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Defibrillation for Out-of-Hospital Cardiac Arrest -- Shocking Results

Public access defibrillation increased survival, but advanced cardiac life support added no benefit.

Survival rates after out-of-hospital cardiac arrest average only 2% to 5%. Rapid defibrillation has been shown to improve outcomes, but prior studies have focused primarily on airports and aircraft, and that experience may not be generalizable to other public settings.

In the Public Access Defibrillator Trial, investigators assessed the benefit of automated external defibrillator (AED) use by CPR-trained laypersons in community settings (e.g., shopping malls, apartments, hotels). The community locations were randomly assigned to a CPR-only monitored emergency response system or a CPR-plus-AED response system. More than 19,000 volunteers from 993 communities in the U.S. and Canada participated and received training three times during the 2-year study.

Of 526 events that occurred during the study, 239 were considered definite or probable cardiac arrests (event rate, 1 per location every 7.4 years). Twice as many patients in the CPR-plus-AED group as in the CPR-only group survived to hospital discharge. Interestingly, fewer arrests occurred in public areas than in homes, and the survival rate was much higher among people who had public-area arrests than among those who had arrests at home (43 of 165 vs. 2 of 70; 26% vs. 3%). The increase in survival in the CPR-plus-AED group did not come at the expense of increased neurologic deficit.

The first three of the four steps in the American Heart Association's "chain of survival" for out-of-hospital cardiac arrest (early access to emergency care, early CPR, early defibrillation, and early advanced cardiac life support) have been shown to improve outcomes, but the incremental benefit of advanced life support (ALS) has not been established. In the Ontario Prehospital Advanced Life Support Study, researchers compared survival rates in 17 communities before and after ALS was added to the existing emergency medical services, which already included "optimized" early defibrillation (arrival of first responder with a defibrillator in 8 minutes or less after call). In each community, a 12-month early-defibrillation phase and a 36-month ALS phase were separated by a period of 6 to 36 months.

The addition of ALS made no significant difference in survival to hospital discharge (5.0% before vs. 5.1% after ALS). Multivariate analyses confirmed the value of witnessed arrest, early CPR, and defibrillation within 8 minutes. The authors note that pessimists might say that the addition of ALS only increased the burden on ICUs, whereas optimists might say that we just need to improve hospital care to improve survival rates. The authors recommend that we invest in resources to increase awareness of the value of bystander CPR and early defibrillation.

An editorialist points out that cumulative evidence proves that early CPR and early defibrillation save lives. He notes that sixth graders are as adept at using AEDs as cardiologists. On the down side, these programs provide little benefit for most cardiac arrest victims -- those who die at home.

Comment: Unfortunately, cost per year of life saved was not addressed in the community volunteer model. At first glance, it appears that "scoop and run" should now become "shock and run," but one wonders whether even ED interventions are beneficial. One also wonders how long it will take to undo the ALS model for cardiac arrest, and, if insurers move to evidence-based payment, how long it will take for them to stop paying for such treatment.

— J. Stephen Bohan, MD, MS, FACP, FACEP

Published in Journal Watch Emergency Medicine September 29, 2004

Citation(s):

The Public Access Defibrillation Trial Investigators. Public-access defibrillation and survival after out-of-hospital cardiac arrest. N Engl J Med 2004 Aug 12; 351:637-46.

• Original article (Subscription may be required)
• Medline abstract (Free)

Stiell IG et al. Advanced cardiac life support in out-of-hospital cardiac arrest. N Engl J Med 2004 Aug 12; 351:647-56.

• Original article (Subscription may be required)
• Medline abstract (Free)

Callans DJ. Out-of-hospital cardiac arrest -- The solution is shocking. N Engl J Med 2004 Aug 12; 351:632-4.

• Original article (Subscription may be required)
• Medline abstract (Free)