Abstract: AIM: To study the minimum volume of local anesthetic ( mixture with 1 % lidocaine and 0.375 % ropivocaine) in the effective axillary brachial plexus block guided by high-frequency ultrasound and neurostimulator.METHODS: Patients scheduled for elective surgery of the forearm and hand were allocated to several groups ( the groups were determined by clinical progression, n =30 each).An axillary brachial plexus block was performed under real-time monitoring by ultrasound and neurostimulator.A setted dosage were respectively infused near the radial nerve ( RN), median nerve, ulnar nerve ( UN) and musculocutaneous nerve.The starting dose of local anesthetic was setted at 10 mL per point.The volume in the subsequent group was decreased by 50 %, or the median volume of the previous two volumes according to the success rate. A minimum volume was achieved until the volume difference between the two consecutive groups was less than 0.5 mL.The operation time, onset time of the four nerves, duration time and complications were observed.RESULTS: A 100 % success rate was achieved in groups using 10 mL, 7.5 mL, 6.2 mL and 5.6 mL of local anesthetic.Each 2 of the 10 patients of the two groups ( 5.3 mL, 5.0 mL) did not get the demanding effects, and were all retrieved by another ultrasound- guided infraclavicula brachial plexus block. The operating times were similar in all groups.The mean operation time was 8.4 min.The onset time of each nerve and duration of anesthesia were comparable in all groups.Therewere no occurrence of wrongly vascular puncture, haematoma in the puncture site, local anesthetics poisoning and paresthesia of affected extremities. CONCLUSION: The minimum volume of local anesthetic in the effective axillary brachial plexus block guided by ultrasound and neurostimulator is 5.6 mL per point.

Key words: ultrasound, neurostimulator, brachial plexus, axillary, volume