The minimum local anesthetic concentration of ropivacaine in patient receiving infraclavicular brachial plexus block

Objective To study the minimum local anesthetic concentration(MLAC) of ropivacaine in patients receiving infraclavicular brachial plexus block,under which concentration the effective anaesthesia was obtained with minimal motor block without local anesthetic systemic toxicity and neurotoxicity.It is better for surgeon to find nerve injury during the operation and to evaluate the effect after the operation.Methods Forty patients scheduled for surgical procedures below elbow were enrolled.All patients who were distributed to ASA physical status class Ⅰ-Ⅱ and aged between 18 and 65 years old received an infraclavicular brachial plexus block by nerve stimulator.The total volume was 60 mL,and the concentration started at 0.25% with concentration gradient of 0.01%,depending on the response of the previous patient,using the technique of up-down sequential allocation.Half-effective concentration(EC50) and 95% confidence interval(95% CI) were obtained by probit analysis.Results The EC50 and 95% CI for ropivacaine was 0.176% and(0.116%-0.212%).Conclusions The minimum local anesthetic concentration of ropivacaine in patient receiving infraclavicular brachial plexus block was 0.176%.The effective concentration of ropivacaine can provide effective anaesthesia with minimal motor block.