Appropriate concentration of ropivacaine for differential sensory and motor block of brachial plexus

Abstract

Objective To determine the appropriate concentration of ropivacaine for differential sensory and motor block of brachial plexus.Methods Ninety ASA Ⅰ - Ⅲ patients aged 16-75 yr weighing 40-85 kg undergoing upper extremity operation under axillary brachial plexus block were randomly divided into 3 groups according to the concentration of ropivacaine used for the block(n = 30 each): group A 0.15% ropivacaine;group B 0.10% ropivacaine and group C 0.05% ropivacaine.Axillary brachial plexus block was performed using ultrasound guidance and electric nerve stimulation.Sensory and motor block were assessed and recorded at 10,30,60and 240 min after local anesthetic injection(T1-4).The rate of adequate sensory block,the rate of differential sensory and motor block(the areas innervated by radial,median and ulnar nerves were numb but the patients could still move their elbow,wrist and fingers)and effectiveness of the block(excellent - completely no pain;good slight pain,iv fentanyl was needed;poor -rescue brachial plexus block was needed or general anesthesia was induced).Operation time and duration of analgesia and success rate of the block were recorded.Results 0.15%ropivacaine produced excellent or good block and no failure in group A.The rate of differential sensory and motor block was significantly higher in group B(0.10% ropivacaine)than in group A.The effect of block with 0.05% ropivacaine was unsatisfactory in group C.Conclusion Axillary brachial plexus block with 0.10% ropivacaine can induce differential sensory and motor block in the majority of patients. Key words: Androstanols; Brachial plexus; Nerve block