Effects of propofol and isoflurane on auditory evoked potential index during surgery

Objective To assess the effect of intravenous anesthetics propofol and inhaled anesthetics isoflurane on auditory evoked potential index (AEPI) and the value of AEPI in the monitoring of anesthetic depth. Methods Thirty patients scheduled for elective surgery with no audition obstacle and non-neurotic were randomly divided into 2 groups and received propofol TCI 2 μg/mL (group I, n=15), or inhaled isoflurane P ET1.5% (group II, n=15), respectively. The induction of anesthesia with midazolam 0.08 mg/kg, propofol or isoflurane, fentanyl 5 μg/kg, vecuronium 0.15 mg/kg and then tracheal intubation were performed. The auditory evoked potential indexes (AEPI) were recorded during anesthesia period. Results The AEPI was decreased to less than 30 in group I and II. The time from induction to AEPI under 30 was (6.2±2.5)min(group I),(15.2±1.9)min (group II) respectively. During anesthesia, the incidence of AEPI instability were much more profound in group I (40%) than in group II (13%) (P0.01). Conclusion The propofol and isoflurane decrease the APEI to less than 30. The changes of AEPI were not accorded between the propofol and isoflurane during surgery. The AEPI monitoring is valuable in assessment of anesthetic depth during anesthesia with propofol or isoflurane.