title: Minimal alveolar concentration of sevoflurane for induction of isoelectric electroencephalogram in middle-aged adults.
abstract: BACKGROUND
  We determined the minimal alveolar concentration (MAC) of sevoflurane inducing an isoelectric EEG in 50% of adult subjects (MACie).
  
  
  METHODS
  We included 31 middle-aged subjects; 30 subjects finished the study protocol and received sevoflurane at preselected concentrations according to a modified Dixon 'up-and-down' design starting at 1.7 vol% with 0.2 vol% steps size. General anaesthesia was induced and maintained with sevoflurane; tracheal intubation was facilitated with cisatracurium. After a period of 30 min before skin incision, the state of isoelectric EEG was considered as significant when a burst suppression ratio of 100% lasted for >1 min. The haemodynamic responses to skin incision and the vasopressor requirement to maintain stable haemodynamic status were also analysed according to the EEG state.
  
  
  RESULTS
  MACie was 3.5% (95% confidence interval, 3.4-3.7%) in middle-aged subjects. When compared with subjects not in isoelectric EEG state, subjects in isoelectric EEG state received more phenylephrine to maintain stable haemodynamics (10 of 10 compared with 7 of 20 subjects, P=0.001) and experienced less sympathetic responses to skin incision (1 of 10 compared with 11 of 20 subjects, P=0.024).
  
  
  CONCLUSIONS
  MACie for sevoflurane was ∼2.1 times MAC for immobilization in phenobarbital premedicated middle-aged adults. Sevoflurane-induced isoelectric EEG state is associated with significant cardiovascular depression but reduced haemodynamic responses to skin incision.
authors: Department of Anaesthesiology and Pain Medicine, Tongji Hospital.
authors: B
authors: B
authors: Niu
authors: Y
authors: Y
authors: Fang
authors: J M
authors: JM
authors: Miao
authors: Y
authors: Y
authors: Yu
authors: F
authors: F
authors: Cao
authors: H X
authors: HX
authors: Chen
authors: Z G
authors: ZG
authors: Zhang
authors: W
authors: W
authors: Mei
authors: Y K
authors: YK
authors: Tian
mesh_terms: D000368:Aged; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D062186:Arterial Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane
keywords: anaesthetics volatile, sevoflurane; cardiovascular system, responses; monitoring, depth of anaesthesia; monitoring, electroencephalography