The Minimum Effective Volume Of Ropivacaine For Ultrasound-guided Costoclavicular Brachial Plexus Block In The Critical Patients' Upper Limb Surgery:A Sequential Allocation Dose-Finding Study

Objective:This dose finding study was aimed to determine the minimum effective volume in 90%of critical patients(MEV90)of ropivacaine 0.4%for ultrasound-guided costoclavicular brachial plexus block(BPB).Methods:This was a prospective dose finding study,using the biased coin up-and-down design.Forty critical patients undergoing surgery under ultrasound-guided costoclavicular block which using an in-plane technique and a lateral-to-medial direction in the costoclavicular space received a set intermittent ropivacaine volume of either 15,17,19,21,23,25mL.The total volume of local anesthetic administered to each patient depended on the response of the previous one.In case of failure,the next subject received a higher volume(defined as the previous volume with an increment of 2.0 mL).If the previous patient had a successful block,the next subject was randomized to a lower volume(defined as the previous volume with a decrement of 2.OmL),with a probability of 1/9,or the same volume,with a probability of 8/9.Success was defined,at 30 minutes,as a VRS?30,3-point scale ?1,and being able to complete surgery.The MEV90 and ED95%confidence intervals(CI)were estimated using both truncated Dixon and Mood(DM)and isotonic regression methods.Result:Forty patients were included in the study.The estimated MEV90 of ropivacaine o.4%was 19.2mL(95%CI 18.0-20.4mL)using the truncated Dxion and Mood(DM)methods and 20.3mL(95%CI 17.5-23.1mL)using the isotonic regression method.Conclusion:For ultrasound-guided costoclavicular block in critical patients' upper limb surgery,the volume of ropivacaine 0.4%we suggested is 20mL,in practically.