[Effect of propofol at different effect-site concentrations on approximate entropy of transient evoked otoacoustic emission signals in adults].

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 μg/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(P0.05).Conclusion 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.