Intravenous anesthesia


Anesthesia and Pain Medicine. 2002 Sept. 6(3): 153-158
ⓒ Korean Society for Intravenous Anesthesia
The Effects of Mild Hypothermia on Recovery Profile and BIS50 during Propofol or Isoflurane Anesthesia
Dae Woo Kim, Keon Jung Yoon, Jin Deok Joo
Department of Anesthesiology, College of Medicine, The Catholic University of Korea, Seoul, Korea

BACKGROUND: Although mild intraoperative hypothermia is common and prolongs duration of postanesthetic recovery, the effects of mild hypothermia on anesthetic drug pharmacology are not well known. We compared the effects of normothermia and mild hypothermia on recovery profile, and the BIS50 of effect site concentrations (CE) or expired tidal concentrations (CET) during propofol or isoflurane anesthesia, respectively.
METHODS: Sixty unpremedicated patients were scheduled to undergo endoscopic sinus surgery. Group 1 (n = 15) received propofol anesthesia with normothermia, group 2 (n = 15) received propofol anesthesia with mild hypothermia, group 3 (n = 15) received isoflurane anesthesia with normothermia, and group 4 (n = 15) received isoflurane anesthesia with mild hypothermia. In the mild hypothermia groups, any interventions were not taken to maintain normothermia. In contrast, patients in the normothermia group had their core temperatures maintained at preoperative levels throughout the perioperative period. This was achieved by active warming of the intravenous fluids at 37oC with a blood warmer, application of a Bair Hugger forced-air warmer, and airway humidification circuit.
RESULTS: The eye opening and orientation time in four groups were similar, whereas, the total requirements of propofol in group 2 were significantly more increased than those in group 1. In the normothermia groups, the core temperatures remained unchanged, whereas, in the hypothermia groups, these core temperatures decreased significantly from 15 minutes after intubation on the range of 37.1 to 35.1oC. Mild hypothermia was associated with increased CE for the BIS50 in propofol anesthesia, while, it was associated with decreased CET for the BIS50 in isoflurane anesthesia (P < 0.05).
CONCLUSIONS: In contrast to isoflurane anesthesia, mild hypothermia significantly increased effect site concentrations for the BIS50 and drug requirements in propofol anesthesia, even though recovery time were similar in all cases of both type of anesthesia.
Key words : Anesthetic equipment, bispectral index, Anesthetics, propofol, isoflurane, Temperature, hypothermia
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