['Corticosteroids have been used successfully to prolong the duration of local anesthetic action after peripheral nerve and epidural blockade. We hypothesized that the addition of dexamethasone to mepivacaine would prolong the duration of analgesia after ultrasound-guided supraclavicular brachial plexus block for patients undergoing upper-limb surgery.', 'After Federal Health Department and institutional review board approval, 45 adult patients undergoing elective hand or forearm surgery under supraclavicular brachial plexus blockade were randomized to receive either 30 mL mepivacaine 1.5% plus dexamethasone 8 mg (4 mg/mL), or 30 mL mepivacaine 1.5% plus 2 mL normal saline. The primary outcome measure was duration of analgesia. Secondary outcomes included onset times of sensory and motor blockade, pain and satisfaction scores, analgesic consumption, and block-related complications.', 'Patient characteristics were similar between groups. The median duration of analgesia was significantly prolonged in the Dexamethasone group (332 mins; interquartile range, 225-448 mins) compared with the Normal Saline group (228 mins; interquartile range, 207-263 mins; P = 0.008). The onset times of sensory and motor block were similar between the groups. Complications were minor and transient and did not differ between groups at 2 weeks postoperatively.'] Does dexamethasone added to mepivacaine prolong the duration of analgesia after supraclavicular brachial plexus blockade?