Background: Total body hypothermia is used to slow metabolic processes, thereby reducing oxygen and glucose utilization, during surgery and other life saving procedures. However, ventricular fibrillation with subsequent circulatory collapse limits this therapy. Since electrical defibrillation is the only effective means of terminating ventricular fibrillation, it is imperative to determine the effects of hypothermia on defibrillation energy requirements (DER). Methods: 15 swine were randomized to a hypothermia group (n=8) or a control group (n=7). All animals were instrumented with a transvenous defibrillation system where a right ventricular apex coil served as the anode and the cathode consisted of a superior vena cavae coil. This was connected to a defibrillator that was capable of delivering a biphasic truncated waveform with a 60/40 phase ratio, variable tilt, and pulse duration of 12 ms. DER values were measured at baseline (normothermia=38°-40°C) and during treatment with total body hypothermia (30°C) or no temperature change for control. Hypothermia was induced by circulating ice water through anterior and posterior surgical thermal blankets. DER values were determined using an up/down method. Results: The graph below represents the mean ± SEM of DER values for successful defibrillation 50% of the time. In the hypothermia group (left panel) DER50 values at baseline (solid bar) were 14±2 J and did not significantly change during hypothermia (hatched bar) (15±2 J). These results were similar to those during control experiments (right panel) (12±1J versus 13±1J). Conclusions: Total body cooling to 30°C does not significantly alter defibrillation energy requirements. These data suggest that hypothermia may be used to slow metabolic processes without concern over the ability to successfully defibrillate and prevent arrhythmic death.
|Original language||English (US)|
|Journal||Critical care medicine|
|Issue number||1 SUPPL.|
|Publication status||Published - Dec 1 1999|
ASJC Scopus subject areas
- Critical Care and Intensive Care Medicine