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Berger D, Werner Moller P, Bachmann KF. Cardiopulmonary interactions-which monitoring tools to use? Front Physiol 2023; 14:1234915. [PMID: 37621761 PMCID: PMC10445648 DOI: 10.3389/fphys.2023.1234915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 07/18/2023] [Indexed: 08/26/2023] Open
Abstract
Heart-lung interactions occur due to the mechanical influence of intrathoracic pressure and lung volume changes on cardiac and circulatory function. These interactions manifest as respiratory fluctuations in venous, pulmonary, and arterial pressures, potentially affecting stroke volume. In the context of functional hemodynamic monitoring, pulse or stroke volume variation (pulse pressure variation or stroke volume variability) are commonly employed to assess volume or preload responsiveness. However, correct interpretation of these parameters requires a comprehensive understanding of the physiological factors that determine pulse pressure and stroke volume. These factors include pleural pressure, venous return, pulmonary vessel function, lung mechanics, gas exchange, and specific cardiac factors. A comprehensive knowledge of heart-lung physiology is vital to avoid clinical misjudgments, particularly in cases of right ventricular (RV) failure or diastolic dysfunction. Therefore, when selecting monitoring devices or technologies, these factors must be considered. Invasive arterial pressure measurements of variations in breath-to-breath pressure swings are commonly used to monitor heart-lung interactions. Echocardiography or pulmonary artery catheters are valuable tools for differentiating preload responsiveness from right ventricular failure, while changes in diastolic function should be assessed alongside alterations in airway or pleural pressure, which can be approximated by esophageal pressure. In complex clinical scenarios like ARDS, combined forms of shock or right heart failure, additional information on gas exchange and pulmonary mechanics aids in the interpretation of heart-lung interactions. This review aims to describe monitoring techniques that provide clinicians with an integrative understanding of a patient's condition, enabling accurate assessment and patient care.
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Affiliation(s)
- David Berger
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Per Werner Moller
- Department of Anaesthesia, SV Hospital Group, Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Kaspar F. Bachmann
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department of Anaesthesiology and Intensive Care, University of Tartu, Tartu, Estonia
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2
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Moller PW, Berger DC. Commentary: Feasibility to estimate mean systemic filling pressure with inspiratory holds at the bedside. Front Physiol 2023; 14:1135769. [PMID: 36950297 PMCID: PMC10025291 DOI: 10.3389/fphys.2023.1135769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 02/21/2023] [Indexed: 03/08/2023] Open
Affiliation(s)
- Per Werner Moller
- Department of Anaesthesia, SV Hospital Group, Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- *Correspondence: Per Werner Moller,
| | - David Christian Berger
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Yastrebov K, Brunel L, Paterson HS, Williams ZA, Burrows CS, Wise IK, Robinson BM, Bannon PG. Analogue Mean Systemic Filling Pressure: a New Volume Management Approach During Percutaneous Left Ventricular Assist Device Therapy. J Cardiovasc Transl Res 2022; 15:1455-1463. [PMID: 35543833 PMCID: PMC9722875 DOI: 10.1007/s12265-022-10265-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 04/20/2022] [Indexed: 12/16/2022]
Abstract
The absence of an accepted gold standard to estimate volume status is an obstacle for optimal management of left ventricular assist devices (LVADs). The applicability of the analogue mean systemic filling pressure (Pmsa) as a surrogate of the mean circulatory pressure to estimate volume status for patients with LVADs has not been investigated. Variability of flows generated by the Impella CP, a temporary LVAD, should have no physiological impact on fluid status. This translational interventional ovine study demonstrated that Pmsa did not change with variable circulatory flows induced by a continuous flow LVAD (the average dynamic increase in Pmsa of 0.20 ± 0.95 mmHg from zero to maximal Impella flow was not significant (p = 0.68)), confirming applicability of the human Pmsa equation for an ovine LVAD model. The study opens new directions for future translational and human investigations of fluid management using Pmsa for patients with temporary LVADs.
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Affiliation(s)
- Konstantin Yastrebov
- Department of Intensive Care, Prince of Wales Hospital, Sydney, NSW, 2031, Australia.
- The University of New South Wales, Sydney, NSW, 2052, Australia.
| | - Laurencie Brunel
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
| | - Hugh S Paterson
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
| | - Zoe A Williams
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
| | - Chris S Burrows
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
| | - Innes K Wise
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
| | - Benjamin M Robinson
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
- Royal Prince Alfred Hospital, Sydney, NSW, 2050, Australia
| | - Paul G Bannon
- Charles Perkins Research Facility, University of Sydney, Sydney, NSW, 2006, Australia
- Royal Prince Alfred Hospital, Sydney, NSW, 2050, Australia
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Moller PW, Parkin WG. Correct calculation of the mean systemic pressure analogue. Intensive Care Med 2022; 48:1679-1680. [PMID: 36006450 DOI: 10.1007/s00134-022-06862-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2022] [Indexed: 11/05/2022]
Affiliation(s)
- Per Werner Moller
- Department of Anesthesia, Surgery and Intensive Care, SV Hospital Group, Alingsås, Sweden. .,Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
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Chalkias A, Xenos M. Relationship of Effective Circulating Volume with Sublingual Red Blood Cell Velocity and Microvessel Pressure Difference: A Clinical Investigation and Computational Fluid Dynamics Modeling. J Clin Med 2022; 11:jcm11164885. [PMID: 36013124 PMCID: PMC9410298 DOI: 10.3390/jcm11164885] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 08/12/2022] [Accepted: 08/18/2022] [Indexed: 11/18/2022] Open
Abstract
The characteristics of physiologic hemodynamic coherence are not well-investigated. We examined the physiological relationship between circulating blood volume, sublingual microcirculatory perfusion, and tissue oxygenation in anesthetized individuals with steady-state physiology. We assessed the correlation of mean circulatory filling pressure analogue (Pmca) with sublingual microcirculatory perfusion and red blood cell (RBC) velocity using SDF+ imaging and a modified optical flow-based algorithm. We also reconstructed the 2D microvessels and applied computational fluid dynamics (CFD) to evaluate the correlation of Pmca and RBC velocity with the obtained pressure and velocity fields in microvessels from CFD (pressure difference, (Δp)). Twenty adults with a median age of 39.5 years (IQR 35.5−44.5) were included in the study. Sublingual velocity distributions were similar and followed a log-normal distribution. A constant Pmca value of 14 mmHg was observed in all individuals with sublingual RBC velocity 6−24 μm s−1, while a Pmca < 14 mmHg was observed in those with RBC velocity > 24 μm s−1. When Pmca ranged between 11 mmHg and 15 mmHg, Δp fluctuated between 0.02 Pa and 0.1 Pa. In conclusion, the intact regulatory mechanisms maintain a physiological coupling between systemic hemodynamics, sublingual microcirculatory perfusion, and tissue oxygenation when Pmca is 14 mmHg.
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Affiliation(s)
- Athanasios Chalkias
- Department of Anesthesiology, Faculty of Medicine, University of Thessaly, 41500 Larisa, Greece
- Outcomes Research Consortium, Cleveland, OH 44195, USA
- Committee on Shock, Hellenic Society of Cardiopulmonary Resuscitation, 10434 Athens, Greece
- Correspondence:
| | - Michalis Xenos
- Section of Applied and Computational Mathematics, Department of Mathematics, University of Ioannina, 45110 Ioannina, Greece
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Werner-Moller P, Heinisch PP, Hana A, Bachmann KF, Sondergaard S, Jakob SM, Takala J, Berger D. Experimental validation of a mean systemic pressure analog against zero-flow measurements in porcine VA-ECMO. J Appl Physiol (1985) 2022; 132:726-736. [PMID: 35085032 DOI: 10.1152/japplphysiol.00804.2021] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 01/24/2022] [Indexed: 11/22/2022] Open
Abstract
The mean systemic pressure analog (Pmsa), calculated from running hemodynamic data, estimates mean systemic filling pressure (MSFP). This post hoc study used data from a porcine veno-arterial extracorporeal membrane oxygenation (ECMO) model [n = 9; Sus scrofa domesticus; ES breed (Schweizer Edelschwein)] with eight experimental conditions; Euvolemia [a volume state where ECMO flow produced normal mixed venous saturation (SVO2) without vascular collapse]; three levels of increasing norepinephrine infusion (Vasoconstriction 1-3); status after stopping norepinephrine (Post Vasoconstriction); and three steps of volume expansion (10 mL/kg crystalloid bolus) (Volume Expansion 1-3). In each condition, Pmsa and a "reduced-pump-speed-Pmsa" (Pmsared) were calculated from baseline and briefly reduced pump speeds, respectively. We calculated agreement for absolute values (per condition) and changes (between consecutive conditions) of Pmsa and Pmsared, against MSFP at zero ECMO flow. Euvolemia venous return driving pressure was 5.1 ± 2.0 mmHg. Bland-Altman analysis for Pmsa vs. MSFP (all conditions; 72 data pairs) showed bias (confidence interval) 0.5 (0.1-0.9) mmHg; limits of agreement (LoA) -2.7 to 3.8 mmHg. Bias for ΔPmsa vs. ΔMSFP (63 data pairs): 0.2 (-0.2 to 0.6) mmHg, LoA -3.2 to 3.6 mmHg. Bias for Pmsared vs. MSFP (72 data pairs): 0.0 (-0.3 to -0.3) mmHg; LoA -2.3 to 2.4 mmHg. Bias for ΔPmsared vs. ΔMSFP (63 data pairs) was 0.2 (-0.1 to 0.4) mmHg; LoA -1.8 to 2.1 mmHg. In conclusion, during veno-arterial ECMO, under clinically relevant levels of vasoconstriction and volume expansion, Pmsa accurately estimated absolute and changing values of MSFP, with low between-method precision. The within-method precision of Pmsa was excellent, with a least significant change of 0.15 mmHg.NEW & NOTEWORTHY This is the first study ever to validate the mean systemic pressure analog (Pmsa) against the reference mean systemic filling pressure (MSFP) determined at full arterio-venous pressure equilibrium. Using a porcine ECMO model with clinically relevant levels of vasoconstriction and volume expansion, we showed that Pmsa accurately estimated absolute and changing values of MSFP, with a poor between-method precision. The within-method precision of Pmsa was excellent.
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Affiliation(s)
- Per Werner-Moller
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department of Anesthesia, Surgery and Intensive Care, SV Hospital Group, Alingsas, Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Paul Philipp Heinisch
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department of Congenital and Pediatric Heart Surgery, German Heart Center Munich, Technische Universität München, Munich, Germany
| | - Anisa Hana
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Department of Intensive Care Medicine, Laurentius Hospital, Roermond, The Netherlands
| | - Kaspar F Bachmann
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Centre for Intensive Care Medicine, Cantonal Hospital Lucerne, Lucerne, Switzerland
| | - Soren Sondergaard
- Department of Intensive Care and Neurointensive Stepdown Unit, Elective Surgery Centre, Silkeborg Regional Hospital, Silkeborg, Denmark
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Jukka Takala
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - David Berger
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Alvarado Sánchez JI, Caicedo Ruiz JD, Diaztagle Fernández JJ, Ospina Tascon GA, Monge Garcia MI, Ruiz Narvaez GA, Cruz Martínez LE. Changes of operative performance of pulse pressure variation as a predictor of fluid responsiveness in endotoxin shock. Sci Rep 2022. [DOI: https://doi.org/10.1038/s41598-022-06488-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AbstractSeveral limitations regarding pulse pressure variation (PPV) use have been reported. Our aim was to describe changes in the PPV operative performance as a predictor of fluid responsiveness during the development of a swine endotoxin shock model and to assess hemodynamic variables associated with PPV changes. A swine porcine endotoxin shock model was established (Escherichia Coli 055:B5 endotoxin) in 7 pigs, and 3 pigs were included in the control group. The endotoxin was infused until the mean arterial pressure (MAP) dropped below 50 mmHg (TH0); then, the model animal was reanimated with fluids and vasopressors. We performed fluid challenges every hour for 6 h. ROC curve analysis and a linear mixed model were performed. The area under the curve of PPV decreased from 0.95 (0.81–1.00) to 0.60 (0.17–1.00) at TH0. Its cutoff increased from 10.5 to 22.00% at TH0. PPV showed an inverse relationship with stroke volume, mean systemic filling pressure, MAP, and systemic vascular resistance (SVR) (p < 0.001, AIC = 111.85). The PPV operative performance as a predictor of fluid responsiveness decreased with the progression of shock. This could lead to an inverse association between PPV and the following variables: MAP and SVR.
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Alvarado Sánchez JI, Caicedo Ruiz JD, Diaztagle Fernández JJ, Ospina Tascon GA, Monge Garcia MI, Ruiz Narvaez GA, Cruz Martínez LE. Changes of operative performance of pulse pressure variation as a predictor of fluid responsiveness in endotoxin shock. Sci Rep 2022; 12:2590. [PMID: 35173214 PMCID: PMC8850593 DOI: 10.1038/s41598-022-06488-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Accepted: 01/31/2022] [Indexed: 11/09/2022] Open
Abstract
Several limitations regarding pulse pressure variation (PPV) use have been reported. Our aim was to describe changes in the PPV operative performance as a predictor of fluid responsiveness during the development of a swine endotoxin shock model and to assess hemodynamic variables associated with PPV changes. A swine porcine endotoxin shock model was established (Escherichia Coli 055:B5 endotoxin) in 7 pigs, and 3 pigs were included in the control group. The endotoxin was infused until the mean arterial pressure (MAP) dropped below 50 mmHg (TH0); then, the model animal was reanimated with fluids and vasopressors. We performed fluid challenges every hour for 6 h. ROC curve analysis and a linear mixed model were performed. The area under the curve of PPV decreased from 0.95 (0.81–1.00) to 0.60 (0.17–1.00) at TH0. Its cutoff increased from 10.5 to 22.00% at TH0. PPV showed an inverse relationship with stroke volume, mean systemic filling pressure, MAP, and systemic vascular resistance (SVR) (p < 0.001, AIC = 111.85). The PPV operative performance as a predictor of fluid responsiveness decreased with the progression of shock. This could lead to an inverse association between PPV and the following variables: MAP and SVR.
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Affiliation(s)
- Jorge Iván Alvarado Sánchez
- Department of Physiological Sciences, Faculty of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia. .,Department of Anaesthesiology, Centro Policlínico del Olaya, Bogotá, Colombia.
| | - Juan Daniel Caicedo Ruiz
- Department of Physiological Sciences, Faculty of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Juan Jose Diaztagle Fernández
- Department of Physiological Sciences, Faculty of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia.,Department of Internal Medicine, Hospital de San José, Fundación Universitaria de Ciencias de la Salud, Bogotá, Colombia
| | | | | | | | - Luis Eduardo Cruz Martínez
- Department of Physiological Sciences, Faculty of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia.,Department of Internal Medicine, Hospital de San José, Fundación Universitaria de Ciencias de la Salud, Bogotá, Colombia
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Wijnberge M, Jansen JRC, Pinsky MR, Klanderman RB, Terwindt LE, Bosboom JJ, Lemmers N, Vlaar AP, Veelo DP, Geerts BF. Feasibility to estimate mean systemic filling pressure with inspiratory holds at the bedside. Front Physiol 2022; 13:1041730. [PMID: 36523553 PMCID: PMC9745184 DOI: 10.3389/fphys.2022.1041730] [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: 09/11/2022] [Accepted: 10/25/2022] [Indexed: 11/30/2022] Open
Abstract
Background: A decade ago, it became possible to derive mean systemic filling pressure (MSFP) at the bedside using the inspiratory hold maneuver. MSFP has the potential to help guide hemodynamic care, but the estimation is not yet implemented in common clinical practice. In this study, we assessed the ability of MSFP, vascular compliance (Csys), and stressed volume (Vs) to track fluid boluses. Second, we assessed the feasibility of implementation of MSFP in the intensive care unit (ICU). Exploratory, a potential difference in MSFP response between colloids and crystalloids was assessed. Methods: This was a prospective cohort study in adult patients admitted to the ICU after cardiac surgery. The MSFP was determined using 3-4 inspiratory holds with incremental pressures (maximum 35 cm H2O) to construct a venous return curve. Two fluid boluses were administered: 100 and 500 ml, enabling to calculate Vs and Csys. Patients were randomized to crystalloid or colloid fluid administration. Trained ICU consultants acted as study supervisors, and protocol deviations were recorded. Results: A total of 20 patients completed the trial. MSFP was able to track the 500 ml bolus (p < 0.001). In 16 patients (80%), Vs and Csys could be determined. Vs had a median of 2029 ml (IQR 1605-3164), and Csys had a median of 73 ml mmHg-1 (IQR 56-133). A difference in response between crystalloids and colloids was present for the 100 ml fluid bolus (p = 0.019) and in a post hoc analysis, also for the 500 ml bolus (p = 0.010). Conclusion: MSFP can be measured at the bedside and provides insights into the hemodynamic status of a patient that are currently missing. The clinical feasibility of Vs and Csys was judged ambiguously based on the lack of required hemodynamic stability. Future studies should address the clinical obstacles found in this study, and less-invasive alternatives to determine MSFP should be further explored. Clinical Trial Registration: ClinicalTrials.gov Identifier NCT03139929.
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Affiliation(s)
- Marije Wijnberge
- Amsterdam UMC Location Academic Medical Center, Department of Anesthesiology, Amsterdam, Netherlands
- Amsterdam UMC Location Academic Medical Center, Department of Intensive Care Medicine, Amsterdam, Netherlands
- *Correspondence: Marije Wijnberge, Alexander P. Vlaar,
| | - Jos R. C. Jansen
- Leiden University Medical Center, Department of Intensive Care Medicine, Leiden, Netherlands
| | - Michael R. Pinsky
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Robert B. Klanderman
- Amsterdam UMC Location Academic Medical Center, Department of Anesthesiology, Amsterdam, Netherlands
- Amsterdam UMC Location Academic Medical Center, Department of Intensive Care Medicine, Amsterdam, Netherlands
| | - Lotte E. Terwindt
- Amsterdam UMC Location Academic Medical Center, Department of Anesthesiology, Amsterdam, Netherlands
| | - Joachim J. Bosboom
- Amsterdam UMC Location Academic Medical Center, Department of Anesthesiology, Amsterdam, Netherlands
- Amsterdam UMC Location Academic Medical Center, Department of Intensive Care Medicine, Amsterdam, Netherlands
| | - Nikki Lemmers
- Amsterdam UMC Location Academic Medical Center, Department of Anesthesiology, Amsterdam, Netherlands
| | - Alexander P. Vlaar
- Amsterdam UMC Location Academic Medical Center, Department of Intensive Care Medicine, Amsterdam, Netherlands
- *Correspondence: Marije Wijnberge, Alexander P. Vlaar,
| | - Denise P. Veelo
- Amsterdam UMC Location Academic Medical Center, Department of Anesthesiology, Amsterdam, Netherlands
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van der Ster BJP, Kim YS, Westerhof BE, van Lieshout JJ. Central Hypovolemia Detection During Environmental Stress-A Role for Artificial Intelligence? Front Physiol 2021; 12:784413. [PMID: 34975538 PMCID: PMC8715014 DOI: 10.3389/fphys.2021.784413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/18/2021] [Indexed: 11/19/2022] Open
Abstract
The first step to exercise is preceded by the required assumption of the upright body position, which itself involves physical activity. The gravitational displacement of blood from the chest to the lower parts of the body elicits a fall in central blood volume (CBV), which corresponds to the fraction of thoracic blood volume directly available to the left ventricle. The reduction in CBV and stroke volume (SV) in response to postural stress, post-exercise, or to blood loss results in reduced left ventricular filling, which may manifest as orthostatic intolerance. When termination of exercise removes the leg muscle pump function, CBV is no longer maintained. The resulting imbalance between a reduced cardiac output (CO) and a still enhanced peripheral vascular conductance may provoke post-exercise hypotension (PEH). Instruments that quantify CBV are not readily available and to express which magnitude of the CBV in a healthy subject should remains difficult. In the physiological laboratory, the CBV can be modified by making use of postural stressors, such as lower body "negative" or sub-atmospheric pressure (LBNP) or passive head-up tilt (HUT), while quantifying relevant biomedical parameters of blood flow and oxygenation. Several approaches, such as wearable sensors and advanced machine-learning techniques, have been followed in an attempt to improve methodologies for better prediction of outcomes and to guide treatment in civil patients and on the battlefield. In the recent decade, efforts have been made to develop algorithms and apply artificial intelligence (AI) in the field of hemodynamic monitoring. Advances in quantifying and monitoring CBV during environmental stress from exercise to hemorrhage and understanding the analogy between postural stress and central hypovolemia during anesthesia offer great relevance for healthy subjects and clinical populations.
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Affiliation(s)
- Björn J. P. van der Ster
- Department of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Anesthesiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Yu-Sok Kim
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Internal Medicine, Medisch Centrum Leeuwarden, Leeuwarden, Netherlands
| | - Berend E. Westerhof
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Department of Pulmonary Medicine, Amsterdam University Medical Center, Vrije Universiteit Amsterdam, Amsterdam Cardiovascular Sciences, Amsterdam, Netherlands
| | - Johannes J. van Lieshout
- Department of Internal Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Laboratory for Clinical Cardiovascular Physiology, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
- Medical Research Council Versus Arthritis Centre for Musculoskeletal Ageing Research, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, The Medical School, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, United Kingdom
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Valeanu L, Bubenek-Turconi SI, Ginghina C, Balan C. Hemodynamic Monitoring in Sepsis-A Conceptual Framework of Macro- and Microcirculatory Alterations. Diagnostics (Basel) 2021; 11:1559. [PMID: 34573901 PMCID: PMC8469937 DOI: 10.3390/diagnostics11091559] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/22/2021] [Accepted: 08/26/2021] [Indexed: 12/29/2022] Open
Abstract
Circulatory failure in sepsis is common and places a considerable burden on healthcare systems. It is associated with an increased likelihood of mortality, and timely recognition is a prerequisite to ensure optimum results. While there is consensus that aggressive source control, adequate antimicrobial therapy and hemodynamic management constitute crucial determinants of outcome, discussion remains about the best way to achieve each of these core principles. Sound cardiovascular support rests on tailored fluid resuscitation and vasopressor therapy. To this end, an overarching framework to improve cardiovascular dynamics has been a recurring theme in modern critical care. The object of this review is to examine the nature of one such framework that acknowledges the growing importance of adaptive hemodynamic support combining macro- and microhemodynamic variables to produce adequate tissue perfusion.
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Affiliation(s)
- Liana Valeanu
- 1st Department of Cardiovascular Anesthesiology and Intensive Care, “Prof. C. C. Iliescu” Emergency Institute for Cardiovascular Diseases, 258 Fundeni Road, 022328 Bucharest, Romania; (L.V.); (S.-I.B.-T.)
- Department of Anesthesiology and Intensive Care, University of Medicine and Pharmacy “Carol Davila”, 8 Eroii Sanitari Blvd, 050474 Bucharest, Romania
| | - Serban-Ion Bubenek-Turconi
- 1st Department of Cardiovascular Anesthesiology and Intensive Care, “Prof. C. C. Iliescu” Emergency Institute for Cardiovascular Diseases, 258 Fundeni Road, 022328 Bucharest, Romania; (L.V.); (S.-I.B.-T.)
- Department of Anesthesiology and Intensive Care, University of Medicine and Pharmacy “Carol Davila”, 8 Eroii Sanitari Blvd, 050474 Bucharest, Romania
| | - Carmen Ginghina
- 3rd Department of Cardiology, “Prof. C. C. Iliescu” Emergency Institute for Cardiovascular Diseases, 258 Fundeni Road, 022328 Bucharest, Romania;
- Department of Cardiology, University of Medicine and Pharmacy “Carol Davila”, 8 Eroii Sanitari Blvd, 050474 Bucharest, Romania
| | - Cosmin Balan
- 1st Department of Cardiovascular Anesthesiology and Intensive Care, “Prof. C. C. Iliescu” Emergency Institute for Cardiovascular Diseases, 258 Fundeni Road, 022328 Bucharest, Romania; (L.V.); (S.-I.B.-T.)
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He H, Yuan S, Long Y, Liu D, Zhou X, Ince C. Effect of norepinephrine challenge on cardiovascular determinants assessed using a mathematical model in septic shock: a physiological study. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:561. [PMID: 33987259 PMCID: PMC8105783 DOI: 10.21037/atm-20-6686] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 01/12/2021] [Indexed: 11/06/2022]
Abstract
BACKGROUND The present study investigated the cardiovascular determinants of cardiac output (CO), mean systemic filling pressure analogue (Pmsa) derived by Geoffrey Parkin, efficiency of heart (Eh) and related parameters to a norepinephrine (NE) challenge [an increase of 10 mmHg mean arterial pressure (MAP) by NE] in septic shock patients using of a mathematical model. METHODS Twenty-seven septic shock patients with pulse index continuous cardiac output (PiCCO) monitoring were enrolled. These patients required NE to maintain an individualized MAP for organ perfusion after early fluid resuscitation based on their clinical condition. NE was decreased to obtain a decrease of 10 mmHg from base MAP (MAP-10mmHg), and the NE doses were adjusted to return MAP to baseline (MAPbase) and produce an increase of 10 mmHg from MAPbase (MAP+10mmHg). Two NE challenge episodes were analyzed for each patient: from MAP-10mmHg to MAPbase and from MAPbase to MAP+10mmHg. The Pmsa, pressure gradient for venous return (PGvr), and Eh (PGvr relative to Pmsa) were estimated using a mathematical model for the three MAP levels (MAP-10mmHg, MAPbase and MAP+10mmHg). RESULTS A total of 54 episodes of NE challenges were obtained in 27 patients. Significant and consistent increases were observed in the central venous pressure (CVP), Pmsa, and PGvr in response during the NE titration. ΔCO negatively and significantly correlated with ΔCVP (r=-0.722, P<0.0001), ΔPmsa (r=-0.549, P<0.0001), ΔResistance of venous return (Rvr) (r=-0.597, P<0.0001), and ΔResistance of systemic vascular beds (Rsys) (r=-0.597, P<0.0001). Episodes of decreasing CO/Eh were associated with a higher ΔCVP than the CO/Eh-increasing episodes. The area under the curve (AUC) of ΔCVP to predict decreased CO by the incremental NE was 0.86, and the AUC of ΔCVP to predict decreased Eh was 0.94. A cutoff of ΔCVP >1.5 mmHg for detecting decreased CO resulted in a sensitivity of 75% and a specificity of 94.1%. A cutoff of ΔCVP >1.5 mmHg for detecting decreased Eh resulted in a sensitivity of 64.3% and a specificity of 100%. CONCLUSIONS There were a highly divergent response in Eh and CO to afterload challenge episodes of an NE-induced 10mmHg increase in MAP. An increase in CVP may be an early alarm to identify the reduction in CO/Eh during an NE-induced increase of MAP.
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Affiliation(s)
- Huaiwu He
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing, China
| | - Siyi Yuan
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing, China
| | - Yun Long
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing, China
| | - Dawei Liu
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing, China
| | - Xiang Zhou
- Department of Critical Care Medicine, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing, China
| | - Can Ince
- Department of Intensive Care, Erasmus MC University Hospital, Rotterdam, The Netherlands
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13
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Meijs LPB, van Houte J, Conjaerts BCM, Bindels AJGH, Bouwman A, Houterman S, Bakker J. Clinical validation of a computerized algorithm to determine mean systemic filling pressure. J Clin Monit Comput 2021; 36:191-198. [PMID: 33791920 PMCID: PMC8011774 DOI: 10.1007/s10877-020-00636-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 12/14/2020] [Indexed: 11/29/2022]
Abstract
Mean systemic filling pressure (Pms) is a promising parameter in determining intravascular fluid status. Pms derived from venous return curves during inspiratory holds with incremental airway pressures (Pms-Insp) estimates Pms reliably but is labor-intensive. A computerized algorithm to calculate Pms (Pmsa) at the bedside has been proposed. In previous studies Pmsa and Pms-Insp correlated well but with considerable bias. This observational study was performed to validate Pmsa with Pms-Insp in cardiac surgery patients. Cardiac output, right atrial pressure and mean arterial pressure were prospectively recorded to calculate Pmsa using a bedside monitor. Pms-Insp was calculated offline after performing inspiratory holds. Intraclass-correlation coefficient (ICC) and assessment of agreement were used to compare Pmsa with Pms-Insp. Bias, coefficient of variance (COV), precision and limits of agreement (LOA) were calculated. Proportional bias was assessed with linear regression. A high degree of inter-method reliability was found between Pmsa and Pms-Insp (ICC 0.89; 95%CI 0.72–0.96, p = 0.01) in 18 patients. Pmsa and Pms-Insp differed not significantly (11.9 mmHg, IQR 9.8–13.4 vs. 12.7 mmHg, IQR 10.5–14.4, p = 0.38). Bias was −0.502 ± 1.90 mmHg (p = 0.277). COV was 4% with LOA –4.22 − 3.22 mmHg without proportional bias. Conversion coefficient Pmsa ➔ Pms-Insp was 0.94. This assessment of agreement demonstrates that the measures Pms-Insp and the computerized Pmsa-algorithm are interchangeable (bias −0.502 ± 1.90 mmHg with conversion coefficient 0.94). The choice of Pmsa is straightforward, it is non-interventional and available continuously at the bedside in contrast to Pms-Insp which is interventional and calculated off-line. Further studies should be performed to determine the place of Pmsa in the circulatory management of critically ill patients. (www.clinicaltrials.gov; TRN NCT04202432, release date 16-12-2019; retrospectively registered). Clinical Trial Registrationwww.ClinicalTrials.gov, TRN: NCT04202432, initial release date 16-12-2019 (retrospectively registered).
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Affiliation(s)
- Loek P B Meijs
- Department of Intensive Care, Catharina Hospital, Eindhoven, The Netherlands. .,Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands.
| | - Joris van Houte
- Department of Intensive Care, Catharina Hospital, Eindhoven, The Netherlands.,Department of Anesthesiology, Catharina Hospital, Eindhoven, The Netherlands
| | - Bente C M Conjaerts
- Department of Anesthesiology, Maastricht University Medical Center, Maastricht, The Netherlands
| | | | - Arthur Bouwman
- Department of Anesthesiology, Catharina Hospital, Eindhoven, The Netherlands
| | - Saskia Houterman
- Department of Research and Education, Catharina Hospital, Eindhoven, The Netherlands
| | - Jan Bakker
- Department of Intensive Care, Erasmus MC University Medical Centre, Rotterdam, The Netherlands.,Division of Pulmonary, Allergy, and Critical Care Medicine, Columbia University Medical Center, New York, NY, USA.,Department of Pulmonary and Critical Care, New York University, New York, NY, USA.,Department of Intensive Care, Pontificia Universidad Católica de Chile, Santiago, Chile
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14
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Vasopressor Responsiveness Beyond Arterial Pressure: A Conceptual Systematic Review Using Venous Return Physiology. Shock 2021; 56:352-359. [PMID: 33756500 DOI: 10.1097/shk.0000000000001762] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
ABSTRACT We performed a systematic review to investigate the effects of vasopressor-induced hemodynamic changes in adults with shock. We applied a physiological approach using the interacting domains of intravascular volume, heart pump performance, and vascular resistance to structure the interpretation of responses to vasopressors. We hypothesized that incorporating changes in determinants of cardiac output and vascular resistance better reflect the vasopressor responsiveness beyond mean arterial pressure alone.We identified 28 studies including 678 subjects in Pubmed, EMBASE, and CENTRAL databases.All studies demonstrated significant increases in mean arterial pressure (MAP) and systemic vascular resistance during vasopressor infusion. The calculated mean systemic filling pressure analogue increased (16 ± 3.3 mmHg to 18 ± 3.4 mmHg; P = 0.02) by vasopressors with variable effects on central venous pressure and the pump efficiency of the heart leading to heterogenous changes in cardiac output. Changes in the pressure gradient for venous return and cardiac output, scaled by the change in MAP, were positively correlated (r2 = 0.88, P < 0.001). Changes in the mean systemic filling pressure analogue and heart pump efficiency were negatively correlated (r2 = 0.57, P < 0.001) while no correlation was found between changes in MAP and heart pump efficiency.We conclude that hemodynamic changes induced by vasopressor therapy are inadequately represented by the change in MAP alone despite its common use as a clinical endpoint. The more comprehensive analysis applied in this review illustrates how vasopressor administration may be optimized.
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15
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van Loon LM, van der Hoeven H, Veltink PH, Lemson J. The inspiration hold maneuver is a reliable method to assess mean systemic filling pressure but its clinical value remains unclear. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:1390. [PMID: 33313135 PMCID: PMC7723632 DOI: 10.21037/atm-20-3540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background The upstream pressure for venous return (VR) is considered to be a combined conceptual blood pressure of the systemic vessels: the mean systemic filling pressure (MSFP). The relevance of estimating the MSFP during dynamic changes of the circulation at the bedside is controversial. Herein, we studied the effect of high ventilatory pressures on the relationship between VR and central venous pressure (CVP). Methods In 9 healthy pigs under anaesthesia and mechanically ventilated, MSFP was estimated from extrapolated VR versus CVP relationships during inspiratory hold maneuvers (IHMs) with different levels of ventilatory pressure (Pvent). MSFP was measure 3 times per animal during euvolemia and hypovolemia. Hypovolemia was induced by bleeding with 10 mL/kg. The estimated MSFP values were compared to the blood pressure recording after induced ventricle fibrillation (i.e., mean circulatory filling pressure). Results Our results revealed a strong linear correlation between VR and CVP [R2 of 0.92 (range, 0.67–0.99)], during IHMs with different levels of Pvent. Volume status significantly alters the resulting MSFP, 20±1 and 16±2 mmHg for euvolemia and hypovolemia respectively. This estimation of the MSFP was strongly correlated—but not interchangeable—to the blood pressure recording after induced ventricle fibrillation (R2=0.8 and P=0.045). Conclusions In conclusion, we showed a strong linear correlation between VR and CVP—when applying IHMs with high levels of Pvent—however the clinical applicability of this method to guide volume therapy in its current form is improbable.
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Affiliation(s)
- Lex M van Loon
- Cardiovascular and Respiratory Physiology Group, Faculty of Science and Technology, Technical Medical Centre, University of Twente, Enschede, The Netherlands.,Department of Intensive Care Medicine, Radboud university medical center, Nijmegen, The Netherlands
| | - Hans van der Hoeven
- Department of Intensive Care Medicine, Radboud university medical center, Nijmegen, The Netherlands.,Radboud Center for Infectious Diseases, Nijmegen, The Netherlands
| | - Peter H Veltink
- Biomedical Signals and Systems, Faculty of Electrical Engineering, Mathematics and Computer Science, Technical Medical Centre, University of Twente, Enschede, The Netherlands
| | - Joris Lemson
- Department of Intensive Care Medicine, Radboud university medical center, Nijmegen, The Netherlands
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16
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Berger D, Hobi J, Möller PW, Haenggi M, Takala J, Jakob SM. Right ventricular stroke volume assessed by pulmonary artery pulse contour analysis. Intensive Care Med Exp 2020; 8:58. [PMID: 33026562 PMCID: PMC7539259 DOI: 10.1186/s40635-020-00347-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 09/29/2020] [Indexed: 02/06/2023] Open
Abstract
Background Stroke volume measurement should provide estimates of acute treatment responses. The current pulse contour method estimates left ventricle stroke volume. Heart-lung interactions change right ventricular stroke volume acutely. We investigated the accuracy, precision, and trending abilities of four calibrated stroke volume estimates based on pulmonary artery pulse contour analysis. Results Stroke volume was measured in 9 pigs with a pulmonary artery ultrasound flow probe at 5 and 10 cmH2O of PEEP and three volume states (baseline, bleeding, and retransfusion) and compared against stroke volume estimates of four calibrated pulmonary pulse contour algorithms based on pulse pressure or pressure integration. Bland-Altman comparison with correction for multiple measurements and trend analysis were performed. Heart rate and stroke volumes were 104 ± 24 bpm and 30 ± 12 mL, respectively. The stroke volume estimates had a minimal bias: − 0.11 mL (95% CI − 0.55 to 0.33) to 0.32 mL (95% CI − 0.06 to 0.70). The limits of agreement were − 8.0 to 7.8 mL for calibrated pulse pressure to − 10.4 to 11.5 mL for time corrected pressure integration, resulting in a percentage error of 36 to 37%. The calibrated pulse pressure method performed best. Changes in stroke volume were trended very well (concordance rates 73–100%, r2 0.26 to 0.987, for pulse pressure methods and 71–100%, r2 0.236 to 0.977, for integration methods). Conclusions Pulmonary artery pulse contour methods reliably detect acute changes in stroke volume with good accuracy and moderate precision and accurately trend short-term changes in cardiac output over time.
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Affiliation(s)
- David Berger
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, CH-3010, Bern, Switzerland.
| | - Jan Hobi
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, CH-3010, Bern, Switzerland
| | - Per W Möller
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, CH-3010, Bern, Switzerland.,Department of Anaesthesiology, Alingsas Hospital, Alingsås, Sweden
| | - Matthias Haenggi
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, CH-3010, Bern, Switzerland
| | - Jukka Takala
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, CH-3010, Bern, Switzerland
| | - Stephan M Jakob
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, CH-3010, Bern, Switzerland
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17
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Yastrebov K, Brunel L, Williams ZA, Paterson HS, Yata M, Burrows CS, Wise IK, Robinson BM, Bannon PG. Comparison of dynamic changes in stressed intravascular volume, mean systemic filling pressure and cardiovascular compliance: Pilot investigation and study protocol. PLoS One 2020; 15:e0238045. [PMID: 32857803 PMCID: PMC7454998 DOI: 10.1371/journal.pone.0238045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 08/07/2020] [Indexed: 11/18/2022] Open
Abstract
The mean systemic filling pressure (MSFP) represents an interaction between intravascular volume and global cardiovascular compliance (GCC). Intravascular volume expansion using fluid resuscitation is the most frequent intervention in intensive care and emergency medicine for patients in shock and with haemodynamic compromise. The relationship between dynamic changes in MSFP, GCC and left ventricular compliance is unknown. We conducted prospective interventional pilot study following euthanasia in post cardiotomy adult sheep, investigating the relationships between changes in MSFP induced by rapid intravascular filling with fluids, global cardiovascular compliance and left ventricular compliance. This pilot investigation suggested a robust correlation between a gradual increase in the intravascular stressed volume from 0 to 40 ml/kg and the MSFP r = 0.708 95% CI 0.435 to 0.862, making feasible future prospective interventional studies. Based on the statistical modelling from the pilot results, we expect to identify a strong correlation of 0.71 ± 0.1 (95% CI) between the MSFP and the stressed intravascular volume in a future study.
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Affiliation(s)
- Konstantin Yastrebov
- Department of Intensive Care, Prince of Wales Hospital, Sydney, Australia
- The University of New South Wales, Sydney, Australia
| | | | | | | | - Mariko Yata
- Royal Prince Alfred Hospital, Sydney, Australia
| | | | - Innes K. Wise
- DVC Research, University of Sydney, Sydney, Australia
| | - Benjamin M. Robinson
- DVC Research, University of Sydney, Sydney, Australia
- Royal Prince Alfred Hospital, Sydney, Australia
| | - Paul G. Bannon
- DVC Research, University of Sydney, Sydney, Australia
- Royal Prince Alfred Hospital, Sydney, Australia
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18
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Affiliation(s)
- G L Brengelmann
- Department of Physiology and Biophysics, University of Washington , Seattle, Washington
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19
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Brengelmann GL. Venous return and the physical connection between distribution of segmental pressures and volumes. Am J Physiol Heart Circ Physiol 2019; 317:H939-H953. [PMID: 31518160 DOI: 10.1152/ajpheart.00381.2019] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
More than sixty years ago, Guyton and coworkers related their observations of venous return to a mathematical model. Showing steady-state flow (F) as proportional to the difference between mean systemic pressure (Pms) and right atrial pressure (Pra), the model fit their data. The parameter defined by the ratio (Pms - Pra)/F, first called an "impedance," came to be called the "resistance to venous return." The interpretation that Pra opposes Pms and that, to increase output, the heart must act to reduce back pressure at the right atrium was widely accepted. Today, the perceived importance of Pms is evident in the efforts to find reliable ways to estimate it in patients. This article reviews concepts about venous return, criticizing some as inconsistent with elementary physical principles. After review of basic background topics-the steady-state vascular compliance; stressed versus unstressed volume-simulations from a multicompartment model based on data and definitions from Rothe's classical review of the venous system are presented. They illustrate the obligatory connection between flow-dependent compartment pressures and the distribution of volume among vascular compartments. An appendix shows that the pressure profile can be expressed either as decrements relative to arterial pressure or as increments relative to Pra (the option taken in the original model). Conclusion: The (Pms - Pra)/F formulation was never about Pms physically driving venous return; it was about how intravascular volume distributes among compliant compartments in accordance with their flow-dependent distending pressures, arbitrarily expressed relative to Pra rather than arterial pressure.
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Affiliation(s)
- George L Brengelmann
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
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20
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Affiliation(s)
- Rafael Dalmau
- Department of Anesthesiology, Hospital Español de Rosario, Rosario, Argentina
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