AED接上後就電擊，還是先CPR三分鐘再電擊比較優？

How Much CPR Before Defibrillation Shock?

Administering more cardiopulmonary resuscitation before defibrillation and rhythm analysis does not improve outcomes.〔先CPR3分鐘再電擊和AED接上後就立即電擊，效果沒有差別〕

To examine the theory that a more perfused heart will respond better to defibrillation shock, researchers conducted a cluster-randomized study in 9933 patients with nontraumatic out-of-hospital cardiac arrest at 10 Resuscitation Outcomes Consortium sites in the U.S. and Canada. Patients were divided into two groups and received cardiopulmonary resuscitation (CPR) by emergency medical services (EMS) providers for either 30 to 60 seconds (until pads were applied) or 180 seconds before defibrillation and initial electrocardiograph rhythm analysis. EMS providers received study-specific training every 6 months that emphasized uninterrupted compressions and ventilations in a 30:2 ratio.

The primary outcome — survival to hospital discharge with satisfactory neurological function as measured by the modified Rankin score — was 5.9% in both groups. The authors concluded that delaying analysis of cardiac rhythm during EMS-administered CPR provided no advantage. Of note, despite aggressive training of already "high-functioning" EMS providers, the duration of CPR before the first rhythm analysis did not fall within the assigned target for 36% of patients.

Comment: 
Even the best CPR delivers only a small fraction of normal cardiac output, which, as this study shows, is insufficient to "prime" the heart for defibrillation shock. Achieving a normal effective rhythm as soon as possible remains the single most important goal of resuscitation. The 64% adherence to the assigned duration of CPR by EMS providers shows how messy things are in real-life delivery of care for out-of-hospital cardiac arrest. This study does not alter the mantra for bystander-delivered CPR: "Always push early and often."

—
J. Stephen Bohan, MD, MS, FACP, FACEP
Published in Journal Watch Emergency Medicine September 9, 2011

Citation(s): Stiell IG et al. Early versus later rhythm analysis in patients with out-of-hospital cardiac arrest. N Engl J Med 2011 Sep 1; 365:787.