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Ciaraglia AV, Convertino VA, Johnson MC, DeRosa M, Nicholson SE, Eastridge BJ. Compensatory reserve and pulse character: Enhanced potential to predict urgency for transfusion and other life-saving interventions after traumatic injury. Transfusion 2022; 62 Suppl 1:S130-S138. [PMID: 35748680 DOI: 10.1111/trf.16972] [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: 01/12/2022] [Revised: 02/15/2022] [Accepted: 02/15/2022] [Indexed: 11/28/2022]
Abstract
BACKGROUND Field triage of trauma patients requires timely assessment of physiologic status to determine resuscitative needs. Vital signs and rudimentary assessments such as pulse character (PC) are used by first responders to guide decision making. The compensatory reserve measurement (CRM) has demonstrated utility as an easily interpretable method for assessing patient status. We hypothesized that the ability to identify injured patients requiring transfusion and other life-saving interventions (LSI) using a measurement of pulse character could be enhanced by the addition of the CRM. METHODS We performed a prospective observational study on 300 trauma patients admitted to a level I trauma center. CRM was recorded continuously after device placement on arrival. Patient demographics, field and trauma resuscitation unit vital signs, therapeutic interventions, and outcomes were collected. A field SBP <100 mmHg was utilized as a surrogate for abnormal PC as previously validated. A patient with a CRM threshold value of <60% was considered clinically compromised with a risk of onset of decompensated shock. Data were analyzed to assess the capacity of CRM and pulse character separately or in combination to predict LSI defined as need for transfusion, intubation, tube thoracostomy, or operative/ angiographic hemorrhage control. RESULTS An improvement in the predictive capability for LSI, transfusion, or a composite outcome was demonstrated by the combination of CRM and PC compared to either measure alone. CONCLUSIONS Combining PC assessment with CRM has the potential to enhance the recognition of injured patients requiring life-saving intervention thus improving sensitivity of decision support for prehospital providers.
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Affiliation(s)
- Angelo V Ciaraglia
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
| | - 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
| | - Michael C Johnson
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
| | - Mark DeRosa
- 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
| | - Brian J Eastridge
- Division of Trauma and Emergency Surgery, UT Health San Antonio, San Antonio, Texas, USA
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Measurement of Intravascular Volume Status in Infants Undergoing Cranial Vault Reconstruction for Craniosynostosis. SURGERY IN PRACTICE AND SCIENCE 2022. [DOI: 10.1016/j.sipas.2022.100067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Prehospital Hemorrhage Assessment Criteria: A Concise Review. J Trauma Nurs 2021; 28:332-338. [PMID: 34491952 DOI: 10.1097/jtn.0000000000000608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Early assessment of the clinical status of trauma patients is crucial for guiding the treatment strategy, and it requires a rapid and systematic approach. The aim of this report is to critically review the assessment parameters currently used in the prehospital setting to quantify blood loss in trauma. DATA SOURCES Studies regarding hemorrhagic shock in trauma were pooled from PubMed, EMBASE, and Cochrane databases using key words such as "hemorrhagic shock," "vital signs evaluation," "trauma," "blood loss," and "emergency medical service," alone or combined. STUDY SELECTION Articles published since 2009 in English and Italian were considered eligible if containing data on assessment parameters in blood loss in adults. DATA EXTRACTION Sixteen articles matching the inclusion criteria were considered in our study. DATA SYNTHESIS Current prehospital assessment measures lack precise correlation with blood loss. CONCLUSIONS Traditional assessment parameters such as heart rate, systolic blood pressure, shock index, and Glasgow Coma Scale score often lag in providing accurate blood loss assessment. The current literature supports the need for a noninvasive, continuously monitored assessment parameter to identify early shock in the prehospital setting.
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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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Abstract
Hemorrhagic shock can be mitigated by timely and accurate resuscitation designed to restore adequate delivery of oxygen (DO2) by increasing cardiac output (CO). However, standard care of using systolic blood pressure (SBP) as a guide for resuscitation may be ineffective and can potentially be associated with increased morbidity. We have developed a novel vital sign called the compensatory reserve measurement (CRM) generated from analysis of arterial pulse waveform feature changes that has been validated in experimental and clinical models of hemorrhage. We tested the hypothesis that thresholds of DO2 could be accurately defined by CRM, a noninvasive clinical tool, while avoiding over-resuscitation during whole blood resuscitation following a 25% hemorrhage in nonhuman primates. To accomplish this, adult male baboons (n = 12) were exposed to a progressive controlled hemorrhage while sedated that resulted in an average (± SEM) maximal reduction of 508 ± 18 mL of their estimated circulating blood volume of 2,130 ± 60 mL based on body weight. CRM increased from 6 ± 0.01% at the end of hemorrhage to 70 ± 0.02% at the end of resuscitation. By linear regression, CRM values of 6% (end of hemorrhage), 30%, 60%, and 70% (end of resuscitation) corresponded to calculated DO2 values of 5.9 ± 0.34, 7.5 ± 0.87, 9.3 ± 0.76, and 11.6 ± 1.3 mL O2·kg·min during resuscitation. As such, return of CRM to ∼65% during resuscitation required only ∼400 mL to restore SBP to 128 ± 6 mmHg, whereas total blood volume replacement resulted in over-resuscitation as indicated by a SBP of 140 ± 7 mmHg compared with an average baseline value of 125 ± 5 mmHg. Consistent with our hypothesis, thresholds of calculated DO2 were associated with specific CRM values. A target resuscitation CRM value of ∼65% minimized the requirement for whole blood while avoiding over-resuscitation. Furthermore, 0% CRM provided a noninvasive metric for determining critical DO2 at approximately 5.3 mL O2·kg·min.
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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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Chen Y, Yoon JH, Pinsky MR, Ma T, Clermont G. Development of hemorrhage identification model using non-invasive vital signs. Physiol Meas 2020; 41:055010. [PMID: 32325439 PMCID: PMC7894612 DOI: 10.1088/1361-6579/ab8cb2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE Early detection and timely management of bleeding is critical as failure to recognize physiologically significant bleeding is associated with significant morbidity and mortality. Many such instances are detected late, even in highly monitored environments, contributing to delay in recognition and intervention. We propose a non-invasive early identification model to detect bleeding events using continuously collected photoplethysmography (PPG) and electrocardiography (ECG) waveforms. APPROACH Fifty-nine York pigs undergoing fixed-rate, controlled hemorrhage were involved in this study and a least absolute shrinkage and selection operator regression-based early detection model was developed and tested using PPG and ECG derived features. The output of the early detection model was a risk trajectory indicating the future probability of bleeding. MAIN RESULTS Our proposed models were generally accurate in predicting bleeding with an area under the curve of 0.89 (95% CI 0.87-0.92) and achieved an average time of 16.1 mins to detect 16.8% blood loss when a false alert rate of 1% was tolerated. Models developed on non-invasive data performed with similar discrimination and lead time to hemorrhage compared to models using invasive arterial blood pressure as monitoring data. SIGNIFICANCE A bleed detection model using only non-invasive monitoring performs as well as those using invasive arterial pressure monitoring.
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Affiliation(s)
- Yang Chen
- Department of Electronic and Information Engineering, Harbin Institute of Technology at Shenzhen, Shenzhen, China
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Joo Heung Yoon
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
- Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Michael R. Pinsky
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Ting Ma
- Department of Electronic and Information Engineering, Harbin Institute of Technology at Shenzhen, Shenzhen, China
- Pengcheng Laboratory, Shenzhen, China
| | - Gilles Clermont
- Department of Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, U.S.A
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Leopold DK, Phillips RC, Shahi N, Gien J, Marwan AI, Kinsella JP, Mulligan J, Liechty KW, Moulton SL. Low postnatal CRI values are associated with the need for ECMO in newborns with CDH. J Pediatr Surg 2020; 55:39-44. [PMID: 31679772 DOI: 10.1016/j.jpedsurg.2019.09.050] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Accepted: 09/29/2019] [Indexed: 10/25/2022]
Abstract
INTRODUCTION Accurate, real-time technology is needed to predict which newborns with congenital diaphragmatic hernia (CDH) will require ECMO. The Compensatory Reserve Index (CRI) is a noninvasive monitoring technology that continuously trends an individual's capacity to compensate from normovolemia (CRI = 1) to decompensation (CRI = 0). We hypothesized that postnatal CRI values would be lower in CDH newborns that required ECMO than those who did not require ECMO. METHODS Newborns with a CDH were prospectively monitored with a CipherOx® CRI M1 device. We compared CRI values from delivery to ECMO (ECMO group) versus delivery to clinical stabilization (non-ECMO group). RESULTS Postnatal CRI values were available from 26 newborns. Eight underwent ECMO within 33 h of delivery, and median CRI prior to ECMO was 0.068 (IQR: 0.057, 0.078). Eighteen did not require ECMO. Median CRI from birth to 48 h was 0.112 (IQR: 0.082, 0.15). CRI values were significantly lower in newborns that required ECMO versus those who did not (p = 0.0035). Postnatal CRI had the highest AUC (0.85) compared to other prenatal prognostic measures. CONCLUSION Humans from newborns to adults share elemental features of the pulsatile waveform that are associated with progression to decompensation. CRI may be helpful when deciding when to initiate ECMO. LEVEL OF EVIDENCE Level III. TYPE OF STUDY Diagnostic test.
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Affiliation(s)
- David K Leopold
- Department of Surgery, Division of Pediatric Surgery, University of Colorado School of Medicine, Aurora, CO.
| | - Ryan C Phillips
- Department of Surgery, Division of Pediatric Surgery, University of Colorado School of Medicine, Aurora, CO
| | - Niti Shahi
- Department of Surgery, Division of Pediatric Surgery, University of Colorado School of Medicine, Aurora, CO
| | - Jason Gien
- Department of Pediatrics, Division of Neonatology, University of Colorado School of Medicine, Aurora, CO; Colorado Fetal Care Center, Children's Hospital Colorado, Aurora, CO
| | - Ahmed I Marwan
- Department of Surgery, Division of Pediatric Surgery, University of Colorado School of Medicine, Aurora, CO; Colorado Fetal Care Center, Children's Hospital Colorado, Aurora, CO
| | - John P Kinsella
- Department of Pediatrics, Division of Neonatology, University of Colorado School of Medicine, Aurora, CO; Colorado Fetal Care Center, Children's Hospital Colorado, Aurora, CO
| | | | - Kenneth W Liechty
- Department of Surgery, Division of Pediatric Surgery, University of Colorado School of Medicine, Aurora, CO; Colorado Fetal Care Center, Children's Hospital Colorado, Aurora, CO
| | - Steven L Moulton
- Department of Surgery, Division of Pediatric Surgery, University of Colorado School of Medicine, Aurora, CO; Flashback Technologies Inc., Louisville, CO
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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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Choi YM, Leopold D, Campbell K, Mulligan J, Grudic GZ, Moulton SL. Noninvasive monitoring of physiologic compromise in acute appendicitis: New insight into an old disease. J Pediatr Surg 2018; 53:241-246. [PMID: 29217323 DOI: 10.1016/j.jpedsurg.2017.11.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 11/08/2017] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Physiologic compromise in children with acute appendicitis has heretofore been difficult to measure. We hypothesized that the Compensatory Reserve Index (CRI), a novel adjunctive cardiovascular status indicator, would be low for children presenting with acute appendicitis in proportion to their physiological compromise, and that CRI would rise with fluid resuscitation and surgical management of their disease. METHODS Ninety-four children diagnosed with acute appendicitis were monitored with a CipherOx CRI™ M1 pulse oximeter (Flashback Technologies Inc., Boulder, CO). For clarity, CRI=1 indicates supine normovolemia, CRI=0 indicates hemodynamic decompensation (systolic blood pressure<80mmHg), and CRI values between 1 and 0 indicate the proportion of volume reserve remaining before collapse. Results are presented as counts with proportion (%), or mean with 95% confidence interval (CI). RESULTS Mean age was 11years old (95% CI: 10-12), and 49 (52%) of the children were male. Fifty-four (57%) had nonperforated appendicitis and 40 (43%) had perforated appendicitis. Mean initial CRI was significantly higher in those with nonperforated appendicitis compared to those with perforated appendicitis (0.57, 95% CI: 0.52-0.63 vs. 0.36, 95% CI: 0.29-0.43; P<0.001). The significant differences in mean CRI values between the two groups remained throughout the course of treatment, but lost its significance at 2h after surgery (0.63, 95% CI: 0.57-0.70 vs. 0.53, 95% CI: 0.46-0.61; P=0.05). CONCLUSION Low CRI values in children with perforated appendicitis are indicative of their lower reserve capacity owing to peritonitis and hypovolemia. CRI offers a real-time, noninvasive adjunctive tool to monitor tolerance to volume loss in children. LEVEL OF EVIDENCE Study of diagnostic test; Level of evidence: Level III.
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Affiliation(s)
- Young Mee Choi
- Division of Pediatric Surgery, Children's Hospital Colorado, Aurora, CO, USA
| | - David Leopold
- Division of Pediatric Surgery, Children's Hospital Colorado, Aurora, CO, USA
| | - Kristen Campbell
- Department of Biostatistics and Informatics, University of Colorado School of Medicine, Aurora, CO, USA
| | | | | | - Steven L Moulton
- Division of Pediatric Surgery, Children's Hospital Colorado, Aurora, CO, USA; Flashback Technologies, Inc., Boulder, CO, USA; Department of Surgery, University of Colorado School of Medicine, Aurora, CO, USA.
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The Effect of Passive Heat Stress and Exercise-Induced Dehydration on the Compensatory Reserve During Simulated Hemorrhage. Shock 2018; 46:74-82. [PMID: 27183303 DOI: 10.1097/shk.0000000000000653] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Compensatory reserve represents the proportion of physiological responses engaged to compensate for reductions in central blood volume before the onset of decompensation. We hypothesized that compensatory reserve would be reduced by hyperthermia and exercise-induced dehydration, conditions often encountered on the battlefield. Twenty healthy males volunteered for two separate protocols during which they underwent lower-body negative pressure (LBNP) to hemodynamic decompensation (systolic blood pressure <80 mm Hg). During protocol #1, LBNP was performed following a passive increase in core temperature of ∼1.2°C (HT) or a normothermic time-control period (NT). During protocol #2, LBNP was performed following exercise during which: fluid losses were replaced (hydrated), fluid intake was restricted and exercise ended at the same increase in core temperature as hydrated (isothermic dehydrated), or fluid intake was restricted and exercise duration was the same as hydrated (time-match dehydrated). Compensatory reserve was estimated with the compensatory reserve index (CRI), a machine-learning algorithm that extracts features from continuous photoplethysmograph signals. Prior to LBNP, CRI was reduced by passive heating [NT: 0.87 (SD 0.09) vs. HT: 0.42 (SD 0.19) units, P <0.01] and exercise-induced dehydration [hydrated: 0.67 (SD 0.19) vs. isothermic dehydrated: 0.52 (SD 0.21) vs. time-match dehydrated: 0.47 (SD 0.25) units; P <0.01 vs. hydrated]. During subsequent LBNP, CRI decreased further and its rate of change was similar between conditions. CRI values at decompensation did not differ between conditions. These results suggest that passive heating and exercise-induced dehydration limit the body's physiological reserve to compensate for further reductions in central blood volume.
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Validation of a noninvasive monitor to continuously trend individual responses to hypovolemia. J Trauma Acute Care Surg 2017; 83:S104-S111. [PMID: 28463939 DOI: 10.1097/ta.0000000000001511] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Humans are able to compensate for significant blood loss with little change in traditional vital signs, limiting early detection and intervention. We hypothesized that the Compensatory Reserve Index (CRI), a new hemodynamic parameter that trends changes in intravascular volume relative to the individual patient's response to hypovolemia, would accurately trend each subject's progression from normovolemia to decompensation (systolic blood pressure < 80) and back to normovolemia in humans. METHODS Men and women, ages 19 years to 36 years, underwent stepwise (~333 mL aliquot) removal and replacement of 20% blood volume (men, 15 mL/kg; women, 13 mL/kg) via a large bore intravenous (i.v.) line. During each experiment, subjects were monitored with four CipherOx CRI Tablets. Withdrawn blood was reinfused at the end of each experiment. RESULTS Forty-two subjects (24 men; 18 women) were enrolled in the study, of which 32 completed the protocol. Seven subjects became symptomatic and collapsed (systolic blood pressure < 80), six never achieving maximum blood loss; each was rescued with a saline infusion followed by reinfusion of their stored blood. The mean CRI at baseline for all 42 subjects was 0.9 ± 0.04. The mean CRI for the 32 subjects while asymptomatic at maximum blood loss was 0.611 ± 0.028. For the asymptomatic subjects, the average blood loss volume was 1018 mL ± 286 mL. In comparison, the mean CRI at maximum blood loss for the seven subjects who collapsed was 0.15 ± 0.007 and their average blood loss volume was 860 ± 183 mL. Mean CRI after reinfusion of blood was 0.89 ± 0.02. In addition symptomatic subjects demonstrated three times larger average decrease in CRI per liter of blood removed, 0.85 versus 0.28 for asymptomatic subjects. CONCLUSION CRI trends change in intravascular volume relative to an individual's response to hypovolemia and is sensitive to the differing risks associated with individuals' differing tolerance to volume loss. LEVEL OF EVIDENCE Prognostic study, level II.
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The effect of blood transfusion on compensatory reserve: A prospective clinical trial. J Trauma Acute Care Surg 2017; 83:S71-S76. [PMID: 28383467 DOI: 10.1097/ta.0000000000001474] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Bleeding activates the body's compensatory mechanisms, causing changes in vital signs to appear late in the course of progressive blood loss. These vital signs are maintained even when up to 30% to 40% of blood volume is lost. Laboratory tests such as hemoglobin, hematocrit, lactate, and base deficit levels do not change during acute phase of bleeding. The compensatory reserve measurement (CRM) represents a new paradigm that measures the total of all physiological compensatory mechanisms, using noninvasive photoplethysmography to read changes in arterial waveforms. This study compared CRM to traditional vital signs and laboratory tests in actively bleeding patients. METHODS Study patients had gastrointestinal bleeding and required red blood cell (RBC) transfusion (n = 31). Control group patients had similar demographic and medical backgrounds. They were undergoing minor surgical procedures and not expected to receive RBC transfusion. Vital signs, mean arterial pressure, pulse pressure, hemoglobin and hematocrit levels, and CRM were recorded before and after RBC transfusion or the appropriate time interval for the control group. Receiver operator characteristic curves were plotted and areas under the curves (AUCs) were compared. RESULTS CRM increased 10.5% after RBC transfusion, from 0.77 to 0.85 (p < 0.005). Hemoglobin level increased 22.4% after RBC transfusion from 7.3 to 8.7 (p < 0.005). Systolic and diastolic blood pressure, mean arterial pressure, pulse pressure, and heart rate did change significantly. The AUC for CRM as a single measurement for predicting hemorrhage at admission was 0.79, systolic blood pressure was 0.62, for heart rate was 0.60, and pulse pressure was 0.36. CONCLUSIONS This study demonstrated that CRM is more sensitive to changes in blood volume than traditional vital signs are and could be used to monitor and assess resuscitation of actively bleeding patients. LEVEL OF EVIDENCE Care management, level II.
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Bennis FC, van der Ster BJ, van Lieshout JJ, Andriessen P, Delhaas T. A machine-learning based analysis for the recognition of progressive central hypovolemia. Physiol Meas 2017; 38:1791-1801. [PMID: 28671554 DOI: 10.1088/1361-6579/aa7d3d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Traditional patient monitoring during surgery includes heart rate (HR), blood pressure (BP) and peripheral oxygen saturation. However, their use as predictors for central hypovolemia is limited, which may lead to cerebral hypoperfusion. The aim of this study was to develop a monitoring model that can indicate a decrease in central blood volume (CBV) at an early stage. APPROACH Twenty-eight healthy subjects (aged 18-50 years) were included. Lower body negative pressure (-50 mmHg) was applied to induce central hypovolemia until the onset of pre-syncope. Ten beat-to-beat and four discrete parameters were measured, normalized, and filtered with a 30 s moving window. Time to pre-syncope was scaled from 100%-0%. A total of 100 neural networks with 5, 10, 15, 20, or 25 neurons in their respective hidden layer were trained by 10, 20, 40, 80, 160, or 320 iterations to predict time to pre-syncope for each subject. The network with the lowest average slope of a fitted line over all subjects was chosen as optimal. MAIN RESULTS The optimal generalized model consisted of 10 hidden neurons, trained using 80 iterations. The slope of the fitted line on the average prediction was -0.64 (SD 0.35). The model recognizes in 75% of the subjects the need for intervention at >200 s before pre-syncope. SIGNIFICANCE We developed a neural network based on a set of physiological variables, which indicates a decrease in CBV even in the absence of HR and BP changes. This should allow timely intervention and prevent the development of symptomatic cerebral hypoperfusion.
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Affiliation(s)
- Frank C Bennis
- Department of Biomedical Engineering, Maastricht University, PO Box 616, 6200 MD, Maastricht, Netherlands. MHeNS School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD, Maastricht, Netherlands
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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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Carter R, Hinojosa-Laborde C, Convertino VA. Variability in integration of mechanisms associated with high tolerance to progressive reductions in central blood volume: the compensatory reserve. Physiol Rep 2016; 4:4/4/e12705. [PMID: 26884477 PMCID: PMC4759043 DOI: 10.14814/phy2.12705] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
High tolerance to progressive reductions in central blood volume has been associated with higher heart rate (HR), peripheral vascular resistance (PVR), sympathetic nerve activity (SNA), and vagally mediated cardiac baroreflex sensitivity (BRS). Using a database of 116 subjects classified as high tolerance to presyncopal‐limited lower body negative pressure (LBNP), we tested the hypothesis that subjects with greater cardiac baroreflex withdrawal (i.e., BRS > 1.0) would demonstrate greater LBNP tolerance associated with higher HR, PVR, and SNA. Subjects underwent LBNP to presyncope. Mean and diastolic arterial pressure (MAP; DAP) was measured by finger photoplethysmography and BRS (down sequence) was autocalculated (WinCPRS) as ∆R‐R Interval/∆DAP. DownBRS(ms/mmHg) was used to dichotomize subjects into two groups (Group 1 = DownBRS > 1.0, N = 49, and Group 2 = DownBRS < 1.0, N = 67) at the time of presyncope. Muscle SNA was measured directly from the peroneal nerve via microneurography (N = 19) in subjects from Groups 1 (n = 9) and 2 (n = 10). Group 1 (DownBRS > 1.0) had lower HR (107 ± 19 vs. 131 ± 20 bpm), higher stroke volume (45 ± 15 vs. 36 ± 15 mL), less SNA (45 ± 13 vs. 53 ± 7 bursts/min), and less increase in PVR (4.1 ± 1.3 vs. 4.5 ± 2.6) compared to Group 2 (DownBRS < 1.0). Both groups had similar tolerance times (1849 ± 260 vs. 1839 ± 253 sec), MAP (78 ± 11 vs. 79 ± 12 mmHg), compensatory reserve index (CRI) (0.10 ± 0.03 vs. 0.09 ± 0.01), and cardiac output (4.5 ± 1.2 vs. 4.7 ± 1.1 L/min) at presyncope. Contrary to our hypothesis, higher HR, PVR, SNA, and BRS were not associated with greater tolerance to reduced central blood volume. These data are the first to demonstrate the variability and uniqueness of individual human physiological strategies designed to compensate for progressive reductions in central blood volume. The sum total of these integrated strategies is accurately reflected by the measurement of the compensatory reserve.
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Affiliation(s)
- Robert Carter
- US Army Institute of Surgical Research, Fort Sam Houston, Texas
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A noninvasive computational method for fluid resuscitation monitoring in pediatric burns: a preliminary report. J Burn Care Res 2015; 36:145-50. [PMID: 25383980 DOI: 10.1097/bcr.0000000000000178] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The fluid resuscitation needs of children with small area burns are difficult to predict. The authors hypothesized that a novel computational algorithm called the compensatory reserve index (CRI), calculated from the photoplethysmogram waveform, would correlate with percent total body surface area (%TBSA) and fluid administration in children presenting with ≤20% TBSA burns. The authors recorded photoplethysmogram waveforms from burn-injured children that were later processed by the CRI algorithm. A CRI of 1 represents supine normovolemia; a CRI of 0 represents the point at which a subject is predicted to experience hemodynamic decompensation. CRI values from the first 10 minutes of monitoring were compared to clinical data. Waveform data were available for 27 children with small to moderate sized burns (4-20 %TBSA). The average age was 6.3 ± 1.1 years, the average %TBSA was 10.4 ± 0.8%, and the average CRI was 0.36 ± 0.03. CRI inversely correlated with the %TBSA (P < .001). Twenty children were transferred with an average reported %TBSA of 16.5 ± 1.4%, which was significantly higher than the actual %TBSA (P < .001). CRI correlated better with actual %TBSA compared to reported %TBSA (P = .02). CRI correlated with the amount of fluid resuscitation given at the time of CRI measurement (P = .02) and was inversely related to total fluids given per 24 hours for children with adequate urine output (>0.5 ml/kg/hr) (P < .001). The CRI is decreased in children with small to moderate size burns, and correlates with %TBSA and fluid administration. This suggests that the CRI may be useful for fluid resuscitation guidance, warranting further study.
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Bridges EJ, McNeill MM. Trauma resuscitation and monitoring: military lessons learned. Crit Care Nurs Clin North Am 2015; 27:199-211. [PMID: 25981723 DOI: 10.1016/j.cnc.2015.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Over the past 13 years, the military health care system has made improvements that are associated with an unprecedented survival rate for severely injured casualties. Monitoring for indications of deterioration as the critically injured patient moves across the continuum of care is difficult given the limitations of routinely used vital signs. Research by both military and civilian researchers is revolutionizing monitoring, with an increased focus on noninvasive, continuous, dynamic measurements to provide earlier, more sensitive indications of the patient's perfusion status.
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Affiliation(s)
- Elizabeth J Bridges
- Biobehavioral Nursing and Health Systems, University of Washington School of Nursing, Box 357266, Seattle, WA 98195, USA.
| | - Margaret M McNeill
- University of Washington Medical Center, Seattle, WA, USA; Department of Professional and Clinical Development, Frederick Memorial Hospital, 400 West Seventh Street, Frederick, MD 21701, USA
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Poh PYS, Carter R, Hinojosa-Laborde C, Mulligan J, Grudic GZ, Convertino VA. Respiratory pump contributes to increased physiological reserve for compensation during simulated haemorrhage. Exp Physiol 2014; 99:1421-6. [PMID: 25016024 DOI: 10.1113/expphysiol.2014.081208] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Intrathoracic pressure regulation (IPR) represents a therapy for increasing systemic circulation through the creation of negative intrathoracic pressure. We hypothesized that using this 'respiratory pump' effect would slow the diminution of the physiological reserve to compensate during progressive reductions in central blood volume. The compensatory reserve index (CRI) algorithm was used to measure the proportion (from 100 to 0%) of reserve capacity that remained to compensate for central volume loss before the onset of cardiovascular decompensation. Continuous analog recordings of arterial waveforms were extracted from data files of seven healthy volunteers. Subjects had previously participated in experiments designed to induce haemodynamic decompensation (presyncope) by progressive reduction in central blood volume using graded lower-body negative pressure. The lower-body negative pressure protocol was completed while breathing spontaneously through a standard medical face mask without (placebo) and with a resistance (approximately -7 cmH2O; active IPR) applied during inspiration. At the onset of presyncope in the placebo conditions, CRI was smaller than the CRI observed at the same time point in the active IPR conditions. The CRI at the onset of presyncope during active IPR (0.08 ± 0.01) was similar to the CRI at presyncope with placebo. Kaplan-Meier and log rank tests indicated that CRI survival curves were shifted to the right by active IPR. Optimizing the respiratory pump contributed a small but significant effect of increasing tolerance to progressive reductions in central blood volume by extending the compensatory reserve.
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Affiliation(s)
- Paula Y S Poh
- US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, 78234, USA
| | - Robert Carter
- US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, 78234, USA
| | | | | | | | - Victor A Convertino
- US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, 78234, USA
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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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Convertino VA, Grudic G, Mulligan J, Moulton S. Estimation of individual-specific progression to impending cardiovascular instability using arterial waveforms. J Appl Physiol (1985) 2013; 115:1196-202. [DOI: 10.1152/japplphysiol.00668.2013] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Trauma patients with “compensated” internal hemorrhage may not be identified with standard medical monitors until signs of shock appear, at which point it may be difficult or too late to pursue life-saving interventions. We tested the hypothesis that a novel machine-learning model called the compensatory reserve index (CRI) could differentiate tolerance to acute volume loss of individuals well in advance of changes in stroke volume (SV) or standard vital signs. Two hundred one healthy humans underwent progressive lower body negative pressure (LBNP) until the onset of hemodynamic instability (decompensation). Continuously measured photoplethysmogram signals were used to estimate SV and develop a model for estimating CRI. Validation of the CRI was tested on 101 subjects who were classified into two groups: low tolerance (LT; n = 33) and high tolerance (HT; n = 68) to LBNP (mean LBNP time: LT = 16.23 min vs. HT = 25.86 min). On an arbitrary scale of 1 to 0, the LT group CRI reached 0.6 at an average time of 5.27 ± 1.18 (95% confidence interval) min followed by 0.3 at 11.39 ± 1.14 min. In comparison, the HT group reached CRI of 0.6 at 7.62 ± 0.94 min followed by 0.3 at 15.35 ± 1.03 min. Changes in heart rate, blood pressure, and SV did not differentiate HT from LT groups. Machine modeling of the photoplethysmogram response to reduced central blood volume can accurately trend individual-specific progression to hemodynamic decompensation. These findings foretell early identification of blood loss, anticipating hemodynamic instability, and timely application of life-saving interventions.
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Affiliation(s)
| | - Greg Grudic
- Flashback Technologies Incorporated, Boulder, Colorado; and
| | - Jane Mulligan
- Flashback Technologies Incorporated, Boulder, Colorado; and
| | - Steve Moulton
- Flashback Technologies Incorporated, Boulder, Colorado; and
- University of Colorado, Denver, Colorado
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