Changes in core temperature associated with lower extremity tourniquet--the influence of ambient temperature and warming equipments

BACKGROUND: We investigated changes in core temperature associated with lower extremity tourniquet (TQ) under two different ambient temperatures (1) and two different warming equipments (2) under general anesthesia combined with lumbar epidural anesthesia. METHODS: (1) The values of core temperature at ambient temperature of either 22 degrees C (n = 15) or 20 degrees C (n=15) were recorded after induction of anesthesia, at start of TQ application, at the termination of TQ application, and 14 minute after TQ release. (2) The values of core temperature using either air-forced warming or active heated i.v. at ambient temperature 20 degrees C were recorded at four points as mentioned above. RESULTS: (1) Changes in core temperature were not observed during TQ application at ambient temperature both 20 degrees C and 22 degrees C. Core temperatures in both groups decreased significantly after TQ release, and core temperatures at termination of TQ application and after TQ release at ambient temperature 20 degrees C were significantly lower than those at ambient temperature 22 degrees C. (2) Significant increases in core temperatures using two different warming equipments were observed at termination of TQ application and after TQ release at ambient temperature 20 degrees C. Core temperatures using air-forced warming were maintained during the investigation, though significant decrease in core temperature using active heated i.v. was recorded after TQ release. CONCLUSIONS: Air-forced warming maintains core temperature efficiently associated with lower extremity tourniquet.