A Randomized Comparison Between Interscalene and Small-Volume Supraclavicular Blocks for Arthroscopic Shoulder Surgery

Background and Objectives This randomized trial compared ultrasound (US)–guided interscalene block (ISB) and small-volume supraclavicular block (SCB) for arthroscopic shoulder surgery. We hypothesized that SCB would provide equivalent analgesia to ISB 30 minutes after surgery without the risk of hemidiaphragmatic paralysis (HDP). Methods All patients received an US-guided intermediate cervical plexus block. In the ISB group, US-guided ISB was performed with 20 mL of levobupivacaine 0.5% and epinephrine 5 μg/mL. In the SCB group, US-guided SCB was carried out using 20 mL of the same local anesthetic agent: 3 and 17 mL were deposited at the "corner pocket" (ie, intersection of the first rib and subclavian artery) and posterolateral to the brachial plexus, respectively. A blinded investigator assessed ISBs and SCBs every 5 minutes until 30 minutes using a composite scale that encompassed the sensory function of the supraclavicular nerves, the sensorimotor function of the axillary nerve, and the motor function of the suprascapular nerve. We considered the blocks complete if, at 30 minutes, a composite score equal or superior to 6 points (out of 8 points) was achieved. Thus, onset time was defined as the time required to reach a minimal composite score of 6 points. The blinded investigator also assessed the presence of HDP at 30 minutes with US. Subsequently, all patients underwent general anesthesia. Postoperatively, a blinded investigator recorded pain scores at rest at 0.5, 1, 2, 3, 6, 12, and 24 hours. Patient satisfaction at 24 hours, consumption of intraoperative and postoperative narcotics, and opioid-related adverse effects were also tabulated. Results Both groups displayed equivalent postoperative pain scores at 0.5, 1, 2, 3, 6, 12, and 24 hours. Interscalene blocks resulted in a higher incidence of HDP (95% vs 9%; P

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