When used on CPB, chlorpromazine (Thorazine) does what?

• A. Vasoconstricts
• B. No effect
• C. Increases heart rate
• D. Vasodilates

Answer: (D)

Chlorpromazine on CPB works through alpha-adrenergic blockade, which relaxes vascular smooth muscle and causes peripheral vasodilation. This lowers systemic vascular resistance and arterial pressure, making it easier for the bypass circuit to perfuse the body and reducing afterload. In other words, it dilates vessels rather than constricting them. It’s not an agent with no effect, nor does it inherently raise heart rate as its primary action (any rate change would be a secondary response to changing pressures).