Effective Dose of Intravenous Dexmedetomidine to Prolong the Analgesic Duration of Interscalene Brachial Plexus Block: A Single-Center, Prospective, Double-Blind, Randomized Controlled Trial

Background and Objectives Intravenous (IV) dexmedetomidine (DEX) is reported to prolong the analgesic duration after single-shot interscalene brachial plexus block (ISBPB). However, the effective analgesic dose of IV DEX remains undetermined. Therefore, we aimed to elucidate the clinically relevant dose of IV DEX to prolong the analgesic duration of ISBPB. Methods Seventy-two patients scheduled for arthroscopic shoulder surgery received ISBPB with 15 mL of 0.5% ropivacaine with 1:200,000 epinephrine and were randomly assigned to 1 of 4 groups (n = 18, each): (1) IV normal saline (control), (2) IV DEX 0.5 μg/kg (DEX 0.5), (3) IV DEX 1.0 μg/kg (DEX 1.0), and (4) IV DEX 2.0 μg/kg (DEX 2.0). The primary outcome was time to the first pain at surgical site. Results The median (interquartile range) duration of analgesia was significantly prolonged for the DEX 2.0 (874 minutes [727–1153 minutes]) compared with 656 minutes (590–751 minutes), 703 minutes (644–761 minutes), and 696 minutes (615–814 minutes) for the control, DEX 0.5 and DEX 1.0 groups, respectively (P = 0.001, P = 0.008, and P = 0.003, respectively). Postoperative cumulative IV morphine equivalent consumption at 24 hours was significantly lower in the DEX 2.0 compared with the control, DEX 0.5 and DEX 1.0 groups (P

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