[The thermoregulatory threshold during surgery with propofol-nitrous oxide anaesthesia].
BACKGROUND
Thermoregulatory responses are thought to be drastically suppressed by general anesthesia. In previous studies, it was shown that halothane, isoflurane and fentanyl-N2O combination decrease the threshold of vasoconstriction in general anesthesia. Propofol is a recently introduced intravenous anesthetic. The thermoregulatory threshold of its administration during surgery has not been quantified.


METHODS
Fourteen unpremedicated ASA class I patients were anesthetized with N2O (67%) and propofol (2 mg/kg in bolus followed by 6 mg/kg/h infusion) during elective surgery of free flap. Patients were randomly assigned either to receive additional warming (n = 5) or standard (n = 9) management. Significant vasoconstriction was prospectively defined as the temperature gradient between forearm surface and finger-tip surface is > or = 4 degrees C, and the thermoregulatory threshold was defined as the esophageal temperature (core temperature) at a point where the skin temperature gradient between two tested zones exceeds 4 degrees C.


RESULTS
Vasoconstriction did not occur in patients who received additional warming and they remained in nearly normothermia. The average minimum core temperature was 36.3 +/- 0.4 degrees C. In patients who underwent standard management the core temperature ranged from 32.8 to 34.6 degrees C (33.6 +/- 0.7 degrees C), signifying significant vasoconstriction.


CONCLUSIONS
General anesthesia with propofol/N2O during surgery drastically inhibits thermoregulatory vasoconstriction. This effect should also be noted during long-term use of propofol (e.g. ICU-sedation).
Lin
C S
CS
Department of Anesthesiology, Taiwan Provincial Taur-Yuan General Hospital.
Lin
I S
IS
Liu
C H
CH
Wang
C F
CF
Wu
H S
HS
Liu
C G
CG
Chen
L W
LW
D000328:Adult; D000768:Anesthesia, General; D001833:Body Temperature Regulation / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects
D009609:Nitrous Oxide; D015742:Propofol