threshold pressures for accurate diagnosis. Because of this and the attendant issues with invasive measurements, investigators have been searching over the last 25 years for a noninvasive means to quantitatively measure IMP or perfusion to the limb. The purpose of this review is to summarize the current state of the art of noninvasive devices that could potentially be used to diagnose ACS accurately and objectively. To do this, we divide the discussion into those medical devices that primarily measure mechanical surrogates of IMP (e.g., tissue hardness or myofascial displacement) and those that primarily measure indices of tissue perfusion (e.g., tissue oxygen saturation via near-infraredspectroscopy). While near-infrared spectroscopy-basedtechnologies have shown the most promise, whether such technologies will be of diagnostic benefit await the completion of ongoing clinical trials. LEVEL OF EVIDENCE: Systematic Review, level II.
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Affiliation(s)
- Thomas J Walters
- From the US Army Institute of Surgical Research (T.J.W., M.A.K., K.L.R.), Fort Sam Houston, San Antonio, Texas; and Department of Orthopaedic Surgery, Altman Clinical and Translational Research Institute (A.R.H.), University of California San Diego, San Diego, California
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Convertino VA, Lye KR, Koons NJ, Joyner MJ. Physiological comparison of hemorrhagic shock and V˙ O 2max: A conceptual framework for defining the limitation of oxygen delivery. Exp Biol Med (Maywood) 2019; 244:690-701. [PMID: 31042073 PMCID: PMC6552402 DOI: 10.1177/1535370219846425] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
IMPACT STATEMENT Disturbance of normal homeostasis occurs when oxygen delivery and energy stores to the body's tissues fail to meet the energy requirement of cells. The work submitted in this review is important because it advances the understanding of inadequate oxygen delivery as it relates to early diagnosis and treatment of circulatory shock and its relationship to disturbance of normal functioning of cellular metabolism in life-threatening conditions of hemorrhage. We explored data from the clinical and exercise literature to construct for the first time a conceptual framework for defining the limitation of inadequate delivery of oxygen by comparing the physiology of hemorrhagic shock caused by severe blood loss to maximal oxygen uptake induced by intense physical exercise. We also provide a translational framework in which understanding the fundamental relationship between the body's reserve to compensate for conditions of inadequate oxygen delivery as a limiting factor to V ˙ O2max helps to re-evaluate paradigms of triage for improved monitoring of accurate resuscitation in patients suffering from hemorrhagic shock.
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Affiliation(s)
- Victor A Convertino
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, Fort Sam Houston, TX 78234, USA
| | - Kristen R Lye
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, Fort Sam Houston, TX 78234, USA
| | - Natalie J Koons
- Battlefield Health & Trauma Center for Human Integrative Physiology, U. S. Army Institute of Surgical Research, Fort Sam Houston, TX 78234, USA
| | - Michael J Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA
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Trauma Hemostasis and Oxygenation Research Network position paper on the role of hypotensive resuscitation as part of remote damage control resuscitation. J Trauma Acute Care Surg 2019; 84:S3-S13. [PMID: 29799823 DOI: 10.1097/ta.0000000000001856] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The Trauma Hemostasis and Oxygenation Research (THOR) Network has developed a consensus statement on the role of permissive hypotension in remote damage control resuscitation (RDCR). A summary of the evidence on permissive hypotension follows the THOR Network position on the topic. In RDCR, the burden of time in the care of the patients suffering from noncompressible hemorrhage affects outcomes. Despite the lack of published evidence, and based on clinical experience and expertise, it is the THOR Network's opinion that the increase in prehospital time leads to an increased burden of shock, which poses a greater risk to the patient than the risk of rebleeding due to slightly increased blood pressure, especially when blood products are available as part of prehospital resuscitation.The THOR Network's consensus statement is, "In a casualty with life-threatening hemorrhage, shock should be reversed as soon as possible using a blood-based HR fluid. Whole blood is preferred to blood components. As a part of this HR, the initial systolic blood pressure target should be 100 mm Hg. In RDCR, it is vital for higher echelon care providers to receive a casualty with sufficient physiologic reserve to survive definitive surgical hemostasis and aggressive resuscitation. The combined use of blood-based resuscitation and limiting systolic blood pressure is believed to be effective in promoting hemostasis and reversing shock".
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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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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: 117] [Impact Index Per Article: 23.4] [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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Compensatory Reserve Index: Performance of A Novel Monitoring Technology to Identify the Bleeding Trauma Patient. Shock 2019; 49:295-300. [PMID: 28767544 DOI: 10.1097/shk.0000000000000959] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
INTRODUCTION Hemorrhage is one of the most substantial causes of death after traumatic injury. Standard measures, including systolic blood pressure (SBP), are poor surrogate indicators of physiologic compromise until compensatory mechanisms have been overwhelmed. Compensatory Reserve Index (CRI) is a novel monitoring technology with the ability to assess physiologic reserve. We hypothesized CRI would be a better predictor of physiologic compromise secondary to hemorrhage than traditional vital signs. METHODS A prospective observational study of 89 subjects meeting trauma center activation criteria at a single level I trauma center was conducted from October 2015 to February 2016. Data collected included demographics, SBP, heart rate, and requirement for hemorrhage-associated, life-saving intervention (LSI) (i.e., operation or angiography for hemorrhage, local or tourniquet control of external bleeding, and transfusion >2 units PRBC). Receiver-operator characteristic (ROC) curves were formulated and appropriate thresholds were calculated to compare relative value of the metrics for predictive modeling. RESULTS For predicting hemorrhage-related LSI, CRI demonstrated a sensitivity of 83% and a negative predictive value (NPV) of 91% as compared with SBP with a sensitivity to detect hemorrhage of 26% (P < 0.05) and an NPV of 78%. ROC curves generated from admission CRI and SBP measures demonstrated values of 0.83 and 0.62, respectively. CRI identified significant hemorrhage requiring potentially life-saving therapy more reliably than SBP (P < 0.05). CONCLUSION The CRI device demonstrated superior capacity over systolic blood pressure in predicting the need for posttraumatic hemorrhage intervention in the acute resuscitation phase after injury.
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Suresh MR, Chung KK, Schiller AM, Holley AB, Howard JT, Convertino VA. Unmasking the Hypovolemic Shock Continuum: The Compensatory Reserve. J Intensive Care Med 2018; 34:696-706. [PMID: 30068251 DOI: 10.1177/0885066618790537] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Hypovolemic shock exists as a spectrum, with its early stages characterized by subtle pathophysiologic tissue insults and its late stages defined by multi-system organ dysfunction. The importance of timely detection of shock is well known, as early interventions improve mortality, while delays render these same interventions ineffective. However, detection is limited by the monitors, parameters, and vital signs that are traditionally used in the intensive care unit (ICU). Many parameters change minimally during the early stages, and when they finally become abnormal, hypovolemic shock has already occurred. The compensatory reserve (CR) is a parameter that represents a new paradigm for assessing physiologic status, as it comprises the sum total of compensatory mechanisms that maintain adequate perfusion to vital organs during hypovolemia. When these mechanisms are overwhelmed, hemodynamic instability and circulatory collapse will follow. Previous studies involving CR measurements demonstrated their utility in detecting central blood volume loss before hemodynamic parameters and vital signs changed. Measurements of the CR have also been used in clinical studies involving patients with traumatic injuries or bleeding, and the results from these studies have been promising. Moreover, these measurements can be made at the bedside, and they provide a real-time assessment of hemodynamic stability. Given the need for rapid diagnostics when treating critically ill patients, CR measurements would complement parameters that are currently being used. Consequently, the purpose of this article is to introduce a conceptual framework where the CR represents a new approach to monitoring critically ill patients. Within this framework, we present evidence to support the notion that the use of the CR could potentially improve the outcomes of ICU patients by alerting intensivists to impending hypovolemic shock before its onset.
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Affiliation(s)
- Mithun R Suresh
- 1 Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Kevin K Chung
- 2 Department of Medicine, Brooke Army Medical Center, JBSA Fort Sam Houston, TX, USA.,3 Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Alicia M Schiller
- 4 Department of Anesthesiology, University of Nebraska Medical Center, Omaha, NE, USA
| | - Aaron B Holley
- 2 Department of Medicine, Brooke Army Medical Center, JBSA Fort Sam Houston, TX, USA.,3 Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Jeffrey T Howard
- 1 Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Victor A Convertino
- 1 Battlefield Health & Trauma Center for Human Integrative Physiology, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
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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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Vishwanath K, Gurjar R, Wolf D, Riccardi S, Duggan M, King D. Diffuse optical monitoring of peripheral tissues during uncontrolled internal hemorrhage in a porcine model. BIOMEDICAL OPTICS EXPRESS 2018; 9:569-580. [PMID: 29552394 PMCID: PMC5854059 DOI: 10.1364/boe.9.000569] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 12/11/2017] [Accepted: 12/22/2017] [Indexed: 05/06/2023]
Abstract
Reliable, continuous and noninvasive blood flow and hemoglobin monitoring in trauma patients remains a critical, but generally unachieved goal. Two optical sensing methods - diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS) - are used to monitor and detect internal hemorrhage. Specifically, we investigate if cutaneous perfusion measurements acquired using DCS and DRS in peripheral (thighs and ear-lobe) tissues could detect severe hemorrhagic shock in a porcine model. Four animals underwent high-grade hepato-portal injury in a closed abdomen, to induce uncontrolled hemorrhage and were subsequently allowed to bleed for 10 minutes before fluid resuscitation. DRS and DCS measurements of cutaneous blood flow were acquired using fiber optical probes placed on the thigh and earlobe of the animals and were obtained repeatedly starting from 1 to 5 minutes pre-injury, up to several minutes post shock. Clear changes were observed in measured optical spectra across all animals at both sites. DCS-derived cutaneous blood flow decreased sharply during hemorrhage, while DRS-derived vascular saturation and hemoglobin paralleled cardiac output. All derived optical parameters had the steepest changes during the rapid initial hemorrhage unambiguously. This suggests that a combined DCS and DRS based device might provide an easy-to-use, non-invasive, internal-hemorrhage detection system that can be used across a wide array of clinical settings.
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Affiliation(s)
- Karthik Vishwanath
- Department of Physics, Miami University, Oxford, OH 45056, USA
- Affiliations of authors when experiments were conducted: Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA
| | - Rajan Gurjar
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, MA 02420, USA
- Affiliations of authors when experiments were conducted: Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA
| | - David Wolf
- Warner Babcock Institute for Green Chemistry, 100 Research Drive, Wilmington, MA 01887, USA
- Affiliations of authors when experiments were conducted: Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA
| | - Suzannah Riccardi
- MIT Lincoln Laboratory, 244 Wood Street, Lexington, MA 02420, USA
- Affiliations of authors when experiments were conducted: Radiation Monitoring Devices Inc., 44 Hunt Street, Watertown, MA 02472, USA
| | - Michael Duggan
- Division of Trauma, Emergency Surgery, and Surgical Critical Care, Massachusetts General Hospital, 165 Cambridge Street, Suite 810 Boston, MA 02114, USA
| | - David King
- Division of Trauma, Emergency Surgery, and Surgical Critical Care, Massachusetts General Hospital, 165 Cambridge Street, Suite 810 Boston, MA 02114, USA
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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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Comparison of compensatory reserve and arterial lactate as markers of shock and resuscitation. J Trauma Acute Care Surg 2017; 83:603-608. [PMID: 28930955 DOI: 10.1097/ta.0000000000001595] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND During traumatic hemorrhage, the ability to identify shock and intervene before decompensation is paramount to survival. Lactate is extremely sensitive to shock, and its clearance has been demonstrated a useful gauge of shock and resuscitation status. Though lactate can be measured in the field, logistical constraints render it impractical in certain environments. The compensatory reserve represents a new clinical measurement reflecting the remaining capacity to compensate for hypoperfusion. We hypothesized the compensatory reserve index (CRI) would be an effective surrogate marker of shock and resuscitation compared to lactate. METHODS The CRI device was placed on consecutive patients meeting trauma center activation criteria and remained on the patient until discharge, admission, or transport to operating suite. All subjects had a lactate level measured as part of their routine admission metabolic analysis. Time-corresponding CRI and lactate values were matched in regards to initial and subsequent lactate levels. Mean time from lactate sample collection to data availability in the electronic medical record was calculated. Predictive capacity of CRI and lactate in predicting hemorrhage was determined by receiver-operator characteristic curve analysis. Correlation analysis was performed to determine if any association existed between changing CRI and lactate values. RESULTS Receiver-operator characteristic (ROC) curves were generated and area under the curve was 0.8052 and 0.8246 for CRI and lactate, respectively. There was no significant difference in each parameter's ability to predict hemorrhage (p = 0.8015). The mean duration from lactate sample collection to clinical availability was 44 minutes whereas CRI values were available immediately. Analysis of the concomitant change in serial CRI and lactate levels revealed a Spearman's correlation coefficient of -0.73 (p < 0.01). CONCLUSION CRI performed with equivalent predictive capacity to lactate with respect to identifying initial perfusion status associated with hemorrhage and subsequent resuscitation. LEVEL OF EVIDENCE Diagnostic, Level II.
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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: 20] [Impact Index Per Article: 2.9] [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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Schiller AM, Howard JT, Convertino VA. The physiology of blood loss and shock: New insights from a human laboratory model of hemorrhage. Exp Biol Med (Maywood) 2017; 242:874-883. [PMID: 28346013 DOI: 10.1177/1535370217694099] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The ability to quickly diagnose hemorrhagic shock is critical for favorable patient outcomes. Therefore, it is important to understand the time course and involvement of the various physiological mechanisms that are active during volume loss and that have the ability to stave off hemodynamic collapse. This review provides new insights about the physiology that underlies blood loss and shock in humans through the development of a simulated model of hemorrhage using lower body negative pressure. In this review, we present controlled experimental results through utilization of the lower body negative pressure human hemorrhage model that provide novel insights on the integration of physiological mechanisms critical to the compensation for volume loss. We provide data obtained from more than 250 human experiments to classify human subjects into two distinct groups: those who have a high tolerance and can compensate well for reduced central blood volume (e.g. hemorrhage) and those with low tolerance with poor capacity to compensate.We include the conceptual introduction of arterial pressure and cerebral blood flow oscillations, reflex-mediated autonomic and neuroendocrine responses, and respiration that function to protect adequate tissue oxygenation through adjustments in cardiac output and peripheral vascular resistance. Finally, unique time course data are presented that describe mechanistic events associated with the rapid onset of hemodynamic failure (i.e. decompensatory shock). Impact Statement Hemorrhage is the leading cause of death in both civilian and military trauma. The work submitted in this review is important because it advances the understanding of mechanisms that contribute to the total integrated physiological compensations for inadequate tissue oxygenation (i.e. shock) that arise from hemorrhage. Unlike an animal model, we introduce the utilization of lower body negative pressure as a noninvasive model that allows for the study of progressive reductions in central blood volume similar to those reported during actual hemorrhage in conscious humans to the onset of hemodynamic decompensation (i.e. early phase of decompensatory shock), and is repeatable in the same subject. Understanding the fundamental underlying physiology of human hemorrhage helps to test paradigms of critical care medicine, and identify and develop novel clinical practices and technologies for advanced diagnostics and therapeutics in patients with life-threatening blood loss.
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Affiliation(s)
- Alicia M Schiller
- U. S. Army Institute of Surgical Research, Houston, TX 78234-6315, USA
| | - Jeffrey T Howard
- U. S. Army Institute of Surgical Research, Houston, TX 78234-6315, USA
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van Helmond N, Johnson BD, Curry TB, Cap AP, Convertino VA, Joyner MJ. White blood cell concentrations during lower body negative pressure and blood loss in humans. Exp Physiol 2016; 101:1265-1275. [DOI: 10.1113/ep085952] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 08/11/2016] [Indexed: 11/08/2022]
Affiliation(s)
| | - Blair D. Johnson
- Department of Anesthesiology; Mayo Clinic; Rochester MN USA
- Center for Research and Education in Special Environments; Department of Exercise and Nutrition Sciences; University at Buffalo; Buffalo NY USA
| | | | - Andrew P. Cap
- US Army Institute of Surgical Research; Fort Sam Houston; TX USA
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Scully CG, Daluwatte C, Marques NR, Khan M, Salter M, Wolf J, Nelson C, Salsbury J, Enkhbaatar P, Kinsky M, Kramer GC, Strauss DG. Effect of hemorrhage rate on early hemodynamic responses in conscious sheep. Physiol Rep 2016; 4:4/7/e12739. [PMID: 27044850 PMCID: PMC4831318 DOI: 10.14814/phy2.12739] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 02/19/2016] [Indexed: 11/24/2022] Open
Abstract
Physiological compensatory mechanisms can mask the extent of hemorrhage in conscious mammals, which can be further complicated by individual tolerance and variations in hemorrhage onset and duration. We assessed the effect of hemorrhage rate on tolerance and early physiologic responses to hemorrhage in conscious sheep. Eight Merino ewes (37.4 ± 1.1 kg) were subjected to fast (1.25 mL/kg/min) and slow (0.25 mL/kg/min) hemorrhages separated by at least 3 days. Blood was withdrawn until a drop in mean arterial pressure (MAP) of >30 mmHg and returned at the end of the experiment. Continuous monitoring included MAP, central venous pressure, pulmonary artery pressure, pulse oximetry, and tissue oximetry. Cardiac output by thermodilution and arterial blood samples were also measured. The effects of fast versus slow hemorrhage rates were compared for total volume of blood removed and stoppage time (when MAP < 30 mmHg of baseline) and physiological responses during and after the hemorrhage. Estimated blood volume removed when MAP dropped 30 mmHg was 27.0 ± 4.2% (mean ± standard error) in the slow and 27.3 ± 3.2% in the fast hemorrhage (P = 0.47, paired t test between rates). Pressure and tissue oximetry responses were similar between hemorrhage rates. Heart rate increased at earlier levels of blood loss during the fast hemorrhage, but hemorrhage rate was not a significant factor for individual hemorrhage tolerance or hemodynamic responses. In 5/16 hemorrhages MAP stopping criteria was reached with <25% of blood volume removed. This study presents the physiological responses leading up to a significant drop in blood pressure in a large conscious animal model and how they are altered by the rate of hemorrhage.
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Affiliation(s)
- Christopher G Scully
- Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland
| | - Chathuri Daluwatte
- Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, Silver Spring, Maryland
| | - Nicole R Marques
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - Muzna Khan
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - Michael Salter
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - Jordan Wolf
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - Christina Nelson
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - John Salsbury
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - Perenlei Enkhbaatar
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - Michael Kinsky
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - George C Kramer
- Department of Anesthesiology, The University of Texas Medical Branch, Galveston, Texas
| | - David G Strauss
- Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, US Food and Drug Administration, Silver Spring, Maryland
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Specificity of Compensatory Reserve and Tissue Oxygenation as Early Predictors of Tolerance to Progressive Reductions in Central Blood Volume. Shock 2016; 46:68-73. [DOI: 10.1097/shk.0000000000000632] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Sprick JD, Soller BR, Rickards CA. The efficacy of novel anatomical sites for the assessment of muscle oxygenation during central hypovolemia. Exp Biol Med (Maywood) 2016; 241:2007-2013. [PMID: 27439541 DOI: 10.1177/1535370216660213] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 06/27/2016] [Indexed: 11/16/2022] Open
Abstract
Muscle tissue oxygenation (SmO2) can track central blood volume loss associated with hemorrhage. Traditional peripheral measurement sites (e.g., forearm) may not be practical due to excessive movement or injury (e.g., amputation). The aim of this study was to evaluate the efficacy of three novel anatomical sites for the assessment of SmO2 under progressive central hypovolemia. 10 male volunteers were exposed to stepwise prone lower body negative pressure to decrease central blood volume, while SmO2 was assessed at four sites-the traditional site of the flexor carpi ulnaris (ARM), and three novel sites not previously investigated during lower body negative pressure, the deltoid, latissimus dorsi, and trapezius. SmO2 at the novel sites was compared to the ARM sensor and to stroke volume responses. A reduction in SmO2 was detected by the ARM sensor at the first level of lower body negative pressure (-15 mmHg; P = 0.007), and at -30 (the deltoid), -45 (latissimus dorsi), and -60 mmHg lower body negative pressure (trapezius) at the novel sites (P ≤ 0.04). SmO2 responses at all novel sites were correlated with responses at the ARM (R ≥ 0.89), and tracked the reduction in stroke volume (R ≥ 0.87); the latissimus dorsi site exhibited the strongest linear correlations (R ≥ 0.96). Of the novel sensor sites, the latissimus dorsi exhibited the strongest linear associations with SmO2 at the ARM, and with reductions in central blood volume. These findings have important implications for detection of hemorrhage in austere environments (e.g., combat) when use of a peripheral sensor may not be ideal, and may facilitate incorporation of these sensors into uniforms.
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Affiliation(s)
- Justin D Sprick
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | | | - Caroline A Rickards
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
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Hinojosa-Laborde C, Howard JT, Mulligan J, Grudic GZ, Convertino VA. Comparison of compensatory reserve during lower-body negative pressure and hemorrhage in nonhuman primates. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1154-9. [PMID: 27030667 DOI: 10.1152/ajpregu.00304.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 03/14/2016] [Indexed: 11/22/2022]
Abstract
Compensatory reserve was measured in baboons (n = 13) during hemorrhage (Hem) and lower-body negative pressure (LBNP) using a machine-learning algorithm developed to estimate compensatory reserve by detecting reductions in central blood volume during LBNP. The algorithm calculates compensatory reserve index (CRI) from normovolemia (CRI = 1) to cardiovascular decompensation (CRI = 0). The hypothesis was that Hem and LBNP will elicit similar CRI values and that CRI would have higher specificity than stroke volume (SV) in predicting decompensation. Blood was removed in four steps: 6.25%, 12.5%, 18.75%, and 25% of total blood volume. Four weeks after Hem, the same animals were subjected to four levels of LBNP that was matched on the basis of their central venous pressure. Data (mean ± 95% confidence interval) indicate that CRI decreased (P < 0.001) from baseline during Hem (0.69 ± 0.10, 0.57 ± 0.09, 0.36 ± 0.10, 0.16 ± 0.08, and 0.08 ± 0.03) and LBNP (0.76 ± 0.05, 0.66 ± 0.08, 0.36 ± 0.13, 0.23 ± 0.11, and 0.14 ± 0.09). CRI was not different between Hem and LBNP (P = 0.20). Linear regression analysis between Hem CRI and LBNP CRI revealed a slope of 1.03 and a correlation coefficient of 0.96. CRI exhibited greater specificity than SV in both Hem (92.3 vs. 82.1) and LBNP (94.8 vs. 83.1) and greater ROC AUC in Hem (0.94 vs. 0.84) and LBNP (0.94 vs. 0.92). These data support the hypothesis that Hem and LBNP elicited the same CRI response, suggesting that measurement of compensatory reserve is superior to SV as a predictor of cardiovascular decompensation.
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Affiliation(s)
- Carmen Hinojosa-Laborde
- U.S. Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, Texas; and
| | - Jeffrey T Howard
- U.S. Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, Texas; and
| | | | | | - Victor A Convertino
- U.S. Army Institute of Surgical Research, Joint Base San Antonio Fort Sam Houston, Texas; and
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Kay VL, Rickards CA. The role of cerebral oxygenation and regional cerebral blood flow on tolerance to central hypovolemia. Am J Physiol Regul Integr Comp Physiol 2016; 310:R375-83. [DOI: 10.1152/ajpregu.00367.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 12/14/2015] [Indexed: 11/22/2022]
Abstract
Tolerance to central hypovolemia is highly variable, and accumulating evidence suggests that protection of anterior cerebral blood flow (CBF) is not an underlying mechanism. We hypothesized that individuals with high tolerance to central hypovolemia would exhibit protection of cerebral oxygenation (ScO2), and prolonged preservation of CBF in the posterior vs. anterior cerebral circulation. Eighteen subjects (7 male/11 female) completed a presyncope-limited lower body negative pressure (LBNP) protocol (3 mmHg/min onset rate). ScO2 (via near-infrared spectroscopy), middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv) (both via transcranial Doppler ultrasound), and arterial pressure (via finger photoplethysmography) were measured continuously. Subjects who completed ≥70 mmHg LBNP were classified as high tolerant (HT; n = 7) and low tolerant (LT; n = 11) if they completed ≤60 mmHg LBNP. The minimum difference in LBNP tolerance between groups was 193 s (LT = 1,243 ± 185 s vs. HT = 1,996 ± 212 s; P < 0.001; Cohen's d = 3.8). Despite similar reductions in mean MCAv in both groups, ScO2 decreased in LT subjects from −15 mmHg LBNP ( P = 0.002; Cohen's d=1.8), but was maintained at baseline values until −75 mmHg LBNP in HT subjects ( P < 0.001; Cohen's d = 2.2); ScO2 was lower at −30 and −45 mmHg LBNP in LT subjects ( P ≤ 0.02; Cohen's d ≥ 1.1). Similarly, mean PCAv decreased below baseline from −30 mmHg LBNP in LT subjects ( P = 0.004; Cohen's d = 1.0), but remained unchanged from baseline in HT subjects until −75 mmHg ( P = 0.006; Cohen's d = 2.0); PCAv was lower at −30 and −45 mmHg LBNP in LT subjects ( P ≤ 0.01; Cohen's d ≥ 0.94). Individuals with higher tolerance to central hypovolemia exhibit prolonged preservation of CBF in the posterior cerebral circulation and sustained cerebral tissue oxygenation, both associated with a delay in the onset of presyncope.
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Affiliation(s)
- Victoria L. Kay
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
| | - Caroline A. Rickards
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
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Torres Filho I, Nguyen NM, Jivani R, Terner J, Romfh P, Vakhshoori D, Ward KR. Oxygen saturation monitoring using resonance Raman spectroscopy. J Surg Res 2015; 201:425-31. [PMID: 27020828 DOI: 10.1016/j.jss.2015.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/02/2015] [Accepted: 12/04/2015] [Indexed: 11/13/2022]
Abstract
BACKGROUND The knowledge of hemoglobin oxygen saturation (SO2) and tissue oxygenation is critical to identify the presence of shock and therapeutic options. The resonance vibrational enhancement of hemoglobin allows measurement of oxy- and deoxy species of hemoglobin and resonance Raman spectroscopy (RRS-StO2) has been successfully used to measure aggregate microvascular oxygenation. We tested the hypothesis that noninvasive oxygen saturation measured by RRS-StO2 could serve as surrogate of systemic central venous SO2. METHODS In anesthetized rats, measurements of RRS-StO2 made in oral mucosa, skin, muscle, and liver were compared with measurements of central venous SO2 using traditional multi-wavelength oximetry. Various oxygenation levels were obtained using a stepwise hemorrhage while over 100 paired blood samples and Raman-based measurements were performed. The relationships between RRS-StO2 and clinically important systemic blood parameters were also evaluated. RRS-StO2 measurements were made in 3-mm diameter tissue areas using a microvascular oximeter and a handheld probe. RESULTS Significant correlations were found between venous SO2 and RRS-StO2 measurements made in the oral mucosa (r = 0.913, P < 0.001), skin (r = 0.499, P < 0.01), and liver (r = 0.611, P < 0.05). The mean difference between sublingual RRS-StO2 and blood sample SO2 values was 5.4 ± 1.6%. Sublingual RRS-StO2 also correlated with lactate (r = 0.909, P < 0.01), potassium (r = 0.757, P < 0.01), and pH (r = 0.703, P < 0.05). CONCLUSIONS Raman-based oxygen saturation is a promising technique for the noninvasive evaluation of oxygenation in skin, thin tissues, and solid organs. Under certain conditions, sublingual RRS-StO2 measurements correlate with central venous SO2.
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Affiliation(s)
- Ivo Torres Filho
- Department of Anesthesiology, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia; Department of Emergency Medicine, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia; Damage Control Resuscitation, U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas.
| | - Nguyen M Nguyen
- Department of Anesthesiology, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia
| | - Rizwan Jivani
- Department of Anesthesiology, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia
| | - James Terner
- Department of Chemistry, Virginia Commonwealth University and the Virginia Commonwealth University Reanimation Engineering Science Center, Richmond, Virginia
| | | | | | - Kevin R Ward
- Department of Emergency Medicine and the Michigan Center for Integrative Research in Critical Care, University of Michigan, Ann Arbor, Michigan
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Kay VL, Rickards CA. Reproducibility of a continuous ramp lower body negative pressure protocol for simulating hemorrhage. Physiol Rep 2015; 3:3/11/e12640. [PMID: 26607173 PMCID: PMC4673656 DOI: 10.14814/phy2.12640] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Central hypovolemia elicited by application of lower body negative pressure (LBNP) has been used extensively to simulate hemorrhage in human subjects. Traditional LBNP protocols incorporate progressive steps in pressure held for specific time intervals. The aim of this study was to assess the reproducibility of applying continuous LBNP at a constant rate until presyncope to replicate actual bleeding. During two trials (≥4 weeks intervening), LBNP was applied at a rate of 3 mmHg/min in 18 healthy human subjects (12M; 6F) until the onset of presyncopal symptoms. Heart rate (HR), mean arterial pressure (MAP), stroke volume (SV), total peripheral resistance (TPR), mean middle and posterior cerebral artery velocities (MCAv, PCAv), and cerebral oxygen saturation (ScO2) were measured continuously. Time to presyncope (TTPS) and hemodynamic responses were compared between the two trials. TTPS (1649 ± 98 sec vs. 1690 ± 88 sec; P = 0.47 [t-test]; r = 0.77) and the subsequent magnitude of central hypovolemia (%Δ SV −54 ± 4% vs. −53 ± 4%; P = 0.55) were similar between trials. There were no statistically distinguishable differences at either baseline (P ≥ 0.17) or presyncope between trials for HR, MAP, TPR, mean MCAv, mean PCAv, or ScO2 (P ≥ 0.19). The rate of change from baseline to presyncope for all hemodynamic responses was also similar between trials (P ≥ 0.12). Continuous LBNP applied at a rate of 3 mmHg/min was reproducible in healthy human subjects, eliciting similar reductions in central blood volume and subsequent reflex hemodynamic responses.
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Affiliation(s)
- Victoria L Kay
- Institute for Cardiovascular & Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
| | - Caroline A Rickards
- Institute for Cardiovascular & Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
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Helmond NV, Johnson BD, Curry TB, Cap AP, Convertino VA, Joyner MJ. Coagulation changes during lower body negative pressure and blood loss in humans. Am J Physiol Heart Circ Physiol 2015; 309:H1591-7. [DOI: 10.1152/ajpheart.00435.2015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 09/04/2015] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that markers of coagulation activation are greater during lower body negative pressure (LBNP) than those obtained during blood loss (BL). We assessed coagulation using both standard clinical tests and thrombelastography (TEG) in 12 men who performed a LBNP and BL protocol in a randomized order. LBNP consisted of 5-min stages at 0, −15, −30, and −45 mmHg of suction. BL included 5 min at baseline and following three stages of 333 ml of blood removal (up to 1,000 ml total). Arterial blood draws were performed at baseline and after the last stage of each protocol. We found that LBNP to −45 mmHg is a greater central hypovolemic stimulus versus BL; therefore, the coagulation markers were plotted against central venous pressure (CVP) to obtain stimulus-response relationships using the linear regression line slopes for both protocols. Paired t-tests were used to determine whether the slopes of these regression lines fell on similar trajectories for each protocol. Mean regression line slopes for coagulation markers versus CVP fell on similar trajectories during both protocols, except for TEG α° angle (−0.42 ± 0.96 during LBNP vs. −2.41 ± 1.13°/mmHg during BL; P < 0.05). During both LBNP and BL, coagulation was accelerated as evidenced by shortened R-times (LBNP, 9.9 ± 2.4 to 6.2 ± 1.1; BL, 8.7 ± 1.3 to 6.4 ± 0.4 min; both P < 0.05). Our results indicate that LBNP models the general changes in coagulation markers observed during BL.
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Affiliation(s)
- Noud van Helmond
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Blair D. Johnson
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
- Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, New York; and
| | | | - Andrew P. Cap
- U.S. Army Institute of Surgical Research, Fort Sam Houston, Texas
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Investigation of noninvasive muscle pH and oxygen saturation during uncontrolled hemorrhage and resuscitation in swine. Shock 2015; 42:44-51. [PMID: 24667624 DOI: 10.1097/shk.0000000000000174] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This study evaluated noninvasively determined muscle pH (pHm) and muscle oxygen saturation (SmO2) in a swine shock model that used uncontrolled hemorrhage and restricted volume resuscitation. Anesthetized 40-kg female swine underwent hemorrhage until 24 mL/kg of blood was removed (n = 26), followed by transection of the spleen, causing uncontrolled hemorrhage throughout the remainder of the protocol. After 15 min, 15 mL/kg of resuscitation fluid (Hextend, fresh-frozen plasma or platelets) was given for 30 min. Arterial and venous blood gases were measured at baseline, shock, end of resuscitation, and end of the study (death or 5 h), along with lactate and base excess. In addition, seven animals underwent a sham procedure. Spectra were collected continuously from the posterior thigh using a prototype CareGuide 1100 Oximeter, and pHm and SmO2 were calculated from the spectra. A two-factor analysis of variance with repeated measures followed by Tukey post hoc comparisons was used to compare experimental factors. It was shown that, for both pH and SO2, venous and muscle values were similar to each other at the end of the resuscitation period and at the end of the study for both surviving and nonsurviving animals. pH and SO2, venous and muscle, significantly declined as a result of bleeding, but lactate and base excess did not show significant changes during this period. Noninvasive pHm and SmO2 tracked the adequacy of resuscitation in real time, indicating at the time all of the fluid was delivered, which animals would live and which would die. The results of this swine study indicate that further evaluation on trauma patients is warranted.
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Abstract
The environmental and logistical constraints of the prehospital setting make it a challenging place for the treatment of trauma patients. This is perhaps more pronounced in the management of battlefield casualties before extraction to definitive care. In seeking solutions, interest has been renewed in implementing damage control resuscitation principles in the prehospital setting, a concept termed remote damage control resuscitation. These developments, while improving conflict survival rates, are not exclusive to the military environment, with similar situations existing in the civilian setting. By understanding the pathophysiology of shock, particularly the need for oxygen debt repayment, improvements in the assessment and management of trauma patients can be made. Technology gaps have previously hampered our ability to accurately monitor the prehospital trauma patient in real time. However, this is changing, with devices such as tissue hemoglobin oxygen saturation monitors and point-of-care lactate analysis currently being refined. Other monitoring modalities including newer signal analysis and artificial intelligence techniques are also in development. Advances in hemostatic resuscitation are being made as our understanding and ability to effectively monitor patients improve. The reevaluation of whole-blood use in the prehospital environment is yielding favorable results and challenging the negative dogma currently associated with its use. Management of trauma-related airway and respiratory compromise is evolving, with scope to improve on currently accepted practices. The purpose of this review is to highlight the challenges of treating patients in the prehospital setting and suggest potential solutions. In doing so, we hope to maintain the enthusiasm from people in the field and highlight areas for prehospital specific research and development, so that improved rates of casualty survival will continue.
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Abstract
Trauma is the leading cause of death during the first four decades of life in the developed countries. Its haemodynamic response underpins the patient's initial ability to survive, and the response to treatment and subsequent morbidity and resolution. Trauma causes a number of insults including haemorrhage, tissue injury (nociception) and, predominantly, in military casualties, blast from explosions. This article discusses aspects of the haemodynamic responses to these insults and subsequent treatment. 'Simple' haemorrhage (blood loss without significant volume of tissue damage) causes a biphasic response: mean arterial blood pressure (MBP) is initially maintained by the baroreflex (tachycardia and increased vascular resistance, Phase 1), followed by a sudden decrease in MAP initiated by a second reflex (decrease in vascular resistance and bradycardia, Phase 2). Phase 2 may be protective. The response to tissue injury attenuates Phase 2 and may cause a deleterious haemodynamic redistribution that compromises blood flow to some vital organs. In contrast, thoracic blast exposure augments Phase 2 of the response to haemorrhage. However, hypoxaemia from lung injury limits the effectiveness of hypotensive resuscitation by augmenting the attendant shock state. An alternative strategy ('hybrid resuscitation') whereby tissue perfusion is increased after the first hour of hypotensive resuscitation by adopting a revised normotensive target may ameliorate these problems. Finally, morphine also attenuates Phase 2 of the response to haemorrhage in some, but not all, species and this is associated with poor outcome. The impact on human patients is currently unknown and is the subject of a current physiological investigation.
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Affiliation(s)
- E Kirkman
- Biomedical Sciences Department, Defence Science and Technology Laboratory, Porton Down, Salisbury, UK
| | - S Watts
- Biomedical Sciences Department, Defence Science and Technology Laboratory, Porton Down, Salisbury, UK
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Soller B, Srikiatkachorn A, Zou F, Rothman AL, Yoon IK, Gibbons RV, Kalayanarooj S, Thomas SJ, Green S. Preliminary evaluation of near infrared spectroscopy as a method to detect plasma leakage in children with dengue hemorrhagic fever. BMC Infect Dis 2014; 14:396. [PMID: 25033831 PMCID: PMC4223418 DOI: 10.1186/1471-2334-14-396] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 06/30/2014] [Indexed: 11/26/2022] Open
Abstract
Background Dengue viral infections are prevalent in the tropical and sub-tropical regions of the world, resulting in substantial morbidity and mortality. Clinical manifestations range from a self-limited fever to a potential life-threatening plasma leakage syndrome (dengue hemorrhagic fever). The objective of this study was to assess the utility of near infrared spectroscopy (NIRS) measurements of muscle oxygen saturation (SmO2) as a possible continuous measure to detect plasma leakage in children with dengue. Methods Children ages 6 months to 15 years of age admitted with suspected dengue were enrolled from the dengue ward at Queen Sirikit National Institute for Child Health. Children were monitored daily until discharge. NIRS data were collected continuously using a prototype CareGuide Oximeter 1100 with sensors placed on the deltoid or thigh. Daily ultrasound of the chest and a right lateral decubitus chest x-ray the day after defervescence were performed to detect and quantitate plasma leakage in the pleural cavity. Results NIRS data were obtained from 19 children with laboratory-confirmed dengue. Average minimum SmO2 decreased for all subjects prior to defervescence. Average minimum SmO2 subsequently increased in children with no ultrasound evidence of pleural effusion but remained low in children with pleural effusion following defervescence. Average minimum SmO2 was inversely correlated with pleural space fluid volume. ROC analysis revealed a cut-off value for SmO2 which yielded high specificity and sensitivity. Conclusions SmO2 measured using NIRS may be a useful guide for real-time and non-invasive identification of plasma leakage in children with dengue. Further investigation of the utility of NIRS measurements for prediction and management of severe dengue syndromes is warranted.
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Affiliation(s)
- Babs Soller
- Reflectance Medical, Inc,, 116 Flanders Rd, Suite 1000, Westborough, MA 01581, USA.
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Tissue oxygenation monitoring using resonance Raman spectroscopy during hemorrhage. J Trauma Acute Care Surg 2014; 76:402-8. [PMID: 24378619 DOI: 10.1097/ta.0000000000000088] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND The ability to monitor the patient of hemorrhage noninvasively remains a challenge. We examined the ability of resonance Raman spectroscopy to monitor tissue hemoglobin oxygenation (RRS-StO2) during hemorrhage and compared its performance with conventional invasive mixed venous (SmvO2) and central venous (ScvO2) hemoglobin oxygen saturation as well as with near-infrared spectroscopy tissue hemoglobin oxygenation (NIRS-StO2). METHODS Five male swine were anesthetized and instrumented followed by hemorrhage at a rate of 30 mL/min for 60 minutes. RRS-StO2 was continuously measured from the buccal mucosa, and NIRS-StO2 was continuously measured from the forelimb. Paired interval measures of SmvO2, ScvO2, and lactate were made. Pearson correlation was used to quantify the degree to which any two variables are related. Receiver operating characteristic (ROC) area under the curve values were used for pooled data for RRS-StO2, NIRS-StO2, SmvO2, and ScvO2 to compare performance in the ability of tissue oxygenation methods to predict the presence of an elevated arterial blood lactate level. RESULTS Sequential RRS-StO2 changes tracked changes in SmvO2 (r = 0.917; 95% confidence interval [CI], 0.867-0.949) and ScvO2 (r = 0.901; 95% CI, 0.828-0.944) during hemorrhage, while NIRS-StO2 failed to do so for SmvO2 (r = 0.283; 95% CI, 0.04919-0.4984) and ScvO2 (r = 0.142; 95% CI, -0.151 to 0.412). ROC curve performance of oxygenation measured to indicate lactate less than or greater than 3 mM yielded the following ROC area under the curve values: SmvO2 (1.0), ScvO2 (0.994), RRS-StO2 (0.972), and NIRS-StO2 (0.611). CONCLUSION RRS-StO2 seems to have significantly better ability to track central oxygenation measures during hemorrhage as well as to predict shock based on elevated lactate levels when compared with NIRS-StO2.
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Abstract
BACKGROUND Hemorrhage is a leading cause of traumatic death. We hypothesized that state-of-the-art feature extraction and machine learning techniques could be used to discover, detect, and continuously trend beat-to-beat changes in arterial pulse waveforms associated with the progression to hemodynamic decompensation. METHODS We exposed 184 healthy humans to progressive central hypovolemia using lower-body negative pressure to the point of hemodynamic decompensation (systolic blood pressure > 80 mm Hg with or without bradycardia). Initial models were developed using continuous noninvasive blood pressure waveform data. The resulting algorithm calculates a compensatory reserve index (CRI), where 1 represents supine normovolemia and 0 represents the circulatory volume at which hemodynamic decompensation occurs (i.e., "running on empty"). Values between 1 and 0 indicate the proportion of reserve remaining before hemodynamic decompensation-much like the fuel gauge of a car indicates the amount of fuel remaining in the tank. A CRI estimate is produced after the first 30 heart beats, followed by a new CRI estimate after each subsequent beat. RESULTS The CRI model with a 30-beat window has an absolute difference between actual and expected time to decompensation of 0.1, with a SD of 0.09. The model distinguishes individuals with low tolerance to reduced central blood volume (i.e., those most likely to develop early shock) from those with high tolerance and are able to estimate how near or far an individual may be from hemodynamic decompensation. CONCLUSION Machine modeling can quickly and accurately detect and trend central blood volume reduction in real time during the compensatory phase of hemorrhage as well as estimate when an individual is "running on empty" and will decompensate (CRI, 0), well in advance of meaningful changes in traditional vital signs.
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Hinojosa-Laborde C, Shade RE, Muniz GW, Bauer C, Goei KA, Pidcoke HF, Chung KK, Cap AP, Convertino VA. Validation of lower body negative pressure as an experimental model of hemorrhage. J Appl Physiol (1985) 2013; 116:406-15. [PMID: 24356525 DOI: 10.1152/japplphysiol.00640.2013] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Lower body negative pressure (LBNP), a model of hemorrhage (Hem), shifts blood to the legs and elicits central hypovolemia. This study compared responses to LBNP and actual Hem in sedated baboons. Arterial pressure, pulse pressure (PP), central venous pressure (CVP), heart rate, stroke volume (SV), and +dP/dt were measured. Hem steps were 6.25%, 12.5%, 18.75%, and 25% of total estimated blood volume. Shed blood was returned, and 4 wk after Hem, the same animals were subjected to four LBNP levels which elicited equivalent changes in PP and CVP observed during Hem. Blood gases, hematocrit (Hct), hemoglobin (Hb), plasma renin activity (PRA), vasopressin (AVP), epinephrine (EPI), and norepinephrine (NE) were measured at baseline and maximum Hem or LBNP. LBNP levels matched with 6.25%, 12.5%, 18.75%, and 25% hemorrhage were -22 ± 6, -41 ± 7, -54 ± 10, and -71 ± 7 mmHg, respectively (mean ± SD). Hemodynamic responses to Hem and LBNP were similar. SV decreased linearly such that 25% Hem and matching LBNP caused a 50% reduction in SV. Hem caused a decrease in Hct, Hb, and central venous oxygen saturation (ScvO2). In contrast, LBNP increased Hct and Hb, while ScvO2 remained unchanged. Hem caused greater elevations in AVP and NE than LBNP, while PRA, EPI, and other hematologic indexes did not differ between studies. These results indicate that while LBNP does not elicit the same effect on blood cell loss as Hem, LBNP mimics the integrative cardiovascular response to Hem, and validates the use of LBNP as an experimental model of central hypovolemia associated with Hem.
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Zöllei E, Bertalan V, Németh A, Csábi P, László I, Kaszaki J, Rudas L. Non-invasive detection of hypovolemia or fluid responsiveness in spontaneously breathing subjects. BMC Anesthesiol 2013; 13:40. [PMID: 24188480 PMCID: PMC3829671 DOI: 10.1186/1471-2253-13-40] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 11/01/2013] [Indexed: 02/06/2023] Open
Abstract
Background In the assessment of hypovolemia the value of functional hemodynamic monitoring during spontaneous breathing is debated. The aim of our study was to investigate in spontaneously breathing subjects the changes in hemodynamic parameters during graded central hypovolemia and to test whether slow patterned breathing improved the discriminative value of stroke volume (SV), pulse pressure (PP), and their variations (SVV, PPV). In addition, we tested the alterations in labial microcirculation. Methods 20 healthy volunteers participated in our study. Central hypovolemia was induced by lower body negative pressure (LBNP). Continuous signals of ECG, non-invasive blood pressure and central venous pressure were recorded. During baseline and each stage of LBNP the labial microcirculation was investigated by orthogonal polarization spectral imaging, 3 minute periods of patterned breathing at 6 and 15/min respiratory rate were performed, and central venous blood gas analysis was done. Data from baseline and those of different LBNP levels were compared by analysis of variance and those of different breathing rates by t-test. Finally, we performed ROC analysis to assess the discriminative values of SV, PP, SVV and PPV. Results Moderate central hypovolemia induced by LBNP caused significant, clinically relevant falls in PP (p < 0.05) and SV and central venous oxygen saturation (ScvO2) (p < 0.001). The proportion of perfused vessels (p < 0.001) and microvascular flow index decreased (p < 0.05). PPV increased (p < 0.001), however the magnitude of fluctuations was greater during slow patterned breathing (p < 0.001). SVV increased only during slow patterned breathing (p < 0.001). ROC analysis confirmed the best predictive value for SV (at 56 ml cut-off AUC 0.97, sensitivity 94%, specificity 95%). Slow patterned breathing improved the discriminative value of SVV (p = 0.0023). Conclusions Functional hemodynamic monitoring with slow patterned breathing to control spontaneous respiration may be worthy for further study in different populations for the assessment of hypovolemia and the prediction of volume responsiveness.
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Affiliation(s)
- Eva Zöllei
- Department of Anaesthesiology and Intensive Therapy, University of Szeged, Semmelweis u, 6, Szeged 6725, Hungary.
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Central Venous-to-Arterial CO2 Gap Is a Useful Parameter in Monitoring Hypovolemia-Caused Altered Oxygen Balance: Animal Study. Crit Care Res Pract 2013; 2013:583598. [PMID: 24069537 PMCID: PMC3773396 DOI: 10.1155/2013/583598] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2013] [Revised: 07/10/2013] [Accepted: 07/19/2013] [Indexed: 01/20/2023] Open
Abstract
Monitoring hypovolemia is an everyday challenge in critical care, with no consensus on the best indicator or what is the clinically relevant level of hypovolemia. The aim of this experiment was to determine how central venous oxygen saturation (ScvO2) and central venous-to-arterial carbon dioxide difference (CO2 gap) reflect hypovolemia-caused changes in the balance of oxygen delivery and consumption. Anesthetized, ventilated Vietnamese minipigs (n = 10) were given a bolus followed by a continuous infusion of furosemide. At baseline and then in five stages hemodynamic, microcirculatory measurements and blood gas analysis were performed. Oxygen extraction increased significantly, which was accompanied by a significant drop in ScvO2 and a significant increase in CO2 gap. There was a significant negative correlation between oxygen extraction and ScvO2 and significant positive correlation between oxygen extraction and CO2 gap. Taking ScvO2 < 73% and CO2 gap >6 mmHg values together to predict an oxygen extraction >30%, the positive predictive value is 100%; negative predicted value is 72%. Microcirculatory parameters, capillary perfusion rate and red blood cell velocity, decreased significantly over time. Similar changes were not observed in the sham group. Our data suggest that ScvO2 < 73% and CO2 gap >6 mmHg can be complementary tools in detecting hypovolemia-caused imbalance of oxygen extraction.
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Ellerby GEC, Smith CP, Zou F, Scott P, Soller BR. Validation of a spectroscopic sensor for the continuous, noninvasive measurement of muscle oxygen saturation and pH. Physiol Meas 2013; 34:859-71. [PMID: 23859848 DOI: 10.1088/0967-3334/34/8/859] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
New patient monitoring technologies can noninvasively and directly provide an assessment of the adequacy of tissue perfusion through the simultaneous determination of muscle oxygen saturation (SmO2) and muscle pH (pHm). Non-pulsatile near infrared spectroscopy is used to determine these microvascular parameters. Two separate studies were conducted using an isolated perfused swine limb preparation to widely vary venous blood oxygen saturation (SviO2) and pH (pHvi) to assess the accuracy of a noninvasive sensor with the capability to simultaneously measure both parameters. The isolated limb model is necessary to establish equilibrium between the venous output of the perfusion circuit and the venule measurement of the spectroscopic sensor. The average absolute difference between SmO2 and SviO2 determined over 50 conditions of SviO2 between 13% and 83% on 3 pig limbs was 3.8% and the coefficient of determination (R(2)) was 0.95. The average absolute difference between pHm and pHvi determined over 69 conditions of pHvi between pHvi 6.9 and pHvi 7.5 on 3 pig limbs was 0.045 pH units with an R(2) of 0.92. Measured accuracy was acceptable to support clinically relevant decision making for the assessment of impaired tissue perfusion and acidosis. Sensors were also evaluated on human subjects. There was no statistical difference in SmO2 by gender or location when multiple sensors were evaluated on the right and left calf, deltoid, and thigh of resting men and women (N = 33). SmO2 precision for subjects at rest was 5.6% over the six locations with four different sensors.
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Affiliation(s)
- G E C Ellerby
- Reflectance Medical Inc., 116 Flanders Road, Suite 1000, Westborough, MA 01581, USA
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Abstract
Survival after severe traumatic shock can be complicated by a number of pathophysiologic processes that ensue after the initial trauma. One of these is trauma-induced coagulopathy (TIC) whose onset may occur before initial fluid resuscitation. The pathogenesis of TIC has not yet been fully elaborated, but evolving evidence appears to link severe tissue hypoxia and damage to the endothelium as key factors, which evolve into measurable structural and biochemical changes of the endothelium resulting in a coagulopathic state. This paper will provide a general review of these linkages and identify knowledge gaps as well as suggest new approaches and areas of investigation, which may both limit the development of TIC as well as produce insights into its pathophysiology. A better understanding of these issues will be necessary in order to advance the practice of remote damage control resuscitation.
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Affiliation(s)
- Kevin R Ward
- Department of Emergency Medicine, University of Michigan, Michigan Center for Integrative Research in Critical Care, Ann Arbor, MI 48109, USA.
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Pacagnella RC, Souza JP, Durocher J, Perel P, Blum J, Winikoff B, Gülmezoglu AM. A systematic review of the relationship between blood loss and clinical signs. PLoS One 2013; 8:e57594. [PMID: 23483915 PMCID: PMC3590203 DOI: 10.1371/journal.pone.0057594] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 01/24/2013] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION This systematic review examines the relationship between blood loss and clinical signs and explores its use to trigger clinical interventions in the management of obstetric haemorrhage. METHODS A systematic review of the literature was carried out using a comprehensive search strategy to identify studies presenting data on the relationship of clinical signs & symptoms and blood loss. Methodological quality was assessed using the STROBE checklist and the general guidelines of MOOSE. RESULTS 30 studies were included and five were performed in women with pregnancy-related haemorrhage (other studies were carried in non-obstetric populations). Heart rate (HR), systolic blood pressure (SBP) and shock index were the parameters most frequently studied. An association between blood loss and HR changes was observed in 22 out of 24 studies, and between blood loss and SBP was observed in 17 out of 23 studies. An association was found in all papers reporting on the relationship of shock index and blood loss. Seven studies have used Receiver Operating Characteristic Curves to determine the accuracy of clinical signs in predicting blood loss. In those studies the AUC ranged from 0.56 to 0.74 for HR, from 0.56 to 0.79 for SBP and from 0.77 to 0.84 for shock index. In some studies, HR, SBP and shock index were associated with increased mortality. CONCLUSION We found a substantial variability in the relationship between blood loss and clinical signs, making it difficult to establish specific cut-off points for clinical signs that could be used as triggers for clinical interventions. However, the shock index can be an accurate indicator of compensatory changes in the cardiovascular system due to blood loss. Considering that most of the evidence included in this systematic review is derived from studies in non-obstetric populations, further research on the use of the shock index in obstetric populations is needed.
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Affiliation(s)
| | - João Paulo Souza
- Department of Reproductive Health and Research, World Health Organization, Geneva, Switzerland
| | - Jill Durocher
- Gynuity Health Projects, New York, New York, United States of America
| | - Pablo Perel
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jennifer Blum
- Gynuity Health Projects, New York, New York, United States of America
| | - Beverly Winikoff
- Gynuity Health Projects, New York, New York, United States of America
| | - Ahmet Metin Gülmezoglu
- Department of Reproductive Health and Research, World Health Organization, Geneva, Switzerland
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Danninger T, Stundner O, Ma Y, Bae JJ, Memtsoudis SG. The Impact of Hypotensive Epidural Anesthesia on Distal and Proximal Tissue Perfusion in Patients Undergoing Total Hip Arthroplasty. ACTA ACUST UNITED AC 2013; 4:366. [PMID: 24563810 PMCID: PMC3931466 DOI: 10.4172/2155-6148.1000366] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Little data exists to detail the effect of hypotensive epidural anesthesia on differential tissue oxygenation changes above and below the level of neuraxial blockade. This study was designed to investigate tissue oxygenation in a clinical setting, using non-invasive near-infrared spectroscopy.
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Affiliation(s)
- Thomas Danninger
- Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, NY, USA
| | - Ottokar Stundner
- Department of Anesthesiology, Perioperative Medicine and Intensive Care Medicine, Paracelsus Medical University, Salzburg, Austria
| | - Yan Ma
- Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, NY, USA
| | - James J Bae
- Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, NY, USA
| | - Stavros G Memtsoudis
- Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, NY, USA
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