BACKGROUND: Bupivacaine is a potent, and commonly used, long acting local anesthetic. If accidentally injected into the systemic circulation, bupivacaine can cause lethal dysrhythmias and circulatory collapse. Attempts to treat bupivacaine induced cardiac toxicity have been varied and controversial, and they have not been very successful. The aim of this study was to investigate the electrophysiologic effects of bupivacaine in Purkinje fibers. METHODS: Effects of bupivacaine on the membrane potential were studied in 12 isolated canine Purkinje fibers. Purkinje fibers from ventricle were dissected and mounted in a tissue chamber perfused with Tyrode's solution. Transmembrane potentials recorded through glass microelectrodes filled with 3M KCI in the beating or quiescent Purkinje fibers during infusions of bupivacaine at concentratons of 3*10/-7M,10/-6M, 3*10/-6M,10/-5M, and 3*10/-5M. RESULTS: Bupivacaine reduced action potential druation in a dose-dependent manner. Bupivacaine produced a decrease in intracelullar sodium ion activity in driven(1Hz) and quiescent canine Purkinje fibers. Bupivacaine-induced hyperpolarizaton of diastolic membrane potential in quiescent Purkinje fibers was dose dependent, and the hyperpolarization by bupivacaine was attenuated by depolarization induced by high potassium extracellular concentration in part. CONCLUSIONS: These results suggest that bupivacaine decreases the fast inward sodium current, and inhibits pacemaker current in canine Purkinje fibers.
Action Potentials ; Bupivacaine* ; Glass ; Membrane Potentials* ; Membranes* ; Microelectrodes ; Potassium ; Purkinje Fibers ; Shock ; Sodium ; Sodium Channels

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