Association between the number of prehospital defibrillation attempts and neurologic outcomes in out-of-hospital cardiac arrest patients without on-scene return of spontaneous circulation

Objective Delivery of prehospital defibrillation for shockable rhythms by emergency medical service providers is crucial for successful resuscitation in out-of-hospital cardiac arrest (OHCA) patients. The optimal range of prehospital defibrillation attempts for refractory shockable rhythms is unknown. This study evaluated the association between the number of prehospital defibrillation attempts and neurologic outcomes in OHCA patients. Methods A retrospective observational study was conducted using the nationwide OHCA registry. Adult OHCA patients who were treated by emergency medical service providers due to presumed cardiac origin with initial shockable rhythm were enrolled from 2013 to 2016. The final analysis was performed on patients without on-scene return of spontaneous circulation. The number of prehospital defibrillation attempts was categorized as follows: 2-3, 4-5, and >= 6 attempts. The primary outcome was a good neurologic recovery at hospital discharge. Multivariate logistic regression analysis was performed to evaluate the association between neurologic outcomes and the number of prehospital defibrillation attempts. Results A total of 4,513 patients were included in the final analysis. The numbers of patients for whom 2-3, 4-5, and >= 6 defibrillation attempts were made were 2,720 (60.3%), 1,090 (24.2%), and 703 (15.5%), respectively. Poorer outcomes were associated with >= 6 defibrillation attempts: survival to hospital discharge (adjusted odds ratio, 0.38; 95% confidence interval, 0.21-0.65) and good neurologic recovery (adjusted odds ratio, 0.42; 95% confidence interval, 0.21-0.84). Conclusion Six or more prehospital defibrillation attempts were associated with poorer neurologic outcomes in OHCA patients with an initial shockable rhythm who were unresponsive to on-scene defibrillation and resuscitation.