Which vasopressor is commonly used as an adjunct to norepinephrine in septic shock?

• A. Vasopressin (0.03 units/min)
• B. Epinephrine
• C. Dopamine
• D. Phenylephrine

Answer: (A)

In septic shock, norepinephrine is the primary vasopressor to restore blood pressure, but adding a second, nonadrenergic agent helps sustain vascular tone and allows lowering the norepinephrine dose. Vasopressin at a low fixed rate (0.03 units/min) serves this role by acting on V1 receptors to constrict vascular smooth muscle, improving mean arterial pressure through a mechanism independent of adrenergic receptors. Endogenous vasopressin can become depleted in septic shock, so supplementing with a constant small infusion helps stabilize perfusion without relying solely on catecholamines. It also reduces catecholamine exposure, which can lessen arrhythmogenic and metabolic side effects associated with higher doses of norepinephrine.

This approach is preferred over other choices because while epinephrine can raise pressure, it increases heart rate and myocardial oxygen demand and can worsen lactate production; dopamine has more arrhythmia risk and less favorable outcomes in many septic populations; phenylephrine raises afterload without supporting cardiac output and can compromise organ perfusion. Vasopressin provides a vasoconstrictive effect without these adrenergic drawbacks, making it a commonly used adjunct in septic shock. Monitor for potential adverse effects like mesenteric or digital ischemia and hyponatremia, and adjust treatment to maintain adequate perfusion.