title: Evaluation of bispectral index and auditory evoked potentials for hypnotic depth monitoring during balanced xenon anaesthesia compared with sevoflurane.
abstract: BACKGROUND
  None of the currently available hypnosis monitoring systems have evaluated balanced xenon anaesthesia. We investigated the performance of the bispectral index (BIS) and the composite A-line autoregressive index (cAAI) while comparing balanced xenon with sevoflurane anaesthesia.
  
  
  METHODS
  Sixty patients undergoing elective abdominal surgery participated in this registered double-blinded, controlled trial and-after written informed consent-were randomly assigned to one of the study groups (xenon, n=30; sevoflurane, n=30). After induction, general anaesthesia was maintained with xenon 60% or sevoflurane 2.0% in 30% O2. Remifentanil was titrated to clinical needs. BIS and cAAI values were recorded electronically and blinded to the performing physician. Emergence from anaesthesia was evaluated and during 12 h follow-up, patients were questioned twice for signs of recalls.
  
  
  RESULTS
  During induction and maintenance of anaesthesia, BIS values in the xenon group were comparable with sevoflurane anaesthesia and within the recommended range. Although the cAAI remained stable in the sevoflurane group, values increased during balanced xenon anaesthesia and exceeded the recommended upper limit after 65 min. Emergence from xenon anaesthesia was significantly faster than from sevoflurane (eye opening at 3.8 vs 10.3 min, P<0.001), and BIS values were concordant with the washout of both anaesthetics. No incident of recall was reported.
  
  
  CONCLUSIONS
  During surgery, xenon/remifentanil anaesthesia can be monitored using BIS and cAAI. However, cAAI values changed after about 1 h of anaesthesia. Further studies will be needed to address the question whether auditory signal processing is altered during extended xenon exposure.
authors.affiliation: Department of Anaesthesiology, University Hospital Aachen, RWTH Aachen, Pauwelsstr. 30, D-52074 Aachen, Germany.
authors.forename: A V
authors.initials: AV
authors.lastname: Fahlenkamp
authors.forename: D
authors.initials: D
authors.lastname: Peters
authors.forename: I A
authors.initials: IA
authors.lastname: Biener
authors.forename: C
authors.initials: C
authors.lastname: Billoet
authors.forename: C C
authors.initials: CC
authors.lastname: Apfel
authors.forename: R
authors.initials: R
authors.lastname: Rossaint
authors.forename: M
authors.initials: M
authors.lastname: Coburn
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects; D005072:Evoked Potentials, Auditory / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D000077149:Sevoflurane; D014978:Xenon / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D014978:Xenon