title: [Effect of propofol at different effect-site concentrations on approximate entropy of transient evoked otoacoustic emission signals in adults].
abstract: OBJECTIVE
  To study the effect of propofol at different effect-site concentrations on approximate entropy (ApEn) of transient evoked otoacoustic emission (TEOAE) signals in adults and investigate the possibility of using ApEn for monitoring anesthesia depth.
  
  
  METHODS
  Fifteen ASA class I or II patients (aged 18-49 years with normal hearing) undergoing elective surgery under general anesthesia were enrolled in this study. Anesthesia was maintained with target-controlled infusion of propofol. With the effect-site concentrations of 1, 2, 3 and 4 microg/ml, TEOAE signals were monitored and recorded before and after anesthesia. ApEn of TEOAE in 4 frequency ranges (0-2, 1-3, 2.5-4.5, and 4-6 kHz) were calculated using MATLAB software.
  
  
  RESULTS
  The ApEn of TEOAE in different frequency ranges showed no significant differences at the same effect-site concentration of propofol, or at different effect-site concentrations in the same frequency range (P>0.05).
  
  
  CONCLUSIONS
  Anesthesia with propofol at different effect-site concentrations does not obviously affect ApEn of TEOAE signals in adults, and ApEn can not be used as the indicator for evaluating the depth of anesthesia.
authors.affiliation: Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China. zaj2006@yahoo.com.cn
authors.forename: Xin-jian
authors.initials: XJ
authors.lastname: Zhang
authors.forename: Miao-ning
authors.initials: MN
authors.lastname: Gu
authors.forename: Jin-fang
authors.initials: JF
authors.lastname: Xiao
mesh_terms: D000293:Adolescent; D000328:Adult; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D019277:Entropy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D017084:Otoacoustic Emissions, Spontaneous / Q000187:drug effects*; D015742:Propofol / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol