When you see a cardiac arrest, your brain fights you - "No, this isn't really happening" - and the circumstances fight you - "Dang! in CPR class the manikin didn't weigh very much and wasn't sitting in a deep chair. This blog deals with practical details and presents reports of "saves." Let me have your questions and comments - they will steer the course of this blog.
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Shockable rhythms are more common in public settings.
In a prospective, multicenter cohort study of 14,420 adult patients with nontraumatic out-of-hospital cardiac arrest in the U.S. and Canada between 2005 and 2007, researchers assessed initial rhythm, use of automated external defibrillators (AEDs), survival, and location of arrest (residential vs. public setting).
Among 12,930 patients who had known initial rhythms or had received at least one shock from a bystander-applied AED, arrests were witnessed by bystanders in 39%, AEDs were applied by bystanders in 2%, and arrests were witnessed by emergency medical services (EMS) in 9%. Ventricular fibrillation/pulseless ventricular tachycardia was the initial rhythm in significantly more public arrests than home arrests among those witnessed by bystanders (60% vs. 35%; adjusted odds ratio, 2.28), those witnessed by EMS (38% vs. 25%; AOR, 1.63), and those with AEDs applied by bystanders (79% vs. 36%; AOR, 4.48). The overall rate of survival to hospital discharge for patients with known initial rhythms was 7%. Among patients at home, survival rates were 2% for unwitnessed arrests, 8% for witnessed arrests overall, 10% for witnessed arrests with bystander cardiopulmonary resuscitation (CPR), and 12% for witnessed arrests with bystander-applied AEDs. For patients with bystander-witnessed public arrests, survival rates were 20% overall, 34% for those with bystander-applied AEDs, and 42% for those with bystander-administered shocks. Survival rates were comparable for patients who received bystander-administered AED shocks in public and at home.
Comment: This large multicenter study reaffirms the clear survival benefit of AED programs for public settings. AEDs do not substantially improve the benefits of bystander CPR for arrests at home, suggesting that CPR training should take precedence over widespread deployment of AEDs for the home setting.