Association Between Emergency Medical Services Intervention Volume and Out-Of-Hospital Cardiac Arrest Survival: A Propensity Score Matching Analysis

Abstract

BackgroundOut of hospital cardiac arrest (OHCA) survival rates are very low. An association between institutional OHCA case volume and patient outcomes has been documented. However, whether this applies to prehospital emergency medicine services (EMS) is unknown. ObjectivesTo investigate the association between the volume of interventions by mobile intensive care units (MICU) and outcomes of patients experiencing an OHCA. MethodsA retrospective cohort study using including adult patients with OHCA managed by medical EMS in five French centers between 2013 and 2020. Two groups were defined depending on the overall annual numbers of MICU interventions: low-volume and high-volume. Primary endpoint was 30-day survival. Secondary endpoints were prehospital return of spontaneous circulation (ROSC), ROSC at hospital admission and favorable neurological outcome. Patients were then matched 1:1 using a propensity score. Conditional logistic regression was then used. ResultsA total of 2,014 adult patients (69% male, median age 68 [57 - 79] years) were analyzed, 50.5% (n=1,017) were managed by low-volume MICU and 49.5% (n=997) by high-volume MICU. Survival on day 30 was 3.6% in the low-volume group compared to 5.1% in the high-volume group. There was no significant association between MICU volume of intervention and survival on day 30 (OR=0.92, 95%CI [0.55;1.53]), prehospital ROSC (OR=1.01, 95%CI [0.78;1.3]), ROSC at hospital admission (OR=0.92, CI95% [0.69;1.21]), or favorable neurologic prognosis on day 30 (OR=0.92 CI95% [0.53;1.62]). ConclusionsThe study suggest that there is no association between MICU volume of intervention and patients with OHCA outcomes. However, further research involving a larger number of centers is necessary to draw definitive conclusions.