Abstract 88: Initial CPR and Delayed Defibrillation Do Not Compromise Outcomes
Introduction. Timing of defibrillation after cardiac arrest has been controversial. We hypothesized that when CPR is effectively performed, the exact timing of defibrillation does not alter the outcomes of CPR.
Methods. In 10 domestic male pigs weighing 40 ± 2 kg, ventricular fibrillation (VF) was induced by balloon occlusion of the left anterior descending coronary artery. Cardiac arrest was untreated for 5 minutes. Animals were then randomized to either 3 min of CPR prior to attempted defibrillation or defibrillation-first followed by 3 min of CPR. Chest compressions were delivered at a rate of 100/min with the aid of a mechanical chest compressor (Thumper, Model 1000, Michigan Instruments, Grand Rapids, MI). Chest compression force was adjusted to decrease the anterior posterior diameter of the chest by 25%. Defibrillation was attempted with a single biphasic 150 Joule shock.
Results. Each animal was successfully resuscitated and survived for more than 72 hours. When CPR preceded the delivery of the shock, only one shock was required for restoration of spontaneous circulation (ROSC) (p < 0.05). No differences in the incidence of recurrent VF were observed. Lesser ST segment elevation was observed when chest compression preceded defibrillation (p < 0.05). Post resuscitation (PR) myocardial function and specifically the ejection fraction (EF), measured hourly during the first 4 hours following ROSC was significantly greater when chest compression was the initial intervention (Table⇓).
Conclusions. In this model of ischemically induced cardiac arrest, consistently better outcomes in terms of the number of shocks required, the severity of post resuscitation myocardial function, and the severity of early post resuscitation ischemia were observed when chest compression preceded defibrillation attempt. However, no significant differences in late outcomes were documented.