What is the expected hemodynamic effect of isoproterenol administration?

What is the expected hemodynamic effect of isoproterenol administration?

• A. Decreased heart rate and vasoconstriction
• B. Increased heart rate and vasodilation
• C. No change in heart rate
• D. Increased afterload only

Answer: (B)

Isoproterenol is a nonselective beta-adrenergic agonist, so it acts on both beta-1 receptors in the heart and beta-2 receptors in vascular smooth muscle. Stimulation of beta-1 increases heart rate (positive chronotropy) and contractility (positive inotropy), while beta-2 activation causes vascular smooth muscle relaxation, leading to vasodilation and lower systemic vascular resistance. The combination of a faster heart rate with dilated vessels fits the expected hemodynamic effect: increased heart rate with vasodilation. This also helps explain why it can raise cardiac output but may lower blood pressure due to the vasodilatory effect. The other options describe either decreased heart rate, vasoconstriction, no heart-rate change, or increased afterload, which do not align with isoproterenol’s beta-adrenergic actions.

Isoproterenol is a nonselective beta-adrenergic agonist, so it acts on both beta-1 receptors in the heart and beta-2 receptors in vascular smooth muscle. Stimulation of beta-1 increases heart rate (positive chronotropy) and contractility (positive inotropy), while beta-2 activation causes vascular smooth muscle relaxation, leading to vasodilation and lower systemic vascular resistance. The combination of a faster heart rate with dilated vessels fits the expected hemodynamic effect: increased heart rate with vasodilation.

This also helps explain why it can raise cardiac output but may lower blood pressure due to the vasodilatory effect. The other options describe either decreased heart rate, vasoconstriction, no heart-rate change, or increased afterload, which do not align with isoproterenol’s beta-adrenergic actions.