Continuous standard bupivacaine versus single liposomal bupivacaine injection for interscalene brachial plexus block for pain management after proximal humerus fracture fixation: a study protocol of a non-inferiority randomized controlled trial (CLIP-H study)

Abstract Interscalene brachial plexus nerve blocks (ISB) are commonly used to reduce postoperative pain for proximal humerus fracture fixation. Good pain control minimizes opioid consumption, facilitates mobilization and enhances functional recovery. While ISB continuous nerve block infusion can prolong postoperative analgesia, it is technically demanding and associated with problems such as catheter displacement and obstruction. Liposomal bupivacaine allows prolonged duration of analgesia up to 72 hours after single injection. Single ISB injection using liposomal bupivacaine can perhaps provide extended pain relief without the potential problems associated with continuous nerve catheters. The analgesic efficacy of single injection of liposomal bupivacaine versus continuous nerve infusion with standard bupivacaine has not been investigated. In this study protocol, we describe a single centre, double blind, non-inferiority randomized controlled trial to compare the analgesic effect of single ISB injection using liposomal bupivacaine (LP-ISB group) versus continuous ISB nerve infusion using standard bupivacaine (C-ISB) after proximal humeral fracture fixation. Seventy-eight patients will be recruited after obtaining informed consent. Patients in the LP-ISB group will receive ISB injection with 10ml of 1.33% liposomal bupivacaine, followed by nerve catheter infusion using normal saline at 5ml/hr. Patients in the C-ISB group will receive ISB injection with 10ml of 0.25% standard bupivacaine, followed by nerve catheter infusion with 0.2% standard bupivacaine at 5ml/hr. All patients will receive the same perioperative general anaesthetic and analgesic management. The primary outcome is the weighted AUC NRS pain score (scale 0-10) at rest and with movement during the acute postoperative period. Secondary outcomes in the acute postoperative period include postoperative opioid consumption, overall analgesic benefit score and adverse effects. Longer-term secondary outcomes that will be assessed include health related quality of life, upper limb functional scores (QuickDASH) and chronic pain. This clinical study has been registered at ClinicalTrials.gov (NCT04928664).