Intrapulmonary administration of vasodilating agents during cardiac surgery primarily has emerged to reduce pulmonary vascular resistance (PVR) in the setting of eminent or present right heart failure after separation from cardiopulmonary bypass. The intravenous formulation of milrinone, a commonly used inotrope with vasodilating properties, may reduce PVR but lends itself to diminishing systemic vascular resistance; resultant hypoperfusion of the right ventricular myocardium, yielding a net reduction in right heart contractility; and worsening right heart failure. Intrapulmonary delivery of such vasodilating medications, therefore, serves to avoid this reduction in systemic vascular resistance, provide adequate systemic blood pressure for optimal right ventricular performance, and decrease PVR related to pulmonary arterial hypertension and precapillary arteriolar vasoconstriction.