A prospective comparative study between prewarming and cowarming to prevent intraoperative hypothermia

Inadvertent perioperative hypothermia defined as the perioperative core temperature of <36°C is a common problem in day-to-day anesthesia practice. It is not clear from the literature whether prewarming, that is, initiation of convective warming of the patient at a time point prior to induction of anesthesia is superior or comparable to cowarming, that is, initiation of convective warming simultaneously with induction of anesthesia. We conducted this study to find whether cowarming is as good as prewarming in preventing the occurrence of intraoperative hypothermia.

Sixty-two adult patients undergoing major abdominal surgery under general anesthesia were randomized to receive either prewarming for 60 min at 40° C or cowarming using the Level 1® Equator ® body warmer. All patients who were prewarmed also received cowarming during induction of anesthesia. In both the groups, convective warming was continued during intraoperative period. Incidence of intraoperative hypothermia, core, and peripheral body temperatures were compared between the two groups.

Among 27 patients in each group who completed the study core temperature decreased to <35° C toward the end of surgery in 17 patients in group prewarming [mean (SD) 34.59 (1.17° C)] and 18 patients in group cowarming [mean (SD) 34.31 (1.34° C)]. The incidence of intraoperative hypothermia and the core temperature at the end of surgery were comparable (P = 0.42).

Cowarming is as effective as prewarming to prevent intraoperative hypothermia.