Incidence of Hemidiaphragmatic Paresis After Low Volume of Anterior Suprascapular Nerve Block for Arthroscopic Shoulder Surgery: A Randomized, Double-Blind Controlled Trial

Background: The anterior suprascapular nerve block (ASSB) is an alternative block to the interscalene block (ISB) for arthroscopic shoulder surgery. Notably, using ASSB can mitigate the incidence of hemidiaphragmatic paralysis while providing comparable analgesia to that achieved using ISB. However, hemidiaphragmatic paralysis still occurs in a considerable proportion of patients receiving a 10 mL local anesthesia dose. This study investigates whether reducing the local anesthetic volume to 5 mL in ASSB significantly lowers the incidence of hemidiaphragmatic paralysis. Methods: Seventy-eight patients undergoing arthroscopic shoulder surgery were randomly administered either 5 mL (V5 group) or 10 mL (V10 group) of 0.5% bupivacaine for ultrasound-guided ASSB. The primary outcome was the incidence of hemidiaphragmatic paralysis 30 minutes after the block, as determined by ultrasound assessment of diaphragmatic excursion. Secondary outcomes were the time to first opioid request, 24-hour morphine consumption, block success rate, length of hospital stay, patient satisfaction, and pain scores determined in the PACU, 6, 12, and 24 hours after surgery. Results: A total of 72 patients were eligible for analysis. All type of hemidiaphragmatic paralysis occurred in 33.33% of the patients in the V10 group and 5.56% of the patients in the V5 group (p = 0.006). Complete hemidiaphragmatic paralysis was observed in 16.67% of the V10 group and 0% of the V5 group (p = 0.025). There were no significant differences in secondary outcomes between the groups. Conclusion: Decreasing the volume of the ASSB from 10 to 5 mL of 0.5% bupivacaine effectively mitigated the risk of complete hemidiaphragmatic paralysis while maintaining comparable pain control.