Objective: We evaluated the association between prehospital epinephrine administration by emergency medical services (EMS) and the long-term outcomes of out-of-hospital cardiac arrest (OHCA) with initial pulseless electrical activity (PEA) or asystole.
Methods: We conducted a controlled, propensity-matched, retrospective cohort study by using Japan's nationwide OHCA registry database. We studied 110,239 bystander-witnessed OHCA patients aged 15-94 years with initial non-shockable rhythms registered between January 2008 and December 2012. We created 1-1 matched pairs of patients with or without epinephrine by using sequential risk set matching based on time-dependent propensity scores to balance the patients' severity and characteristics. We compared overall and neurologically intact survival 1 month after OHCA between cases and controls using conditional logistic regression models by category of the initial rhythm.
Results: Propensity matching created 7,431 pairs in patients with PEA and 8,906 pairs in those with asystole. Epinephrine administration was associated with higher overall survival (4.49% vs. 2.96%; odds ratio [OR], 1.55; 95% confidence interval [CI], 1.30-1.85) but not with neurologically intact survival (0.98% vs. 0.78%; OR, 1.26; 95% CI, 0.89-1.78) in patients with PEA, and with higher overall survival (2.38% vs. 1.04%; OR, 2.34; 95% CI, 1.82-3.00) and neurologically intact survival (0.48% vs. 0.22%; OR, 2.28; 95% CI, 1.31-3.96) in those with asystole.
Conclusions: Prehospital epinephrine administration by EMS is favorably associated with long-term neurological outcomes in patients with initial asystole and with long-term survival outcomes in those with PEA.
Keywords: cardiac arrest; cardiopulmonary resuscitation; emergency medical service; epinephrine; non-shockable rhythms.