[Comparative study of 0.5% racemic bupivacaine versus enantiomeric mixture (S75-R25) of 0.5% bupivacaine in brachial plexus block for orthopedic surgery.].

BACKGROUND AND OBJECTIVES Several studies were performed with bupivacaine isomers in the attempt to find a safer drug than racemic bupivacaine. This study aimed at evaluating the efficacy of 0.5% bupivacaine enantiomeric mixture (MEE50%) as compared to 0.5% racemic bupivacaine in brachial plexus block for upper limb orthopedic surgery. METHODS Participated of this randomized double-blind study 40 patients aged 18 to 90 years, physical status ASA I and II, submitted to upper limb orthopedic surgeries, who were divided in two groups: Group R received 0.5% racemic bupivacaine; and Group L received 0.5% enantiomeric mixture (S75-R25) of bupivacaine both with 1:200,000 epinephrine, in a volume of 0.6 mL.kg-1 (3 mg.kg-1), limited to 40 mL. Motor and/or sensory characteristics of each nerve involved (musculocutaneous, radial, median, ulnar and medial cutaneous nerve of forearm), as well as the incidence of side effects were evaluated. RESULTS There were no statistical differences in demographics. Hemodynamic parameters were similar between groups but systolic pressure was higher for Group R. There were no statistically significant differences in time to reach the greatest intensity of sensory and motor blocks. With one exception, the onset of motor block within the muscles innervated by the ulnar nerve was longer for Group L (10.75 versus 14.25 minutes). CONCLUSIONS There were adequate sensory and motor blocks in both groups, with few side effects, suggesting that the 0.5% enantiomeric mixture (S75-R25) of bupivacaine with epinephrine is safe and effective for brachial plexus block of upper limb orthopedic surgeries.