NPLEX II Minor Surgery Practice Test

What is the mechanism underlying cardiovascular toxicity of local anesthetics?

Potassium channel activation Calcium channel blockade Sodium channel blockade Beta-adrenergic receptor antagonism

Correct Answer:

Sodium channel blockade

Explanation:

Sodium channel blockade in cardiac tissue is what drives cardiovascular toxicity from local anesthetics. These drugs bind to voltage-gated sodium channels and stabilize them in the inactivated state, preventing sodium influx during the rapid depolarization (phase 0). In the heart, this slows conduction across the myocardium and through the His-Purkinje system, leading to slower atrioventricular conduction, QRS widening, bradycardia, and, in severe cases, heart block or asystole. This is the same basic mechanism by which local anesthetics block nerve impulses, but at toxic levels the effect extends to the heart. While very high concentrations can have other effects, the clinically relevant cardiovascular toxicity stems primarily from Na+ channel blockade.

Access more questions from this quiz

Continue to NPLEX II Minor Surgery Practice Test for more practice questions and the full quiz experience.

Access More Questions