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Bystander-administered AEDs increase odds of survival in cardiac arrest
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Patients with a public out-of-hospital cardiac arrest treated with an automated external defibrillator by a bystander had an increased chance of survival and improved functional outcomes, according to a study published in Circulation.
“We estimate that about 1,700 lives are saved in the United States per year by bystanders using an AED,” Myron Weisfeldt, MD, university distinguished service professor at Johns Hopkins School of Medicine, said in a press release. “Unfortunately, not enough Americans know to look for AEDs in public locations, nor are they trained on how to use them despite great and effective efforts of the American Heart Association.”
Ross A. Pollack, BS, medical student at Johns Hopkins University School of Medicine, and colleagues analyzed data from 49,555 patients from the Resuscitation Outcomes Consortium Epistry dataset who had a shockable observed public out-of-hospital cardiac arrest from 2011 to 2015. Patients were from six regions in the United States and three regions from Canada. To confirm the findings, data from patients with private and unobserved out-of-hospital cardiac arrests were also reviewed.
The primary outcome measure was discharge with favorable or normal functional status, which was defined as a modified Rankin Scale score of 2 or less. The secondary outcome measure was survival to hospital discharge.
From 2011 to 2015, 8.3% of patients had public out-of-hospital cardiac arrests (median age, 62 years; 80% men). Of those, 60.8% of patients had cardiac arrests that were shockable (median age, 61 years; 85% men). Bystanders used an AED to deliver a shock before emergency medical services (EMS) arrived in 18.8% of shockable observed public out-of-hospital cardiac arrests.
Patients who were shocked by a bystander were more likely to survive to discharge (66.5% vs. 43%; P < .001) and have a favorable functional outcome at discharge (57.1% vs. 32.7%; P < .001) compared with patients who received a shock by EMS. After adjustment, the OR for survival to discharge was 2.62 (95% CI, 2.07-3.31) and the OR for favorable functional outcome at discharge was 2.73 (95% CI, 2.17-3.44) in patients who received shocks from bystanders.
Compared with EMS initial shock, the adjusted OR for favorable functional outcome in patients who received a shock from a bystander increased with the EMS response interval at 4 minutes (OR = 1.86; 95% CI, 1.03-3.37), 8 minutes (OR = 3.49; 95% CI, 1.59-7.67) and 12 minutes (OR = 6.54; 95% CI, 2.15-19.91).
“We contend that the results presented here, therefore, are readily generalizable and serve as an example of the benefit provided by rigorously optimizing the pre- and posthospital systems as many [Resuscitation Outcomes Consortium] sites have done,” Pollack and colleagues wrote. – by Darlene Dobkowski
Disclosures: Weisfeldt and Pollack report no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
Perspective
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Clifton W. Callaway, MD, PhD
While the use of automated external defibrillators for cardiac arrest in public settings was widely acknowledged to be beneficial, there were few data quantifying how much benefit they provide. This paper shows that overall, a layperson using an AED prior to EMS arrival more than doubles the odds of survival and good outcome for patients with a shockable cardiac rhythm.
The paper also examines some key subgroups, taking advantage of the detailed data collected by the ROC network. In particular, the benefit of layperson AED use over waiting for EMS was present whenever EMS arrival took longer than 2 minutes, and the benefit increased with each minute delay in EMS arrival.
Regrettably, this large sample of cardiac arrests from across the U.S. and Canada found only 19% of arrests had layperson AED use.\
Laypersons need to be empowered and expected to use AEDs anytime that they see a person collapse. This intervention would be more powerful for some patients than any other medical intervention.
The AED use might be a surrogate for a layperson taking action: perhaps persons with AED shock were also more likely to have good chest compressions and rapid recognition of their situations. Did persons for whom an AED was deployed but no shock required also do better than persons for whom laypersons did not use an AED? It would be useful to know what made the AED use more successful in some cases than in others: availability, signage, 911 operator prompting, etc.
Bystanders who respond and act should be called layperson rescuers, because they are no longer standing by.
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