Effect of low-volume ropivacaine in ultrasound-guided superior trunk block on diaphragmatic movement in patients undergoing shoulder arthroscopy: a randomized controlled trial.

Objectives: The incidence of hemidiaphragmatic paresis (HDP) in superior trunk block (STB) usually depends on the dose of local anesthetic. This study aimed to further evaluate the impact of a lower volume (10 mL) of the same low concentration (0.25%) ropivacaine compared to a conventional volume (15 mL), on diaphragmatic function and analgesic efficacy under a multimodal analgesia regimen for shoulder arthroscopy.
Methods: Patients scheduled to undergo shoulder arthroscopy were randomized allocated to receive either 10 mL or 15 mL of 0.25% ropivacaine in the STB under ultrasound guidance prior to general anesthesia. The primary outcome was the percentage reduction in diaphragm excursion (ΔDE) between baseline and 30 min after block. Secondary outcomes included DE and diaphragm thickening fraction (DTF) before and after block, incidence of HDP, onset of sensory/motor block, duration of analgesia/motor block, dermatomal coverage area of the block, postoperative pain severity, pre- and post-block respiratory function and intraoperative hemodynamic parameters, the use of other anesthetic and analgesic drugs, post-block complications, and adverse events post-surgery.
Results: Compared with 15 mL volume, 10 mL ropivacaine significantly reduced the incidence of post-block HDP (as measured by ΔDE: 39.47% vs. 64.10%; and by post-block DTF: 13.16% vs. 33.33%). There was no significant difference in onset of sensory block, duration of analgesia/motor block, dermatomal coverage area of the block, postoperative pain severity between the two groups, except that the onset of motor block was significantly slower in the 10 mL group than in the 15 mL group. Pre- and post-block respiratory function and intraoperative hemodynamic parameters, the use of other anesthetic and analgesic drugs, post-block complications, or postoperative adverse events were not significantly different between the two groups.
Conclusion: In shoulder arthroscopy, STB with 10 mL of ropivacaine can reduce the incidence of HDP with no significant difference in analgesic effects under a multimodal analgesia regimen compared with 15 mL.
Trial Registration: We registered the study at chictr.org ( ChiCTR2200057543 , 14/03/2022. https://www.chictr.ogr.cn.
(© 2024. The Author(s).)