Bupivacaine cardiotoxicity and subendocardial microcirculation

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Ventricular fibrillation (VF) and depression of myocardial contractility are two important factors for bupivacaine-induced cardiotoxicity. The efficacy of lidocaine for bupivacaine-induced VF and the vasoconstricting effects of bupivacaine were examined in the beating hearts in vivo. In the first set of the experiment, 0.25% bupivacaine, 1% lidocaine and 0.25% bupivacaine plus lidocaine solutions were infused into the left anterior descending coronary artery (LAD) in an increasing sequence of 0,1,2,4,8 and 16 mL/hr for 15 min into the LAD in three groups consisting of eight pigs. Regional myocardial function was evaluated by the sonomicrometry technique. While there were no VF in the Lid group, VF occurred in one at 4 mL/hr and seven at 8 mL/hr infusion rates in the bupivacaine group, and in one at 8 mL/hr and seven at 16 mL/hr infusion rates in the bupivacaine plus lidocaine group. Although regional myocardial function decreased in a dose-related manner in the three groups, the myocardial depressant effects of bupivacaine were significantly greater than that of lidocaine, and did not differ with that of bupivacaine plus lidocaine. In the second set of the experiment, six samples of bupivacaine-containing autologous blood (0,0.25,1.25,2.5,5,10mug/mL) were injected into the coronary artery via a catheter placed in the first diagonal branch in the five pigs, while left ventricular subendocardial microvessels (50-100mum in diameter) in the septal region were visualized by a needle type video microscope. Diameter of the