title: Electroencephalographic approximate entropy changes in healthy volunteers during remifentanil infusion.
abstract: BACKGROUND
  The aim of this study was to investigate the independent effect of remifentanil on the approximate entropy (ApEn) in frontoparietal montages. The authors investigated which montages were relevant to assess the remifentanil effect on the electroencephalogram. Spectral edge frequency and the canonical univariate parameter were used as comparators.
  
  
  METHODS
  Twenty-eight healthy volunteers were enrolled. With recording of the electroencephalogram at the F3, F4, Cz, P3, and P4 montages, remifentanil was infused at the rate of 1-8 mug . kg . min for 15-20 min. The relation between remifentanil concentration and the electroencephalographic parameters were tested by Spearman correlation. Signal-to-noise ratio, artifact robustness, coefficient of variation of the median baseline and maximal electroencephalographic effects, and ratio of average maximal electroencephalographic effect to interindividual baseline variability were measured. The performance of ApEn as an index of remifentanil effect site concentrations was tested by prediction probability.
  
  
  RESULTS
  Approximate entropy showed significant correlation (R = -0.6465, P < 0.0001) with remifentanil concentration. It provided comparable signal-to-noise ratio, artifact robustness, and ratio of average maximal electroencephalographic effect to interindividual baseline variability to 95% spectral edge frequency. The coefficients of variation of the median baseline and maximal electroencephalo graphic effects were smallest in ApEn. Parietal montages showed higher ratios of average maximal electroencephalographic effect to interindividual baseline variability for all electroencephalographic parameters and lower coefficients of variation of the baseline values for ApEn and 95% spectral edge frequency than frontal montages. The prediction probability of ApEn was 0.7730.
  
  
  CONCLUSIONS
  Approximate entropy derived from a parietal montage is appropriate for the assessment of the remifentanil effect on the electroencephalogram.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Gyu-Jeong
authors.initials: GJ
authors.lastname: Noh
authors.forename: Kye-Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Yong-Bo
authors.initials: YB
authors.lastname: Jeong
authors.forename: Seong-Wook
authors.initials: SW
authors.lastname: Jeong
authors.forename: Hee-Suk
authors.initials: HS
authors.lastname: Yoon
authors.forename: Sung-Moon
authors.initials: SM
authors.lastname: Jeong
authors.forename: Sung-Hong
authors.initials: SH
authors.lastname: Kang
authors.forename: Olinto
authors.initials: O
authors.lastname: Linares
authors.forename: Steven E
authors.initials: SE
authors.lastname: Kern
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000465:Algorithms; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D016477:Artifacts; D001499:Bayes Theorem; D003627:Data Interpretation, Statistical; D004569:Electroencephalography / Q000187:drug effects* / Q000706:statistics & numerical data; D019277:Entropy; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007261:Infusions, Intra-Arterial; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D010880:Piperidines / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000077208:Remifentanil
chemical_list: D000701:Analgesics, Opioid; D010880:Piperidines; D000077208:Remifentanil