Bystander-delivered defibrillation improves survival after cardiac arrest

November 05, 2007

ORLANDO, Nov. 5 -- Cardiopulmonary resuscitation (CPR) combined with bystander use of an automated external defibrillator (AED) more than doubled the chances of surviving out-of-hospital cardiac arrest compared with using CPR alone, researchers reported at the American Heart Association's Scientific Sessions 2007.

Based on national statistics related to out-of-hospital cardiac arrest, researchers estimated that bystander CPR plus use of an AED in the United States and Canada saves 522 lives a year, or more than one life per day.

"This is not a randomized, controlled study, but it describes what is going on in the real world, where people at the scene of a cardiac arrest are saving lives," said Myron L. Weisfeldt, M.D., chairman of medicine at Johns Hopkins University in Baltimore and lead investigator of the study.

The findings came from a study involving 11 urban and rural communities in the United States and Canada. The sites are participants in the Resuscitations Outcomes Consortium (ROC), a network of communities involved in studies of prehospital emergency care.

Weisfeldt reported findings from the latest ROC research effort, a study that evaluated the impact of bystander-applied AEDs on survival from out-of-hospital cardiac arrest.

Several years ago, the National Institutes of Health-sponsored Public Access Defibrillation (PAD) trial showed that training lay volunteers to perform CPR and use AEDs placed in public buildings doubled the number of survivors from out-of-hospital arrest compared with training bystanders to deliver CPR alone.

The new study did not train specific bystander to respond, but included patients who had out-of-hospital cardiac arrests between Dec. 1, 2005 and Nov. 30, 2006, and were evaluated by emergency medical service (EMS) personnel.

A total of 10,663 EMS-treated patients were included in the study. Bystanders administered CPR in 3,191 cases (29.9 percent) and used an AED with CPR in 259 cases (2.4 percent). Overall, 7 percent of the 10,663 patients survived to hospital discharge. However, survival varied substantially according to the type and timing of resuscitation attempted.

Of patients who had bystander CPR but no use of an AED, just 9 percent survived to hospital discharge.

When bystanders provided CPR and attached an AED and the device delivered a shock, survival increased to 36 percent - approximately four times that of CPR alone.

Some of this improvement was likely a result of other favorable aspects of the arrest rather than AED use. Thus, in a statistical analysis that accounted for factors such as location of the arrest, EMS response time and bystander CPR attempts, AED application still more than doubled the likelihood of survival to hospital discharge after cardiac arrest.

The findings provide strong support for making AEDs more widely available in communities, Weisfeldt said. The most effective way to do that is for city governments to enact ordinances mandating AEDs in certain public buildings, such as schools and sports arenas, he said. An AED costs about $2,000 each, and materials and labor for a cabinet and appropriate signs would probably increase the cost.

"When you compare that to the cost of other safety measures required by law, such as seat belts in automobiles and sprinkler systems to help control fires in buildings, my own conclusion is that it's not an enormous expense," he said.

"We do many things in the name of public safety that are much more expensive than what a community-based AED program would cost."

The American Heart Association promotes community lay rescuer AED programs and urges training for potential rescuers in CPR and the use of the AED, plus linking the programs to local EMS systems. CPR training is important because early CPR is an integral part of providing lifesaving aid to people suffering sudden cardiac arrest. CPR helps circulate oxygen-rich blood to the brain and other organs. After the AED is attached and delivers a shock, the typical AED will prompt the operator to continue CPR for two minutes while the device continues to analyze the victim's heart rhythm.

"This study reaffirms the importance of the chain of survival," said American Heart Association spokersperson Mary Fran Hazinski, R.N. "Early recognition, early CPR and early defibrillation by bystanders can produce survival as high as 36 percent for out-of-hospital cardiac arrest. Prompt bystander action is the key to this survival."
Co-authors are Colleen Griffith; Tom P. Aufderheide, M.D.; Daniel P. Davis, M.D.; Jonathan Dreyer, M.D.; Erik P. Hess, M.D.; Jonathan Jui, M.D.; Alexander MacQuarrie, Justin P. Maloney, M.D.; Laurie J. Morrison, M.D., M.Sc.; Graham Nichol, M.D., M.P.H.; Joseph P. Ornato, M.D.; Judy Powell; Thomas D. Rea, M.D.; and the ROC investigators.

The study is supported by the National Heart, Lung, and Blood Institute, Canadian Health and Defense Agencies and the American Heart Association.

Statements and conclusions of study authors that are presented at American Heart Association scientific meetings are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.

American Heart Association

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