Effects of propofol versus isoflurane on brainstem auditory evoked potential

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Objective To compare the effects of propofol versus isoflurane on brainstem auditory evoked potential (BAEP) and explore the difference in the effects of the two anesthetics on the brainstem. Methods Thirty ASA Ⅰ or Ⅱ patients aged 20-50 yr without heating disorder, scheduled for elective surgery performed under general anesthesia were randomly divided into 2 groups (n = 15 each): propofol group (group P) and isoflurane group (group Ⅰ). SpO2, PET CO2, BIS and BAEP were continuously monitored before and during anesthesia. Anesthesia was induced by propofol administered by TCI or isoflurane inhalation. Tracheal intubation was facilitated with vecuronium. The patients were mechanically ventilated. PET CO2 was maintained at 35-40 mm Hg and SpO2 at 98%-100%. After intubation BIS was maintained at 70 and 50 respectively ,the latency of the wave Ⅰ , Ⅱ and Ⅴ and the inter-peak latency (IPL) betwecn wave Ⅰ -Ⅲ , Ⅲ-Ⅴ and Ⅰ -Ⅴ were recorded.Results In group P there was no significant difference in the latency of the wave Ⅰ , Ⅲ and Ⅴ and the IPL between wave Ⅰ - Ⅲ , Ⅲ - Ⅴ and Ⅰ - Ⅴ between the baseline before anesthesia and at BIS 70 and 50. In group Ⅰ the latency of wave Ⅲ and Ⅴ and the IPL between wave Ⅰ - Ⅲ , Ⅲ - Ⅴ and Ⅰ - Ⅴ were significantly longer at BIS 50 than the baseline before anesthesia, while the latency of wave Ⅲ and Ⅴ and the IPL between wave Ⅰ -Ⅲ andⅠ -Ⅴ at BIS 50 were significantly longer than that at BIS 70. At BIS 50 the latency of wave Ⅴ and the IPL between wave Ⅰ -Ⅴ were significantly longer in group Ⅰ than in group P. Conclusion At comparable depth of anesthesia propofol exerts less depressant effects on BAEP indicating less depression of brainstem. Key words: Propofol; Isofiurane; Evoked potentials, auditory, brain stem; Electroencephalography