Background: 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).
Methods: 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.
Results: 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).
Conclusions: 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.