title: Age-dependent decrease in desflurane concentration for maintaining bispectral index below 50.
abstract: BACKGROUND
  We examined the hypothesis that the minimum alveolar concentration of desflurane for maintaining bispectral index (BIS) below 50 (MACBIS 50 ) decreases with advance of age.
  
  
  METHODS
  Sixty young (20-30 year), middle-aged (31-65 year) and elderly (66-80 year) patients were included (n = 20, each group). Five minutes following the start of continuous intravenous administration of remifentanil at 0.25 μg/kg/min, general anaesthesia was induced with propofol 2 mg/kg and rocuronium 0.8 mg/kg to facilitate tracheal intubation. Infusion of remifentanil was stopped immediately after tracheal intubation. When BIS began to increase > 60, maintenance of anaesthesia was started with an end-tidal desflurane concentration of 4.0% and maintained for 10 min followed by 1-min assessment of BIS taken at 10-s intervals. MACBIS 50 of each age group was estimated by up-down methodology.
  
  
  RESULTS
  MACBIS 50 of desflurane in young, middle-aged and elderly patients was 4.25% end-tidal (95% confidence intervals 4.04-4.46), 3.58% (3.38-3.79) and 2.75% (2.50-3.00) respectively. MACBIS 50 was higher (P = 0.011) in young patients and lower (P = 0.012) in elderly patients than those in middle-aged patients.
  
  
  CONCLUSIONS
  Advance in age significantly decreased the concentrations of desflurane required to maintain BIS below 50. BIS reflected age-associated decrease in end-tidal concentrations of desflurane required for maintaining adequate depth of anaesthesia during resting state.
authors.affiliation: Department of Anesthesiology, Osaka City General Hospital, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kanazawa
authors.affiliation: Department of Anesthesiology, Osaka City General Hospital, Osaka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Oda
authors.affiliation: Department of Anesthesiology, Osaka City General Hospital, Osaka, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Maeda
authors.affiliation: Department of Anesthesiology, Osaka City General Hospital, Osaka, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Okutani
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000077335:Desflurane; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D018685:Anesthetics, Inhalation; D000077335:Desflurane; D007530:Isoflurane