title: Pregnancy does not enhance volatile anesthetic sensitivity on the brain: an electroencephalographic analysis study.
abstract: BACKGROUND
  Parturients are thought to be more sensitive to inhalational anesthetics because their minimum alveolar concentration is decreased. However, this conventional theory may be wrong, because, according to recent animal studies, minimum alveolar concentration indicates anesthetic effect on the spinal cord but not on the brain. The aim of this electroencephalographic study was to investigate the differences in the hypnotic effect of sevoflurane on parturients and nonpregnant patients.
  
  
  METHODS
  Fifteen parturients undergoing cesarean section and 15 patients undergoing elective gynecologic surgery were enrolled. Anesthesia was induced with 4 mg/kg thiopental, 2 microg/kg fentanyl, and 2 mg/kg suxamethonium or 0.15 mg/kg vecuronium. Anesthesia was maintained with sevoflurane and fentanyl. The electroencephalographic signals, obtained from the bispectral index monitor, were recorded on a computer. We calculated 95% spectral edge frequency, amplitude, and bicoherence using custom software (Bispectrum Analyzer for bispectral index). After confirming that end-tidal sevoflurane had reached equilibrium, we measured electroencephalographic parameters of sevoflurane at 2.0 and 1.5% during surgery and at 1.0 and 0.5% after surgery.
  
  
  RESULTS
  With the decrease of end-tidal sevoflurane concentration from 2.0 to 0.5%, 95% spectral edge frequency, amplitude, bispectral index, and bicoherence values changed dose-dependently in pregnant and nonpregnant women (P<0.0001). However, there were no significant differences in those electroencephalographic parameters in pregnant and nonpregnant women.
  
  
  CONCLUSIONS
  This electroencephalographic study has shown that pregnancy does not enhance hypnotic effect of sevoflurane. These results suggested that the decrease in minimum alveolar concentration during pregnancy does not mean an enhanced volatile anesthetic effect on the brain.
authors.affiliation: Department of Anesthesiology, Osaka University Graduate School of Medicine, and Surgical Center, Osaka University Hospital, Osaka, Japan. ueyama@hp-op.med.osaka-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hagihira
authors.forename: Masaki
authors.initials: M
authors.lastname: Takashina
authors.forename: Aya
authors.initials: A
authors.lastname: Nakae
authors.forename: Takashi
authors.initials: T
authors.lastname: Mashimo
mesh_terms: D000328:Adult; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D002585:Cesarean Section; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D011247:Pregnancy / Q000187:drug effects* / Q000502:physiology; D013990:Tidal Volume / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
chemical_list: D018685:Anesthetics, Inhalation