Brief report: The declining incidence of cerebral hyperthermia during cardiac surgery: A seven-year experience in 6,334 patients

Purpose: Cerebral hyperthermia during rewarming from hypothermic cardiopulmonary bypass (CPB) commonly occurs and has been associated with postoperative neurocognitive dysfunction. Increased awareness of this has likely led to changes in rewarming strategies, including the reduction of rewarming rates and lowering of target rewarming temperatures. As a result, we hypothesized that the maximum temperature reached during cardiac surgery has decreased at our institution over time. Methods: We retrospectively reviewed the maximum intraoperative nasopharyngeal (NP) temperature in 6,334 patients having undergone cardiac surgery utilizing hypothermic CPB from January 1993 to June 2000. The incidence of cerebral hyperthermia (defined by a NP temperature > 38°C) was examined over time using Chisquare testing and the relationship between maximum temperature and date of surgery was studied using linear regression. [Results: Maximum temperature decreased over time (P < 0.0001; r² = 0.40) having the greatest reduction from January 1993 to December 1996 (0.34°C temperature drop per year), while from January 1997 to June 2000, it continued to decrease, but at a slower rate (0. 10°C per yr; P < 0.0001). The incidence of cerebral hyperthermia decreased over time with 83% of the first 10% of patients and 3% of the latter 10% of patients during the study period having a maximum temperature > 38°C (P < 0.0001). Conclusion: The incidence of cerebral hyperthermia has decreased at our institution suggesting that a change in temperature management has occurred at our institution from January 1993 to June 2000 thereby outlining a temporal evolution in temperature management during CPB.