During low systemic vascular resistance, phenylephrine increases perfusion pressure to which organ systems?

During low systemic vascular resistance, phenylephrine increases perfusion pressure to which organ systems?

• A. Lungs
• B. Brain only
• C. Heart only
• D. Brain, kidney, heart

Answer: (D)

Phenylephrine raises mean arterial pressure by vasoconstricting systemic arterioles through alpha-1 receptors. In a state of low systemic vascular resistance, boosting MAP increases the driving pressure for blood flow to organs that tightly regulate their own blood flow across a wide range of pressures. The brain, kidney, and heart have robust autoregulation, so they benefit from the higher arterial pressure with improved perfusion pressure, helping ensure oxygen delivery and function of these vital organs. The lungs behave differently because pulmonary blood flow is governed more by the pressures in the right heart and left atrium, and pulmonary vessels are not driven in the same way by systemic vasoconstriction; thus perfusion pressure to the lungs does not rise in the same manner.

Phenylephrine raises mean arterial pressure by vasoconstricting systemic arterioles through alpha-1 receptors. In a state of low systemic vascular resistance, boosting MAP increases the driving pressure for blood flow to organs that tightly regulate their own blood flow across a wide range of pressures. The brain, kidney, and heart have robust autoregulation, so they benefit from the higher arterial pressure with improved perfusion pressure, helping ensure oxygen delivery and function of these vital organs. The lungs behave differently because pulmonary blood flow is governed more by the pressures in the right heart and left atrium, and pulmonary vessels are not driven in the same way by systemic vasoconstriction; thus perfusion pressure to the lungs does not rise in the same manner.