Certified Registered Nurse Anesthetist (CRNA) Practice Exam

What is the action of Clonidine in the treatment of hypertension?

1. It dilates blood vessels

2. It stimulates peripheral adrenergic receptors

3. It decreases sympathetic outflow from the CNS

4. It increases heart rate

The correct answer is: It decreases sympathetic outflow from the CNS

Clonidine primarily functions as an alpha-2 adrenergic agonist, and its main action in the treatment of hypertension is to decrease sympathetic outflow from the central nervous system (CNS). By activating alpha-2 receptors in the brain, clonidine reduces the release of norepinephrine, which leads to a decrease in heart rate and a reduction in peripheral vascular resistance. This central action effectively lowers blood pressure. In contrast, the other responses suggest different mechanisms that are not characteristic of clonidine’s actions. Clonidine does not primarily dilate blood vessels directly; rather, its action is more related to modulating the central nervous system's sympathetic tone. It does not stimulate peripheral adrenergic receptors in a way that would enhance sympathetic activity; rather, it decreases overall sympathetic drive. Additionally, clonidine does not increase heart rate; in fact, it typically results in a bradycardic effect due to its CNS activity. Thus, the choice reflecting its mechanism of action regarding hypertension is that it decreases sympathetic outflow from the CNS.