Defibrillation in patients with accidental hypothermia and core temperatures ≤30°C – A retrospective observational study

Abstract

Background: Defibrillation often fails in patients in hypothermic cardiac arrest with shockable rhythms. In patients with core temperatures (Tc) ≤30°C the success rate, optimal number, timing of defibrillations, and factors including rewarming associated with successful defibrillation are not well known. Aims: To determine the success rate of defibrillation in patients in hypothermic cardiac arrest with shockable rhythms. We studied Tc at defibrillation attempt, number of shocks, and factors facilitating defibrillation. Methods: This was a retrospective observational study from the International Hypothermia Registry of patients with hypothermic cardiac arrest (Tc ≤30°C) and shockable rhythms undergoing defibrillation attempts before and during rewarming with or without extracorporeal life support. We performed multivariate binomial logistic regression to analyse the probability of defibrillation success according to the defibrillation temperature and ECLS rewarming. Results: Thirty-seven patients with cardiac arrest, shockable rhythm, and Tc ≤30°C were included. Defibrillation was attempted in 20 patients before rewarming and in 17 during rewarming. The overall success rate was 22/37 (59%). Both the success rate of defibrillation (100% [17/17] vs. 25% [5/20]; P < 0.001) and Tc at the time of the defibrillation attempt (29.0°C [28.0–30.0°C] vs 25.8°C [24.0–26.2°C]; P < 0.001) were higher if defibrillation was performed during rewarming. No defibrillation attempt was successful at Tc <24.8°C. Conclusions: Defibrillation attempts can be successful before rewarming at Tc ≤30°C. The success rate is higher during rewarming and at a higher Tc. Tc is a strong and independent predictor of defibrillation success. Defibrillation at Tc <25°C is unlikely. These findings require confirmation in larger studies.