Study On Remifentanil EC₅₀Combined With Propofol 2.0 ?g·ml^-1 Target-Controlled Infusion For Conscious Sedation In Daytime Gynecological Surgery

Objective:To determine the half effect-site concentration(EC50)of remifentanil in daytime gynecologic surgery patients with target-controlled infusion of propofol 0.2 ng·ml-1 at a satisfactory state of conscious sedation.Methods:This study was approved by the Ethics Committee of Hangzhou Hospital of Traditional Chinese Medicine,Zhejiang Province,and implemented after the informed consent of the patient or his immediate/near relatives was signed.Thirty-six patients(aged 18-46 yrs,ASA ???)who were scheduled to undergo daytime gynecological surgery were randomly enrolled in this study.The propofol effect-site concentration was fixed at 2.0 ?g·ml-1 in all patients.The initial remifentanil effect-site concentration was 6 ng·ml-1 and was increased/decreased by 0.2 ng·ml-1 if the unsatisfied/satisfied conscious sedation states happened by Dixon's up and down method.Considering the risk of respiratory depression and severe hypoxemia due to target-controlled infusion of propofol and remifentanil,patients were routinely given mask pre-oxygenation(5 L/min and asked to take 16 deep breaths in 2 minutes)after entering the room.One of the following situations occurred during the operation:? OAA/S score<3 points;? no pain,no frown,no influence on limb movement;? SpO2<90%and cannot be restored to more than 90%by verbal command stimulation,then the patient's state of awakening and sedation was classified as satisfactory;otherwise,it was classified as unsatisfactory,then statistical analysis was made.The EC50 and EC95 of remifentanil for conscious sedation were determined using probit analysis.At the same time,adverse events in SpO2,respiratory and circulatory depression,and memory impairment during the operation were recorded.Results:The EC50 of remifentanil that provides conscious sedation combined with 2.0?g·ml-1 propofol in daytime gynecological surgery patients was 5.43 ng·ml-1(95%CI 4.90-6.79 ng·ml-1),while the EC95 was 6.42 ng·ml-1(95%CI 5.88-27.33 ng·ml-1).Respiratory amnesia and body movement coexisted in 2 patients in this study.Conclusions:We recommended initial dose of remifentanil target-controlled infusion for conscious sedation in patients undergoing daytime gynecological surgery was 5.43 ng·ml-1 when propofol TCI was 2.0 ?g·ml-1.