Inflammation, endothelial injury, and the acute respiratory distress syndrome after out-of-hospital cardiac arrest.

Background: Acute respiratory distress syndrome (ARDS) is often seen in patients resuscitated from out-of-hospital cardiac arrest (OHCA). We aim to test whether inflammatory or endothelial injury markers are associated with the development of ARDS in patients hospitalized after OHCA. Methods: We conducted a prospective, cohort, pilot study at an urban academic medical center in 2019 that included a convenience sample of adults with non-traumatic OHCA. Blood and pulmonary edema fluid (PEF) were collected within 12 hours of hospital arrival. Samples were assayed for cytokines (interleukin [IL]-1, tumor necrosis factor-α [TNF-α], tumor necrosis factor receptor1 [TNFR1], IL-6), epithelial injury markers (pulmonary surfactant-associated protein D), endothelial injury markers (Angiopoietin-2 [Ang-2] and glycocalyx degradation products), and other proteins (matrix metallopeptidase-9 and myeloperoxidase). Patients were followed for 7 days for development of ARDS, as adjudicated by 3 blinded reviewers, and through hospital discharge for mortality and neurological outcome. We examined associations between biomarker concentrations and ARDS, hospital mortality, and neurological outcome using multivariable logistic regression. Latent phase analysis was used to identify distinct biological classes associated with outcomes. Results: 41 patients were enrolled. Mean age was 58 years, 29% were female, and 22% had a respiratory etiology for cardiac arrest. Seven patients (17%) developed ARDS within 7 days. There were no significant associations between individual biomarkers and development of ARDS in adjusted analyses, nor survival or neurologic status after adjusting for use of targeted temperature management (TTM) and initial cardiac arrest rhythm. Elevated Ang-2 and TNFR-1 were associated with decreased survival (RR = 0.6, 95% CI = 0.3-1.0; RR = 0.5, 95% CI = 0.3-0.9; respectively), and poor neurologic status at discharge (RR = 0.4, 95% CI = 0.2-0.8; RR = 0.4, 95% CI = 0.2-0.9) in unadjusted associations. Conclusion: OHCA patients have markedly elevated plasma and pulmonary edema fluid biomarker concentrations, indicating widespread inflammation, epithelial injury, and endothelial activation. Biomarker concentrations were not associated with ARDS development, though several distinct biological phenotypes warrant further exploration. Latent phase analysis demonstrated that patients with low biomarker levels aside from TNF-α and TNFR-1 (Class 2) fared worse than other patients. Future research may benefit from considering other tools to predict and prevent development of ARDS in this population.

Pediatric Out-of-Hospital Cardiac Arrest: The Role of the Telecommunicator in Recognition of Cardiac Arrest and Delivery of Bystander Cardiopulmonary Resuscitation.

BACKGROUND: Telecommunicator CPR (T-CPR), whereby emergency dispatch facilitates cardiac arrest recognition and coaches CPR over the telephone, is an important strategy to increase early recognition and bystander CPR in adult out-of-hospital cardiac arrest (OHCA). Little is known about this treatment strategy in the pediatric population. We investigated the role of T-CPR and related performance among pediatric OHCA. METHODS AND RESULTS: This study was a retrospective cohort investigation of OHCA among individuals <18 years in King County, Washington, from April 1, 2013, to December 31, 2019. We reviewed the 911 audio recordings to determine if and how bystander CPR was delivered (unassisted or T-CPR), key time intervals in recognition of arrest, and key components of T-CPR delivery. Of the 185 eligible pediatric OHCAs, 23% (n=43) had bystander CPR initiated unassisted, 59% (n=109) required T-CPR, and 18% (n=33) did not receive CPR before emergency medical services arrival. Among all cases, cardiac arrest was recognized by the telecommunicator in 89% (n=165). Among those receiving T-CPR, the median (interquartile range) interval from start of call to OHCA recognition was 59 seconds (38-87) and first CPR intervention was 115 seconds (94-162). When stratified by age (≤8 versus >8), the older age group was less likely to receive CPR before emergency medical services arrival (88% versus 69%, P=0.002). For those receiving T-CPR, bystanders spent a median of 207 seconds (133-270) performing CPR. The median compression rate was 93 per minute (82-107) among those receiving T-CPR. CONCLUSIONS: T-CPR is an important strategy to increase early recognition and early CPR among pediatric OHCA.

The impact of COVID-19 pandemic on out-of-hospital cardiac arrest: An individual patient data meta-analysis.

AIM: Prior studies have reported increased out-of-hospital cardiac arrests (OHCA) incidence and lower survival during the COVID-19 pandemic. We evaluated how the COVID-19 pandemic affected OHCA incidence, bystander CPR rate and patients' outcomes, accounting for regional COVID-19 incidence and OHCA characteristics. METHODS: Individual patient data meta-analysis of studies which provided a comparison of OHCA incidence during the first pandemic wave (COVID-period) with a reference period of the previous year(s) (pre-COVID period). We computed COVID-19 incidence per 100,000 inhabitants in each of 97 regions per each week and divided it into its quartiles. RESULTS: We considered a total of 49,882 patients in 10 studies. OHCA incidence increased significantly compared to previous years in regions where weekly COVID-19 incidence was in the fourth quartile (>136/100,000/week), and patients in these regions had a lower odds of bystander CPR (OR 0.49, 95%CI 0.29-0.81, p = 0.005). Overall, the COVID-period was associated with an increase in medical etiology (89.2% vs 87.5%, p < 0.001) and OHCAs at home (74.7% vs 67.4%, p < 0.001), and a decrease in shockable initial rhythm (16.5% vs 20.3%, p < 0.001). The COVID-period was independently associated with pre-hospital death (OR 1.73, 95%CI 1.55-1.93, p < 0.001) and negatively associated with survival to hospital admission (OR 0.68, 95%CI 0.64-0.72, p < 0.001) and survival to discharge (OR 0.50, 95%CI 0.46-0.54, p < 0.001). CONCLUSIONS: During the first COVID-19 pandemic wave, there was higher OHCA incidence and lower bystander CPR rate in regions with a high-burden of COVID-19. COVID-19 was also associated with a change in patient characteristics and lower survival independently of COVID-19 incidence in the region where OHCA occurred.

Wolf Creek XVII part 3: Automated cardiac arrest diagnosis.

Introduction: Automated cardiac arrest diagnosis offers the possibility to significantly shorten the interval between onset of out-of-hospital cardiac arrest (OHCA) and notification of EMS, providing the opportunity for earlier resuscitation and possibly increased survival. Methods: Automated cardiac arrest diagnosis was one of six focus topics for the Wolf Creek XVII Conference held on June 14-17 2023 in Ann Arbor, Michigan, USA. Conference invitees included international thought leaders and scientists in the field of cardiac arrest resuscitation from academia and industry. Participants submitted via online survey knowledge gaps, barriers to translation and research priorities for each focus topic. Expert panels used the survey results and their own perspectives and insights to create and present a preliminary unranked list for each category that was debated, revised and ranked by all attendees to identify the top 5 for each category. Results: Top knowledge gaps include the accuracy of automated OHCA detection technologies and the feasibility and reliability of automated EMS activation. The main barriers to translation are the risk of false positives potentially overburdening EMS, development and application costs of technology and the challenge of integrating new technology in EMS IT systems. The top research priorities are large-scale evaluation studies to measure real world performance and user research regarding the willingness to adopt these technologies. Conclusion: Automated cardiac arrest diagnosis has the potential to significantly impact time to resuscitation and survival of OHCA because it could convert unwitnessed events into witnessed events. Validation and feasibility studies are needed. The specificity of the technology must be high not to overburden limited EMS resources. If adequate event classification is achieved, future research could shift toward event prediction, focusing on identifying potential digital biomarkers and signatures of imminent cardiac arrest. Implementation could be challenging due to high costs of development, regulatory considerations and instantiation logistics.

A retrospective study on machine learning-assisted stroke recognition for medical helpline calls.

Advanced stroke treatment is time-dependent and, therefore, relies on recognition by call-takers at prehospital telehealth services to ensure fast hospitalisation. This study aims to develop and assess the potential of machine learning in improving prehospital stroke recognition during medical helpline calls. We used calls from 1 January 2015 to 31 December 2020 in Copenhagen to develop a machine learning-based classification pipeline. Calls from 2021 are used for testing. Calls are first transcribed using an automatic speech recognition model and then categorised as stroke or non-stroke using a text classification model. Call-takers achieve a sensitivity of 52.7% (95% confidence interval 49.2-56.4%) with a positive predictive value (PPV) of 17.1% (15.5-18.6%). The machine learning framework performs significantly better (p < 0.0001) with a sensitivity of 63.0% (62.0-64.1%) and a PPV of 24.9% (24.3-25.5%). Thus, a machine learning framework for recognising stroke in prehospital medical helpline calls may become a supportive tool for call-takers, aiding in early and accurate stroke recognition.

Overdose and mortality risk following a non-fatal opioid overdose treated by Emergency Medical Services in King County, Washington.

BACKGROUND: Emergency Medical Services (EMS) agencies respond to hundreds of thousands of acute overdose events each year. We conducted a retrospective cohort study of EMS patients who survived a prior opioid overdose in 2019-2021 in King County, Washington. METHODS: A novel record linkage algorithm was applied to EMS electronic health records and the state vital statistics registry to identify repeat overdoses and deaths that occurred up to 3 years following the index opioid overdose. We measured overdose incidence rates and applied survival analysis techniques to assess all-cause and overdose-specific mortality risks. RESULTS: In the year following the index opioid overdose, the overdose (fatal or non-fatal) incidence rate was 23.3 per 100 person-year, overdose mortality rate was 2.7 per 100 person-year, and all-cause mortality rate was 5.2 per 100 person-year in this cohort of overdose survivors (n=4234). Overdose incidence was highest in the first 30 days following the index overdose (43 opioid overdoses and 4 fatal overdoses per 1000 person-months), declined precipitously, and then plateaued from the third month onwards (10-15 opioid overdoses and 1-2 fatal overdoses per 1000 person-months). Overdose incidence rates, measured at 30 days, were highest among overdose survivors who were young, male, and experienced a low severity index opioid overdose, but these differences diminished when measured at 12 months. CONCLUSIONS: Among EMS patients who survived an opioid overdose, the risk of subsequent overdose is high, especially in the weeks following the index opioid overdose. Non-fatal overdose may represent a pivotal time to connect patients with harm-reduction, treatment, and other support services.

Comparison of Intubating Conditions with Succinylcholine Versus Rocuronium in the Prehospital Setting.

OBJECTIVE: Rapid sequence intubation (RSI) is frequently performed by emergency medical services (EMS). We investigated the relationship between succinylcholine and rocuronium use and time until first laryngoscopy attempt, first-pass success, and Cormack-Lehane (CL) grades. METHODS: We included adult patients for whom prehospital RSI was attempted from July 2015 through June 2022 in a retrospective, observational study with pre-post analysis. Timing was verified using recorded defibrillator audio in addition to review of continuous ECG, pulse oximetry, and end-tidal carbon dioxide waveforms. Our primary exposure was neuromuscular blocking agent (NMBA) used, either rocuronium or succinylcholine. Our prespecified primary outcome was the first attempt Cormack-Lehane view. Key secondary outcomes were first laryngoscopy attempt success rate, timing from NMBA administration to first attempt, number of attempts, and hypoxemic events. RESULTS: Of 5,179 patients in the EMS airway registry, 1,475 adults received an NMBA while not in cardiac arrest. Cormack-Lehane grades for succinylcholine and rocuronium were similar: grade I (64%, 59% [95% CI 0.64-1.09]), grade II (16%, 21%), grade III (18%, 16%), grade IV (3%, 3%). The median interval from NMBA administration to start of the first attempt was 57 s for succinylcholine and 83 s for rocuronium (mean difference 28 [95% CI 20-36] seconds). First attempt success was 84% for succinylcholine and 83% for rocuronium. Hypoxemic events were present in 25% of succinylcholine cases and 23% of rocuronium cases. CONCLUSIONS: Prehospital use of either rocuronium or succinylcholine is associated with similar Cormack-Lehane grades, first-pass success rates, and rates of peri-intubation hypoxemia.

Association of small adult ventilation bags with return of spontaneous circulation in out of hospital cardiac arrest.

INTRODUCTION: Little is known about the impact of tidal volumes delivered by emergency medical services (EMS) to adult patients with out-of-hospital cardiac arrest (OHCA). A large urban EMS system changed from standard adult ventilation bags to small adult bags. We hypothesized that the incidence of return of spontaneous circulation (ROSC) at the end of EMS care would increase after this change. METHODS: We performed a retrospective analysis evaluating adults treated with advanced airway placement for nontraumatic OHCA between January 1, 2015 and December 31, 2021. We compared rates of ROSC, ventilation rate, and mean end tidal carbon dioxide (ETCO2) by minute before and after the smaller ventilation bag implementation using linear and logistic regression. RESULTS: Of the 1,994 patients included, 1,331 (67%) were treated with a small adult bag. ROSC at the end of EMS care was lower in the small bag cohort than the large bag cohort, 33% vs 40% (p = 0.003). After adjustment, small bag use was associated with lower odds of ROSC at the end of EMS care [OR 0.74, 95% CI 0.61 - 0.91]. Ventilation rates did not differ between cohorts. ETCO2 values were lower in the large bag cohort (33.2 ± 17.2 mmHg vs. 36.9 ± 19.2 mmHg, p < 0.01). CONCLUSION: Use of a small adult bag during OHCA was associated with lower odds of ROSC at the end of EMS care. The effects on acid base status, hemodynamics, and delivered minute ventilation remain unclear and warrant additional study.

Acute SARS-CoV-2 Infection and Incidence and Outcomes of Out-of-Hospital Cardiac Arrest.

Importance: Little is known about how COVID-19 affects the incidence or outcomes of out-of-hospital cardiac arrest (OHCA), and it is possible that more generalized factors beyond SARS-CoV-2 infection are primarily responsible for changes in OHCA incidence and outcome. Objective: To assess whether COVID-19 is associated with OHCA incidence and outcomes. Design, Setting, and Participants: This retrospective cohort study was conducted in Seattle and King County, Washington. Participants included persons aged 18 years or older with nontraumatic OHCA attended by emergency medical services (EMS) between January 1, 2018, and December 31, 2021. Data analysis was performed from November 2022 to March 2023. Exposures: Prepandemic (2018-2019) and pandemic (2020-2021) periods and SARS-CoV-2 infection. Main Outcomes and Measures: The primary outcomes were OHCA incidence and patient outcomes (ie, survival to hospital discharge). Mediation analysis was used to determine the percentage change in OHCA incidence and outcomes between prepandemic and pandemic periods that was attributable to acute SARS-CoV-2 infection vs conventional Utstein elements related to OHCA circumstances (ie, witness status and OHCA location) and resuscitation care (ie, bystander cardiopulmonary resuscitation, early defibrillation, and EMS response intervals). Results: There were a total of 13 081 patients with OHCA (7102 dead upon EMS arrival and 5979 EMS treated). Among EMS-treated patients, the median (IQR) age was 64.0 (51.0-75.0) years, 3864 (64.6%) were male, and 1027 (17.2%) survived to hospital discharge. The total number of patients with OHCA increased by 19.0% (from 5963 in the prepandemic period to 7118 in the pandemic period), corresponding to an incidence increase from 168.8 to 195.3 events per 100 000 person-years. Of EMS-treated patients with OHCA during the pandemic period, 194 (6.2%) were acutely infected with SARS-CoV-2 compared with 7 of 191 EMS-attended but untreated patients with OHCA (3.7%). In time-series correlation analysis, there was a positive correlation between community SARS-CoV-2 incidence and overall OHCA incidence (r = 0.27; P = .01), as well as OHCA incidence with acute SARS-CoV-2 infection (r = 0.43; P < .001). The survival rate during the pandemic period was lower than that in the prepandemic period (483 patients [15.4%] vs 544 patients [19.2%]). During the pandemic, those with OHCA and acute SARS-CoV-2 infection had lower likelihood of survival compared with those without acute infection (12 patients [6.2%] vs 471 patients [16.0%]). SARS-CoV-2 infection itself accounted for 18.5% of the pandemic survival decline, whereas Utstein elements mediated 68.2% of the survival decline. Conclusions and Relevance: In this cohort study of COVID-19 and OHCA, a substantial proportion of the higher OHCA incidence and lower survival during the pandemic was not directly due to SARS-CoV-2 infection but indirect factors that challenged OHCA prevention and treatment.

Prehospital Administration of Norepinephrine and Epinephrine for Shock after Resuscitation from Cardiac Arrest.

INTRODUCTION: Shock after resuscitation from out-of-hospital cardiac arrest (OHCA) is often treated with vasopressors. We examined whether infusion of epinephrine versus norepinephrine was associated with prehospital rearrest and neurologically favorable survival among OHCA patients. METHODS: This retrospective study included OHCA cases in Seattle, Washington from 2014-2021 who had return of spontaneous circulation (ROSC) followed by vasopressor infusion. Our primary exposure was infusion of epinephrine or norepinephrine. Our primary outcome was prehospital rearrest. Secondary outcomes included survival and neurologically favorable outcome (Cerebral Performance Category score of 1 or 2). We used multivariable logistic regression to test associations between exposures and outcomes adjusting for key covariates. RESULTS: Of 451 OHCA patients with ROSC followed by vasopressor infusion, 253 (56%) received norepinephrine and 198 (44%) received epinephrine infusions. Those who received epinephrine were older (median 66 [interquartile ranges {IQR} 53-79] vs 63 [IQR 47-75] years), but otherwise had similar baseline characteristics. Patients who received epinephrine were twice as likely to rearrest (55% vs 25%). After adjustment, the difference in rearrest rates between epinephrine and norepinephrine persisted (OR 3.28, 95%CI 2.25-5.08), and the odds of pulses at hospital arrival were lower in the epinephrine group (OR 0.52 95%CI 0.32-0.83). After adjustment, there was no difference in neurologically favorable survival, survival to hospital admission, or survival to discharge. CONCLUSION: Patients who received epinephrine infusions after ROSC suffered prehospital rearrest more frequently than those who received norepinephrine. Survival and neurological status at hospital discharge were similar. Future trials should examine the optimal approach to hemodynamic management for post-OHCA shock.

THE COMPENSATORY RESERVE INDEX FOR PREDICTING HEMORRHAGIC SHOCK IN PREHOSPITAL TRAUMA.

ABSTRACT: Background: The compensatory reserve index (CRI) is a noninvasive, continuous measure designed to detect intravascular volume loss. CRI is derived from the pulse oximetry waveform and reflects the proportion of physiologic reserve remaining before clinical hemodynamic decompensation. Methods: In this prospective, observational, prehospital cohort study, we measured CRI in injured patients transported by emergency medical services (EMS) to a single Level I trauma center. We determined whether the rolling average of CRI values over 60 s (CRI trend [CRI-T]) predicts in-hospital diagnosis of hemorrhagic shock, defined as blood product administration in the prehospital setting or within 4 h of hospital arrival. We hypothesized that lower CRI-T values would be associated with an increased likelihood of hemorrhagic shock and better predict hemorrhagic shock than prehospital vital signs. Results: Prehospital CRI was collected on 696 adult trauma patients, 21% of whom met our definition of hemorrhagic shock. The minimum CRI-T was 0.14 (interquartile range [IQR], 0.08-0.31) in those with hemorrhagic shock and 0.31 (IQR 0.15-0.50) in those without ( P = <0.0001). The positive likelihood ratio of a CRI-T value <0.2 predicting hemorrhagic shock was 1.85 (95% confidence interval [CI], 1.55-2.22). The area under the ROC curve (AUC) for the minimum CRI-T predicting hemorrhagic shock was 0.65 (95% CI, 0.60-0.70), which outperformed initial prehospital HR (0.56; 95% CI, 0.50-0.62) but underperformed EMS systolic blood pressure and shock index (0.74; 95% CI, 0.70-0.79 and 0.72; 95% CI, 0.67-0.77, respectively). Conclusions: Low prehospital CRI-T predicts blood product transfusion by EMS or within 4 hours of hospital arrival but is less prognostic than EMS blood pressure or shock index. The evaluated version of CRI may be useful in an austere setting at identifying injured patients that require the most significant medical resources. CRI may be improved with noise filtering to attenuate the effects of vibration and patient movement.

Metronome use improves achievement of a target compression rate in out-of-hospital cardiac arrest: A retrospective analysis.

Aim: The aim of this study was to evaluate chest compression rates (CCR) with and without the use of a metronome during treatment of out-of-hospital cardiac arrest (OHCA). Methods: We performed a retrospective cohort investigation of non-traumatic OHCA cases treated by Seattle Fire Department from January 1, 2013, to December 31, 2019. The exposure was a metronome running during CPR at a rate of 110 beats per minute. The primary outcome was the median CCR for all periods of CPR with a metronome compared to periods without a metronome. Results: We included 2,132 OHCA cases with 32,776 minutes of CPR data; 15,667 (48%) minutes had no metronome use, and 17,109 (52%) minutes had a metronome used. Without a metronome, the median CCR was 112.8 per minute with an interquartile range of 108.4 - 119.1, and 27% of minutes were above 120 or less than 100. With a metronome, the median CCR was 110.5 per minute with an interquartile range of 110.0-112.0, and less than 4% of minutes were above 120 or less than 100. The compression rate was 109, 110, or 111 in 62% of minutes with a metronome compared to 18% of minutes with no metronome. Conclusion: The use of a metronome during CPR resulted in increased compliance to a predetermined compression rate. Metronomes are a simple tool that improves achievement of a target compression rate with little variance from that target.

Diagnostic yield, safety, and outcomes of Head-to-pelvis sudden death CT imaging in post arrest care: The CT FIRST cohort study.

AIM: Our aim was to test whether a head-to-pelvis CT scan improves diagnostic yield and speed to identify causes for out of hospital circulatory arrest (OHCA). METHODS: CT FIRST was a prospective observational pre-/post-cohort study of patients successfully resuscitated from OHCA. Inclusion criteria included unknown cause for arrest, age >18 years, stability to undergo CT, and no known cardiomyopathy or obstructive coronary artery disease. A head-to-pelvis sudden death CT (SDCT) scan within 6 hours of hospital arrival was added to the standard of care for patients resuscitated from OHCA (post-cohort) and compared to standard of care (SOC) alone (pre-cohort). The primary outcome was SDCT diagnostic yield. Secondary outcomes included time to identifying OHCA cause and time-critical diagnoses, SDCT safety, and survival to hospital discharge. RESULTS: Baseline characteristics between the SDCT (N = 104) and the SOC (N = 143) cohorts were similar. CT scans (either head, chest, and/or abdomen) were ordered in 74 (52%) of SOC patients. Adding SDCT scanning identified 92% of causes for arrest compared to 75% (SOC-cohort; p value < 0.001) and reduced the time to diagnosis by 78% (SDCT 3.1 hours, SOC alone 14.1 hours, p < 0.0001). Identification of critical diagnoses was similar between cohorts, but SDCT reduced delayed (>6 hours) identification of critical diagnoses by 81% (p < 0.001). SDCT safety endpoints were similar including acute kidney injury. Patient survival to discharge was similar between cohorts. DISCUSSION: SDCT scanning early after OHCA resuscitation safely improved the efficiency and diagnostic yield for causes of arrest compared to the standard of care alone. CLINICAL TRIALS NUMBER: NCT03111043.

Scoping review of echocardiographic parameters associated with diagnosis and prognosis after resuscitated sudden cardiac arrest.

AIM: Current international guidelines recommend early echocardiography after resuscitated sudden death despite limited data. Our aim was to analyze published data on early post-resuscitation echocardiography to identify cardiac causes of sudden death and prognostic implications. METHODS: We reviewed MEDLINE, EMBASE, and CENTRAL databases to December 2021 for echocardiographic studies of adult patients after resuscitation from non-traumatic sudden death. Studies were included if echocardiography was performed <48 hours after resuscitation and reported (1) diagnostic accuracy to detect cardiac etiologies of sudden death or (2) prognostic outcomes. Diagnostic endpoints were associations of regional wall motion abnormalities (RWMA), ventricular function, and structural abnormalities with cardiac etiologies of arrest. Prognostic endpoints were associations of echocardiographic findings with survival to hospital discharge and favorable neurological outcome. RESULTS: Of 2877 articles screened, 16 (0.6%) studies met inclusion criteria, comprising 2035 patients. Two of six studies formally reported diagnostic accuracy for echocardiography identifying cardiac etiology of arrest; RWMA (in 5 of 6 studies) were associated with presumed cardiac ischemia in 17-89% of cases. Among 12 prognostic studies, there was no association of reduced left ventricular ejection fraction with hospital survival (v10) or favorable neurologic status (n = 5). Echocardiographic high mitral E/e' ratio (n = 1) and right ventricular systolic dysfunction (n = 2) were associated with poor survival. CONCLUSION: This scoping review highlights the limited data on early echocardiography in providing etiology of arrest and prognostic information after resuscitated sudden death. Further research is needed to refine the clinical application of early echocardiographic findings in post arrest care.

Increase in end-tidal carbon dioxide after defibrillation predicts sustained return of spontaneous circulation during out-of-hospital cardiac arrest.

INTRODUCTION: Guidelines recommend monitoring end-tidal carbon dioxide (ETCO2) during out-of-hospital cardiac arrest (OHCA), though its prognostic value is poorly understood. This study investigated the relationship between ETCO2 and return of spontaneous circulation (ROSC) after defibrillation in intubated non-traumatic OHCA patients. METHODS: This retrospective, observational cohort analysis included adult OHCA patients who received a defibrillation shock during treatment by an urban EMS agency from 2015 to 2021. Peak ETCO2 values were determined for the 90-second periods before and after the first defibrillation in an intubated patient (shock of interest [SOI]). Values were analyzed for association between the change in ETCO2 from pre- to post-shock and the presence of ROSC on the subsequent pulse check. RESULTS: Of 518 eligible patients, mean age was 61, 72% were male, 50% had a bystander-witnessed arrest, and 62% had at least one episode of ROSC. The most common arrest etiology was medical (92%). Among all patients, peak ETCO2 during resuscitation prior to SOI was 36.8 mmHg (18.6). ETCO2 increased in patients who achieved ROSC immediately after SOI (from 38.3 to 47.6 mmHg; +9.3 CI: 6.5, 12.1); patients with sustained ROSC experienced the greatest increase in ETCO2 after SOI (from 37.8 to 48.2 mmHg; +10.4 CI: 7.2, 13.6), while ETCO2 in patients who did not achieve ROSC after SOI rose (from 36.4 to 37.8 mmHg; +1.4 CI: -0.1, 2.8). CONCLUSIONS: ETCO2 rises after defibrillation in most patients during cardiac arrest. Patients with sustained ROSC experience larger rises, though the majority experience rises of less than 10 mmHg.

The association between arterial-end-tidal carbon dioxide difference and outcomes after out-of-hospital cardiac arrest.

AIM: We sought to determine if the difference between PaCO2 and ETCO2 is associated with hospital mortality and neurologic outcome following out-of-hospital cardiac arrest (OHCA). METHODS: This was a retrospective cohort study of adult patients who achieved return of spontaneous circulation (ROSC) after OHCA over 3 years. The primary exposure was the PaCO2-ETCO2 difference on hospital arrival. The primary outcome was survival to hospital discharge. The secondary outcome was favorable neurologic status at discharge. We used receiver operating characteristic (ROC) curves to determine discrimination threshold and multivariate logistic regression to examine the association between the PaCO2-ETCO2 difference and outcome. RESULTS: Of 698 OHCA patients transported to the hospitals, 381 had sustained ROSC and qualifying ETCO2 and PaCO2 values. Of these, 160 (42%) survived to hospital discharge. Mean ETCO2 was 39 mmHg among survivors and 43 mmHg among non-survivors. Mean PaCO2-ETCO2 was 6.8 mmHg and 9.0 mmHg (p < 0.05) for survivors and non-survivors. After adjustment for Utstein characteristics, a higher PaCO2-ETCO2 difference on hospital arrival was not associated with hospital mortality (OR 0.99, 95% CI: 0.97-1.0) or neurological outcome. Area under the ROC curve or PaCO2-ETCO2 difference was 0.56 (95% CI 0.51-0.62) compared with 0.58 (95% CI 0.52-0.64) for ETCO2. CONCLUSION: Neither PaCO2-ETCO2 nor ETCO2 were strong predictors of survival or neurologic status at hospital discharge. While they may be useful to guide ventilation and resuscitation, these measures should not be used for prognostication after OHCA.

Analysis of Epinephrine Dose, Targeted Temperature Management, and Neurologic and Survival Outcomes Among Adults With Out-of-Hospital Cardiac Arrest.

Importance: Epinephrine improves return of spontaneous circulation after out-of-hospital cardiac arrest (OHCA). These beneficial cardiac effects do not directly translate to better neurologic outcomes, possibly because of epinephrine-induced microvascular effects that produce critical brain ischemia. Objective: To examine whether targeted temperature management (TTM) modifies the adverse association between increasing prehospital epinephrine dose and neurologically favorable survival. Design, Setting, and Participants: This retrospective cohort study assessed 14 612 adults from Seattle and King County, Washington, with nontraumatic OHCA between January 1, 2008, and December 31, 2018, and included those who achieved return of spontaneous circulation and were unconscious at hospital admission. Data analysis was performed from April 2021 to May 2022. Exposures: Epinephrine dose and TTM during prehospital resuscitation. Main Outcomes and Measures: Favorable neurologic survival (Cerebral Performance Category [CPC] 1 or 2) and survival to hospital discharge. Results: Of the 14 612 assessed adults, 5253 (median age, 63 years; IQR, 51-74 years; 3460 [65.8%] male) were eligible for the study. The median epinephrine dose was 2.0 mg (IQR, 1.0-3.0 mg); 3052 patients (58.1%) received TTM. In all, 1889 patients (36.0%) survived with CPC 1 to 2, and 2177 (41.4%) survived to discharge. Increasing doses of epinephrine were associated with a decreasing likelihood of CPC 1 to 2 (odds ratio [OR], 0.46; 95% CI 0.42-0.50 for each additional milligram of epinephrine) and survival (OR, 0.47; 95% CI, 0.43-0.51). The dose-dependent epinephrine association was modified by TTM. After adjusting for Utstein covariates, TTM was associated with a relative stepwise improvement in odds of CPC 1 to 2 (interaction OR, 1.36; 95% CI, 1.22-1.51) and survival (interaction OR, 1.37; 95% CI, 1.24-1.51). A significant interaction was also observed when the analysis was stratified according to initial rhythm among shockable OHCA and nonshockable OHCA (shockable interaction OR, 1.20; 95% CI, 1.04-1.39; and nonshockable interaction OR, 1.24, 95% CI, 1.07-1.45). Conclusions and Relevance: This cohort study found an interaction between TTM and epinephrine dose such that the beneficial association of TTM increased with increasing epinephrine dose, suggesting that TTM may attenuate the adverse effects of higher-dose epinephrine.

Investigating the Airway Opening Index during cardiopulmonary resuscitation.

INTRODUCTION: Chest compressions during CPR induce oscillations in capnography (ETCO2) waveforms. Studies suggest ETCO2 oscillation characteristics are associated with intrathoracic airflow dependent on airway patency. Oscillations can be quantified by the Airway Opening Index (AOI). We sought to evaluate multiple methods of computing AOI and their association with return of spontaneous circulation (ROSC). METHODS: We conducted a retrospective study of 307 out-of-hospital cardiac arrest (OHCA) cases in Seattle, WA during 2019. ETCO2 and chest impedance waveforms were annotated for the presence of intubation and CPR. We developed four methods for computing AOI based on peak ETCO2 and the oscillations in ETCO2 during chest compressions (ΔETCO2). We examined the feasibility of automating ΔETCO2 and AOI calculation and evaluated differences in AOI across the methods using nonparametric testing (α = 0.05). RESULTS: Median [interquartile range] AOI across all cases using Methods 1-4 was 28.0 % [17.9-45.5 %], 20.6 % [13.0-36.6 %], 18.3 % [11.4-30.4 %], and 22.4 % [12.8-38.5 %], respectively (p < 0.001). Cases with ROSC had a higher median AOI than those without ROSC across all methods, though not statistically significant. Cases with ROSC had a significantly higher median [interquartile range] ΔETCO2 of 7.3 mmHg [4.5-13.6 mmHg] compared to those without ROSC (4.8 mmHg [2.6-9.1 mmHg], p < 0.001). CONCLUSION: We calculated AOI using four proposed methods resulting in significantly different AOI. Additionally, AOI and ΔETCO2 were larger in cases achieving ROSC. Further investigation is required to characterize AOI's ability to predict OHCA outcomes, and whether this information can improve resuscitation care.