[Body temperature changes during combined inhalational and epidural anesthesia]

We investigated the effects of combined inhalational and lumbar epidural anesthesia on body temperature in 8 women for long-lasting lower abdominal surgery. Probes for forehead deep temperature and skin-surface temperatures were placed on the forehead, forearm, fingertip and toe tip on patients' arrival at the operating room. Tympanic membrane temperature was also measured. Lumbar epidural block was established with 2% lidocaine 10 ml. Twenty minutes later, general anesthesia was induced and maintained with nitrous oxide-oxygen-isoflurane. Epidural anesthesia was maintained with intermittent dose of 1% mepivacaine. Before the end of surgery, isoflurane concentration was increased from about 0.5% to 2% and was maintained at this level for 20 minutes, after which it was reduced. With the establishment of epidural blockade, toe tip temperature increased and fingertip temperature decreased, while core temperature remained unchanged. After induction of general anesthesia, fingertip temperature increased, while core temperature decreased. The core temperature drop during the anesthetic induction was significantly affected by the increase in toe tip temperature. Before the end of surgery, core temperature remained at a reduced but constant level, while fingertip temperature continued to decrease. With the application of 2% isoflurane, fingertip temperature increased, while core temperature decreased. The core temperature drop was significantly affected by the increase in fingertip temperature. After the reduction of isoflurane concentration, these temperature changes were reversed fully. At the end of surgery, fingertip temperature decreased, while core temperature increased. During mild hypothermia, isoflurane depressed thermoregulatory vasoconstriction dose-dependently until its concentration reached 0.6-0.7%. In conclusion, anesthetics-induced redistribution of body heat significantly affects the core temperature throughout anesthesia. Peripheral hypothermia results in core temperature drop when the redistribution is induced by anesthetics. Thermoregulatory vasoconstriction may not only suppress heat loss but also increase core temperature through centralization of body heat.