Sixty patients undergoing arthroscopic rotator cuff repair were randomized to receive costoclavicular block with either 20 mL of 0.75% ropivacaine (CCB20, n=30) or 40 mL of 0.375% ropivacaine (CCB40, n=30). The primary outcome was the rate of complete analgesia (numeric rating scale [NRS] score of 0) 1 hour postoperatively. Secondary outcomes included sonographic assessment of local anesthetic spread, diaphragmatic and pulmonary function, cumulative opioid use, and patient-reported pain outcomes up to 24 hours postoperatively. Overall, the results revealed no significant difference in complete analgesia rates (23.3% vs. 33.3%, p=0.567) or other secondary outcomes between the two groups. Using 40 mL of local anesthetic did not guarantee better supraclavicular spreading or improved analgesic efficacy.