Perineural but not systemic low-dose dexamethasone prolongs the duration of interscalene block with ropivacaine: a prospective randomized trial

PURPOSE: To determine the effects of intravenous and perineural dexamethasone on the duration of interscalene brachial plexus block (ISB) with ropivacaine in patients undergoing arthroscopic shoulder surgery. PATIENTS AND METHODS: In this prospective, randomized, placebo-controlled trial, patients presenting for arthroscopic shoulder surgery with an ISB were randomized to receive ropivacaine 0.75% (group C), ropivacaine 0.75% plus perineural dexamethasone 4 mg (group Dperi), or ropivacaine 0.75% plus intravenous dexamethasone 4 mg (group Div). The primary outcome was the duration of analgesia, defined as the time between performance of the block and the first request for analgesic. RESULTS: Thirty-nine patients were randomized. The median times of sensory block in groups C, Dperi, and Div were 11.2 hours (interquartile range [IQR] 8.0–15.0 hours), 18.0 hours (IQR 14.5–19.0 hours), and 14.0 hours (IQR 12.7–15.1 hours), respectively. Significant differences were observed between groups Dperi and C (P=0.001). Kaplan–Meier analysis for the first analgesic request showed significant differences between groups Dperi and C (P=0.005) and between groups Dperi and Div (P=0.008), but not between groups C and Div. CONCLUSION: Perineural but not intravenous administration of 4 mg of dexamethasone significantly prolongs the duration of effective postoperative analgesia resulting from a single-shot ISB with ropivacaine 0.75%.