What is the effect of phenylephrine on heart function?

Phenylephrine is a selective alpha-1 adrenergic agonist commonly used as a decongestant and vasopressor. Its primary action is to cause vasoconstriction in the blood vessels, which leads to an increase in systemic vascular resistance and, consequently, an increase in blood pressure. This elevation in blood pressure can trigger a reflex bradycardia, which is a compensatory response whereby the heart rate decreases in reaction to the increased blood pressure.

In this context, the increase in blood pressure due to phenylephrine's vasoconstrictor effects results in a decrease in heart rate as the body attempts to maintain homeostasis. Therefore, during the administration of phenylephrine, one would expect elevated blood pressure alongside a reduction in heart rate.

This understanding clarifies why the choice highlighting the increase in blood pressure and decrease in heart rate accurately reflects the pharmacological effects of phenylephrine on heart function.