title: [Impact of beach chair position on the value of bispectral index during general anesthesia].
abstract: BACKGROUND
  Although the bispectral index (BIS) has been established as a common index of anesthetic depth, there is a possibility that head-up position may influence BIS values under general anesthesia. This study examined whether beach chair position with 57 degrees head-up would cause the variation of BIS values during shoulder surgery.
  
  
  METHODS
  Two groups of patients were scheduled for surgery, one was supine position group, and the other was beach chair position group. Anesthesia was induced with propofol and rocuronium, and maintained with sevoflurane (end-tidal concentration 1.0-1.2%). The BIS values were recorded manually until 120 minutes after the onset of positioning and evaluated at each 30 min interval.
  
  
  RESULTS
  There was no time-dependent difference in BIS values during supine position. In contrast, BIS values in beach chair position group showed a marked downward-trend through the measurement period. End-tidal anesthetic gas concentration and mean blood pressure did not significantly differ between the groups consistently.
  
  
  CONCLUSIONS
  To our knowledge, this is the first report of the effect of beach chair position on BIS values intraoperatively. This result indicates that the beach chair position causes a time-dependent decrease in BIS under general anesthesia.
authors.affiliation: Emergency and Critical Care Center Tsuyama Central Hospital, Tsuyama 708-0841.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kawanishi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Hamanami
authors.forename: Toru
authors.initials: T
authors.lastname: Takahashi
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsumi
mesh_terms: D000368:Aged; D000732:Androstanols; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000493:pharmacokinetics; D056805:Consciousness Monitors; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000493:pharmacokinetics; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D015742:Propofol; D000077123:Rocuronium; D000077149:Sevoflurane; D013997:Time Factors
chemical_list: D000732:Androstanols; D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D000077123:Rocuronium; D015742:Propofol