Warm air convection system and heat loss during vascular surgery

OBJECTIVES: To assess the efficacy of a warm air convection (WAC) system to supplement the usual physical means (electric blanket, warm i.v. fluids and covering of exposed surfaces) for preventing an correcting hypothermia during surgery in 2 patient groups scheduled for vascular surgery. PATIENTS AND METHODS: We studied 70 consecutive patients scheduled for vascular surgery. Group I: a WAC system, in addition to the usual methods, was used to attempt to maintain normal body temperatures in 35 consecutive patients. Fifteen were undergoing aortic surgery (group Ia) and 20 were undergoing revascularization of the lower extremities (group Ib). Group II: only the usual physical methods were used to maintain normal temperature in the remaining 35 patients, 15 of whom required aortic surgery (group IIa) and 20 of whom were undergoing revascularization of the lower extremities (group IIb). Type of anesthesia and monitoring were the same in all cases. Esophageal temperature (ET) and room temperatures were recorded at baseline and every 30 min until the end of surgery. ET was not allowed to fall below 35 degrees C in any patient and WAC was provided to patients in group II if they required it. RESULTS: All patients in group II experienced a gradual decrease in ET, which became significant 30 min after start of surgery in group IIa and 60 min after start of surgery in group IIb. Temperature was stable during surgery in all patients in group I. All patients with ET of 35 degrees C in group II experienced a rise in temperature, which was significant after 60 min. when WAC was used. CONCLUSIONS: In vascular surgery, whether aortic or peripheral, patient temperature fell in spite of use of the usual physical methods for warming. Adding WAC for upper body warming prevented loss of heat. The WAC system was also effective for patients who needed to be rewarmed.