In septic shock, how do norepinephrine and vasopressin differ in their roles?

• A. Norepinephrine is the primary vasopressor; vasopressin is an adjunct that can reduce norepinephrine requirements and add vasoconstriction via V1
• B. Vasopressin is the primary vasopressor; norepinephrine is never used
• C. They have identical roles and are interchangeable
• D. Vasopressin should replace norepinephrine entirely

Answer: (A)

In septic shock, restoring vascular tone is essential because the vessels are massively dilated. Norepinephrine is the primary vasopressor because it strongly activates alpha-1 receptors, causing robust vasoconstriction that increases systemic vascular resistance and improves mean arterial pressure, with some supportive effect on cardiac output through beta-1 stimulation. Vasopressin adds a complementary mechanism by acting on V1 receptors to constrict vascular smooth muscle, which can help restore tone especially when endogenous vasopressin is depleted in septic shock. When used together, vasopressin allows lowering the norepinephrine dose while maintaining blood pressure and may provide additional vasoconstrictive benefit. Therefore, the best choice is that norepinephrine is the main vasopressor, and vasopressin is an adjunct that can reduce norepinephrine requirements and contribute vasoconstriction via V1 receptors, rather than replacing norepinephrine entirely or being used as the sole agent.