The effect of skin surface warming during anesthesia preparation on preventing redistribution hypothermia in the early operative period of off-pump coronary artery bypass surgery

Objective: Redistribution hypothermia adversely affects hemodynamics and postoperative recovery in patients undergoing cardiac surgery. In off-pump coronary bypass surgery (OPCAB), maintaining the temperature is important because warming by cardiopulmonary bypass is omitted. Prewarming studies reported earlier showing prewarming as an effective means of preventing redistribution hypothermia was time consuming since it required at least 1-2 h to prewarm the patients before the surgery. Because prewarming for such a long time is impractical in clinical practice, this study evaluated the efficacy of active warming during the preanesthetic period for the prevention of redistribution hypothermia in the early operative period of OPCAB. Methods: After gaining the approval of Institutional Review Board and informed consent from the patients, 40 patients undergoing OPCAB were divided into control and prewarming groups. The patients in control group (n = 20) were managed with warm mattresses and cotton blankets, whereas patients in prewarming group (n = 20) were actively warmed with a forced-air warming device before the induction of anesthesia. Hemodynamic variables and temperature were recorded before anesthesia (Tpre) and at 30 min intervals after anesthesia for 90 min (T30, T60, and T90). Results: Active warming duration was 49.7 ± 9.9 min. There were no statistically significant differences in skin temperature, core temperature and hemodynamic variables between the two groups at preinduction period except for mean arterial pressure and central venous pressure. The core temperature at T30, T60, and T90 was statistically higher in prewarming group than that in control group. Core temperature of six (30%) and seven patients (35%) in control group was reduced below 35°C at T60 and T90, respectively, whereas core temperature of only one patient (5%) in prewarming group was reduced below 35°C at T90 (P = 0.02). Conclusions: Active warming using forced air blanket before the induction of anesthesia reduced the incidence and degree of redistribution hypothermia in patients undergoing OPCAB. It is a simple method with reasonable cost, which does not delay the induction of anesthesia nor the surgery.