Background Previous research has demonstrated significant relationships between peri-shock pause and survival to discharge from out-of-hospital shockable cardiac arrest (OHCA). Objective To determine the impact of peri-shock pause on survival from OHCA during the ROC PRIMED randomized controlled trial. Methods We included patients in the ROC PRIMED trial who suffered OHCA between June 2007 and November 2009, presented with a shockable rhythm and had CPR process data for at least one shock. We used multivariable logistic regression to determine the association between peri-shock pause duration and survival to hospital discharge. Results Among 2006 patients studied, the median (IQR) shock pause duration was: pre-shock pause 15 s (8, 22); post-shock pause 6 s (4, 9); and peri-shock pause 22.0 s (14, 31). After adjusting for Utstein predictors of survival as well as CPR quality measures, the odds of survival to hospital discharge were significantly higher for patients with pre-shock pause <10 s (OR: 1.52, 95% CI: 1.09, 2.11) and peri-shock pause <20 s (OR: 1.82, 95% CI: 1.17, 2.85) when compared to patients with pre-shock pause ≥20 s and peri-shock pause ≥40 s. Post-shock pause was not significantly associated with survival to hospital discharge. Results for neurologically intact survival (Modified Rankin Score ≤ 3) were similar to our primary outcome. Conclusions In patients with cardiac arrest presenting in a shockable rhythm during the ROC PRIMED trial, shorter pre- and peri-shock pauses were significantly associated with higher odds of survival. Future cardiopulmonary education and technology should focus on minimizing all peri-shock pauses.

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BACKGROUND Peri-shock pauses are pauses in chest compressions prior to and following defibrillatory shock. We examined the relationship between peri-shock pauses and survival to hospital discharge. METHODS We included out-of-hospital cardiac arrest (OHCA) patients in the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest who suffered arrest between December 2005 and June 2007, presented with a shockable rhythm (ventricular fibrillation or pulseless ventricular tachycardia) and had CPR process data for at least one shock (n=815). We used multivariable logistic regression to determine the association between survival and peri-shock pauses. RESULTS In an analysis adjusted for Utstein predictors of survival, the odds of survival were significantly lower for patients with pre-shock pause ≥20 seconds (OR: 0.47, 95%CI: 0.27, 0.82) and peri-shock pause ≥40 seconds (OR: 0.54, 95%CI: 0.31, 0.97) when compared to patients with pre-shock pause <10 seconds and peri-shock pause <20 seconds. Post-shock pause was not independently associated with a significant change in the odds of survival. Log linear modeling depicted a decrease in survival to hospital discharge of 18% and 14% for every 5 second increase in both pre- and peri-shock pause interval (up to 40 and 50 seconds respectively) with no significant association noted with changes in the post-shock pause interval. CONCLUSIONS In patients with cardiac arrest presenting in a shockable rhythm longer peri-shock and pre-shock pauses were independently associated with a decrease in survival to hospital discharge. The impact of pre-shock pause on survival suggests refinement of automatic defibrillator software and paramedic education to minimize pre-shock pause delays may have significant impact on survival.