RESUMO
OBJECTIVE: This study investigated interscalene block for shoulder arthroplasty with various ropivacaine concentrations in the presence of clonidine, dexamethasone, and buprenorphine. The goal was prolonged analgesia with minimal motor blockade. DESIGN: Prospective, double-blind, randomized controlled trial. SETTING: University-affiliated orthopedic hospital. METHODS: Patients (20/group) received acetaminophen, ketorolac, pregabalin, opioids, and "Control"; interscalene block, 0.375% ropivacaine, intravenous additives (buprenorphine, clonidine, dexamethasone); "High Dose"; 0.375% ropivacaine, perineural additives; "Medium Dose"; 0.2% ropivacaine, perineural additives; and "Low Dose"; 0.1% ropivacaine, perineural additives. RESULTS: Pain with movement at 24 hours was 4.9 ± 2.5 (mean ± standard deviation [SD]) (Control), 4.5 ± 3.0 (High Dose), 3.4 ± 1.8 (Medium Dose), 4.2 ± 2.4 (Low Dose). The difference between Medium Dose and Control was -1.5 (95% CI: -2.9, -0.1) (P = 0.040). Median time until need for opioids was 16.1 hours (Control) vs 23.7 hours (High Dose); hazard ratio 0.37 [95% CI: 0.17, 0.79]. High Dose had less pain with movement the morning after surgery, vs Control; 2.9 ± 2.5 vs 4.9 ± 2.7; P = 0.027. Pain with movement in the Post-Anesthesia Care Unit was higher in Low Dose, vs Control; 0.9 ± 1.4 vs 0 ± 0, P = 0.009. Low Dose had superior hand strength in the Post-Anesthesia Care Unit (mean ± SD of pre-operative strength: 44.0 ± 20.3%) compared to Control (27.5 ± 24.5%) (P = 0.031). CONCLUSIONS: For maximum pain reduction, combining perineural additives with ropivacaine 0.375% or 0.2% is suggested. To minimize motor blockade, perineural additives can be combined with ropivacaine, 0.1%.
