Effect of bupivacaine concentration on the efficacy of ultrasound-guided interscalene brachial plexus block

Background: Interscalene brachial plexus block (ISBPB) is an effective technique for shoulder surgery and postoperative pain control. The aim of this study is to compare the analgesic efficacy of 0.1% vs 0.2% bupivacaine for continuous postoperative pain control following arthroscopic shoulder surgery. Methods: A total of 40 adult patients divided into two groups (each 20 patients) undergoing arthroscopic shoulder surgery were randomized to receive an ultrasound-guided ISBPB of either 0.1% or 0.2% bupivacaine 10 ml bolus plus 5 ml/h infusion through interscalene catheter. Standard general anesthesia was given. Both groups received rescue postoperative PCA morphine. Pain, sensory, and motor power were assessed before for all patients, 20 minute after the block, postoperatively in the recovery room, and at 2, 6, 12, and 24 hours thereafter. The patient and surgeon satisfaction and the analgesic consumption of morphine were recorded in the first 24 hours postoperatively. A nonparametric MannWhitney was used to compare between the two groups for numerical rating scale, morphine consumption in different time interval. Results: Group 1 (0.1% bupivacaine) patients had significantly received more intraoperative fentanyl and postoperative morphine with higher pain scores at 24 hours postoperatively vs group 2 (0.2% bupivacaine) patients. Conclusions: The use of ultrasound-guided ISBPB with 0.2% bupivacaine provided better intra- and post-operative pain relief vs 0.1% bupivacaine in arthroscopic shoulder surgery.