Timing of intravenous dexamethasone and analgesia after brachial plexus block: a randomized, double-blind, placebo-controlled trial

Background The addition of intravenous dexamethasone can significantly prolong analgesia and reduce opioid-related side effects after brachial plexus blockade, but the most effective administration time is yet unknown. The objective of this study is to determine if the timing of administration of dexamethasone affects the duration of analgesia after supraclavicular brachial plexus block. Methods This is a double-blind, placebo-controlled, randomized trial performed at a single-center, tertiary academic health sciences center. Patients were randomly assigned to one of four treatment groups to receive dexamethasone 8 mg intravenously (or normal saline infusions) at 1-hour preblock, at the time of the block, and 1 or 2 hours postblock. Results 197 patients were randomized and received the intervention (in one of four treatment groups) between January 2018 and November 2023. 39 patients were excluded due to loss to follow-up and unavailability of primary outcome data. The remaining 158 patients have complete data sets and were analyzed. The time to first reported pain was not significantly different between groups (p=0.904). Secondary outcomes including pain scores and opioid consumption, recovery scores and block recovery time did not vary significantly among groups up to 48 hours. Adverse effects such as postoperative neurological symptoms and nausea were similar across groups up to 3 months postoperatively. Conclusions and relevance Our results suggest that perioperative administration of 8 mg of intravenous dexamethasone (from 1 hour prior and up to 2 hours postblock) provides similar duration of analgesia to administration at the time of brachial plexus block. Trial registration number NCT03394820 .