Transchest defibrillation under conditions of hypothermia

This study was conducted to determine whether or not hypothermia changes ventricular defibrillation threshold. Ventricular fibrillation was induced by electrical stimulation of the endocardium in pentobarbital anesthetized dogs, both during normothermia and hypothermia produced by circulating 8 °C water through a rubber bladder implanted in the peritoneal cavity. Defibrillation threshold was determined as the shock strength needed to defibrillate the ventricles and differing no more than 10 percent from a shock strength that failed to defibrillate. Defibrillation threshold current was stable for body temperatures ranging from 37 oC to 22 oC. Threshold energy increased linearly with decreasing temperature in keeping with the expected temperature-dependent changes in body fluid resistance. Normothermic electrical doses are probably appropriate for defibrillation of hypothermic children