How Does the Addition of Dexamethasone to a Brachial Plexus Block Change Pain Patterns After Surgery for Distal Radius Fractures? A Randomized, Double-blind Study

Background Although brachial plexus block in volar plating surgery for distal radius fractures is reportedly associated with lower postoperative pain scores, rebound pain has been reported to occur after the initial block wears off. Dexamethasone can be used in multimodal strategies for antiemesis and to control pain postoperatively. Although prior studies have suggested that anesthesia can be prolonged by adding dexamethasone to regional blocks, no randomized trials we are aware of have ascertained whether doing so will make a clinically important difference in pain after surgery for distal radius fractures. Questions/purposes Do patients who receive supplemental dexamethasone in a brachial plexus block for volar plating of unstable distal radius fractures have (1) better pain scores at 4, 8, 24, and 48 hours postoperatively than patients who have not received dexamethasone, and (2) lower fentanyl consumption and administration of antiemetic drugs without change in serum blood glucose, as well as a longer analgesic duration from the block after surgery than patients who have not received dexamethasone? Methods This randomized, double-blind trial included 69 patients undergoing surgery for distal radius fractures under ultrasound-guided supraclavicular brachial plexus blocks who were randomly allocated into two groups: a nondexamethasone group receiving a brachial plexus block with 0.5% ropivacaine and a dexamethasone group receiving 0.5% ropivacaine and 5 mg of dexamethasone. Thirty-four patients were allocated to the dexamethasone group and 35 were allocated to the nondexamethasone group. Nine patients (four in the dexamethasone group and five in the nondexamethasone group) were excluded after randomization because local anesthetics were used during their surgical procedures owing to an incomplete block or they requested patient-controlled analgesia after surgery. The treatment groups did not differ in any important ways, including age, gender, BMI, hand dominance, and AO/Orthopaedic Trauma Association classification. All patients received the same surgical procedure and perioperative care protocol, except for the injected agents during their brachial plexus block. The primary outcome was postoperative pain, evaluated using a 10-mm VAS at 4, 8, 12, 24, and 48 hours after surgery. The minimum clinically important difference for the VAS score was 2 of 10 points. Secondary outcome variables included fentanyl administration as a rescue analgesic, the number of patients receiving antiemetic medications because of fentanyl administration, and the duration of brachial plexus block. Serum blood glucose was measured 1 day before, immediately after, and 24 hours after surgery. Patients, surgeons, and outcome assessors were blinded to treatment allocation. Results The only clinically important between-group difference in VAS pain scores was at 8 hours, favoring the group that received dexamethasone over the group that did not (1.9 +/- 1.6 versus 4.7 +/- 2.7; mean difference -2.8 [95% CI -3.9 to -1.6]; p < 0.001). After brachial plexus block, the most severe pain score in both groups was reported at 12 hours postoperatively and gradually diminished over time. There was no between-group difference in fentanyl use between those who received dexamethasone and those who did not (21 +/- 38 mcg versus 31 +/- 29 mcg; mean difference -10 [95% CI -27.4 to 7.4]; p = 0.26). Furthermore, the use of antiemetics did not differ between the groups (27% [eight of 30] versus 37% [11 of 30]; odds ratio 1.6 [95% CI 0.5 to 4.8]; p = 0.41). Baseline and 24-hour postoperative serum blood glucose level did not differ between the groups. However, the immediately postoperative serum blood glucose level was higher in the dexamethasone group than in the nondexamethasone group (121 +/- 29 versus 104 +/- 20; mean difference 16 [95% CI 3.3 to 28.8]; p = 0.02). The brachial plexus block duration was 3 hours longer (95% CI 0.8 to 5.2 hours) in the dexamethasone group than that in the nondexamethasone group (11 +/- 5 hours versus 8 +/- 3 hours; p = 0.01). Conclusion The postoperative pain level in patients who received supplemental dexamethasone in a regional block was not clinically different from that of patients who received conventional brachial plexus block anesthesia when undergoing volar plating for distal radius fractures. However, patients who received a brachial plexus block with dexamethasone experienced slight prolongation of their block and decrease in pain 8 hours after surgery.