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Vasopressin Dose and Mechanism Sepsis — FRCA Final MCQ

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ModerateIntensive Care MedicineVasopressin Dose and Mechanism SepsisFRCA Final

A 50-year-old man on ICU requires vasopressin as an adjunct vasopressor in septic shock. What is the standard dose of vasopressin in septic shock and what is its mechanism?

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Correct answer: B — 0.03 units/min (up to 0.03 units/min) – V1 receptor agonist causing vasoconstriction independently of adrenergic receptors

Vasopressin (arginine vasopressin/ADH) is used in septic shock at a FIXED dose of up to 0.03 units/min (not titrated) as an adjunct to noradrenaline. It acts on V1 receptors on vascular smooth muscle, causing vasoconstriction via a non-adrenergic mechanism (independent of catecholamine receptors, which may be downregulated in prolonged septic shock). The VASST trial (2008) showed it was non-inferior to noradrenaline as second-line and may reduce noradrenaline requirements. It should NOT be used as a single vasopressor. V2 receptor effects cause water retention (antidiuretic effect).

Reference: SSC – 2021 – Sepsis guidelines; Russell JA et al – 2008 – VASST trial