Abstract 10611: Variation in Out-of-Hospital Cardiac Arrest Survival Across EMS Agencies

Abstract

Background: Although some studies have reported variation in out-of-hospital cardiac arrest (OHCA) survival by neighborhood and geographic region, little is known about variation in OHCA survival at the level of EMS agencies—which, unlike neighborhoods and regions, may have modifiable resuscitation practices. Methods: Within the national Cardiac Arrest Registry to Enhance Survival, we identified 258,320 non-traumatic OHCAs from 764 EMS agencies with ≥10 OHCAs annually between 2015-2019. Using multivariable hierarchical logistic regression, we computed risk-adjusted rates of survival to hospital admission for each EMS agency. We quantified the extent of variation in survival with the median odds ratios (MOR) and assessed the extent to which variation in survival was explained by two EMS agency resuscitation practices: time from 911 call to EMS arrival and the proportion of OHCAs at each EMS agency with termination of resuscitation (TOR) without meeting TOR futility criteria. Results: Of 258,320 persons with OHCA, mean age was 62.2 ± 17.0 years and 36.1% were female. Overall, 85.0% were of presumed cardiac etiology, 82.3% occurred at home, 44.0% were witnessed by a bystander, and ~75% were due to a non-shockable initial rhythm. Across the 764 EMS agencies, the median risk-adjusted rate of survival to hospital admission was 27.4% (IQR, 24.5% - 30.2%). The adjusted MOR was 1.35 (95% CI: 1.32, 1.39), suggesting that the odds of survival to hospital admission after an OHCA varied by 35% in two identical patients in one randomly selected EMS agency vs. another. EMS agencies in the lowest quartile of risk-adjusted survival had a mean EMS response time of 12.0 ± 3.4 minutes, whereas those in the highest quartile had a mean EMS response time of 9.0 ± 2.6 minutes ( P <0.001). The mean proportion of OHCA cases where CPR was terminated in the field without meeting TOR futility criteria was 27.9% ±16.1% in quartile 1 and 18.9% ±11.4% in quartile 4 ( P <0.001). Adjustment for the EMS-level variation in both resuscitation practices attenuated the MOR to 1.30 (95% CI: 1.27, 1.33). Conclusions: Rates of survival to hospital admission for OHCA vary significantly by EMS agency, and some of this variation in survival is explained by differences in EMS arrival time and TOR practice patterns.