Effects of Enflurane and Isoflurane in Air-Oxygen on Changes in Thermal Balance During and After Surgery

Abstract

The temperatures in the aural canal (core), skeletal muscle and skin surface were measured during anaesthesia and surgery in 32 healthy females undergoing total abdominal hysterectomy and for 4 h after operation. The patients were allocated randomly to one of four groups according to the end-tidal concentration of volatile anaesthetic: 1 MAC isoflurane, 1 MAC enflurane, 1.8 MAC isoflurane and 1.8 MAC enflurane. The lungs were ventilated with an air-oxygen mixture. Neuromuscular block was produced with pancuronium. Room temperature and i.v. fluid administration were standardized. Aural canal, muscle and mean skin temperatures decreased significantly in all groups during surgery (P less than 0.001). The decrease in core and muscle temperatures, and mean body heat was significantly greater in the 1.8 MAC groups than in the 1 MAC groups for both volatile agents (P less than 0.001). However, there was a significantly greater decrease in core temperature and mean body heat in the isoflurane compared with the enflurane group (P less than 0.026). Body temperature returned to preoperative values during the recovery period. There was a significantly greater rate of rewarming during the first 1 h of recovery in the 1.8 MAC groups compared with the 1 MAC equivalent (P less than 0.001), and this was independent of the volatile agent used. The present results are compared with those reported previously in which nitrous oxide was added to the volatile agents. The decrease in body temperature depends upon the concentration of vapour used. However, it appears that isoflurane, without nitrous oxide, caused greater loss of body heat than enflurane.

Perioperative plasma endothelin-1 concentrations and vasoconstriction during prolonged plastic surgical procedures

“…7^ decreased during anaesthesia, but not to very low levels. Considerably larger decreases in central temperature have been observed during isoflurane-nitrous oxide anaesthesia of shorter duration [15][16][17] and therefore it would appear that our techniques for conserving heat loss were satisfactory. After an initial vasodilatation, which typically occurs during isoflurane anaesthesia [11], 7^ decreased slowly, and was 31.9 (2.5) °C at the end of operation.…”

TRPA1 mediates the hypothermic action of acetaminophen

“…Isoflurane and other irritant general anaesthetics act as TRPA1 agonists 30 31 and produce hypothermia in humans and rodents 32 33 34 35 . We therefore examined body temperature during isoflurane anaesthesia in wild-type and Trpa1 −/− mice.…”