3 mL Versus 5 mL of 0.75% Ropivacaine for Ultrasound-Guided Interscalene Block: A Randomized Clinical Trial

Background: Ropivacaine is a local anesthetic used in nerve blocks for post-operative analgesia with dose-dependent side effects. Research indicated that ropivacaine may have better safety profiles than most local anesthetics, but toxicity and other dose-dependent side effects can still occur. Our aim is to show that a lower dose of ropivacaine is as effective when it comes to anesthesia and has a lower rate of complications. Methods: This study aims to compare 3 mL and 5 mL of 0.75% ropivacaine used for ultrasound-guided interscalene nerve block in shoulder arthroscopy in terms of postoperative analgesia and complications. We compared two groups (group 3 and group 5). Each group consisted of 30 patients. One group received 3 mL of 0.75% ropivacaine while the other group received 5 mL of the same product. The pain scale was evaluated in the post-anesthesia care unit (PACU) every 30 minutes up to two hours, then via phone call questionnaire for patients discharged during the first 24 hours. The incidence of complications was also evaluated in both groups. Results: Both groups had the same analgesic effect. No difference in the incidence of postoperative complications was noted however, more hemidiaphragmatic paralysis was observed in group 5 (p=0.023). Conclusion: Both 3 mL and 5 mL of 0.75% ropivacaine had the same post-operative analgesic effect with a lower incidence of hemidiaphragmatic paralysis seen in group 3, Further investigation on respiratory function must be undertaken.