Competence of health professionals to check the carotid pulse

A Monte Carlo method for the quantitative analysis of triage algorithms in mass casualty events

Objective.In mass casualty scenarios, efficient triage algorithms are used to prioritize medical care when resources are outnumbered by victims. This research proposes a computational approach to quantitatively analyze and optimize triage algorithms by developing a Monte Carlo code which is subsequently validated against the few quantitative data.Approach. The developed Monte Carlo code is used to simulate several mass casualty events, namely car accidents, burns, shootings, sinking ships and a human stampede. Four triage algorithms- modified simple triage and rapid treatment, primäres Ranking zur initialen Orientierung im Rettungsdienst, CareFlight, and field triage score (FTS)-are evaluated using metrics like mortality, overtriage, undertriage, sensitivity, and specificity.Main results.Results indicate that, on average, the analyzed algorithms achieve about 35% accuracy in classifying critical casualties when compared to a perfect algorithm, with FTS being the less accurate. However, when all casualties are considered, algorithm performance improves to around 63% of a perfect algorithm, except for FTS. The study identifies an increased probability of false positives for red categorization due to comorbidities and a higher tendency for false negatives in casualties with burns or internal trunk injuries.Significance.Despite variations in vital sign measurements, triage classification results do not depend on the measurement uncertainties of the paramedics. The ethically challenging decision, of withholding medical care from low-survival probability victims, leads to a 63% reduction in mortality among critical casualties. This research establishes a quantitative method for triage algorithm studies, highlighting their robustness to measurement uncertainties.

Point-of-Care Ultrasound Pulse Checks During Cardiopulmonary Resuscitation on a Patient Simulator (PUPRAS)

Background/Objectives: During cardiopulmonary resuscitation (CPR), patients must be checked for signs of return of spontaneous circulation (ROSC). Point-of-care ultrasound (POCUS) may be more reliable for detecting the ROSC. We investigated whether a POCUS pulse check algorithm could be used in compliance with the CPR guidelines. Methods: This was a prospective controlled and blinded multicentre manikin study involving staff from two tertiary clinical centres and their emergency medical services. A standard operating procedure for POCUS pulse checks during CPR was evaluated using a simulator in a team of four. The POCUS pulse checks were performed at the central artery following basic and advanced life support. The first pulse check was performed in the setting of pulseless electrical activity, and the second was performed in the presence of ROSC. The participants also completed a questionnaire. Results: A total of 444 pulse checks (244 manual/200 POCUS) were performed in 100 scenarios. The participants comprised physicians (34%), nurses (15%), non-physician emergency medical services personnel (37%), and other medical personnel (14%). The pulse checks took an average of 6.7 s (SD 3.9 s). Manual pulse checks (7.3 s) took longer than ultrasound pulse checks (6.1 s; p < 0.01), which were performed after a mean of 7.1 min (SD 1.7 min), during the fourth rhythm analysis in 93% of cases, and at the femoral artery in 62% of cases. They were rated as "easy" to perform by 77% and "useful" by 94%. Conclusions: POCUS pulse checks basically seem easy to implement and appear to be feasible during CPR.

Emergency medicine updates: Cardiopulmonary resuscitation

INTRODUCTION

Cardiac arrest is the loss of functional cardiac activity; emergency clinicians are integral in the management of this condition.

OBJECTIVE

This paper evaluates key evidence-based updates concerning cardiopulmonary resuscitation (CPR).

DISCUSSION

Cardiac arrest includes shockable rhythms (i.e., pulseless ventricular tachycardia and ventricular fibrillation) and non-shockable rhythms (i.e., asystole and pulseless electrical activity). The goal of cardiac arrest management is to achieve survival with a good neurologic outcome, in part by restoring systemic perfusion and obtaining return of spontaneous circulation (ROSC), while seeking to diagnose and treat the underlying etiology of the arrest. CPR includes high-quality chest compressions to optimize coronary and cerebral perfusion pressure. Chest compressions should be centered over the mid-sternum, with the compressor's body weight over the middle of the chest. A compression depth of 5-6 cm is recommended at a rate of 100-120 compressions per minute, while allowing the chest to fully recoil between each compression. Clinicians should seek to minimize any interruptions in compressions. When performed by bystanders, compression-only CPR may be associated with improved survival to hospital discharge when compared to conventional CPR with ventilations. However, in trained personnel, there is likely no difference with compression-only versus conventional CPR. Mechanical approaches for CPR are not associated with improved patient outcomes, including ROSC or survival with good neurologic function, but mechanical compression devices may be beneficial in select circumstances (e.g., few rescuers available, prolonged arrest/transport). Monitoring of chest compressions is not associated with improved ROSC, survival, or neurologic outcomes, but it can improve guideline adherence. Types of monitoring include real-time feedback, a CPR coach, end tidal CO2, arterial line monitoring, regional cerebral tissue oxygenation, and point-of-care ultrasound.

CONCLUSIONS

An understanding of CPR literature updates can improve the ED care of patients in cardiac arrest.

Visual detection of pulselessness by carotid artery sonography - A prospective observational study among medical students

AIM

This cross-sectional study aimed to determine whether medical students with little to no ultrasound experience could correctly distinguish between 'pulsation present' and 'no pulsation present' after a short introductory video on the subject using ultrasound videos of the common carotid artery (CCA).

METHODS

Ultrasound videos (B-mode, M-mode, and Color Doppler) of pulsatile (systolic blood pressure 70-80 mmHg) and non-pulsatile (cardiopulmonary bypass surgery, clamped aorta) CCA were created. These were demonstrated to the medical students for a period of ten seconds - corresponding to the duration of the manual pulse palpation during cardiopulmonary resuscitation (CPR). All participants viewed twenty of these videos in random order on a tablet and were asked to decide whether or not a CCA pulse was present.

RESULTS

432 participants completed the study in full on 20 cases, enabling a total of 8640 decisions on CCA pulse 'present' or 'not present' to be evaluated. M-mode: in 96 % (1244/1296) of the cases, the participants correctly identified the presence of pulsatile CCA. In the videos without pulsatile CCA, the correct decision 'no pulsation present' was made in 95 % (1231/1296) of the cases. B-mode: the decision 'pulsation present' was made correctly in 69 % (889/1296) of the cases, and in the remaining 31 % (407/1296) the option 'no pulsation present' was incorrectly chosen, although a video with CCA pulsation was shown. In contrast, the correct decision 'no pulsation present' was selected in 99 % of the cases (2142/2160). Color Doppler: CCA pulsation was correctly detected in 99.5 % (1290/1296) of the cases. In the videos without CCA pulsation, 99 % (1281/1296) of the videos were correctly evaluated as 'no pulsation present'.

CONCLUSION

Medical students seem to be able to detect the absence of a pulse with a high degree of accuracy using 2D ultrasound of the CCA in a controlled study setting, using different ultrasound modes. The results of this study suggest that a combination of Color Doppler and B-mode may be useful when evaluating the CCA during CPR to answer the question 'pulsation present' or 'no pulsation present'.

Contextualizing Pseudo-Pulseless Electrical Activity in Cardiac Arrest: A Meta-Analysis and Systematic Review

OBJECTIVE

Nonshockable cardiac arrest rhythms have demonstrably poor outcomes. Pseudo-pulseless electrical activity (PEA), a subset of PEA in which visible cardiac contractility is present, is being described more frequently in recent literature. Physiology suggests that presence of cardiac motion even without a palpable pulse is energetically more favorable than true PEA, which is more like asystole. Therefore, we hypothesize that there is an increase in the survivability of PEA compared with asystole which may in part be due to a subset of pseudo-PEA.

METHODS

A PICOST research question was generated which guided the composition of a systematic review and meta-analysis in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist.

RESULTS

A total of 494,355 patients were identified from 12 pieces of literature. Meta-analyses revealed an overall increased survivability of PEA compared with asystole (odds ratio [OR] 2.08, 95% confidence interval [CI] 1.52-2.86). When differentiating between location of arrest, PEA was more survivable in both in-hospital cardiac arrest and out-of-hospital cardiac arrest than asystole (out-of-hospital cardiac arrest OR 4.17, 95% CI 3.78-4.60, and in-hospital cardiac arrest OR 1.60, 95% CI 1.42-1.79). Finally, when comparing neurological outcome of PEA with asystole, PEA was more favorable (OR 3.32, 95% CI 1.39-7.94).

CONCLUSION

Pseudo-PEA may be one of the explanations attributed to better outcomes of PEA, especially neurological, due to the presence of cerebral and coronary flow. The presence of PEA likely requires evidence-based tailored management with presence of pseudo-PEA being more like a profound shock state. More evidence is required to investigate the true incidence of pseudo-PEA and its outcomes compared with true PEA.

A Protocol for Using Point-of-Care Ultrasound as an Adjunct in Pediatric Cardiac Arrest: Pediatric Ultrasound for Life-Supporting Efforts

ABSTRACT

Pediatric cardiac arrest is a rare but time-critical event that poses significant challenges to health care providers. Initiation of point-of-care ultrasound (POCUS) early in resuscitation can help optimize the location of chest compressions, identify inadequate compressions, evaluate for sonographic pulse, and help direct management. Although several algorithms currently exist to incorporate POCUS into adult cardiac arrest, none, to our knowledge, currently exist for the pediatric population. We propose a novel protocol for POCUS use as an adjunct to existing standard-of-care measures in pediatric cardiac arrest, which we call the Pediatric Ultrasound for Life-Supporting Efforts protocol.

Hands-free continuous carotid Doppler ultrasound for detection of the pulse during cardiac arrest in a porcine model

Background/Purpose

Pulse palpation is an unreliable method for diagnosing cardiac arrest. To address this limitation, continuous hemodynamic monitoring may be a viable solution. Therefore, we developed a novel, hands-free Doppler system, RescueDoppler, to detect the pulse continuously in the carotid artery.

Methods

In twelve pigs, we evaluated RescueDoppleŕs potential to measure blood flow velocity in three situations where pulse palpation of the carotid artery was insufficient: (1) systolic blood pressure below 60 mmHg, (2) ventricular fibrillation (VF) and (3) pulseless electrical activity (PEA). (1) Low blood pressure was induced using a Fogarty balloon catheter to occlude the inferior vena cava. (2) An implantable cardioverter-defibrillator induced VF. (3) Myocardial infarction after microembolization of the left coronary artery caused True-PEA. Invasive blood pressure was measured in the contralateral carotid artery. Time-averaged blood flow velocity (TAV) in the carotid artery was related to mean arterial pressure (MAP) in a linear mixed model.

Results

RescueDoppler identified pulsatile blood flow in 41/41 events with systolic blood pressure below 60 mmHg, with lowest blood pressure of 19 mmHg. In addition the absence of spontaneous circulation was identified in 21/21 VF events and true PEA in 2/2 events. The intraclass correlation coefficient within animals for TAV and MAP was 0.94 (95% CI. 0.85-0.98).

Conclusions

In a porcine model, RescueDoppler reliably identified pulsative blood flow with blood pressures below 60 mmHg. During VF and PEA, circulatory arrest was rapidly and accurately demonstrated. RescueDoppler could potentially replace unreliable pulse palpation during cardiac arrest and cardiopulmonary resuscitation.

Cardiopulmonary Resuscitation: The Importance of the Basics

Cardiac arrest is the loss of organized cardiac activity. Unfortunately, survival to hospital discharge is poor, despite recent scientific advances. The goals of cardiopulmonary resuscitation (CPR) are to restore circulation and identify and correct an underlying etiology. High-quality compressions remain the foundation of CPR, optimizing coronary and cerebral perfusion pressure. High-quality compressions must be performed at the appropriate rate and depth. Interruptions in compressions are detrimental to management. Mechanical compression devices are not associated with improved outcomes but can assist in several situations.

Point-of-Care Ultrasound Compression of the Carotid Artery for Pulse Determination in Cardiopulmonary Resuscitation

AIM

To identify whether a novel pulse check technique, carotid artery compression using an ultrasound probe, can reduce pulse check times compared to manual palpation (MP).

METHODS

This prospective study was conducted in an emergency department between February and December 2021. A physician applied point-of-care ultrasound-carotid artery compression (POCUS-CAC) and assessed the carotid artery compressibility and pulsatility by probe compression during rhythm check time. Another clinician performed MP of the femoral artery. The primary outcome was the difference in the average time for pulse assessment between POCUS-CAC and MP. The secondary outcomes included the time difference in each pulse check between methods, the proportion of times greater than 5 s and 10 s, and the prediction of return of spontaneous circulation (ROSC) during ongoing chest compression.

RESULTS

25 cardiac arrest patients and 155 pulse checks were analyzed. The median (interquartile range) average time to carotid pulse identification per patient using POCUS-CAC was 1.62 (1.14-2.14) s compared to 3.50 (2.99-4.99) s with MP. In all 155 pulse checks, the POCUS-CAC time to determine ROSC was significantly shortened to 0.44 times the MP time (P < 0.001). The POCUS-CAC approach never exceeded 10 s, and the number of patients who required more than 5 s was significantly lower (5 vs. 37, P < 0.001). Under continuous chest compression, six pulse checks predicted the ROSC.

CONCLUSIONS

We found that emergency physicians could quickly determine pulses by applying simple POCUS compression of the carotid artery in cardiac arrest patients.

Effectiveness of alternative shock strategies for out-of-hospital cardiac arrest: A systematic review

Aim

To determine the optimal first-shock energy level for biphasic defibrillation and whether fixed or escalating protocols for subsequent shocks are most effective.

Methods

We searched Medline, Embase, Cochrane CENTRAL, CINAHL, the Web of Science and national and international trial registry databases for papers published from database inception to January 2022. We reviewed reference lists of key papers to identify additional references. The population included adults sustaining non traumatic out-of-hospital cardiac arrest subject to attempted defibrillation. Studies of internal or monophasic defibrillation and studies other than randomised controlled trials or prospective cohorts were excluded. Two reviewers assessed study relevance. Data extraction and risk of bias assessment, using the ROBINS-I tool, were conducted by one reviewer and checked by a second reviewer. Data underwent intention-to-treat analysis.

Results

We identified no studies evaluating first shock energy. Only one study (n = 738) comparing fixed versus escalating energy met eligibility criteria: a prospective cohort analysis of a randomised controlled trial of manual versus mechanical CPR. High fixed (360 J) energy was compared with an escalating (200-200/300-360 J) strategy. Researchers found 27.5% (70/255) of patients in the escalating energy group and 27.61% (132/478) in the fixed high energy group survived to hospital discharge (unadjusted risk ratio 0.99, 95% CI 0.73, 1.23). Results were of very low certainty as the study was at serious risk of bias.

Conclusion

This systematic review did not identify an optimal first-shock energy for biphasic defibrillation. We identified no survival advantage at 30 days when comparing 360 J fixed with 200 J escalating strategy.

Initiation of Invasive Arterial Pressure Monitoring by Critical Care Transport Crews

Noninvasive blood pressure monitoring is convenient in the prehospital setting, but its use in the critically ill patient should be carefully considered given documented inaccuracies. Countless therapeutic patient interventions are based on blood pressure parameters, and the prehospital paramedic, nurse, and physician should strongly consider the use of invasive blood pressure monitoring, especially during critical care transport. Radial artery cannulation for arterial blood pressure monitoring is a safe and effective procedure that can reasonably be performed in the prehospital setting by both physicians and nonphysicians. Critical care transport teams should consider clinical guidelines that outline indications and training to safely implement this as a clinical skill.

Machine learning and feature engineering for predicting pulse presence during chest compressions

Current resuscitation protocols require pausing chest compressions during cardiopulmonary resuscitation (CPR) to check for a pulse. However, pausing CPR when a patient is pulseless can worsen patient outcomes. Our objective was to design and evaluate an ECG-based algorithm that predicts pulse presence with or without CPR. We evaluated 383 patients being treated for out-of-hospital cardiac arrest with real-time ECG, impedance and audio recordings. Paired ECG segments having an organized rhythm immediately preceding a pulse check (during CPR) and during the pulse check (without CPR) were extracted. Patients were randomly divided into 60% training and 40% test groups. From training data, we developed an algorithm to predict the clinical pulse presence based on the wavelet transform of the bandpass-filtered ECG. Principal component analysis was used to reduce dimensionality, and we then trained a linear discriminant model using three principal component modes as input features. Overall, 38% (351/912) of checks had a spontaneous pulse. AUCs for predicting pulse presence with and without CPR on test data were 0.84 (95% CI (0.80, 0.88)) and 0.89 (95% CI (0.86, 0.92)), respectively. This ECG-based algorithm demonstrates potential to improve resuscitation by predicting the presence of a spontaneous pulse without pausing CPR with moderate accuracy.

Initial Outcomes and Survival of Out-of-Hospital Cardiac Arrest: EuReCa Serbia Multicenter Cohort Study

Introduction Although the global survival rate of patients after out-of-hospital cardiac arrest (OHCA) has increased in the previous years, there still remain significant multifactorial public health challenges with many important aspects influencing the overall survival rate of these patients. The objective of this article is to analyze basic epidemiological parameters of OHCA in Serbia and to evaluate the influence of pre-hospitalization factors on the survival of OHCA patients. Methods Data on OHCA within the EuReCa Serbia Registry was collected according to the EuReCa Study protocol during the period October 1, 2014 - December 31, 2019, and included basic demographic data of the patients, data related to OHCA prior to hospital arrival, as well as data regarding subsequent hospitalization. Results The study included 6,266 EuReCa events (54% males), with a median age of 73 years [interquartile range (IQR) 63-82]. Cardiac arrest was witnessed in 3,111 out of 6,266 cases (49.6%), of which 2,725 cases (87.6%) were witnessed by bystanders and 286 cases (12.4%) by the emergency medical service (EMS) team. Resuscitation measures were attempted in 2,097 of 3,111 (67.4%) witnessed OHCA cases. Bystander cardiopulmonary resuscitation (CPR) was initiated in 288 cases within the bystander-witnessed group of 2,725 cases (10.6%). An initial shockable rhythm was detected in 323 out of 3,111 witnessed cases (10.4%). Any return of spontaneous circulation (ROSC) prior to hospital arrival was observed in 441 out of 2,097 cases where CPR was initiated (21.0%). Within the group of 2,097 events where CPR was initiated, in 287 cases the patient was transported to the hospital with ROSC (13.7%). An automated external defibrillator (AED) was used by bystanders in three cases. The collapse in locations other than the place of residence [p < 0.01; odds ratio (OR) 3.928], attempt to initiate CPR by a bystander (p < 0.01; OR 2.169), and presence of initial shockable rhythm (p = 0.01; OR 2.070) were observed as significant predictors of any ROSC in OHCA patients. Out of 287 patients hospitalized with ROSC, 54 (18.8%) were discharged alive. Conclusion Collapse outside of residence place, bystander CPR initiation, and initially detected shockable rhythm are important predictors of ROSC prior to hospital arrival and overall survival. Key factors of CPR-providing performance observed in this study were witnessing OHCA, CPR initiated by a bystander, presence of initial shockable rhythm, and any ROSC prior to hospital arrival.

Singapore Paediatric Resuscitation Guidelines 2021

We present the 2021 Singapore Paediatric Resuscitation Guidelines. The International Liaison Committee on Resuscitation's Pediatric Taskforce Consensus Statements on Science and Treatment Recommendations, which was published in October 2020, and the updated resuscitation guidelines from the American Heart Association and European Resuscitation Council, were reviewed and discussed by the committee. These recommendations were derived after deliberation of peer-reviewed evidence updates on paediatric resuscitation and took into consideration the local setting and clinical practice.

Differences in Basic Life Support Knowledge Between Junior Medical Students and Lay People: Web-Based Questionnaire Study

BACKGROUND

Early cardiopulmonary resuscitation and prompt defibrillation markedly increase the survival rate in the event of out-of-hospital cardiac arrest (OHCA). As future health care professionals, medical students should be trained to efficiently manage an unexpectedly encountered OHCA.

OBJECTIVE

Our aim was to assess basic life support (BLS) knowledge in junior medical students at the University of Geneva Faculty of Medicine (UGFM) and to compare it with that of the general population.

METHODS

Junior UGFM students and lay people who had registered for BLS classes given by a Red Cross-affiliated center were sent invitation links to complete a web-based questionnaire. The primary outcome was the between-group difference in a 10-question score regarding cardiopulmonary resuscitation knowledge. Secondary outcomes were the differences in the rate of correct answers for each individual question, the level of self-assessed confidence in the ability to perform resuscitation, and a 6-question score, "essential BLS knowledge," which only contains key elements of the chain of survival. Continuous variables were first analyzed using the Student t test, then by multivariable linear regression. Fisher exact test was used for between-groups comparison of binary variables.

RESULTS

The mean score was higher in medical students than in lay people for both the 10-question score (mean 5.8, SD 1.7 vs mean 4.2, SD 1.7; P<.001) and 6-question score (mean 3.0, SD 1.1 vs mean 2.0, SD 1.0; P<.001). Participants who were younger or already trained scored consistently better. Although the phone number of the emergency medical dispatch center was well known in both groups (medical students, 75/80, 94% vs lay people, 51/62, 82%; P=.06), most participants were unable to identify the criteria used to recognize OHCA, and almost none were able to correctly reorganize the BLS sequence. Medical students felt more confident than lay people in their ability to perform resuscitation (mean 4.7, SD 2.2 vs mean 3.1, SD 2.1; P<.001). Female gender and older age were associated with lower confidence, while participants who had already attended a BLS course prior to taking the questionnaire felt more confident.

CONCLUSIONS

Although junior medical students were more knowledgeable than lay people regarding BLS procedures, the proportion of correct answers was low in both groups, and changes in BLS education policy should be considered.

Checking the pulse in the 21st century: Interobserver reliability of carotid pulse detection by point-of-care ultrasound

INTRODUCTION

Detection of a pulse is crucial to decision-making in the care of patients who are in cardiac arrest, however, the current standard of manual pulse palpation is unreliable. An emerging alternative is the use of point-of-care ultrasound (POCUS) for direct assessment of the carotid pulse. The primary objective of this study is to determine the interobserver reliability for physician interpretation of pre-recorded point-of-care ultrasound pulse-check clips for patients who are in cardiac arrest.

METHODS

We conducted a web-based survey of residents and physicians working in an academic center. Participants were shown a tutorial demonstrating POCUS detection of the carotid pulse and then asked to interpret 15 carotid pulse ultrasound clips from patients who were in cardiac arrest. The primary outcome was interobserver reliability for carotid pulse assessment. Secondary outcomes included interobserver reliability stratified by physician role and POCUS experience, median tutorial and median pulse assessment duration. Interobserver reliability was determined by Krippendorff's ⍺.

RESULTS

68 participants completed the study, with a response rate of 75%. There was high interobserver reliability for pulse assessment amongst all study participants (⍺ = 0.874, 95% CI 0.869 to 0.879). All sub-groups had ⍺ greater than 0.8. Median tutorial duration was 35 s (IQR 29). Median pulse assessment duration was 6 s (IQR 5) with 76% of assessments completed within 10 s.

CONCLUSION

Interpretation of the carotid pulse by POCUS showed high interobserver reliability. Further work must be done to determine the performance of POCUS pulse assessment in real-time for patients who are in cardiac arrest.

Assessing the validity of two-dimensional carotid ultrasound to detect the presence and absence of a pulse

BACKGROUND

Traditional assessment of return of cardiac output in cardiac arrest by manual palpation has poor accuracy. Point of care ultrasound of a major artery has been suggested as an alternative. We conducted a diagnostic accuracy study of two-dimensional carotid ultrasound to detect the presence or absence of a pulse, using cardiopulmonary bypass patients for pulse and pulseless states.

METHODS

A cross-sectional multi-patient, multi-reader repeated measures diagnostic study was conducted. For patients undergoing routine cardiopulmonary bypass, a portable ultrasound was used to record four 10-s videos the common carotid artery, three aimed for a pulse in high (>90 mmHg), medium (70-90 mmHg) and low (<70 mmHg) systolic blood pressure (SBP) ranges, and a pulseless video was recorded on cardiopulmonary bypass. Critical care physicians viewed the videos and were asked to nominate within 10 s if a pulse was present. True pulse-status was determined via the arterial-line waveform.

RESULTS

Twenty-three patients had all four videos collected. Median patient age was 64 (IQR 14), sixteen were male (70%) and median BMI was 27. The median SBP in high-, medium- and low-SBP groups were 120 mmHg, 83 mmHg and 69 mmHg respectively. Forty-six physicians reviewed a subset of 24 videos. Overall sensitivity was 0.91 (95% confidence interval 0.89-0.93) and specificity 0.90 (95% CI 0.86-0.93). Sensitivity was highest in the high-SBP group (0.96, 95% CI 0.93-0.98) and lowest in the low-SBP group (0.83, 95% CI 0.78-0.87).

CONCLUSION

2D ultrasound of the common carotid artery is both sensitive and specific for detection of the presence or absence of a pulse.

Bedside ultrasound in cardiac standstill: a clinical review

Patients with cardiac arrest present as a relatively frequent occurrence in the Emergency Department. Despite the advances in our understanding of the pathophysiology of cardiac arrest, managing the condition remains a stressful endeavor and currently implemented interventions, while beneficial, are still associated with a disappointingly low survivability. The majority of modern Advanced Life Support algorithms employ a standardized approach to best resuscitate the 'crashed' patient. However, management during resuscitation often encourages a 'one-size-fits-all' policy for most patients, with lesser attention drawn towards causality of the disease and factors that could alter resuscitative care. Life support providers are also often challenged by the limited bedside predictors of survival to guide the course and duration of resuscitation. Over the recent decades, point-of-care ultrasonography (PoCUS) has been gradually proving itself as a useful adjunct that could potentially bridge the gap in the recognition and evaluation of precipitants and end-points in resuscitation, thereby facilitating an improved approach to resuscitation of the arrested patient. Point-of-care ultrasound applications in the critical care field have tremendously evolved over the past four decades. Today, bedside ultrasound is a fundamental tool that is quick, safe, inexpensive and reproducible. Not only can it provide the physician with critical information on reversible causes of arrest, but it can also be used to predict survival. Of note is its utility in predicting worse survival outcomes in patients with cardiac standstill, i.e., no cardiac activity witnessed with ultrasound. Unfortunately, despite the increasing evidence surrounding ultrasound use in arrest, bedside ultrasound is still largely underutilized during the resuscitation process. This article reviews the current literature on cardiac standstill and the application of bedside ultrasound in cardiac arrests.

Critical care echocardiography and outcomes in the critically ill

PURPOSE OF REVIEW

Critical care echocardiography offers a comprehensive assessment of cardiac anatomy and function performed by the intensivist at point of care. This has resulted in widespread use of critical care echocardiography in ICUs leading to the question if this increased usage has resulted in improved patient outcomes.

RECENT FINDINGS

Recent studies have evaluated the role of critical care echocardiography in the ICU with an emphasis on establishing accurate diagnosis and measurement of haemodynamic variables. There are no prospective randomized controlled trials that have examined the effect of critical care echocardiography on patient outcomes SUMMARY: Although the effect of critical care echocardiography on patient outcomes has not yet been established, its value as a diagnostic tool has been well demonstrated. We can only assume that its diagnostic capability leads to an improvement in patient outcomes.

Capnography: A support tool for the detection of return of spontaneous circulation in out-of-hospital cardiac arrest

BACKGROUND

Automated detection of return of spontaneous circulation (ROSC) is still an unsolved problem during cardiac arrest. Current guidelines recommend the use of capnography, but most automatic methods are based on the analysis of the ECG and thoracic impedance (TI) signals. This study analysed the added value of EtCO₂ for discriminating pulsed (PR) and pulseless (PEA) rhythms and its potential to detect ROSC.

MATERIALS AND METHODS

A total of 426 out-of-hospital cardiac arrest cases, 117 with ROSC and 309 without ROSC, were analysed. First, EtCO₂ values were compared for ROSC and no ROSC cases. Second, 5098 artefact free 3-s long segments were automatically extracted and labelled as PR (3639) or PEA (1459) using the instant of ROSC annotated by the clinician on scene as gold standard. Machine learning classifiers were designed using features obtained from the ECG, TI and the EtCO₂ value. Third, the cases were retrospectively analysed using the classifier to discriminate cases with and without ROSC.

RESULTS

EtCO₂ values increased significantly from 41 mmHg 3-min before ROSC to 57 mmHg 1-min after ROSC, and EtCO₂ was significantly larger for PR than for PEA, 46 mmHg/20 mmHg (p < 0.05). Adding EtCO₂ to the machine learning models increased their area under the curve (AUC) by over 2 percentage points. The combination of ECG, TI and EtCO₂ had an AUC for the detection of pulse of 0.92. Finally, the retrospective analysis showed a sensitivity and specificity of 96.6% and 94.5% for the detection of ROSC and no-ROSC cases, respectively.

CONCLUSION

Adding EtCO₂ improves the performance of automatic algorithms for pulse detection based on ECG and TI. These algorithms can be used to identify pulse on site, and to retrospectively identify cases with ROSC.

Deep Neural Networks for ECG-Based Pulse Detection during Out-of-Hospital Cardiac Arrest

The automatic detection of pulse during out-of-hospital cardiac arrest (OHCA) is necessary for the early recognition of the arrest and the detection of return of spontaneous circulation (end of the arrest). The only signal available in every single defibrillator and valid for the detection of pulse is the electrocardiogram (ECG). In this study we propose two deep neural network (DNN) architectures to detect pulse using short ECG segments (5 s), i.e., to classify the rhythm into pulseless electrical activity (PEA) or pulse-generating rhythm (PR). A total of 3914 5-s ECG segments, 2372 PR and 1542 PEA, were extracted from 279 OHCA episodes. Data were partitioned patient-wise into training (80%) and test (20%) sets. The first DNN architecture was a fully convolutional neural network, and the second architecture added a recurrent layer to learn temporal dependencies. Both DNN architectures were tuned using Bayesian optimization, and the results for the test set were compared to state-of-the art PR/PEA discrimination algorithms based on machine learning and hand crafted features. The PR/PEA classifiers were evaluated in terms of sensitivity (Se) for PR, specificity (Sp) for PEA, and the balanced accuracy (BAC), the average of Se and Sp. The Se/Sp/BAC of the DNN architectures were 94.1%/92.9%/93.5% for the first one, and 95.5%/91.6%/93.5% for the second one. Both architectures improved the performance of state of the art methods by more than 1.5 points in BAC.

The POCUS pulse check: A randomized controlled crossover study comparing pulse detection by palpation versus by point-of-care ultrasound

BACKGROUND

Manual pulse checks (MP) are an unreliable skill even in the hands of healthcare providers (HCPs). In the context of cardiac arrest, this may translate into inappropriate chest compressions when a pulse is present, or conversely omitting chest compressions when one is absent. To date, no study has assessed the use of B-mode ultrasound (US) for the detection of a carotid pulse. The primary objective of this study was to assess the time required to detect a carotid pulse in live subjects using US compared to the traditional palpation method.

METHODS

We conducted a prospective randomized controlled crossover non-inferiority trial. HCPs attended a 15 minute focused US workshop on identification of the carotid pulse. Both pulse check methods were timed for each participant on two different subjects in random order. The primary outcome was time to carotid pulse detection in seconds (s). Secondary outcomes included confidence levels of pulse detection measured on a 100 mm visual analog scale (VAS) and rates of prolonged pulse checks (> 5 s or >10 s). The study was powered to determine whether US pulse checks were not slower than MP by greater than two seconds. The results are presented as the difference in means with a 90% two-sided confidence interval (CI).

RESULTS

111 participants completed the study. Mean pulse detection times were 4.22 s (SD 3.26) by US compared to 4.71 s (SD 6.45) by MP with a mean difference in times of -0.49 s (90% CI: -1.77 to 0.39). There were no significant differences between US and MP in the rates of prolonged pulse checks of greater than 5 s (23% vs 19%, p = 0.45) or 10 s (9% vs 8%, p = 0.81). First attempt at detection of pulse checks was more successful in the US group (99.1% vs 85.6%, p = 0.0001). Prior to training, participants reported higher confidence using MP compared to US; 68 (IQR 48-83) vs 15 (IQR 8-42) mm (p < 0.001). Following the study, participants reported higher confidence levels using US than MP; 91 (IQR 82-97) vs 83 (IQR 72-94) mm (p < 0.001).

CONCLUSIONS

Carotid pulse detection in live subjects was not slower using US as compared to palpation, and demonstrated higher first attempt success rate and less variability in measurement times. A brief teaching session was sufficient to improve confidence of carotid pulse identification even in those with no previous US training. The preliminary results from this study provide the groundwork for larger studies to evaluate this pulse check method for patients in cardiac arrest.

Ventricular Fibrillation Waveform Analysis During Chest Compressions to Predict Survival From Cardiac Arrest

BACKGROUND

Quantitative measures of the ventricular fibrillation (VF) ECG waveform can assess myocardial physiology and predict cardiac arrest outcomes, making these measures a candidate to help guide resuscitation. Chest compressions are typically paused for waveform measure calculation because compressions cause ECG artifact. However, such pauses contradict resuscitation guideline recommendations to minimize cardiopulmonary resuscitation interruptions. We evaluated a comprehensive group of VF measures with and without ongoing compressions to determine their performance under both conditions for predicting functionally-intact survival, the study's primary outcome.

METHODS

Five-second VF ECG segments were collected with and without chest compressions before 2755 defibrillation shocks from 1151 out-of-hospital cardiac arrest patients. Twenty-four individual measures and 3 combination measures were implemented. Measures were optimized to predict functionally-intact survival (Cerebral Performance Category score ≤2) using 460 training cases, and their performance evaluated using 691 independent test cases.

RESULTS

Measures predicted functionally-intact survival on test data with an area under the receiver operating characteristic curve ranging from 0.56 to 0.75 (median, 0.73) without chest compressions and from 0.53 to 0.75 (median, 0.69) with compressions ( P<0.001 for difference). Of all measures evaluated, the support vector machine model ranked highest both without chest compressions (area under the receiver operating characteristic curve, 0.75; 95% CI, 0.73-0.78) and with compressions (area under the receiver operating characteristic curve, 0.75; 95% CI, 0.72-0.78; P=0.75 for difference).

CONCLUSIONS

VF waveform measures predict functionally-intact survival when calculated during chest compressions, but prognostic performance is generally reduced compared with compression-free analysis. However, support vector machine models exhibited similar performance with and without compressions while also achieving the highest area under the receiver operating characteristic curve. Such machine learning models may, therefore, offer means to guide resuscitation during uninterrupted cardiopulmonary resuscitation.

The reliability of carotid ultrasound in determining the return of pulsatile flow: A pilot study

Manual palpation of pulses is unreliable in detecting pulsatile flow in human participants, complicating the assessment of return of spontaneous circulation after cardiac arrest. Ultrasound may offer an alternative. This study's objective was to investigate whether return of pulsatile flow in humans can be reliably assessed by common carotid artery ultrasound. We conducted a single-blinded randomised study of common carotid artery ultrasound using 20 cardiopulmonary bypass patients to model the return of pulsatile flow. Synchronised time-stamped videos of radial artery invasive blood pressure and 10 two-dimensional or 10 colour Doppler ultrasounds were recorded. Three independent reviewers recorded the timestamp where they considered pulsatile flow was first visible on ultrasound. Ultrasound times were compared to the onset of arterial line pulsatile flow and reliability assessed by intraclass correlation coefficient. The median difference between radial artery and ultrasound flow time (interquartile range (range)) was 24 seconds (5-40 (0-93)) for two-dimensional and 5 seconds (2-17 (-28 to 188)) for colour Doppler. The intraclass correlation coefficient for two-dimensional ultrasound was 0.86 (95%CI 0.63-0.96) and 0.32 (95%CI -0.01 to 0.71) for colour Doppler. The median (interquartile range (range)) mean arterial pressure where ultrasound flow occurred for two-dimensional ultrasound was 62 mmHg (49-74 (33-82)) and 56 mmHg (52-73 (43-83)) for colour Doppler. In our pilot study, two-dimensional ultrasound was reliable in detecting the return of pulsatile flow. Colour Doppler detected pulsatile flow earlier and at lower mean arterial pressure but was not reliable, although a larger study is needed to determine colour Doppler's utility.

Detection of spontaneous pulse using the acceleration signals acquired from CPR feedback sensor in a porcine model of cardiac arrest

Background

Reliable detection of return of spontaneous circulation with minimal interruptions of chest compressions is part of high-quality cardiopulmonary resuscitation (CPR) and routinely done by checking pulsation of carotid arteries. However, manual palpation was time-consuming and unreliable even if performed by expert clinicians. Therefore, automated accurate pulse detection with minimal interruptions of chest compression is highly desirable during cardiac arrest especially in out-of-hospital settings.

Objective

To investigate whether the acceleration (ACC) signals acquired from accelerometer-based CPR feedback sensor can be used to distinguish perfusing rhythm (PR) from pulseless electrical activity (PEA) in a porcine model of cardiac arrest.

Methods

Cardiac arrest was induced in 49 male adult pigs. ECG, arterial blood pressure (ABP) and ACC waveforms were simultaneously recorded during CPR. 3-second segments containing compression-free signals during chest compression pauses were extracted and only those segments with organized rhythm were used for analysis. PR was defined as systolic arterial pressure >60 mmHg and pulse pressure >10 mmHg, while PEA was defined as an organized rhythm that does not meet the above criteria for PR. Peak correlation coefficient (CCp) of the cross-correlation function between pre-processed ECG and ACC, was used to discriminate PR and PEA.

Results

63 PR and 153 PEA were identified from the total of 1025 extracted segments. CCp was significantly higher for PR as compared to PEA (0.440±0.176 vs. 0.067±0.042, p<0.01) and highly correlated with ABP (r = 0.848, p<0.001). The area under the receiver operating characteristic curve, sensitivity, specificity and accuracy were 0.965, 93.6%, 97.5% and 96.7% for the ACC-based automatic spontaneous pulse detection.

Conclusions

In this animal model, the ACC signals acquired from an accelerometer-based CPR feedback sensor can be used to detect the presence of spontaneous pulse with high accuracy.

Artifact detection in accelerometer signals acquired from the carotid

Manual pulse palpation is the common procedure to assess pulse in unconscious patients. This is an error prone procedure during cardiopulmonary resuscitation and therefore automatic pulse detection techniques are being investigated. Accelerometry is an interesting sensing modality for this type of applications. However, accelerometers are highly prone to movement artifacts. Hence, one challenge in designing a solution using accelerometers is to handle motion artifacts properly. In this paper we investigate computationally simple features and classifier to capture movement artifacts in accelerometer signals acquired from the carotid. In particular, based on data obtained from health subjects we show that it is possible to use simple features to achieve an artifact detection sensitivity and specificity higher than 90%.

Towards an algorithm for automatic accelerometer-based pulse presence detection during cardiopulmonary resuscitation

Manual palpation is still the gold standard for assessment of pulse presence during cardiopulmonary resuscitation (CPR) for professional rescuers. However, this method is unreliable, time-consuming and subjective. Therefore, reliable, quick and objectified assessment of pulse presence in cardiac arrest situations to assist professional rescuers is still an unmet need. Accelerometers may present a promising sensor modality as pulse palpation technology for which pulse detection at the carotid artery has been demonstrated to be feasible. This study extends previous work by presenting an algorithm for automatic, accelerometer-based pulse presence detection at the carotid site during CPR. We show that accelerometers might be helpful in automated detection of pulse presence during CPR.

Circulation detection using the electrocardiogram and the thoracic impedance acquired by defibrillation pads

AIM

To develop and evaluate a method to detect circulation in the presence of organized rhythms (ORs) during resuscitation using signals acquired by defibrillation pads.

METHODS

Segments containing electrocardiogram (ECG) and thoracic impedance (TI) signals free of artifacts were used. The ECG corresponded to ORs classified as pulseless electrical activity (PEA) or pulse-generating rhythm (PR). A first dataset containing 1091 segments was split into training and test sets to develop and validate the circulation detector. The method processed ECG and TI to obtain the impedance circulation component (ICC). Morphological features were extracted from ECG and ICC, and combined into a classifier to discriminate between PEA and PR. The performance of the method was evaluated in terms of sensitivity (PR) and specificity (PEA). A second dataset (86 segments from different patients) was used to assess two application of the method: confirmation of arrest by recognizing absence of circulation during ORs and detection of return of spontaneous circulation (ROSC) during resuscitation. In both cases, time to confirmation of arrest/ROSC was determined.

RESULTS

The method showed a sensitivity/specificity of 92.1%/90.3% and 92.2%/91.9% for training and test sets respectively. The method confirmed cardiac arrest with a specificity of 93.3% with a median delay of 0s after the first OR annotation. ROSC was detected with a sensitivity of 94.4% with a median delay of 57s from ROSC onset.

CONCLUSION

The method showed good performance, and can be reliably used to distinguish perfusing from non-perfusing ORs.

Characteristics of regional cerebral oxygen saturation levels in patients with out-of-hospital cardiac arrest with or without return of spontaneous circulation: A prospective observational multicentre study

AIM

Our study aimed at filling the fundamental knowledge gap on the characteristics of regional brain oxygen saturation (rSO2) levels in out-of-hospital cardiac arrest (OHCA) patients with or without return of spontaneous circulation (ROSC) upon arrival at the hospital for estimating the quality of cardiopulmonary resuscitation and neurological prognostication in these patients.

METHODS

We enrolled 1921 OHCA patients from the Japan - Prediction of Neurological Outcomes in Patients Post-cardiac Arrest Registry and measured their rSO2 immediately upon arrival at the hospital by near-infrared spectroscopy using two independent forehead probes (right and left). We also assessed the percentage of patients with a good neurological outcome (defined as cerebral performance categories 1 or 2) 90 days post cardiac arrest.

RESULTS

After 90 days, 79 (4%) patients had good neurological outcomes and a median lower rSO2 level of 15% (15-20%). Compared to patients without ROSC upon arrival at the hospital, those with ROSC had significantly higher rSO2 levels (56% [39-65%] vs. 15% [15-17%], respectively; P<0.01), and significantly correlated right- and left-sided regional brain oxygen saturation levels (R=0.94 vs. 0.66, respectively). In both groups, the percentage of patients with a good 90-day neurological outcome increased significantly in proportion to their rSO2 levels upon arrival at the hospital (P<0.01).

CONCLUSION

Our data indicate that measuring rSO2 levels might be effective for both monitoring the quality of resuscitation and neurological prognostication in patients with OHCA.

Understanding and improving low bystander CPR rates: a systematic review of the literature

Objectives:

Cardiopulmonary resuscitation (CPR) is a crucial yet weak link in the chain of survival for out-of-hospital cardiac arrest. We sought to understand the determinants of bystander CPR and the factors associated with successful training.

Methods:

For this systematic review, we searched 11 electronic databases, 1 trial registry and 9 scientific websites. We performed hand searches and contacted 6 content experts. We reviewed without restriction all communications pertaining to who should learn CPR, what should be taught, when to repeat training, where to give CPR instructions and why people lack the motivation to learn and perform CPR. We used standardized forms to review papers for inclusion, quality and data extraction. We grouped publications by category and classified recommendations using a standardized classification system that was based on level of evidence.

Results:

We reviewed 2409 articles and selected 411 for complete evaluation. We included 252 of the 411 papers in this systematic review. Differences in their study design precluded a meta-analysis. We classified 22 recommendations; those with the highest scores were 1) 9-1-1 dispatch-assisted CPR instructions, 2) teaching CPR to family members of cardiac patients, 3) Braslow's self-training video, 4) maximizing time spent using manikins and 5) teaching the concepts of ambiguity and diffusion of responsibility. Recommendations not supported by evidence include mass training events, pulse taking prior to CPR by laymen and CPR using chest compressions alone.

Conclusion:

We evaluated and classified the potential impact of interventions that have been proposed to improve bystander CPR rates. Our results may help communities design interventions to improve their bystander CPR rates.

Use of limited transthoracic echocardiography in patients with traumatic cardiac arrest decreases the rate of nontherapeutic thoracotomy and hospital costs

OBJECTIVES

Limited transthoracic echocardiography (LTTE) has been introduced as a hemodynamic tool for trauma patients. The aim of this study was to evaluate the utility of LTTE during the evaluation of nonsurviving patients who presented to the trauma bay with traumatic cardiac arrest.

METHODS

Approval by the Institutional Review Board was obtained. All nonsurviving patients with traumatic cardiac arrest who reached the trauma bay were evaluated retrospectively for 1 year. Comparisons between groups of patients in whom LTTE was performed as part of the resuscitation effort and those in whom it was not performed were conducted.

RESULTS

From January 2012 to January 2013, 37 patients did not survive traumatic cardiac arrest while in the trauma bay: 14 in the LTTE group and 23 in the non-LTTE group. When comparing the LTTE and non-LTTE groups, both were similar in sex distribution (LTTE, 86% male; non-LTTE, 74% male; P = .68), age (34.8 versus 24.1 years; P= .55), Injury Severity Score (41.0 versus 38.2; P= .48), and percentage of penetrating trauma (21.6% versus 21.7%; P = .29). Compared with the non-LTTE group, the LTTE group spent significantly less time in the trauma bay (13.7 versus 37.9 minutes; P = .01), received fewer blood products (7.1% versus 31.2%; P = .789), and were less likely to undergo nontherapeutic thoracotomy in the emergency department (7.14% versus 39.1%; P < .05). The non-LTTE group had a mean of $3040.50 in hospital costs, compared with the mean for the LTTE group of $1871.60 (P = .0054).

CONCLUSIONS

In this study, image-guided resuscitation with LTTE decreased the time in the trauma bay and avoided nontherapeutic thoracotomy in nonsurviving trauma patients. Limited TTE could improve the use of health care resources in patients with traumatic cardiac arrest.

Detection of a spontaneous pulse in photoplethysmograms during automated cardiopulmonary resuscitation in a porcine model

INTRODUCTION

Reliable, non-invasive detection of return of spontaneous circulation (ROSC) with minimal interruptions to chest compressions would be valuable for high-quality cardiopulmonary resuscitation (CPR). We investigated the potential of photoplethysmography (PPG) to detect the presence of a spontaneous pulse during automated CPR in an animal study.

METHODS

Twelve anesthetized pigs were instrumented to monitor circulatory and respiratory parameters. Here we present the simultaneously recorded PPG and arterial blood pressure (ABP) signals. Ventricular fibrillation was induced, followed by 20 min of automated CPR and subsequent defibrillation. After defibrillation, pediatric-guidelines-style life support was given in cycles of 2 min. PPG and ABP waveforms were recorded during all stages of the protocol. Raw PPG waveforms were acquired with a custom-built photoplethysmograph controlling a commercial reflectance pulse oximetry probe attached to the nose. ABP was measured in the aorta.

RESULTS

In nine animals ROSC was achieved. Throughout the protocol, PPG and ABP frequency content showed strong resemblance. We demonstrate that (1) the PPG waveform allows for the detection of a spontaneous pulse during ventilation pauses, and that (2) frequency analysis of the PPG waveform allows for the detection of a spontaneous pulse and the determination of the pulse rate, even during ongoing chest compressions, if the pulse and compression rates are sufficiently distinct.

CONCLUSIONS

These results demonstrate the potential of PPG as a non-invasive means to detect pulse presence or absence, as well as pulse rate during CPR.

Cardiopulmonary resuscitation quality: [corrected] improving cardiac resuscitation outcomes both inside and outside the hospital: a consensus statement from the American Heart Association

The "2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care" increased the focus on methods to ensure that high-quality cardiopulmonary resuscitation (CPR) is performed in all resuscitation attempts. There are 5 critical components of high-quality CPR: minimize interruptions in chest compressions, provide compressions of adequate rate and depth, avoid leaning between compressions, and avoid excessive ventilation. Although it is clear that high-quality CPR is the primary component in influencing survival from cardiac arrest, there is considerable variation in monitoring, implementation, and quality improvement. As such, CPR quality varies widely between systems and locations. Victims often do not receive high-quality CPR because of provider ambiguity in prioritization of resuscitative efforts during an arrest. This ambiguity also impedes the development of optimal systems of care to increase survival from cardiac arrest. This consensus statement addresses the following key areas of CPR quality for the trained rescuer: metrics of CPR performance; monitoring, feedback, and integration of the patient's response to CPR; team-level logistics to ensure performance of high-quality CPR; and continuous quality improvement on provider, team, and systems levels. Clear definitions of metrics and methods to consistently deliver and improve the quality of CPR will narrow the gap between resuscitation science and the victims, both in and out of the hospital, and lay the foundation for further improvements in the future.

Tissue oximetry by near-infrared spectroscopy in a porcine model of out-of-hospital cardiac arrest and resuscitation

INTRODUCTION

Monitoring during resuscitation remains relatively crude. Near-infrared spectroscopy (NIRS) measures aggregate oxygen saturation in a volume of tissue. We assessed the utility of continuous StO2 measurement in a porcine model of cardiac arrest, and explored the effects of differential vasoconstriction on StO2. We hypothesized that (1) StO2 trends correspond with the onset of loss of pulses, resuscitation, and return of spontaneous circulation (ROSC); (2) epinephrine has a dose-dependent effect on StO2.

METHODS

We anesthetized and instrumented 7 female swine, placing a NIRS probe on the left forelimb to recorded StO2. After 8 min of untreated VF and 2 min of CPR, we randomized animals to 0.015 mgkg(-1) (SDE) or 0.1mgkg(-1) (HDE) epinephrine. After 3 min of CPR, animals were defibrillated. Animals with ROSC were given SDE, then HDE for subsequent hemodynamic deteriorations. Data were analyzed with descriptive statistics and generalized linear model (alpha=0.05) to determine overall slope of pooled StO2 across animals for resuscitation segments.

RESULTS

Four animals received HDE and three SDE. All achieved ROSC. Significant coefficients (ΔStO2 min(-1)) were noted for resuscitation segments. StO2 decreased after loss of pulses (-29.1; 95%CI -33.4, -24.7; p<0.01) but plateaued during CPR (-0.2; 95%CI -1.2, 0.8; p=0.71). There was a graded decline in StO2 between SDE (-1.3; 95%CI -1.5, -1.2; p<0.01) and HDE (-3.1; 95%CI -5.8, -0.4; p=0.03). The slowest change occurred with ROSC (0.4; 95%CI 0.3, 0.5; p<0.01).

CONCLUSIONS

In a porcine model of OHCA, peripheral StO2 rapidly decreased after loss of pulses, but did not improve with CPR or epinephrine. It increased extremely slowly after ROSC.