Perishock pause: an independent predictor of survival from out-of-hospital shockable cardiac arrest

Abstract

Background: Perishock pauses are pauses in chest compressions before and after defibrillatory shock. We examined the relationship between perishock pauses and survival to hospital discharge.

Methods and results: We included out-of-hospital cardiac arrest 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 cardiopulmonary resuscitation process data for at least 1 shock (n=815). We used multivariable logistic regression to determine the association between survival and perishock pauses. In an analysis adjusted for Utstein predictors of survival, the odds of survival were significantly lower for patients with preshock pause ≥20 seconds (odds ratio, 0.47; 95% confidence interval, 0.27 to 0.82) and perishock pause ≥40 seconds (odds ratio, 0.54; 95% confidence interval, 0.31 to 0.97) compared with patients with preshock pause <10 seconds and perishock pause <20 seconds. Postshock 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 preshock and perishock pause interval (up to 40 and 50 seconds, respectively), with no significant association noted with changes in the postshock pause interval.

Conclusions: In patients with cardiac arrest presenting in a shockable rhythm, longer perishock and preshock pauses were independently associated with a decrease in survival to hospital discharge. The impact of preshock pause on survival suggests that refinement of automatic defibrillator software and paramedic education to minimize preshock pause delays may have a significant impact on survival.

Figure 1

Diagram of Pre-, Post- and Peri-shock pause Pre-shock pause of 10 seconds, Post-Shock pause of 2.3 seconds and Peri-shock pause of 12.3 seconds depicted in impedance channel of CPR process file.

Figure 2

Study cohort and exclusions VT/VF indicates ventricular tachycardia/ventricular fibrillation: ECG, electrocardiogram; PEA, pulseless electrical activity

Figure 3

Plot of Average Peri-Shock Pause Intervals by Shock Number Defibrillation delivery classifications: Manual – defibrillating shock delivered by a manual defibrillator or a defibrillator with automatic capabilities set to manual mode, wherein the timing of shock delivery is fully operator dependent; AED – defibrillating shock delivered by an Automated External Defibrillator (AED) requiring a minimum analytical period prior to shock delivery.