Intra-operative hypothermia adversely affects hemodynamics and post-operative recovery in cardiac surgery patients. This study evaluated the efficacy of active warming during the preanesthetic period on the prevention of intraoperative hypothermia in cardiac surgery patients.

After gaining the approval of Institutional Review Board and informed consent from the patients, sixty patients undergoing cardiac surgery were divided into control and prewarming group. The control group (n = 30) were managed with warm mattresses and cotton blankets, whereas the prewarming group (n = 30) were actively warmed with a forced-air warming device before anesthesia. Hemodynamic variables and temperature were recorded before anesthesia (Tpre) and at 30 min intervals after anesthesia (T30, T60, and T90).

Before anesthesia, skin temperature was significantly higher in the prewarming group than in the control group. At T90, core temperature was significantly higher in the prewarming group than in the control group. Intraoperative hypothermia (core temperature < 35.5℃) developed by T90 in 78% of patients in the control group and 44% of patients in the prewarming group. Moreover, temperatures below 35℃ developed in 58% of the conrol group and 17% of the prearming group.

Active warming just before anesthesia reduced the incidence and degree of hypothermia in patients undergoing cardiac surgery, with no delay of anesthesia.