The pharmacokinetics of ropivacaine after four different techniques of brachial plexus blockade

Arterial plasma concentrations of ropivacaine were measured after brachial plexus blockade using four different approaches: lateral interscalene (Winnie), posterior interscalene (Pippa), axillary and vertical infraclavicular. Four groups of 10 patients were given a single 3.75 mg.kg-1 injection of ropivacaine 7.5 mg.ml-1. The pharmacokinetics of ropivacaine were evaluated for 1 h after local anaesthetic injection. The supraclavicular techniques (lateral and posterior) were associated with earlier and higher peak plasma concentrations of local anaesthetic than the infraclavicular techniques (axillary and vertical infraclavicular): mean (SD) values=3.30 (0.65) μg.ml-1 vs 2.55 (0.62) μg.ml-1 (p = 0.001) in 13.4 (6.9) min vs 25.0 (10.8) min (p = 0.0002). More ropivacaine is taken up by the systemic circulation in the first hour after the supraclavicular approaches; the mean (SD) area under the concentration-time curve was larger: 2.63 (0.51) μg.ml-1.h vs 2.10 (0.49) μg.ml-1.h (p=0.002). These results show that the technique used for brachial plexus blockade significantly influences the systemic uptake of ropivacaine.

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