A COMPARISON OF 0.5-PERCENT BUPIVACAINE, 0.5-PERCENT ROPIVACAINE, AND0.75-PERCENT ROPIVACAINE FOR INTERSCALENE BRACHIAL-PLEXUS BLOCK

The onset time and duration of action of ropivacaine during an intersc alene block are not known. The potentially improved safety profile of ropivacaine may allow the use of higher concentrations to try and spee d onset time. We compared bupivacaine and ropivacaine to determine the optimal long-acting local anesthetic and concentration for interscale ne brachial plexus block. Seventy-five adult patients scheduled for ou tpatient shoulder surgery under interscalene block were entered into t his double-blind, randomized study. Patients were assigned (n = 25 per group) to receive an interscalene block using 30 mt of 0.5% bupivacai ne, 0.5% ropivacaine, or 0.75% ropivacaine. All solutions contained fr esh epinephrine in a 1:400,000 concentration. At 1-min intervals after local anesthetic injection, patients were assessed to determine loss of shoulder abduction and loss of pinprick in the C5-6 dermatomes. Bef ore discharge, patients were asked to document the time of first oral narcotic use, when incisional discomfort began, and when full sensatio n returned to the shoulder. The mean onset time of both motor and sens ory blockade was <6 min in all groups. Duration of sensory blockade wa s similar in all groups as defined by the three recovery measures. We conclude that there is no clinically important difference in times to onset and recovery of interscalene block for bupivacaine 0.5%, ropivac aine 0.5%, and ropivacaine 0.75% when injected in equal volumes. Impli cations: In this study, we demonstrated a similar efficacy between equ al concentrations of ropivacaine and bupivacaine. in addition, increas ing the concentration of ropivacaine from 0.5% to 0.75% fails to impro ve the onset or duration of interscalene brachial plexus block.