Buprenorphine, Clonidine, Dexamethasone, and Ropivacaine for Interscalene Nerve Blockade: A Prospective, Randomized, Blinded, Ropivacaine Dose-Response Study

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%.