Enflurane decreases the threshold for vasoconstriction more than isoflurane or halothane

Area of Science:

• Anesthesiology
• Pediatric Surgery
• Thermoregulation

Background:

• Intraoperative hypothermia is common, often due to anesthetic-induced inhibition of thermoregulatory vasoconstriction.
• While hypothermia can trigger vasoconstriction, different volatile anesthetics haven't been directly compared for their thermoregulatory effects in children.

Purpose of the Study:

• To compare the thermoregulatory responses of pediatric patients under enflurane, isoflurane, and halothane anesthesia.

Main Methods:

• Twenty-seven pediatric patients undergoing intra-abdominal surgery received 1 minimum alveolar anesthetic concentration (MAC) of halothane, isoflurane, or enflurane.
• Patients were allowed to cool passively, with vasoconstriction identified by a 4°C skin temperature gradient (forearm minus fingertip).
• The core temperature at which vasoconstriction occurred was recorded as the threshold.

Main Results:

• Halothane (n=8) and isoflurane (n=8) groups showed vasoconstriction at core temperatures of 35.5 ± 0.6°C and 35.2 ± 0.5°C, respectively.
• Two isoflurane patients did not vasoconstrict, reaching minimum core temperatures of 34.0°C and 33.8°C.
• Only one enflurane patient (n=8) vasoconstricted (at 34.6°C); the rest (n=6) never vasoconstricted, reaching minimum core temperatures of 33.6 ± 0.4°C.

Conclusions:

• Enflurane profoundly inhibits thermoregulatory responses in pediatric patients.
• Pediatric patients anesthetized with enflurane are likely to experience greater core temperature reduction compared to those under halothane or isoflurane.
• The mechanism behind enflurane's potent inhibition of thermoregulation remains unclear.