A Novel Algorithm for Improving the Prehospital Diagnostic Accuracy of ST-Segment Elevation Myocardial Infarction.

INTRODUCTION: Early detection of ST-segment elevation myocardial infarction (STEMI) on the prehospital electrocardiogram (ECG) improves patient outcomes. Current software algorithms optimize sensitivity but have a high false-positive rate. The authors propose an algorithm to improve the specificity of STEMI diagnosis in the prehospital setting. METHODS: A dataset of prehospital ECGs with verified outcomes was used to validate an algorithm to identify true and false-positive software interpretations of STEMI. Four criteria implicated in prior research to differentiate STEMI true positives were applied: heart rate <130, QRS <100, verification of ST-segment elevation, and absence of artifact. The test characteristics were calculated and regression analysis was used to examine the association between the number of criteria included and test characteristics. RESULTS: There were 44,611 cases available. Of these, 1,193 were identified as STEMI by the software interpretation. Applying all four criteria had the highest positive likelihood ratio of 353 (95% CI, 201-595) and specificity of 99.96% (95% CI, 99.93-99.98), but the lowest sensitivity (14%; 95% CI, 11-17) and worst negative likelihood ratio (0.86; 95% CI, 0.84-0.89). There was a strong correlation between increased positive likelihood ratio (r2 = 0.90) and specificity (r2 = 0.85) with increasing number of criteria. CONCLUSIONS: Prehospital ECGs with a high probability of true STEMI can be accurately identified using these four criteria: heart rate <130, QRS <100, verification of ST-segment elevation, and absence of artifact. Applying these criteria to prehospital ECGs with software interpretations of STEMI could decrease false-positive field activations, while also reducing the need to rely on transmission for physician over-read. This can have significant clinical and quality implications for Emergency Medical Services (EMS) systems.

Association between a Post-Resuscitation Care Bundle and the Odds of Field Rearrest after Successful Resuscitation from Out-of-Hospital Cardiac Arrest: A Pre/Post Study.

OBJECTIVES: Rearrest after successful resuscitation from out-of-hospital cardiac arrest (OHCA) is common and is associated with worse patient outcomes. However, little is known about the effect of interventions designed to prevent rearrest. We assessed the association between a prehospital care protocol for immediate management after return of spontaneous circulation (ROSC) and rates of field rearrest and survival to discharge in patients with prehospital ROSC. METHODS: This was a retrospective study of adult patients with OHCA and field ROSC within a large EMS system before (April 2017-August 2018) and after (April 2019-February 2020) implementation of a structured prehospital post-ROSC care protocol. The protocol was introduced in September 2018 and provided on-scene stabilization direction including guidance on ventilation and blood pressure support. Field data and hospital outcomes were used to compare the frequency of field rearrest, hospital survival, and survival with good neurologic outcome before and after protocol implementation. Logistic regression was used to assess the association between the post-implementation period and these outcomes, and odds ratios were reported. The association between individual interventions on these outcomes was also explored. RESULTS: There were 2,706 patients with ROSC after OHCA in the pre-implementation period and 1,780 patients in the post-implementation period. The rate of prehospital rearrest was 43% pre-implementation vs 45% post-implementation (RD 2%, 95% CI -1, 4%). In the adjusted analysis, introduction of the protocol was not associated with decreased odds of rearrest (OR 0.87, 95% CI 0.73, 1.04), survival to hospital discharge (OR 1.01, 95% CI 0.81, 1.24), or survival with good neurologic outcome (OR 0.81, 95% CI 0.61, 1.06). Post-implementation, post-ROSC administration of saline and push-dose epinephrine increased from 11% to 25% (RD 14%, 95% CI 11, 17%) and from 3% to 12% (RD 9% 95% CI 7, 11%), respectively. In an exploratory analysis, push-dose epinephrine was associated with a decreased odds of rearrest (OR 0.68, 95% CI 0.50, 0.94). CONCLUSIONS: Introduction of a post-ROSC care protocol for patients with prehospital ROSC after OHCA was not associated with reduced odds of field rearrest. When elements of the care bundle were considered individually, push-dose epinephrine was associated with decreased odds of rearrest.

Does Housing Status Matter in Emergency Medical Services Administration of Naloxone? A Prehospital Cross-sectional Study.

Introduction: Persons experiencing homelessness (PEH) use emergency medical services (EMS) at disproportionately high rates relative to housed individuals due to several factors including disparate access to healthcare. Limited access to care is compounded by higher rates of substance use in PEH. Despite growing attention to the opioid epidemic and housing crisis, differences in EMS naloxone administration by housing status has not been systematically examined. Our objective in this study was to describe EMS administration of naloxone by housing status in the City of Los Angeles. Methods: This was a 12-month retrospective, cross-sectional analysis of electronic patient care reports (ePCRs) for all 9-1-1 EMS incidents attended by the Los Angeles Fire Department (LAFD), the sole EMS provider agency for the City of Los Angeles during the study period, January-December 2018. During this time, the City had a population of 3,949,776 with an estimated 31,825 (0.8%) PEH. We included in the study individuals to whom LAFD personnel had administered naloxone. Housing status is a mandatory field on ePCRs. The primary study outcome was the incidence of EMS naloxone administration by housing status. We used descriptive statistics and logistic regression models to examine patterns by key covariates. Results: There were 345,190 EMS incidents during the study period. Naloxone was administered during 2,428 incidents. Of those incidents 608 (25%) involved PEH, and 1,820 (75%) involved housed individuals. Naloxone administration occurred at a rate of 19 per 1,000 PEH, roughly 44 times the rate of housed individuals. A logistic regression model showed that PEH remained 2.38 times more likely to receive naloxone than their housed counterparts, after adjusting for gender, age, and respiratory depression (odds ratio 2.38, 95% confidence interval 2.15-2.64). The most common provider impressions recorded by the EMS responders who administered naloxone were the same for both groups: overdose; altered level of consciousness; and cardiac arrest. Persons experiencing homelessness who received naloxone were more likely to be male (82% vs 67%) and younger (41.4 vs 46.2 years) than housed individuals. Conclusion: In the City of Los Angeles, PEH are more likely to receive EMS-administered naloxone than their housed peers even after adjusting for other factors. Future research is needed to understand outcomes and improve care pathways for patients confronting homelessness and opioid use.

Older Adult Frequent 9-1-1 Callers for Emergency Medical Services in a Large Metropolitan City: Individual- and System-Level Considerations.

BACKGROUND: High utilizers of 9-1-1 place a substantial burden on emergency medical services (EMS). Results of a retrospective review of records data of the City of Los Angeles Fire Department (LAFD) showed a significant increase in older adult high utilizers of 9-1-1. OBJECTIVE: The objective of this study was to explore individual- and system-level factors implicated in EMS use among older adults, and to provide system recommendations to mitigate overuse. METHODS: A phenomenological study was conducted, drawing from LAFD EMS records between 2012 and 2016 to identify and contact high-utilizing patients older than 50 years, their family, agency representatives, and LAFD personnel. Interviews were recorded, transcribed, and coded and a thematic analysis was completed. RESULTS: We conducted in-depth interviews with 27 participants, including patients (n = 8), their families (n = 6), social service agency representatives (n = 3), and LAFD personnel (n = 10). The following cross-cutting themes emerged: nature of 9-1-1 calls, barriers to access, and changing the system. In addition, LAFD and social service agency representatives identified the role of EMS responders and social agency representatives. Patients and their families agreed that previous encounters and interactions with emergency care responders were relevant factors. CONCLUSIONS: This study described reasons for 9-1-1 calls related to medical and social service needs, including mental health care. Our analysis offers insight from different stakeholders' perspectives on access to medical care and types of barriers that interfere with medical care. All groups shared recommendations to advance access to medical and mental health care.

Implementation of a regional extracorporeal membrane oxygenation program for refractory ventricular fibrillation out-of-hospital cardiac arrest.

BACKGROUND: eCPR, the modality of extracorporeal membrane oxygenation (ECMO) applied in the setting of cardiac arrest, has emerged as a novel therapy which may improve outcomes in select patients with out-of-hospital cardiac arrest (OHCA). To date, implementation has been mainly limited to single academic centres. Our objective is to describe the feasibility and challenges with implementation of a regional protocol for eCPR. METHODS: The Los Angeles County Emergency Medical Services (EMS) Agency implemented a regional eCPR protocol in July 2020, which included coordination across multiple EMS provider agencies and hospitals to route patients with refractory ventricular fibrillation (rVF) OHCA to eCPR-capable centres (ECCs). Data were entered on consecutive patients with rVF with suspected cardiac aetiology into a centralized database including time intervals, field and in-hospital care, survival and neurologic outcome. RESULTS: From July 27, 2020 through July 31, 2022, 35 patients (median age 57 years, 6 (17%) female) were routed to ECCs, of whom 11 (31%) received eCPR and 3 (27%) treated with eCPR survived, all of whom had a full neurologic recovery. Challenges encountered during implementation included cost to EMS provider agencies for training, implementation, and purchase of automatic chest compression devices, maintenance of system awareness, hospital administrative support for staffing and equipment for the ECMO program, and interdepartmental coordination at ECCs. CONCLUSION: We describe the successful implementation of a regional eCPR program with ongoing patient enrolment and data collection. These preliminary findings can serve as a model for other EMS systems who seek to implement regional eCPR programs.

Cognitive load during training for out-of-department emergency responses.

Background: Emergency medicine (EM) physicians sometimes respond to critical events outside the emergency department. To prepare for these complex cases-typically called "rapid responses" (RRs)-EM residents receive simulation-based training involving four practice tasks and three exam tasks during a 1-day session. Cognitive load (CL) theory describes how humans function with limited working memories to perform complex tasks. RRs are expected to generate high levels of CL, but the profile of CL across providers and RR cases is not well understood. In this study, we analyzed resident's CL during RR training. We hypothesized variations in CL across individual and case and that exam cases would cause higher CLs than practice cases. Methods: Residents anonymously self-reported CL levels after each case using the Paas scale, a single-item, 9-point scale from "very, very low CL" to "very, very high CL." To examine case-based differences in CL, data were rescaled by individual residents. "High CL" was defined as a score of 9/9. Results: Among 18 residents participating, CLs ranged from 4 to 9, with median of 7 and interquartile range of 7-8. While many cases showed bell curve-like distributions of CLs, one case-a bleeding tracheostomy-showed a rightward skew reflecting higher levels of CL. No significant difference was found in CL between practice and exam cases. There were 20 reports (16.5%) of "high" CL with variation across residents (0/7 [0%] to 5/6 [83.3%] cases) and across cases (1/18 [5.6%) to 8/18 [44.4%]). Conclusions: The CL that EM residents experienced did show considerable interpersonal and intercase variation, but there was no significant difference between practice and exam cases. These results highlight several questions about how to optimally design future training, including how best to balance low and high CL training cases and which cases may require further training.

Prehospital Predictors of Atypical STEMI Symptoms.

Introduction: Rapid prehospital identification of patients with ST-elevation myocardial infarction (STEMI) is a critical step to reduce time to treatment. Broad screening with field 12-lead ECGs can lead to a high rate of false positive STEMI activations due to low prevalence. One strategy to reduce false positive STEMI interpretations is to limit acquisition of 12-lead ECGs to patients who have symptoms strongly suggestive of STEMI, but this may delay care in patients who present atypically and lead to disparities in populations with more atypical presentations. We sought to assess patient factors associated with atypical STEMI presentation.Methods: We retrospectively analyzed consecutive adult patients for whom Los Angeles Fire Department paramedics obtained a field 12-lead ECG from July 2011 through June 2012. The regional STEMI receiving center registry was used to identify patients with STEMI. Patients were designated as having typical symptoms if paramedics documented provider impressions of chest pain/discomfort, cardiac arrest, or cardiac symptoms, otherwise they were designated as having atypical symptoms. We utilized logistic regression to determine patient factors (age, sex, race) associated with atypical STEMI presentation.Results: Of the 586 patients who had STEMI, 70% were male, 43% White, 16% Black, 20% Hispanic, 5% Asian and 16% were other or unspecified race. Twenty percent of STEMI patients (n = 117) had atypical symptoms. Women who had STEMI were older than men (74 years [IQR 62-83] vs. 60 years [IQR 53-70], p < 0.001). Univariate predictors of atypical symptoms were older age and female sex (p < 0.0001), while in multivariable analysis older age [odd ratio (OR) 1.05 per year, [95%CI 1.04-1.07, p < 0.0001] and black race (OR vs White 2.18, [95%CI 1.20-3.97], p = 0.011) were associated with atypical presentation.Conclusion: Limiting prehospital acquisition of 12-lead ECGs to patients with typical STEMI symptoms would result in one in five patients with STEMI having delayed recognition, disproportionally impacting patients of older age, women, and Black patients. Age, not sex, may be a better predictor of atypical STEMI presentation.

Use of Naloxone in 9-1-1 Patients without Respiratory Depression in Los Angeles County, California (USA).

INTRODUCTION: Along with an increase in opioid deaths, there has been a desire to increase the accessibility of naloxone. However, in the absence of respiratory depression, naloxone is unlikely to be beneficial and may be deleterious if it precipitates withdrawal in individuals with central nervous system (CNS) depression due to non-opioid etiologies. OBJECTIVE: The aim of this study was to evaluate how effective prehospital providers were in administering naloxone. METHODS: This is a retrospective study of naloxone administration in two large urban Emergency Medical Service (EMS) systems. The proportion of patients who had a respiratory rate of at least 12 breaths per minute at the time of naloxone administration by prehospital providers was determined. RESULTS: During the two-year study period, 2,580 patients who received naloxone by prehospital providers were identified. The median (interquartile range) respiratory rate prior to naloxone administration was 12 (6-16) breaths per minute. Using an a priori respiratory rate of under 12 breaths per minute to define respiratory depression, only 1,232 (47.8%; 95% CI, 50.3%-54.2%) subjects who received naloxone by prehospital providers had respiratory depression. CONCLUSION: This study showed that EMS providers in Los Angeles County, California (USA) frequently administered naloxone to individuals without respiratory depression.

Spatiotemporal analysis of out-of-hospital cardiac arrest in the City of Los Angeles, 2011-2019.

OBJECTIVE: The goal of this analysis is to spatiotemporally identify and categorize areas in a large urban city according to Out-of-Hospital Cardiac Arrest (OHCA) rates and No Bystander CPR (NBCPR) risk levels. STUDY AREA AND PARTICIPANTS: The study comprised all cardiac arrests within the administrative geographic boundary of the City of Los Angeles. The final sample included 15,904 cases that were geolocated within 985 census tracts. MAIN OUTCOMES AND MEASURES: The primary outcome was stratification of census tracts into risk levels of OHCA and NBCPR by observed spatiotemporal patterns. RESULTS: Of 985 census tracts in the analytical sample, 182 census tracts (18.5%) were identified as having higher risk of OHCA and NBCPR. This assessment resulted in 129 census tracts in Tier 3 (moderate risk), 36 in Tier 2 (moderate-high risk), and 17 in Tier 1 (highest risk). Census tracts in Tiers 2 and 3 had higher amounts incident OHCA, while those in tier 1 had more OHCA events with NBCPR. These areas were largely contiguous and located in the Central and South areas of Los Angeles. CONCLUSIONS: Using a novel three-tiered neighborhood risk classification tool, specific neighborhoods have been identified in the second largest city in the U.S. with consistently high or accelerating rates of OHCA and low bystander CPR. Further study of bystander response and community-based public health campaigns are needed in these communities.

Comparison of Emergency Medical Dispatch Systems for Performance of Telecommunicator-Assisted Cardiopulmonary Resuscitation Among 9-1-1 Callers With Limited English Proficiency.

Importance: Increasing bystander cardiopulmonary resuscitation (CPR) among racial/ethnic minority groups and culturally underserved populations is a key strategy in improving health care disparities in out-of-hospital cardiac arrest. Objective: To ascertain whether implementation of the Los Angeles Tiered Dispatch System (LA-TDS) was associated with improved performance of telecommunicator-assisted CPR (T-CPR) among 9-1-1 callers with limited English proficiency in the City of Los Angeles. Design, Setting, and Participants: This cohort study compared emergency medical services-treated, nontraumatic out-of-hospital cardiac arrest calls using the Medical Priority Dispatch System (MPDS) from January 1 to March 31, 2014, with calls using LA-TDS from January 1 to March 31, 2015. Trained data abstractors evaluated all 9-1-1 audio recordings for the initiation of T-CPR and the elapsed time to predefined events. Data were analyzed between January and December 2017. Main Outcomes and Measures: The primary outcome was the prevalence of T-CPR among 9-1-1 callers with limited English proficiency for field-confirmed nontraumatic cardiac arrests. Additional outcomes included T-CPR among callers with English proficiency and the elapsed time until key events in the call. Results: Of the 1027 emergency medical services calls during the study periods, 597 met the inclusion criteria. A total of 289 calls (48%) were made using MPDS (263 callers with English proficiency, and 26 callers with limited English proficiency), and 308 calls (52%) were made using LA-TDS (273 callers with English proficiency, and 35 callers with limited English proficiency). No differences between MPDS and LA-TDS cohorts were found in age, sex, known comorbidities, arrest location (private vs public), or witnessed status. The prevalence of T-CPR among callers with limited English proficiency was significantly greater using LA-TDS (69%) vs MPDS (28%) (odds ratio [OR], 5.66; 95% CI, 1.79-17.85; P = .003). For callers with English proficiency, the prevalence of T-CPR improved from 55% using MPDS to 67% using LA-TDS (OR, 1.66; 95% CI, 1.15-2.41; P = .007). With LA-TDS, callers with limited English proficiency had a significant decrease in time to recognition of cardiac arrest (OR, 0.59; 95% CI, 0.41-0.84; P = .005) and dispatch of resources (OR, 0.71; 95% CI, 0.54-0.94; P = .02). Conclusions and Relevance: The LA-TDS compared with MPDS was associated with increased performance of T-CPR for out-of-hospital cardiac arrests involving 9-1-1 callers with limited English proficiency. Further studies are needed in communities with a predominance of people with limited English proficiency to characterize bystander response, promote activation of the chain of survival, and clarify the precise elements of LA-TDS that can improve T-CPR performance.