Liposomal Bupivacaine Plus Plain Bupivacaine Versus Dexamethasone Plus Plain Bupivacaine in the Supraclavicular Brachial Plexus Block in Patients With Risk Factors for Severe Acute Postoperative Pain

The supraclavicular brachial plexus block (BPB) is a frequently used anaesthetic method for upper limb surgeries, including distal radial fracture surgery. Adding liposomal bupivacaine to BPB has shown promise in enhancing postoperative pain control. A previous randomized controlled trial demonstrated that it reduced pain scores and OBAS compared to plain bupivacaine alone, especially on postoperative day (POD) 1. Adding adjuncts to non-liposomal local anaesthetics can also enhance and prolong postoperative pain relief. The effectiveness of liposomal bupivacaine compared to adjuncts like dexamethasone and dexmedetomidine remains unclear. Since liposomal bupivacaine is more expensive, it is crucial to compare its analgesic efficacy with these alternatives. A randomized controlled trial comparing liposomal bupivacaine versus dexamethasone in the interscalene BPB for shoulder surgery found that liposomal bupivacaine resulted in statistically significantly lower pain scores and less pain interference in the Brief Pain Inventory, although the reduction was not considered clinically relevant. Its high cost may therefore limit its routine use unless specific clinical contexts where its efficacy is maximized are identified. Notably, patients with risk factors like psychological factors, preoperative pain, and prior analgesic use may benefit most from its application. A randomized controlled trial to compare the analgesic efficacy of liposomal bupivacaine plus plain bupivacaine versus dexamethasone plus plain bupivacaine in supraclavicular BPB for patients at higher risk of poor acute pain control post distal radial fracture surgery will be conducted. Patients with severe preoperative pain, opioid use, depressive symptoms, anxiety symptoms, and/or higher energy and high-grade fracture cases will be selected. The primary outcome measured is the intensity of acute postoperative pain with movement in the first 48 hours after surgery. Important secondary outcomes include pain intensity at rest, opioid consumption, OBAS scores, chronic pain, and upper limb functionality.

Inclusion Criteria: * American Society of Anesthesiologist (ASA) status I-III * Age 18-90 years old * Scheduled for distal radial fracture fixation (Open reduction and internal fixation with volar approaching locking plate) * Informed consent obtained * Patients identified to be at an elevated risk of suffering from poor postoperative pain control. Patients with one or more of the following risk factors: * Severe preoperative pain: defined as worse numerical rating scale (NRS) pain score equal or higher than 6/10 with arm movements at day before surgery. * Preoperative use of opioid: use of strong opioids such as morphine, oxycodone * Depressive symptoms: Patient health questionnaire (PHQ-9) score of 10 or above * Anxiety symptoms: General Anxiety Disorder (GAD-7) score of 10 or above * Higher energy and high-grade fracture cases - road traffic accident, fall from height, open fractures, combined distal radius and distal ulna fractures, fractures requiring external fixation, fractures with severe articular comminution or severe metaphyseal extension, comminuted fractures requiring more than a single volar approach incision and a single volar locking plate implant Exclusion Criteria: * Revision surgery * Previous fractures or surgery in the affected distal radius * Surgery involving more than the affected arm * Cases with baseline (pre-injury) QuickDASH score worse (higher) than 10 out of 100 * Respiratory compromise (requires long term oxygen) * History of seizures * Pre-existing neurological disorder/deficit * Alcohol or substance abuse * Impaired mental state * Local infection * Allergy to analgesic drugs: local anaesthetic drugs, paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), opioids * Impaired renal function (defined as effective glomerular filtration rate \< 30ml/min/1.73m2 * Impaired liver function (defined as plasma bilirubin over 34μmol/L; international normalized ratio \[INR\] ≥1.7, alanine aminotransferase \[ALT\] over 100U/L, aspartate aminotransferase \[AST\] over 100U/L) * Coagulopathy (platelet count \