title: New composite index based on midlatency auditory evoked potential and electroencephalographic parameters to optimize correlation with propofol effect site concentration: comparison with bispectral index and solitary used fast extracting auditory evoked potential index.
abstract: BACKGROUND
  This study investigates the accuracy of a composite index, the A-Line(R) auditory evoked potentials index version 1.6 (AAI1.6; Danmeter A/S, Odense, Denmark), as a measure of cerebral anesthetic drug effect in a model for predicting a calculated effect site concentration of propofol (CePROP). The AAI1.6 algorithm extracts information from the midlatency auditory evoked potentials, the spontaneous electroencephalographic activity, and the detection of burst suppression. The former version of this monitor, the A-Line auditory evoked potential index version 1.5, is only based on fast extracted midlatency auditory evoked potential information.
  
  
  METHODS
  After institutional ethics committee approval (University Hospital, Ghent, Belgium), informed consent was obtained from 13 patients (10 women, 3 men) with an American Society of Anesthesiologists physical status of I, aged 18-65 yr, who were scheduled to undergo ambulatory gynecologic or urologic surgery. The authors evaluated for Bispectral Index, A-Line auditory evoked potential index, version 1.5, AAI1.6 scaled from 0 to 100 and AAI1.6 scaled from 0 to 60, the interpatient stability at baseline, the detection of burst suppression, prediction probability, and correlation with CePROP, during a constant infusion of 1% propofol at 300 ml/h. The authors developed pharmacodynamic models relating the predicted CePROP to each measure of cerebral anesthetic drug effect.
  
  
  RESULTS
  Bispectral Index had the lowest interindividual baseline variability. No significant difference was found with prediction probability analysis for all measures. Comparisons for correlation were performed for all indices. The AAI1.6 scaled to 60 had a significantly higher correlation with CePROP compared with all other measures. The AAI1.6 scaled to 100 had a significant higher correlation with CePROP compared with the A-Line auditory evoked potential index version 1.5 (P < 0.05)
  
  
  CONCLUSIONS
  The authors found that the application of AAI1.6 has a better correlation with a calculated CePROP compared with a solitary fast extracting midlatency auditory evoked potential measure. Whether this improvement in pharmacodynamic tracing is accompanied by an improved clinical performance should be investigated using clinical endpoints.
authors.affiliation: Department of Anesthesia, Ghent University Hospital, Gent, Belgium. hugo.vereecke@ugent.be
authors.forename: Hugo E M
authors.initials: HE
authors.lastname: Vereecke
authors.forename: Pablo Martinez
authors.initials: PM
authors.lastname: Vasquez
authors.forename: Erik Weber
authors.initials: EW
authors.lastname: Jensen
authors.forename: Olivier
authors.initials: O
authors.lastname: Thas
authors.forename: Rudy
authors.initials: R
authors.lastname: Vandenbroecke
authors.forename: Eric P
authors.initials: EP
authors.lastname: Mortier
authors.forename: Michel M R F
authors.initials: MM
authors.lastname: Struys
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D004569:Electroencephalography / Q000187:drug effects*; D005072:Evoked Potentials, Auditory / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015742:Propofol / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol