Comparison of Normothermic Cardiopulmonary Bypass with Conventional Hypothermic Bypass

Abstract

In a prospective randomized study from October to December 1996 at the All India Institute of Medical Sciences, we compared normothermic cardiopulmonary bypass with conventional hypothermic bypass. Sixty patients undergoing open-heart surgery for valvular heart disorders were assigned to undergo either normothermic bypass (35°C to 37°C, n = 30) or moderate hypothermic bypass (28°C, n = 30). Bypass time, pump flow, urine output, need for vasopressors, arterial blood gases on bypass, duration of cardioplegia, need for defibrillation, postoperative blood loss, rewarming time to a peripheral (toe) temperature above 35°C, awakening time, and neurologic outcome were studied. Mean bypass time in the normothermic patients (67.33 ± 23.5 minutes) was 23% less (p < 0.05) than in the hypothermic group (89.6 ± 49.26 minutes). Higher flows were required initially in the normothermic group due to low systemic vascular resistance. Early return of sinus node electrical activity in patients (70%) in the normothermic group required more frequent use of topical ice slush and cardioplegia administration. Postoperative blood loss was similar in both groups but fluid and blood requirements in the normothermic group (514 ± 220 mL·m−2) was significantly less (p < 0.05) than in the hypothermic group (722.3 ± 383 mLm−2). Normothermic patients rewarmed earlier (4.25 ± 1.79 hours) to peripheral (toe) temperatures above 35 °C and awoke earlier compared with the hypothermic group, which took a mean time of 6.1 ± 2.3 hours to rewarm. We concluded that normothermic bypass is more physiologic and significantly reduces bypass time while avoiding the deleterious effects of hypothermia.