Variation in Out-of-Hospital Cardiac Arrest Survival Across Emergency Medical Service Agencies

Abstract

Background: Although studies have reported variation in out-of-hospital cardiac arrest (OHCA) survival by geographic location, little is known about variation in OHCA survival at the level of emergency medical service (EMS) agencies-which may have modifiable practices, unlike counties and regions. We quantified the variation in OHCA survival across EMS agencies and explored whether variation in 2 specific EMS resuscitation practices were associated with survival to hospital admission.

Methods: Within the Cardiac Arrest Registry to Enhance Survival, a prospective registry representing ≈51% of the US population, we identified 258 342 OHCAs from 764 EMS agencies with >10 OHCA cases annually during 2015 to 2019. Using hierarchical logistic regression, risk-standardized rates of survival to hospital admission were computed for each EMS agency. We quantified inter-agency variation in survival with median odds ratios and assessed the association of 2 resuscitation practices (EMS response time and the proportion of OHCAs with termination of resuscitation without meeting futility criteria) with EMS agency survival rates to hospital admission.

Results: Across 764 EMS agencies comprising 258 342 OHCAs, the median risk-standardized rate of survival to hospital admission was 27.3% (interquartile range, 24.5%-30.1%; range: 16.0%-45.6%). The adjusted median odds ratio was 1.35 (95% CI, 1.32-1.39), denoting that the odds of survival of 2 patients with identical covariates varied by 35% at 2 randomly selected EMS agencies. EMS agencies in the lowest quartile of risk-standardized survival had longer EMS response times when compared with the highest quartile (12.0±3.4 versus 9.0±2.6 minutes; P<0.001), and a higher proportion of OHCAs with termination of resuscitation without meeting futility criteria (27.9±16.1% versus 18.9±11.4%; P<0.001).

Conclusions: Survival after OHCA varies widely across EMS agencies. EMS response times and termination of resuscitation practices were associated with agency-level rates of survival to hospital admission, suggesting potentially modifiable practices which can improve OHCA survival.

Keywords: emergency medical services; geographic locations; out-of-hospital cardiac arrest; resuscitation; survival.

Figure 1.. Definition of Study Cohort.

Consort diagram. Abbreviations: EMS, emergency medical services; OHCA, out-of-hospital cardiac arrest.

Figure 2.. Distribution of EMS Agency Rates of Risk-Standardized Survival to Hospital Admission for OHCA.

Histogram of EMS-level risk-standardized survival to hospital admission. Abbreviations: EMS, emergency medical services; OHCA, out-of-hospital cardiac arrest.

Figure 3.. Mean EMS Response Time and EMS Agency Rate of Survival to Hospital Admission.

In this scatterplot, each dot represents a unique EMS agency, and the size of the dot is weighted based on the number of OHCA cases at that EMS agency. The blue line is the average EMS agency rate of OHCA survival for a given mean EMS arrival time, and the shaded region is the 95% confidence interval. EMS agency rates of survival to hospital admission are risk-standardized. Abbreviations: EMS, emergency medical services; OHCA, out-of-hospital cardiac arrest.

Figure 4.. EMS Agency Rate of TOR Without Meeting Futility Criteria and Rate of Survival to Hospital Admission.

In this scatterplot, each dot represents a unique EMS agency, and the size of the dot is weighted based on the number of OHCA cases at that EMS agency. The blue line is the average EMS agency rate of OHCA survival for a given rate of TOR without meeting futility criteria. The shaded region is the 95% confidence interval. EMS agency rates of survival to hospital admission are risk-standardized. Abbreviations: EMS, emergency medical services; OHCA, out-of-hospital cardiac arrest; TOR, termination of resuscitation.