Erin Gabriel
Context: Immediate defibrillation is the traditional approach to resuscitation of cardiac arrest due to ventricular fibrillation or tachycardia (VF/VT). Delaying defibrillation to provide chest compressions may improve survival.
Objective: To estimate the effect of the duration of Emergency Medical Services (EMS) cardiopulmonary resuscitation (CPR) prior to the first defibrillation attempt on survival in patients with out-of-hospital VF/VT.
Design, Setting, and Patients: Prospective multi-center observational study of EMS treated out-of-hospital non-traumatic cardiac arrest with first recorded rhythm VF/VT or “shockable” from December 2005 to May 2007.
Outcome Measure: Survival to hospital discharge as a function of EMS CPR duration prior to first shock.
Results: Of 13,601 EMS-treated cardiac arrests, 3,292 (24%) had VF/VT/shockable rhythm. Of these, 1,661 (60%) had complete data for analysis. Excluded were cases witnessed by EMS (n=143) or with first CPR duration > 315 seconds (n=184). Included patients were aged 0-100 years, 79% were men, 31% occurred in public locations, and 49% received bystander CPR. Time to arrival of first EMS unit was median 5:18 ( IQR 4:06, 6:48 ) minutes. Compared to the reference group of first EMS CPR duration < 45 seconds, the odds of survival was greater among patients who received between 46 seconds to 195 seconds of EMS CPR before first shock. Odds of survival were more than 35% greater than the reference group during much of this EMS CPR interval. An optimal EMS CPR duration was not identified within this range and no individual EMS CPR duration achieved statistical significance. The benefit of EMS CPR before defibrillation was reduced when the duration of CPR exceeded 195 seconds.
Conclusion: In this observational analysis of VF/VT arrest, up to 195 seconds of EMS CPR prior to defibrillation was associated with a trend toward improved survival compared to < 45 seconds. Randomized trials are needed to evaluate this association given the potential for residual confounding in our analysis and to assess the impact on all initial rhythms.
