Comparison of bupivacaine hydrochloride and carbonated bupivacaine in brachial plexus blood by the interscalene technique.

Carbonated local anaesthetics may have shorter latency and greater spread than equivalent hydrochloride salts when used for regional anaesthesia. In brachial plexus anaesthesia produced by the supraclavicular technique, Bromage and Gertel (1970) using 1% lignocaine and Schulte-Steinberg, Hartmuth and Schiitt (1970) using 2% lignocaine, reported a marked decrease in the time of onset of anaesthesia using the carbonated solution compared with the hydrochloride. Bupivacaine is a longer acting agent, but has a slow onset of action: 23min on average for 0.25% bupivacaine hydrochloride compared with 14min for 1% lignocaine hydrochloride in brachial plexus anaesthesia by the supraclavicular technique (Bromage and Gertel, 1970). Carbonation of bupivacaine has been reported to decrease the time of onset of extradural anaesthesia (Eckstein et al., 1978) although Brown and others (1980) failed to verify this in a doubleblind trial. This study was undertaken to compare carbonated bupivacaine with the hydrochloride salt in interscalene brachial plexus block.