ABCP Perfusion Basic Science (PBSE) Practice Exam

During cardiopulmonary bypass with the aorta cross-clamped, reducing afterload can help improve perfusion. The beta blocker that also provides vasodilation does so because it blocks alpha receptors in addition to beta receptors. Alpha-1 blockade lowers systemic vascular resistance, so you get vasodilation along with heart rate and contractility reduction.

Among common beta blockers, those with alpha-1 blockade—like labetalol—will vasodilate, helping to counteract the increased afterload from the clamp. Beta-1 selective agents (such as esmolol or metoprolol) mainly slow the heart and reduce contractility but don’t cause vasodilation. Propranolol blocks both beta receptors, including beta-2, which removes a vasodilatory pathway and typically does not produce the same vasodilating effect you’d want in this setting.

So, the agent that vasodilates in this context is the one with combined alpha- and beta-blockade, which reduces afterload while controlling heart rate.