The precise measurement of body temperature during anesthesia is important to prevent hypothermia. The aim of this study was to compare the urinary bladder temperature to the esophageal, nasopharyngeal, rectal and skin temperatures, and to compare three heating methods during spine surgery.

Forty-two patients with ASA physical status I-II, who were scheduled to undergo spine surgery in the prone position, were included in this study. The patients were randomly divided into 4 groups: Group I was treated without any heating methods; group 2, with fluid-warmers; group 3, with forced air-warmers; and group 4, with a combination of both heating methods. After the induction of anesthesia, the esophageal, nasopharyngeal, rectal, urinary bladder and skin temperature was monitored every 15 minute for 3 hours. The urinary bladder temperature was compared to the esophageal, nasopharyngeal, rectal and skin temperatures.

The urinary bladder temperature was found to be higher than the esophageal and the nasopharyngeal temperatures (P < 0.01). The urinary bladder temperature of group 3 was higher than that of group 1 at 180 minutes after induction of anesthesia (P < 0.05). The urinary bladder temperature of group 4 was higher than that of group 1 at 150 minutes (P < 0.05), as well as at 165 and 180 minutes (P < 0.05). The skin temperatures of groups 3 and 4 were higher than group 1 (P < 0.001).

The urinary bladder temperature was higher than the esophageal temperature and correlated with the esophageal, nasopharyngeal and rectal temperatures. During spine surgery in the prone position, a forced air-warmer was found to be the most effective but a combination of all the methods tested was found to be even more effective.