Low-Dose Dexamethasone as an Adjuvant for Prolonging the Duration of Brachial Plexus Block with Bupivacaine—a Prospective Randomised Controlled Study

Objectives Dexamethasone, in the dose of 8 mg or higher, has been advocated to be used as an adjuvant to prolong the duration of brachial plexus blocks with local anaesthetics. This study aimed to test the hypothesis that a lower dose of dexamethasone (4 mg) added to bupivacaine would prolong the duration of analgesia in brachial plexus blocks. Methods A randomized double-blind placebo-controlled trial was conducted on patients who underwent supraclavicular brachial plexus blocks using an ultrasound. Patients were randomized to receive 19 mL of 0.5% bupivacaine with dexamethasone (4 mg) (study group) and saline (1 mL) (control group). Primary outcome measure was the duration of analgesia. Onset and duration of sensory, motor blocks, postoperative 24-hour morphine requirements were also recorded. Results A total of 46 patients were studied with 24 patients in the dexamethasone group and 22 patients in the control group. Demographic data, type and duration of surgery were comparable between the groups. Dexamethasone group patients had significantly longer duration of analgesia [Mean (SD): 19.8 (3.8) hours], compared to control group patients [Mean (SD): 14.5 (4.2); p< 0.001]. Morphine requirements over a 24-hour period were not significantly different between the groups. Conclusion Low-dose dexamethasone significantly prolongs the duration of analgesia when used with bupivacaine in supraclavicular brachial plexus blocks, although it does not significantly decrease the overall opioid requirements for 24 hours postoperatively.