Thermal energy balance as a measure of adequate rewarming from hypothermic cardiopulmonary bypass

Abstract

Objective: To determine whether the amount of heat (thermal energy) used actively to rewarm patients on cardiopulmonary bypass (CPB) was a better indicator of adequate rewarming from hypothermic CPB than core temperature. Design: Prospective study. Setting: Single hospital. Participants: Fifty-four sequential patients undergoing hypothermic CPB. Interventions: None. Measurements and Main Results: Thermal energy balance (TEB) (net heat supplied to or removed from the body, from initiation to termination of CPB) was measured using previously validated apparatus. Adequacy of rewarming was assessed by measuring the coldest postoperative core (tympanic membrane) temperature and the time to rewarm postoperatively to a core temperature of 37.0°C. Core temperature on termination of CPB did not correlate with the degree of postoperative hypothermia as judged by time to rewarm postoperatively to 37.0°C (r = 0.14; p = 0.33), but did correlate with coldest postoperative core temperature (r = 0.47; p = 0.0003). TEB correlated better with time to rewarm to 37.0°C (r = 0.43; p 0.001) and coldest postoperative core temperature (r = 0.58, p = 0.0001). Conclusion: TEB is a better predictor than corresponding values of core temperature on termination of CPB in predicting the coldest postoperative temperature and time to rewarm to 37°C. Copyright © 2000 by W.B. Saunders Company