1. Purpose of the study
Globally, cardiac arrest is a primary causes of premature death and the majority occur in the out-of-hospital setting. Defibrillation offers survival benefit to patients presenting with a shockable rhythm but there is currently no clear consensus on optimal first-shock energy level or whether subsequent shocks should use the same or higher energy levels. With 11-37% of out-of-hospital cardiac arrests in Europe displaying a shockable rhythm on initial assessment, optimising defibrillation provides an opportunity to impact a significant number of people. We aimed to determine optimal first-shock energy level for biphasic defibrillation and whether fixed or escalating protocols for subsequent shocks are most effective.
2. Methods
We undertook a systematic review, conducting electronic searches of Medline, Embase, Cochrane CENTRAL and CINAHL databases, Web of Science, national and international trial registry databases. We searched for studies reporting data from randomised controlled trials or prospective cohort studies of adults sustaining non traumatic out-of-hospital cardiac arrest subject to attempted biphasic defibrillation. Further articles were identified from reference lists of key papers.
3. Results
We identified no studies evaluating first shock energy. Only one study (n=738) comparing fixed versus escalating energy met eligibility criteria: a prospective cohort analysis of a randomised controlled trial of manual versus mechanical CPR. High fixed (360J) energy was compared with an escalating (200-200/300-360J) strategy. Researchers found 27.5% (70/255) of patients in the escalating energy group and 27.6% (132/478) in the fixed high energy group survived to hospital discharge (unadjusted risk ratio 0.99, 95% CI 0.73, 1.23). Results were of very low certainty as the study was at serious risk of bias.
4. Conclusions
This systematic review did not identify an optimal first-shock energy for biphasic defibrillation. We identified no survival advantage at 30 days when comparing 360J fixed with 200J escalating strategy.
Trial registration: ISRCTN16327029

Systematic review of shock strategies for out-of-hospital cardiac arrest

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