• Hongye Zhang, Jinyu Wu, Yongsheng Miao, Ying Yuan, Zongyang Qu, Yaonan Zhang, and Zhen Hua.
• Department of Anesthesiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China.
• Anesthesiology. 2024 Jul 17.

BackgroundA brachial plexus block plays an important role in providing perioperative analgesia for shoulder surgery; however, the inherent risk of phrenic nerve block and resulting hemidiaphragmatic paralysis may limit its use in patients with compromised pulmonary function. This study aimed to evaluate safety, efficacy, the maximum tolerated volume, and the optimal biological volume of 0.5% ropivacaine used in a single-injection retroclavicular brachial plexus block for arthroscopic shoulder surgery.MethodsIn this seamless single-arm exploratory phase I/II trial, a novel Bayesian optimal interval design was used to guide volume escalation for determination of the maximum tolerated volume, followed by sequential volume expansion using Bayesian optimal phase 2 design to establish the optimal biological volume. Fifty-four patients who underwent arthroscopic shoulder surgery received a single-injection retroclavicular brachial plexus block with 0.5% ropivacaine ranging from 15 mL to 40 mL. The primary outcomes were complete or partial hemidiaphragmatic paralysis in phase I, measured using ultrasound 30 min after block completion, and the block success in phase II, defined as achieving a total sensorimotor score ≥12 points and the total sensory score ≥3, measured through manual sensorimotor testing.ResultsThe maximum tolerated volume for the single-injection retroclavicular brachial plexus block was determined to be 35 mL of 0.5% ropivacaine, with a hemidiaphragmatic paralysis rate of 0.09 (95% credible interval, 0 to 0.29). The optimal biological volume was found to be 25 mL, with a block success rate of 1.0 (95% credible interval, 0.95 to 1.0) and a negligible hemidiaphragmatic paralysis rate of 0.01 (95% credible interval, 0 to 0.06).ConclusionsA single-injection retroclavicular brachial plexus block using 25 mL of 0.5% ropivacaine produced consistent block success with a minimal HDP rate, suggesting the need for further studies to confirm this result in arthroscopic shoulder surgery.Copyright © 2024 American Society of Anesthesiologists. All Rights Reserved.

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