Effect Of Dexmedetomidine On Median Effective Target Effect-site Concentration Of Refentanil Inhibiting Bdy Movement Evoked By Skin Incision Inpatients Undergoing Abdominal Surgry

Objective: To investigate the effect of dexmedetomidine on median effective target effect-site concentration(EC50) of refentanil inhibiting body movement evoked by skin incision in patients undergoing abdominal surgery. Methods:Thirty-eight ASA I or II patients of both 20-60 yr with a body mass index of 20-30kg/m2 undergoing abdominal surgery were randomly divided into 2 groups:control group(group C) and dexmedetomidine group(group D).The patients were premedicated with intramuscular phenobarbital 0.1g and scopolamine 0.3mg.In group D dexmedetomidine 0.6μg/kg was injected iv over 10 min at 5min before induction of anesthesia.Anesthesia was induced with target-controlled infusion(TCI) of propofol and refentanil.The target plasma concentration of propofol was set a 3.oμg/ml.TCI of refentanil was started at 12 min after initiation of propofolTCI.The initial target effect-site concentration was set at 4.5ng/ml and decreased/increased by 20% in the next patient according to whether the patiend’s body moved or not within 1min after skin incision. Laryngeal mask airway was inserted at 3min after initiation of refentanilTCI.Spontaneous breathing was maintained.Skin incision was made when the target concentrations of propofol and refentanil TCI were reached.The EC50 and 95% confidence interval(CI) of refentanil inhibiting skin incision-evoked body movement were calculated with sequential method. Results: EC50 refentanil was 1.23ng/ml(95% CI 1.16-1.30 ng/ml) in group D and 1.52 ng/ml(95%CI 1.44-1.60 ng/ml) in group C,and was significantly lower in group D than group C. Conclusion: Dexmedetomidine 0.6μg/kg infused iv before operation can reduce the EC50 of refentanil inhibiting body movement evoked by skin incision in patients undergoing abdominal surgery,about 19%.