The Impact of Interscalene Brachial Plexus Block with Different Concentrations of Ropivacaine on Diaphragmatic Paralysis: A Randomized Controlled Study.

Background: This study aims to evaluate the degree of diaphragmatic paralysis by assessing diaphragmatic excursion and pulmonary function following an ultrasound-guided interscalene brachial plexus block with two different concentrations of ropivacaine (0.2% and 0.5%). Methods: Forty patients undergoing shoulder arthroscopic surgery were randomly assigned to receive ultrasound-guided interscalene brachial plexus block with 20 mL of either 0.2% or 0.5% ropivacaine. Diaphragmatic excursion (DE) and diaphragm thickening fraction (TF) were measured using M-mode ultrasound before and 30 minutes after the block. Pulmonary function was assessed using a portable spirometer. Additional outcomes included pain scores and the occurrence of adverse effects. Results: DE was significantly reduced 30 minutes after block in the 0.5% group compared to the 0.2% group (p<0.01), as well as the TF (p<0.01). Forced vital capacity (FVC) was also significantly reduced in the 0.5% group 30 minutes after block in the preparation room compared to the 0.2% group (p<0.001). Both 0.2% and 0.5% ropivacaine had similar effects in improving postoperative pain. There were no serious block-related complications in either group. Conclusion: 0.2% ropivacaine may impair pulmonary function less than 0.5% ropivacaine. The clinical significance of these differences requires further investigation.