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You are walking in a mall when you notice a crowd of people around a man lying unconscious on the ground. You run to him. No pulse. You start CPR (counting aloud, “1, 2, 3…”). You look around for an automated external defibrillator (AED) and see a bystander bringing it over. You pull off the man’s shirt, put the pads in place, and hear, “analyzing rhythm…shock advised.” You press the button. His body jumps and before restarting CPR, he begins to wake up. This is the ideal situation for public-access AEDs, but how many patients benefit from this intervention?
Early defibrillation with an AED is now a crucial part of prehospital care. Japan has been a leader in this movement. Since allowing citizens to use public-access AEDs in 2004, Japan has greatly increased the availability of these life-saving machines. In this week’s NEJM, Kitamura and colleagues expand on their previous assessment of the effect of widespread dissemination of public-access AEDs in Japan. Using nation-wide registry data, the investigators evaluated outcomes of out-of-hospital ventricular fibrillation cardiac arrest between 2005 and 2013 in patients who suffered a ventricular fibrillation arrest witnessed by bystanders, were treated by bystanders or emergency medical service (EMS), and were transferred to a medical institution. The primary outcome was one-month survival with favorable neurological outcome.
From 2005 to 2013, the number of public-access AEDs increased 40-fold from 10,961 to 428,821. Of the 43,762 patients with bystander-witnessed ventricular fibrillation arrest, 4499 (10.3%) received public-access defibrillation and 39,263 (89.7%) did not. The percentage of patients who received shocks from public-access AEDs for bystander-witnessed ventricular fibrillation arrest increased from 1.1% in 2005 to 16.5% in 2013 (P<0.001 for trend).
One-month survival in patients who received public-access defibrillation was 44.7%, versus 27.9% in those who did not receive public-access defibrillation (adjusted odds ratio, 1.66; 95% CI, 1.54-1.79). After controlling for confounding factors with propensity-score matching, a higher proportion of patients who received public-access defibrillation had favorable neurological outcomes than patients who did not (38.5% vs. 26.1%; adjusted OR, 1.99; 95% CI, 1.80-2.19). The absolute number of survivors with favorable neurological outcomes attributed to public-access defibrillation increased from 6 per year in 2005 to 201 per year in 2013 (P<0.001 for trend).
Studies based on registry data have several limitations. In this study, patients who received AED shocks had different baseline characteristics than patients who did not; they were less likely to be witnessed by a family member and more likely to receive bystander CPR. Additionally, the registry did not have data on failed AED attempts, AED location, and AED accessibility.
Overall, this study may inform public health policy. The results suggest that early public-access defibrillation, in addition to early CPR, can lead to better survival rates and neurological outcomes in out-of-hospital ventricular fibrillation cardiac arrests. However, a relatively small number of patients in the registry with ventricular fibrillation arrest benefited from the public-access AEDs. The authors argue that many factors could account for this finding, including the location and accessibility of AEDs, lack of CPR training, and inability of EMS dispatchers to inform bystanders of AED locations. Further cost-effectiveness analysis is needed to help guide public-access AED strategies and policies. John Jarcho, deputy editor at NEJM, adds, “This study demonstrates that increasing the number of public-access AEDs is not the only important step in improving the care of patients with out-of-hospital cardiac arrest.”
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Ryan Flanagan is an MD/MPH Candidate, Class of 2017, Tufts University School of Medicine