Intravenous Versus Perineural Dexamethasone for Reducing Rebound Pain After Interscalene Brachial Plexus Block: A Randomized Controlled Trial

BACKGROUND: Interscalene brachial plexus block (ISB) is a common regional technique to manage acute postoperative pain for arthroscopic rotator cuff tear repair. However, rebound pain may compromise its overall benefit. Our aim was to investigate the primary hypothesis that perineural and intravenous dexamethasone have different effects on rebound pain after resolution of ISB for arthroscopic rotator cuff tear repair. METHODS: Patients aged ≥ 20 years scheduled for elective arthroscopic rotator cuff tear repair under general anesthesia with preoperative ISB were included. The participants were randomized to receive dexamethasone either perineurally (perineural group) or intravenously (intravenous group). In the perineural group, patients received ISB with 12 mL of 0.5% ropivacaine containing 5 mg of dexamethasone; simultaneously, 1 mL of 0.9% normal saline was administered intravenously. In the intravenous group, patients received ISB with 12 mL of 0.5% ropivacaine; simultaneously, 1 mL of dexamethasone 5 mg was administered intravenously. The primary outcome was the difference in the pain score (0–10 on numeric rating scale) between before and after ISB resolution. The secondary outcomes were the incidence of rebound pain; onset, duration, and intensity of rebound pain; time to the first analgesic request; and pain-related sleep disturbance. RESULTS: A total of 71 patients were randomized to either perineural group (n = 36) or intravenous group (n = 35). After block resolution, pain scores increased significantly more in the perineural group (mean ± standard deviation, 4.9 ± 2.1) compared to the intravenous group (4.0 ± 1.7, P = 0.043). The duration of ISB was more prolonged in the perineural group (median [interquartile range], 19.9 [17.2–23.1] hours) than the intravenous group (15.1 [13.7–15.9] hours, P < 0.001). The incidence of rebound pain and pain-related sleep disturbance during the first postoperative week was significantly higher in the perineural group than in the intravenous group (rebound pain: 44.4% vs. 20.0%, P = 0.028; sleep disturbance: 55.6% vs. 25.7%, P = 0.011). The duration and intensity of rebound pain were similar between the two groups. CONCLUSION: Although perineural dexamethasone provided longer postoperative analgesia, intravenous dexamethasone was more beneficial in reducing pain increase after ISB resolution, incidence of rebound pain, and pain-related sleep disturbance. TRIAL REGISTRATION: Clinical Research Information Service Identifier: KCT0006795