Time to first defibrillation and survival outcomes of out-of-hospital cardiac arrest with refractory ventricular fibrillation.

Abstract

Timely defibrillation is associated with increased survival in out-of-hospital cardiac arrest (OHCA) cases. This study aimed to determine whether the time to first defibrillation was associated with good neurological outcomes in OHCA patients with refractory ventricular fibrillation. Bystander-witnessed adult OHCA patients with presumed cardiac etiology who presented with ventricular fibrillation and received ≥2 successive prehospital defibrillations from emergency medical services between 2013 and 2018 were included. The times from collapse to first defibrillation were categorized into Group 1 (0-5min), Group 2 (6-10min), Group 3 (11-15min), and Group 4 (16-60min). The primary outcome was a good neurological recovery (cerebral performance category 1-2). Multivariable logistic regression analysis was performed to calculate the adjusted odd ratios (AORs) and 95% confidence intervals (CIs) for outcomes according to time group (Group 1 as the reference) and per 1-min delay. The study included 5753 patients, with overall rates of 34.4% for survival to discharge and 27.2% for good neurological recovery. The median number of prehospital defibrillations was 3 (interquartile range 2-5). Relative to Group 1, the AORs for good neurological recovery were 0.58 in Group 2 (95% CI: 0.41-0.82), 0.42 in Group 3 (95% CI: 0.29-0.60), and 0.19 in Group 4 (95% CI: 0.13-0.29). When time from collapse to first EMS defibrillation was analyzed as a continuous variable, each 1-min delay was associated with a significant decrease in the likelihood of good neurological recovery (AOR: 0.93, 95% CI: 0.91-0.94). A short time from collapse to first defibrillation was associated with good neurological recovery among patients with OHCA and refractory ventricular fibrillation. This result suggests that a failed first shock still has a positive effect if it is delivered quickly.