title: [The thermoregulatory threshold during surgery with propofol-nitrous oxide anaesthesia].
abstract: 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).
authors.affiliation: Department of Anesthesiology, Taiwan Provincial Taur-Yuan General Hospital.
authors.forename: C S
authors.initials: CS
authors.lastname: Lin
authors.forename: I S
authors.initials: IS
authors.lastname: Lin
authors.forename: C H
authors.initials: CH
authors.lastname: Liu
authors.forename: C F
authors.initials: CF
authors.lastname: Wang
authors.forename: H S
authors.initials: HS
authors.lastname: Wu
authors.forename: C G
authors.initials: CG
authors.lastname: Liu
authors.forename: L W
authors.initials: LW
authors.lastname: Chen
mesh_terms: 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
chemical_list: D009609:Nitrous Oxide; D015742:Propofol