An Evaluation of a Full-Access Underbody Forced-Air Warming System During Near-Normothermic, On-pump Cardiac Surgery

Abstract

A new underbody forced-air warming system is available for use during cardiac surgery. We tested the hypothesis combining underbody forced-air warming with standard thermal management would maintain intraoperative core temperature and reduce core temperature after-drop (largest decrease in core temperature in the 60 min after bypass) in patients undergoing near-normothermic cardiopulmonary bypass (CPB). Patients undergoing routine, nonemergent cardiac surgery were randomly assigned to routine thermal management (fluid warming and passive insulation, n = 30) or routine management supplemented by an active underbody forced-air system (n = 30; Arizant Healthcare Model 635, Eden Prairie, MN). Core body temperature was measured by bladder catheter at 15-min intervals during the perioperative period. Comparisons were made between groups for temperature before, during, and after CPB. Data from four patients were excluded for cause, leaving 29 patients in the routine management group and 27 patients in the forced-air group. Initial temperatures were similar, but temperatures in the forced-air group were higher than in the routine group at the start of CPB (36.3 degrees C +/- 0.6 degrees C vs 35.7 degrees C +/- 0.7 degrees C, P = 0.002). There were no differences between groups in the lowest temperatures during CPB (forced air, 35.5 degrees C +/- 1.5 degrees C vs routine, 35.3 degrees C +/- 1.3 degrees C, P = 0.67); the end of CPB (36.7 degrees C +/- 0.4 degrees C vs 36.6 degrees C +/- 0.4 degrees C, P > 0.99); or the temperature at departure from the operating room (36.5 degrees C +/- 0.4 degrees C vs 36.2 degrees C +/- 0.5 degrees C, P = 0.36). After-drop was 0.03 degrees C +/- 0.54 degrees C in patients randomized to underbody forced-air warming and 0.21 degrees C +/- 0.51 degrees C in those assigned to routine management (P = 0.20). Adding an underbody forced-air warming system to the near-normothermic thermal management protocol significantly increased pre-bypass temperature; however, it had no further clinically important effect on core temperature.