Use of AEDs in hospital setting fails to improve survival

Nov. 15, 2010 - PRLog -- KANSAS CITY, Mo. — Use of an Automated External Defibrillator (AED) in the hospital setting on patients experiencing sudden cardiac arrest is not effective – and potentially harmful – when compared with traditional defibrillators, according to a study in the Nov. 17 issue of the Journal of the American Medical Association.

The study was led by a Saint Luke’s Mid America Heart and Vascular Institute cardiologist in collaboration with investigators at the University of Michigan and may guide hospitals as they determine the best strategy to revive patients. Findings will be presented today at the American Heart Association’s annual meeting.

AEDs are portable devices designed to diagnose sudden cardiac arrest (an abrupt loss of pulse and cardiac function), judge whether defibrillation is needed, and deliver an electrical shock to restore the heart’s normal rhythm. If not treated promptly, sudden cardiac arrest is often fatal. While AEDs have been shown to improve survival in out-of-hospital settings such as schools, airports and sporting events, data on their effectiveness in hospitals - where they’re increasingly used - is limited.

Saint Luke’s cardiologist Paul Chan, M.D., M.Sc., lead study author, concluded that use of AEDs in the hospital setting did not improve survival for cardiac arrest patients. The study was based on data from the National Registry of Cardiopulmonary Resuscitation of 11,695 hospitalized patients with cardiac arrest between Jan. 1, 2000, and Aug. 26, 2008, at 204 hospitals following the introduction of AEDs on general hospital wards.

For those cardiac arrests that respond to a defibrillation shock (ventricular fibrillation and pulseless ventricular tachycardia), which comprised 19 percent of the study population, there was no difference in time to defibrillation or rates of survival to discharge between those treated by an AED or a conventional defibrillator.

“It was a disappointing finding,” said Dr. Chan.

In some circumstances, use of AEDs in the hospital was associated with higher death rates.

“For the majority (81 percent) of the cardiac arrests which do not respond to defibrillation (asystole and pulseless electrical activity), the use of AEDs to assess the initial rhythm in patients with cardiac arrest was associated with lower survival than with a conventional defibrillator,” said Dr. Chan.

While on the surface the findings seem surprising, they make sense, said Dr. Chan.

“Because these cardiac arrest rhythms are not treatable by defibrillation, assessment with an AED should not result in any benefit. But given that an AED takes a much longer time to assess a rhythm than a medical provider with a conventional defibrillator, their use likely deprives a cardiac arrest patient with a non-shockable rhythm of critical CPR time during the initial minutes, when perfusion to their organs (brain, liver, kidneys) is paramount. That delay may be hurting the patient, and explains why AEDs may have been associated with lower in-hospital survival.”

Use of AEDs in public settings, when time is of the essence, remains essential.

“Although our study found that an AED does not appear to be useful in the hospital setting, that does not mean that an AED is not useful outside the hospital, especially in public places,” said Dr. Chan. “Because hospitals are equipped with staff that can perform CPR effectively, shock patients when needed, and give important cardiac arrest medications, the benefits of AEDs in a hospital may be harder to realize than outside the hospital.”

While further study is needed, the research concludes that hospitals relying on use of AEDs to assess and treat patients in cardiac arrest may wish to reconsider treatment approaches.

“Our institutional CPR committee has struggled with what to tell the first person who responds to the bedside of a patient in cardiac arrest,” said Steven Kronick, M.D., assistant clinical professor of emergency medicine and director of advanced cardiac life support at the University of Michigan Health System.  

“This study supports that continuous chest compressions should be provided immediately and without interruption until the cardiac arrest rhythm can be determined,” Dr. Kronick said. “It also shows that in the hospital setting, rhythm identification should be done by the medical provider rather than by the AED, where delays in rhythm analysis can be significant.”

More than 50,000 AEDs have been purchased by hospitals alone since 2005 as a strategy to improve in-hospital survival rates.

“Time to defibrillation is an important quality metric, but there has been no silver bullet to achieve shorter times to treatment to date,” said Dr. Chan. “AEDs have been touted as a logical solution, and hospitals are buying these in increasing quantities. But, they do not appear to improve survival. In order to improve the quality of in-hospital resuscitation, we need to go back to the drawing board and do the hard work to identify innovative strategies to improve survival for cardiac arrest patients.”

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Saint Luke's Health System based in Kansas City, Mo., consists of 11 area hospitals in northwest Missouri and eastern Kansas, and several primary and specialty care practices. We provide a range of inpatient, outpatient, and home care services.