Abstract: Objective：To investigate the sedation effect of propofol combined with different dose of midazolam in patients undergoing long-time microsurgery taken auditory evoked potential index (AAI) as an end point. Methods：Forty ASA I～II patients were randomly divided into 4 groups. Normal saline(NS) 2ml for group Ⅰ, midazolam 0.01mg/kg, 0.02mg/kg , 0.04mg/kg for GroupⅡ, Ⅲ, Ⅳ separately. 1 min after given NS or midazolam, propofol was infused at a rate of 300～500mg/h combined with midazolam at a rate of 0.01mg/(kg•h), 0.02mg/(kg•h), 0.04mg/(kg•h) for GroupⅡ, Ⅲ, Ⅳ separately. After the AAI reduced to 40(sedation induction), adjusted the infusion rate of propofol to keep AAI at the level of 30～45, and sustained the level by infusing propofol and midazolam for 5 hours. The dosage of propofol required for sedation induction and sedation sustaining were recorded. 5 hours later, stopped the infusion, and recorded the analepsia time and whether patients had awareness during the operation. Results：According to the sedation target level of AAI30～45, the OAA/S score of all patients in the four groups could reach 0～1.The induction period was obviously shortened and the propofol dosage was dramatically reduced in Group Ⅱ～Ⅳ compared with GroupⅠ. In the stage of sustaining the sedation , the dosage of Propofol in both GroupⅠandⅡ were used more than that in Group Ⅲ and Ⅳ, however there were no significant difference between Group Ⅲ and Ⅳ. The analepsia time in Group Ⅳ was dramatically longer than in the other groups. Conclusion：The patients could got a satisfactory sedation by propofol or combined with midazolam during long-time microsurgical operation .The optimal compatibility program was that midazloam was administered 0.02mg/kg for sedation induction, and propofol was infused combined with midazolam 0.02mg/(kg•h) when sedation sustaining.

Key words: Propofol, Midazolam, AAI, Combined medication, Long-time sedation