Effect Of Continual Midazolam Intravenous Infusion On Availabile Target Concentration Of Propofol

Objective To observed and compared the influence of continuousintravenous infusion of different doses of midazolam on the availabile targetConcentration of propofol required to maintain the same depth of sedation,and the condition of postoperation awaking to select the optimal combinationof these two anesthetics.Methods Sixty female patients with ASA physical status 1-2 scheduledfor larparoscopic gynecologic surgery were randomly divided into threegroups (n=20 each): propofol group (group P), midazolamâ… group (group M₁)and midazolamâ…¡group (group M₂). For all patients, the inductionconcentration of propofol was 3 mg·L^-1 followed by administration offentanyl (2-3μg·kg^-1) and vecuronium brumide (0.12mg·kg^-1). Beforepropofol induction, midazolam (0.05mg·kg^-1) was intravenously injectedfollowed by two doses of midazolam (0.04mg·kg^-1·h^-1 in group M₁,0.08mg·kg^-1·h^-1 in group M₂). Propofol concentration was initially adjustedto keep the BIS value below 50. After trachea intubation, the patients weremechanically ventilated to obtain an end-tidal carbon dioxide partial pressureof 28-35 mmHg. During operation, propofol concentration was adjusted tomaintain the BIS value between 45 and 55,before skin incision the same doseof fentanyl as anesthesia induction was administered intravenously,vecuronium 0.06mg·kg^-1 at an interval of 45～60min.If MAP increase＞30%baseline value lasting moer than 5 rain added fentanyl 0.75～1.5μg·kg^-1.Halfhour before the end of operation stopted adding fentanyl and vecuronium, atthe end of mostly operates stopped midazolam infusion, at the time of sewingskin stopped propofol infusion and gave atropine and neostigmine toreversing muscle paralysis The effective propofol concentration was notedevery 5 min, the time of emergence from anesthesia and OAA/S scores wererecorded in each group. The adverse reactions were recorded the next dayafter surgery.Results Along with the increase of the midazolam doses, the requiredeffective propofol concentration was significant decreased (P＜0.05).Although the times of emergence from anesthesia were increased, there were no significant differences among the three groups (P＞0.05) OAA/S scoreswere higher in the group P than in groups M₁ and M₂ (P＜0.05), and thepostoperative sleepiness was more common in the midazolam groups (P＜0.05). There was no significant difference in the occurrence of the adversereactions among the three groups (P＞0.05).Conclusion There was a dose-dependent decrease in the effectivepropofol concentration required to maintain the same depth of sedation whenmidazolam doses were increased. For propofol-based anesthesia used forlarparoscopic gynecologic surgery, continuous intravenous infusion ofmidazolam at the dose of 0.08mg·kg^-1·h^-1 is the optimal combination of thesetwo anesthetics.