Chlorpromazine's effect on CPB vascular tone is which?

• A. Vasodilates
• B. Increases viscosity
• C. Vasoconstricts
• D. No effect

Answer: (A)

Chlorpromazine causes vasodilation because it blocks alpha-adrenergic receptors on vascular smooth muscle. In CPB, sympathetic vasoconstriction helps maintain vascular tone, so blocking those receptors reduces contractility of the vessels, lowering systemic vascular resistance and widening the vessels. This can lead to lower perfusion pressures if not managed. Increased viscosity isn’t affected by this drug, and having no effect would ignore the known alpha-blocking action. So the effect on CPB vascular tone is vasodilation.