title: Electroencephalographic bicoherence is sensitive to noxious stimuli during isoflurane or sevoflurane anesthesia.
abstract: BACKGROUND
  The authors previously reported changes in electroencephalographic bicoherence during isoflurane anesthesia combined with epidural anesthesia. Here, they examined the influence of noxious stimuli on electroencephalographic bicoherence as well as on the Bispectral Index (BIS) and the 95% spectral edge frequency (SEF95).
  
  
  METHODS
  The authors enrolled 48 elective abdominal surgery patients (aged 22-77 years; American Society of Anesthesiologists physical status I or II). Raw electroencephalographic signals as well as BIS and SEF95 were recorded on a computer using a BIS monitor (A-1050) and Bispectrum Analyzer (BSA) for BIS (the authors' original software). Using BSA for BIS, the authors evaluated the two peak heights of electroencephalographic bicoherence. Anesthesia was induced with 3 mg/kg thiopental and was maintained with, in air-oxygen, 1.0% isoflurane or 1.5% sevoflurane. After confirming the steady state, the authors recorded baseline values. In experiment 1, they administered 3 microg/kg fentanyl 5 min after incision and investigated the changes in electroencephalographic derivatives at 5 and 10 min after incision. In experiment 2, they administered a similar dose of fentanyl 5 min before incision and investigated the changes in electroencephalographic derivatives immediately before and 5 min after incision.
  
  
  RESULTS
  In experiment 1, after incision, both peak heights of electroencephalographic bicoherence significantly decreased but returned to control values after fentanyl administration. By contrast, after incision, BIS and SEF95 showed individual variability. In experiment 2, although fentanyl itself did not affect all electroencephalographic derivatives before incision, the variables remained unchanged after incision.
  
  
  CONCLUSIONS
  Noxious stimuli decreased the peak heights of electroencephalographic bicoherence, an effect that was counteracted by fentanyl analgesia.
authors.affiliation: Department of Anesthesiology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan. hagihara@masui.med.osaka-u.ac.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hagihira
authors.forename: Masaki
authors.initials: M
authors.lastname: Takashina
authors.forename: Takahiko
authors.initials: T
authors.lastname: Mori
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Mashimo
mesh_terms: D000328:Adult; D000368:Aged; D000758:Anesthesia; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D005283:Fentanyl / Q000494:pharmacology; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D010146:Pain / Q000503:physiopathology*; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D005283:Fentanyl