Comparison Study of Bupivacaine and Ropivacaine for Interscalene Block in Shoulder Surgery in Terms of Onset Time, Duration, and Postoperative Muscle Weakness

Background: Interscalene block (ISB) is a gold-standard regional anesthetic for upper extremity procedures, particularly shoulder surgery, offering superior perioperative analgesia, reduced opioid use, shorter PACU stays, and higher patient satisfaction compared to general anesthesia. Objectives: This study investigates the effects of 0.5% ropivacaine and bupivacaine on motor blockade and recovery following ISB in shoulder surgery. Methods: In a randomized, single-blind study with 120 participants, muscle strength reduction and recovery were measured using a handgrip dynamometer over one week. The ISB was performed under ultrasound and nerve stimulator guidance. Muscle strength was recorded before and after ISB. Statistical analysis included repeated measures ANOVA and Pearson correlation. Results: Statistical analysis (repeated measures ANOVA) confirmed significant differences in motor blockade kinetics between groups (P < 0.001). Ropivacaine showed slower onset (peak reduction: Sixty-six percent at 3 hours) but faster recovery (80% baseline strength at 1 week) versus bupivacaine (peak reduction: Seventy-two percent at 3 hours; 70% recovery at 1 week; P < 0.001 for all comparisons). Age-stratified analysis revealed greater motor block persistence in older patients (P < 0.01). Conclusions: Bupivacaine provides stronger motor blockade, making it more effective in older adults, whereas ropivacaine offers faster functional recovery and adequate analgesia, favoring early mobilization post-surgery.