title: Effect of pre-exposure to sevoflurane on the bispectral index in women undergoing Caesarean delivery under general anaesthesia.
abstract: BACKGROUND
  Patients undergoing Caesarean delivery under inhalation anaesthesia are at a high risk of awareness, especially in the period before delivery. We assessed the effects of pre-exposure to sevoflurane on the bispectral index (BIS) in the interval before delivery.
  
  
  METHODS
  Sixty-four patients undergoing elective Caesarean delivery were randomly assigned to receive 1.0-1.1 vol% (control 1) or 1.2-1.3 vol% (control 2) end-tidal sevoflurane, or the same concentrations of end-tidal sevoflurane combined with pre-exposure to 1 vol% sevoflurane for the last 1 min of the preoxygenation period (the preSevo 1 and preSevo 2 groups, respectively). We assessed BIS values, arterial pressure, and heart rate at the time of induction; before intubation; and upon skin incision, uterine incision, and delivery. We also determined the maternal incidence of intraoperative awareness and the neonatal Apgar scores, and conducted umbilical blood gas analysis.
  
  
  RESULTS
  At skin incision, BIS values were significantly lower in the preSevo 1 group than in the control 1 group [50 (13) vs 72 (8), P<0.001] and in the preSevo 2 group than in the control 2 group [44 (11) vs 67 (10), P<0.001]. The mean BIS values in the preSevo 1 and 2 groups were maintained below 60 in the period before delivery. No other parameter differed among groups, and no patient exhibited intraoperative awareness.
  
  
  CONCLUSIONS
  Pre-exposure to low concentrations of sevoflurane reduced BIS values in the interval before delivery, suggesting that this approach may reduce the risk of maternal awareness. Clinical Research Information Service (code KCT0000069, http://cris.cdc.go.kr).
authors.affiliation: Department of Anesthesiology and Pain Medicine,  Asan Medical Center, University of Ulsan College of Medicine, Seoul,  Republic of Korea.
authors.forename: W J
authors.initials: WJ
authors.lastname: Choi
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: W U
authors.initials: WU
authors.lastname: Koh
authors.forename: D I
authors.initials: DI
authors.lastname: Hwang
authors.forename: S K
authors.initials: SK
authors.lastname: Cho
authors.forename: P H
authors.initials: PH
authors.lastname: Park
authors.forename: S M
authors.initials: SM
authors.lastname: Han
authors.forename: J W
authors.initials: JW
authors.lastname: Shin
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D000773:Anesthesia, Obstetrical; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D001364:Awareness; D001794:Blood Pressure / Q000187:drug effects; D002585:Cesarean Section; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D008738:Methyl Ethers / Q000494:pharmacology*; D011247:Pregnancy; D011446:Prospective Studies; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane