title: [Effect of nitrous oxide on the bispectral index during sevoflurane anesthesia].
abstract: We studied the effects of nitrous oxide on the relationship between end-tidal sevoflurane concentration and bispectral index (BIS) in patients undergoing abdominal surgery. Anesthesia was maintained with combination of epidural and sevoflurane anesthesia in air (control group; n = 15) or with 67% nitrous oxide (nitrous oxide group; n = 15). The end-tidal sevoflurane concentration was increased by 0.5% every 15 min to 3% and BIS values were recorded at each step. In both groups, sevoflurane decreased BIS values in a dose-dependent manner and the decrease in BIS reached plateau at 2% of sevoflurane. Nitrous oxide with sevoflurane caused more reduction in BIS in comparison with sevoflurane alone. The sevoflurane concentration for BIS at 50 in the nitrous oxide group (0.9 +/- 0.4%) was significantly lower than that in the control group (1.2 +/- 0.4%). The results suggest that the hypnotic effect of sevoflurane was enhanced by the addition of nitrous oxide during abdominal surgery.
authors.affiliation: Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo 060-8543.
authors.forename: Masayasu
authors.initials: M
authors.lastname: Nakayama
authors.forename: Soushi
authors.initials: S
authors.lastname: Iwasaki
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Ichinose
authors.forename: Shuji
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Osamu
authors.initials: O
authors.lastname: Satoh
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Nakabayashi
authors.forename: Michiko
authors.initials: M
authors.lastname: Hayashi
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Namiki
mesh_terms: D000005:Abdomen / Q000601:surgery; D000328:Adult; D000368:Aged; D000767:Anesthesia, Epidural; D000769:Anesthesia, Inhalation; D004357:Drug Synergism; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D000077149:Sevoflurane
chemical_list: D008738:Methyl Ethers; D000077149:Sevoflurane; D009609:Nitrous Oxide