Résumé
Objective To determine the median effective target plasma concentration (Cp50) of remifentainil inhibiting body movement evoked by puncture during brachial plexus block in pediatric patients.Methods Pediatric patients of both sexes,aged 5-12 yr,who grown normally,scheduled for elective forearm or hand surgery,were enrolled in this study.Children were premedicated with oral midazolam 0.2 mg/kg at 30 min before anesthesia.The initial target Cp of remifentainil was 5.0 ng/ml.The target Cp was determined by up-and-down sequential method.Each time Cp increased/decreased by 20％ in the next patient depending on the response of the previous patient to puncture.The ratio between the two successive concentrations was 1.2.The puncture was performed after the target effect-site and plasma concentrations were balanced.Body movement was defined as puncture-induced movement of truncus,limbs and/or head and neck.The Cp50 and 95 ％ confidence interval of remifentainil were calculated by Dixon method.Results Cp50 of remifentainil inhibiting body movement evoked by puncture during brachial plexus block was 3.9 ng/ml,and 95 ％ confidence interval was 3.6-4.2 ng/ml.Conclusion Cp50 of remifentainil inhibiting body movement evoked by puncture during brachial plexus block is 3.9 ng/ml in pediatric patients.