Time to amiodarone administration and survival outcomes in refractory ventricular fibrillation

International guidelines recommend amiodarone for out-of-hospital cardiac arrest (OHCA) in refractory ventricular fibrillation (VF). While early appropriate interventions have been shown to improve OHCA survival, the association between time to amiodarone and survival remains to be established.

Included were adult OHCA in refractory VF, between January 2015 and December 2019, who received a resuscitation attempt with amiodarone from Queensland Ambulance Service paramedics. Patient characteristics and survival outcomes were described. Factors associated with survival were investigated, with a focus on time from arrest to amiodarone administration. Optimal time window for amiodarone administration was determined, and factors influencing whether amiodarone was given within the optimal time window were examined.

A total of 502 patients were included. The average (range) time from arrest to amiodarone was 25 (4-83) min. Time to amiodarone was negatively associated with survival (adjusted odds ratio 0.93 for event survival; 95% confidence interval 0.89-0.97). The optimal time window for amiodarone was within 23 min following arrest. Patients receiving amiodarone within the optimal time had significantly better survival than those receiving it outside this window (event survival 38.3% vs 20.6%, P < 0.001; discharge survival 25.5% vs 9.7%, P < 0.001; 30-day survival 25.1% vs 9.7%, P < 0.001). Paramedic response time (adjusted odds ratio 0.96; 95% confidence interval 0.92-0.99) and time from arrest to intravenous access (0.71; 0.67-0.76) were independent factors determining whether patients received amiodarone within the optimal time.

Earlier amiodarone administration was associated with improved survival. Strategies aimed at reducing delay to amiodarone administration have the potential to improve outcome.