In-hospital use of automated external defibrillators does not improve survival

Abstract

The use of automated external defibrillators (AEDs) following a cardiac arrest in the out-of-hospital setting has demonstrated increased survival rates, likely because up to 71% of out-of-hospital cardiac arrests are associated with rhythm disturbances that are able to be treated with defibrillation. It is less clear whether the use of AEDs in the hospital setting would be effective because fewer patients (approximately 25%) have initial cardiac rhythms that respond to defibrillation and because survival may be compromised if the use of AEDs contributes to interruptions in the delivery of chest compressions. The authors of this study used data from the National Registry of Cardiopulmonary Resuscitation (NRCPR) to evaluate the association between survival after an in-hospital cardiac arrest and use of an AED. Data was drawn from patients 18 years of age or older, who had an index pulseless, in-hospital cardiac arrest in clinical area where an AED was available for patient treatment. The sample comprised 11,695 patients from 204 hospitals. The primary outcome measure was survival to hospital discharge. The authors also reported secondary outcomes such as return of spontaneous circulation (ROSC) for at least 20 min during the acute resuscitation; survival at 24h; and neurological status among those patients surviving to hospital discharge. Of the 11,695 patients with cardiac arrests, the majority (82.2%; n=9616) were in a nonshockable rhythm, such as asystole or pulseless electrical activity (PEA). Only 17.8% (n=2079) of patients in the study were in a shockable rhythm (ventricular fibrillation and pulseless ventricular tachycardia). AEDs were used on 4515 patients (38.6%). An overall survival to discharge rate of 18.1% (n=2117) was reported. The use of an AED was associated with lower survival rates (16.3% vs 19.3%; adjusted rate ratio [RR], 0.85; 95% confidence interval [CI], 0.78-0.92; P<0.001). AED use in those patients with asystole or PEA (unshockable rhythms) was associated with lower survival (10.4% vs 15.4%; adjusted RR, 0.74; 95% CI, 0.65-0.83; P<0.001). Where shockable rhythms, such as ventricular tachycardia or ventricular fibrillation, were present, AED use did not increase survival (38.4% vs 39.8%; adjusted RR, 1.00; 95% CI, 0.88-1.13; P=0.99). These trends were consistent for AED use in both monitored and nonmonitored hospital units (p>.10). For cardiac arrest due to asystole or PEA the use (or not) of an AED did not influence the rates of ROSC. For cardiac arrests due to ventricular fibrillation or pulseless ventricular tachycardia the rates of ROSC and survival at 24 h did not differ by AED use. AED use did not shorten the time to defibrillation and for those patients with ROSC, and was not associated with shorter CPR times or fewer administered defibrillations. Overall the authors concluded that the use of AEDs in hospitalised patients following cardiac arrest was not associated with improved survival.