Analgesic effects of low-dose ropivacaine for interscalene brachial plexusblock for outpatient shoulder surgery - A dose-finding study

Background and Objectives: Interscalene brachial plexus block (ISB) with lo w-dose bupivacaine provides effective postoperative shoulder analgesia in o utpatients. The analgesic effect of low-dose ropivacaine for ISB is unknown . Methods: In this double-blind study, 66 outpatients scheduled to undergo ar throscopic shoulder surgery were randomly assigned to receive an ISB with 1 0 mL of 0.125%, 0.25%, or 0.5% ropivacaine before surgery. Postoperative ve rbal pain rating score, analgesic consumption, and the extent of motor and sensory block was assessed for 120 minutes after surgery. Results: The degree of shoulder analgesia was dose dependent. Postoperative pain scores were lowest with 0.5% ropivacaine, and analgesic was not requi red in the hospital in 70% of the patients who received 0.25% and 0.5% ropi vacaine, compared to 30% with 0.125% ropivacaine (P < .03). In the patients who required no analgesic in the hospital, the time to first oral analgesi c at home was approximately 10 hours irrespective of ropivacaine concentrat ion. Motor and sensory block distal to the elbow was detected in 25 % of th e patients in the 0.5% group but none in the 0.125% group. Conclusions: Interscalene brachial plexus block with low-dose ropivacaine, 10 mL of 0.25% and 0.5%, provides effective long-lasting shoulder analgesia in a majority of patients after arthroscopic surgery.