Myron L. Weisfeldt MD, Jeremy Sugarman MD, MPH, MA, and Karen Bandeen-Roche PhD

 

The survival rate from out-of-hospital cardiac arrest has remained essentially unchanged in the United States for the past several decades, hovering in the 7% to 10% range overall. In communities with more frequent bystander performance of cardiopulmonary resuscitation (CPR), short emergency medical services response times, and hospitalbased hypothermia, there is significantly better survival, particularly for patients whose cardiac arrests are witnessed and in those for whom ventricular tachycardia or ventricular fibrillation is the first recorded rhythm. Unfortunately, among the many randomized trials in resuscitation from cardiac arrest, few demonstrate improved survival to the point of hospital discharge. In-hospital hypothermia and use of an automated external defibrillator by a bystander are two of the few interventions shown to improve survival. Examples of prehospital interventions that failed to demonstrate improved survival to hospital discharge in clinical trials include antiarrhythmic and vasoactive drugs, as well as agents intended to provide cerebral protection or improved metabolism. In fact, a recent study reported no benefit from drugs versus no drugs used during the initial out-of-hospital resuscitative maneuvers.

 

Recent efforts to improve the outcomes of cardiac arrest have centered on inducing hypothermia in unconscious patients on admission to the hospital and providing better CPR through more consistent and continuous chest compression within a narrow range of compression rates, along with avoiding hyperventilation during resuscitation because it impedes blood flow. The focus of attention during resuscitation on optimizing blood flow through optimal chest compression is a reflection of both animal and human studies in which improved blood flow (via CPR) appears to result in improved survival. Such observations have led to a series of recent changes in the protocols for chest compressions and defibrillation attempts for out-of-hospital resuscitation. These recommended changes were embodied in the 2005 international CPR guidelines and were implemented without definitive testing over the past 5 years. Some of these changes are the focus of a study by Jost and associates in the Paris, France, emergency medical services system. The results are reported in this issue of Circulation.