Comparison Between Subparaneural Upper Trunk and Conventional Interscalene Blocks for Arthroscopic Shoulder Surgery: A Randomized Noninferiority Trial

Abstract

BACKGROUND: Although interscalene nerve block is the standard for shoulder analgesia, the risk of hemidiaphragmatic paralysis restricts its use in patients with compromised pulmonary function. We hypothesized that a novel subparaneural upper trunk block would provide noninferior postoperative analgesia but superior diaphragmatic sparing effect compared to interscalene block. METHODS: This randomized controlled trial comprised 96 patients who underwent arthroscopic shoulder surgery under either subparaneural upper trunk block (5 mL of 0.5% ropivacaine) or interscalene block (15 mL of 0.5% ropivacaine), followed by supraclavicular nerve block (5 mL of 0.5% ropivacaine). General anesthesia was standardized. The coprimary outcomes were (1) recovery room resting pain score at 30 minutes, measured on an 11-point numerical rating scale, with a prespecified noninferiority margin of 1 point and (2) the incidence of hemidiaphragmatic paralysis, diagnosed using ultrasound. Among secondary outcomes, resting pain scores were assessed with numerical rating scale at 4, 8, and 24 hours postoperatively. RESULTS: Recovery room resting pain scores at 30 minutes were 0 (0-1) in the subparaneural upper trunk group versus 0 (0-0) in the interscalene group, with a median difference of 0 (95% CI, 0-0); the upper 95% CI limit was lower than the prespecified noninferiority margin (noninferiority P < .001). Hemidiaphragmatic paralysis was observed in 16.7% of patients in the subparaneural upper trunk group versus 100% of those in the interscalene group (RR, 0.17; 95% CI, 0.09-0.31; P < .001), with complete paralysis occurring in 6.3% and 93.7% of patients, respectively. In this study, any reported differences in pain scores at 4, 8, and 24 hours postoperatively were not clinically important. CONCLUSIONS: The subparaneural upper trunk block compared to interscalene block provided noninferior analgesia at 30 minutes in the recovery room after arthroscopic shoulder surgery but resulted in less hemidiaphragmatic paralysis.

Impact of Peripheral Nerve Block Technique on Incidence of Phrenic Nerve Palsy in Shoulder Surgery

“…The only study of the subparaneural approach's efficacy in clinical practice [ 19 ] corroborated the findings of a prior cadaveric study of this technique [ 52 ]. A possible explanation for this is that the paraneural sheath limits the spread of LA, preventing it from reaching the PN and forcing it to spread within the sheath cranially to the C5/6 nerve roots and SSN and caudally to the lateral pectoral nerve.…”

“…A recent study by Zhang et al [ 19 ] has been the only one to investigate the subparaneural approach's efficacy in clinical practice, showing HDP incidences of 16.7% when using 5 mL of LA.…”

Reply to the comment on: non-inferiority trial comparing ultrasound-guided multi-injection intertransverse process versus thoracic paravertebral blocks

“…However, the data for the worst resting pain score within 30 min in the recovery room showed a skewed distribution; therefore, the Hodges-Lehmann method was used to assess the difference in pain scores between groups, which showed a median difference of 0 (95% CI −0 to 0). The CI of the effect size is −0 to 0, which is difficult for the reader to understand when drawn on a diagram; thus, in a way similar to our previous study,4 we showed the result in text without drawing a diagram.…”

Rate of occurrence of respiratory complications in patients who undergo shoulder arthroplasty with a continuous interscalene brachial plexus block and associated risk factors

“…Previous studies examining respiratory complications after interscalene nerve blocks in shoulder surgery patients have either been limited in scope with small sample sizes and short time frame for follow-up (eg, up to 24 hours only), or focused on diagnostic tests (eg, ultrasound of the diaphragm, pulmonary function tests) rather than clinical respiratory complications and subsequent healthcare interventions 3 17 18. For example, Pere studied the effect of CISB with 0.125% bupivacaine with and without fentanyl on diaphragmatic motility and respiratory function in shoulder surgery patients 17.…”