Vasoactive

Vasoactive refers to substances that have a direct effect on vascular tone, altering the diameter of blood vessels and thereby influencing blood pressure and organ perfusion. The term covers endogenous mediators, such as catecholamines produced by the sympathetic nervous system, as well as pharmacologic agents used to manipulate vascular tone in clinical settings. Clinically, vasoactive drugs are categorized as vasopressors, which constrict vessels to raise mean arterial pressure, and vasodilators, which relax vascular smooth muscle to lower systemic vascular resistance.

Mechanistically, these agents act on vascular smooth muscle through receptor-mediated pathways. Alpha-adrenergic stimulation causes vasoconstriction; beta-adrenergic effects can modify heart rate and contractility; vasopressin receptors and dopaminergic receptors also contribute. Some drugs have combined inotropic and vasodilatory properties, affecting both cardiac output and vascular tone.

Vasoactive drugs are central to management of shock, hypotension, and perioperative hemodynamic instability. They are used in septic shock, cardiogenic shock, hemorrhagic shock, and during anesthesia or major surgery to maintain adequate cerebral and organ perfusion. Dosing is typically via continuous IV infusion and titrated to a target blood pressure or perfusion parameter; frequent hemodynamic monitoring is required. Potent vasopressors are usually given through central lines to reduce extravasation risk.

Common examples include vasopressors such as norepinephrine, epinephrine, phenylephrine, dopamine, and vasopressin; vasodilators such as nitroprusside, nitroglycerin, hydralazine, and nicardipine; and inotropes with vascular effects such as dobutamine and milrinone.

Adverse effects include excessive vasoconstriction causing tissue ischemia, arrhythmias, hypertension, and impaired peripheral or mesenteric perfusion. Careful monitoring and individualized dosing are essential.