Variation in Pre-Hospital Outcomes after Out-of-hospital Cardiac Arrest in Michigan

Aim: Care by emergency medical service (EMS) agencies is critical for optimizing prehospital outcomes following out-of-hospital cardiac arrest (OHCA). We explored whether substantial differences exist in prehospital outcomes across EMS agencies in Michigan-specifically focusing on rates of sustained return of spontaneous circulation (ROSC) upon emergency department (ED) arrival. Methods: Using data from Michigan Cardiac Arrest Registry to Enhance Survival (MI-CARES) for years 2014-2017, we calculated rates of sustained ROSC upon ED arrival across EMS agencies in Michigan. We used hierarchical logistic regression models that accounted for patient, arrest-, community-, and response-level characteristics to determine adjusted rates of sustained ROSC among EMS agencies. Results: A total of 103 EMS agencies and 20,897 OHCA cases were included. Average age of the cohort was 62.5 years (SD = 19.6), 39.7% were female, and 17.9% had an initial shockable rhythm due to ventricular fibrillation or pulseless ventricular tachycardia. The adjusted rate of sustained ROSC upon ED arrival across all EMS agencies was 23.8% with notable variation across EMS agencies (interquartile range [IQR], 20.5-29.2%). The top five EMS agencies had mean adjusted rates of sustained ROSC upon ED arrival of 42.7% (95% CI: 34.6-51.1%) while the bottom five had mean adjusted rates of 9.8% (95% CI: 7.6-12.7%). Conclusions: Substantial variation in sustained ROSC upon ED arrival exists across EMS agencies in Michigan after adjusting for patient-, arrest, community-, and response-level features. Such differences suggest opportunities to identify and improve best practices in EMS agencies to advance OHCA care.