Bupivacaine-answer: e
(katzung, pp 426, brunton, pp 377)
most local anesthetics can block na+ channels in cardiac muscle and thus they can depress
automaticity and conduction. at very high doses they can also depress contractility, likely by
blocking ca++ channels. bupivacaine is more cardiotoxic than most other local anesthetics,
apparently because the drug dissociates much more slowly than other local anesthetics during
diastole, so a significant fraction of na+ channels at physiological heart rates remains blocked
with bupivacaine at the end of the diastole. bupivacaine induced cardiac toxicity is very difficult to
treat and is enhanced by coexisting acidosis and hypoxemia.
a, b, c, d) (see explanation above)
