The effect of body mass index on perioperative thermoregulation

PURPOSE: We evaluated the effects of body mass index (BMI) on thermoregulation in obese patients scheduled to undergo laparoscopic abdominal surgery. METHODS: Sixty patients scheduled to undergo laparoscopic abdominal surgery with no pre-medication were included in the study. The patients were classified into 4 groups according to BMI <24.9, 25–39.9, 40–49.9, and >50. Anesthesia was provided with routine techniques. Tympanic and peripheral temperatures were recorded every 5 minutes starting with the induction of anesthesia. The mean skin temperature (MST), mean body temperature (MBT), vasoconstriction time, and vasoconstriction threshold that triggers core warming were calculated with the following formulas: MST = 0.3 (T(chest) + T(arm)) + 0.2 (T(thigh) + T(calf)). MBT was calculated using the equation 0.64T(core)+0.36T(skin), and vasoconstriction was determined by calculating T(forearm)−T(finger). RESULTS: There was no significant difference between the groups in terms of age, gender, duration of operation, and room temperature. Compared to those with BMI <24.9, the tympanic temperature was significantly higher in those with BMI =25–39.9 in the 10th, 15th, 20th, and 50th minutes. In addition, BMI =40–49.9 in the 5th, 10th, 15th, 20th, 25th, 30th, 40th, 45th, 50th, and 55th minutes and BMI >50 in the 5th, 10th, 15th, 20th, 25th, 30th, 50th, and 55th minutes were less than those with BMI <24.9 (P<0.05). There was no significant difference in terms of MST and MBT. Vasoconstriction occurred later, and that vasoconstriction threshold was significantly higher in patients with higher BMIs. CONCLUSION: Under anesthesia, the core temperature was protected more easily in obese patients as compared to nonobese patients. Therefore, obesity decreases the negative effects of anesthesia on thermoregulation.