Best Shock Interval for Dual Defibrillation?

Written by Michael Stocker

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In out-of-hospital cardiac arrest (OHCA) patients with refractory ventricular fibrillation (RVF), there was an association with short-interval (<75ms) dual sequential external defibrillation (DSED) and higher probability of termination of ventricular fibrillation (VF) and return of spontaneous circulation (ROSC) compared with longer DSED intervals.

Shock me faster, tiny dancer
This retrospective cohort study included 106 OHCA patients >18 years old presenting with RVF and subsequently receiving DSED. RVF was defined as remaining in VF at the fourth rhythm check after three rounds of standard defibrillations and CPR. If a patient received more than one DSED, each DSED was analyzed as a separate event leading to 303 events included in the study. The two shocks performed in each DSED were calculated from defibrillator data, and four groups were defined by these intervals: <75ms, 75-125ms, 125-500ms, >500ms. Termination of VF was defined as ROSC, pulseless electrical activity (PEA), or asystole. The primary outcome was termination of VF, while secondary outcomes included ROSC and survival with good neurological outcome. While the majority of DSED was delivered >500ms apart (n=160), DSED intervals <75ms (n=25) were associated with the highest probability of VF termination and ROSC. Notably, no interval was associated with significant differences in survival or survival with good neurologic outcome.

How will this change my practice?
DSED was already in the toolkit thanks to this NEJM study. However, studies like this one are needed to define DSED best practices. While this seems to suggest simultaneous or near-simultaneous DSED equals more VF termination and ROSC, there weren’t many patients in the <75ms DSED group. More importantly, no significant advantage in patient-centered outcomes was demonstrated. I will eagerly await more DSED studies to boost my confidence this really is a best practice.

Editor’s note: The primary outcome “termination of VF” in this study is suspect. I can see termination of RVF to ROSC…but termination of RVF to ROSC, PEA, or asystole. How is that good? However, termination of VF with ROSC alone was much better with short-interval, which is reassuring. ~Clay Smith

Source
The impact of double sequential shock timing on outcomes during refractory out-of-hospital cardiac arrest. Resuscitation. 2024 Jan;194:110082. doi: 10.1016/j.resuscitation.2023.110082. Epub 2023 Dec 11.