COMPARISON OF S(-)-BUPIVACAINE WITH RACEMIC (RS)-BUPIVACAINE IN SUPRACLAVICULAR BRACHIAL-PLEXUS BLOCK

Bupivacaine is used widely as a local anaesthetic but has potential fo r severe cardiovascular and central nervous system (CNS) toxicity. It has an asymmetric carbon atom giving it a chiral centre, and the comme rcial preparation is a racemic mixture of its two enantiomers: dextro or R(+)-bupivacaine and levo or S(-)-bupivacaine. Preclinical studies have demonstrated reduced cardiotoxicity and CNS toxicity for bupivaca ine. In this study we have compared the clinical efficacy of S(-)-bupi vacaine with racemic RS-bupivacaine for supraclavicular brachial plexu s block in 75 patients undergoing elective hand surgery. Patients rece ived 0.4 ml kg(-1) of either 0.25% or 0.5% S(-)-bupivacaine or 0.5% RS -bupivacaine in a randomized, double-blind study. Clinical assessments of sensory and motor block were performed at regular intervals. There were no significant differences in onset time, dermatomal spread or d uration of both sensory and motor block between the three groups (the power of the study was 81% to detect a 4-h difference in duration). Du ration of sensory block was prolonged with wide interpatient variation : 892 (SD 250) min, 1039 (317) min and 896 (284) min for 0.25% S(-)bup ivacaine, 0.5% S(-)-bupivacaine and 0.5% RS-bupivacaine, respectively. There were no differences in the overall success rate of the techniqu e. We conclude that S(-)-bupivacaine was suitable for local anaestheti c use in brachial plexus block anaesthesia.