Which drug is a phosphodiesterase inhibitor that can lead to significant hypotension in hypovolemic patients?

Milrinone is a phosphodiesterase inhibitor that has a unique mechanism of action, primarily by inhibiting the enzyme phosphodiesterase type III. This action enhances the effects of cyclic AMP, leading to increases in myocardial contractility and vasodilation. In hypovolemic patients, this vasodilation can result in significant hypotension because the reduced volume of blood in the circulation is not sufficient to maintain adequate blood pressure when vascular resistance decreases significantly.

The use of milrinone in such patients must be approached with caution, as the enhanced vasodilatory effect can exacerbate hypotension in individuals who are already hemodynamically unstable due to low blood volume. This characteristic makes it critically important for healthcare providers to monitor vital signs and ensure adequate volume resuscitation before and during the use of milrinone to avoid cardiovascular complications.

Other drugs listed don't share this specific profile as phosphodiesterase inhibitors. For instance, dobutamine and dopamine primarily work as inotropic agents without significant vasodilatory effects that would lead to hypotension in a hypovolemic state. Vasopressin, on the other hand, often works to increase blood pressure through vasoconstriction but doesn’t share the same risk of causing hypot