CHICAGO – Contrary to conventional wisdom, the use of automated external defibrillators for in-hospital cardiac arrests does not improve survival, a large national study shows.
In fact, just the opposite is true. The use of automated external defibrillators (AEDs) for cardiac arrests occurring on general hospital wards actually proved harmful overall, Dr. Paul S. Chan reported at the annual scientific sessions of the American Heart Association.
The study (JAMA 2010 Nov. 15 [doi:10.1001/jama.2010.1576]), published simultaneously with Dr. Chan’s presentation in Chicago, involved 11,695 patients who experienced cardiac arrest in 204 U.S. hospitals with AEDs, which were utilized in 39% of cases. Survival to hospital discharge occurred in 16.3% of patients in whom an AED was used to assess patients and deliver a shock when indicated compared with 19.3% when it was not. The resultant 15% adjusted lower likelihood of survival with AED use was both statistically and clinically significant.
Paul S. Chan
Moreover, among patients who survived to discharge, AED use had no impact on the rate of major neurologic disability, according to Dr. Chan of Saint Luke’s Mid America Heart Institute, Kansas City, Mo.
The data came from the AHA-sponsored National Registry of Cardiopulmonary Resuscitation, a large prospective quality improvement registry. The study was conducted because even though AEDs have repeatedly been shown to improve survival in certain out-of-hospital settings, there has been a lack of data demonstrating that the devices are beneficial for in-hospital cardiac arrests. Until now, that has been assumed to be the case.
Meanwhile, for the best part of a decade, U.S. hospitals have bought more than 10,000 AEDs per year for placement on general medical wards. Recent industry projections were for 9%-15% annual sales growth to hospitals over the next 5 years.
The explanation for the surprising lack of benefit for AEDS in the in-hospital cardiac arrests probably lies in the very different nature of the initial cardiac arrest rhythms occurring in out-of-hospital versus in-hospital settings. Various studies indicate 45%-71% of patients with out-of-hospital cardiac arrest have a shockable rhythm, such as ventricular fibrillation or pulseless ventricular tachycardia. That was the case in less than 18% of patients with in-hospital cardiac arrest.
In hospitalized patients with a shockable rhythm, the use of AEDs had no effect on survival in the study. In contrast, among the 82% of patients who had an in-hospital cardiac arrest marked by a nonshockable rhythm, such as asystole or pulseless electrical activity, the survival rate was 10.4% with AED use, compared with 15.4% with no AED use.
The AED does not deliver shocks to patients who have an unshockable rhythm, but CPR needs to be temporarily halted while the device’s automated rhythm diagnosis feature is at work. It’s likely that this interruption of chest compressions for up to 45-50 seconds during the first critical minutes of the resuscitation effort provides the mechanistic explanation for the lower survival rate in patients with nonshockable rhythms assessed by AED, according to Dr. Chan.
"While randomized controlled trials are needed to confirm these findings, current use of AEDs in hospitalized patients may warrant reconsideration," he concluded.
"This study probably is a practice changer," session cochair Dr. Karl B. Kern said in an interview.
"We’ve really struggled with how to best reach those patients who are not being monitored when they have a cardiac arrest in the hospital. This study would suggest that the strategy that’s out there right now is not very effective," said Dr. Kern, professor of medicine and interim chief of cardiology at the University of Arizona, Tucson, and vice chair of the AHA Cardiopulmonary, Critical Care, Perioperative and Resuscitation Council.
"I think it’s the same message we’ve been saying for a while now, that chest compressions are king, particularly for nonshockable rhythms, which the majority of in-hospital cardiac arrests are. Chest compressions are what save those patients, and anything that interrupts them comes at a cost," he explained.
The study was funded by the AHA. Dr. Chan declared he has no financial conflicts.