The diaphragm-sparing effect of interscalene block with a low-volume of ropivacaine 0.1% vs. 0.5%: A double-blind, controlled, randomised trial.

Study Summary

60 patients undergoing elective arthroscopic shoulder surgery were randomized to receive ultrasound-guided interscalene brachial plexus block (ISB) with 7 mL of either 0.1% or 0.5% ropivacaine. The primary outcome of interest was hemidiaphragmatic dysfunction, defined as a reduction in diaphragmatic excursion greater than 25% from baseline. Secondary outcomes included hemidiaphragmatic paralysis, forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow (PEF), intraoperative opioid consumption, duration of effective postoperative analgesia, morphine requirements, and patient satisfaction. Respiratory outcomes were assessed at baseline and 30 minutes after ISB, while postoperative analgesia and satisfaction were evaluated through 24 hours. Overall, the results of the study revealed significantly lower rates of hemidiaphragmatic dysfunction and paralysis with 0.1% ropivacaine, along with less respiratory impairment. However, more patients required postoperative morphine despite no statistically significant difference in analgesia duration. These findings suggested that low-concentration ropivacaine substantially reduced diaphragmatic impairment, although this benefit may have come at the expense of postoperative analgesia.