Anaes · Anaesthetic adjuncts

Vasopressin

Also known as Antidiuretic hormone (ADH) · Arginine vasopressin (AVP) · Non-adrenergic V1 peptide vasopressor · Catecholamine-sparing vasopressor

Vasopressin (antidiuretic hormone, ADH) is an endogenous PEPTIDE hormone released from the posterior pituitary that is fundamentally NOT a catecholamine — it acts through a completely separate, non-adrenergic receptor family. Its three receptors define its three actions: V1 (V1a) on vascular smooth muscle produces Gq-coupled vasoconstriction, V2 on the renal collecting duct produces Gs-coupled water reabsorption through aquaporin-2, and V3 (V1b) on the anterior pituitary drives ACTH release. As a vasopressor it works through V1 INDEPENDENT of adrenergic receptors, which is its defining advantage: it remains effective when adrenergic receptors are downregulated in septic shock and vasoplegia, the basis of its role as the catecholamine-sparing, catecholamine-resistant agent (taught mechanism; timely vasopressin addition at moderate noradrenaline requirements — Hiroto 2026). The principal use is as a SECOND-LINE vasopressor in septic shock, added to noradrenaline when noradrenaline alone is insufficient — given at a FIXED dose of 0.03 to 0.04 units per min (NOT titrated to effect; taught formulary, local protocol governs) and catecholamine-sparing, reducing the noradrenaline requirement (Hiroto 2026). Other uses are vasoplegia after cardiopulmonary bypass (vasopressin among the discussed strategies — Torre 2026) and — via its V2-selective synthetic analogue desmopressin (DDAVP) — central diabetes insipidus, haemophilia and von Willebrand disease (factor VIII and vWF release — Vinjamuri 2025). It is given by IV infusion. The adverse-effect profile is the direct consequence of V1 vasoconstriction (peripheral, digital and MESENTERIC ISCHAEMIA) plus V2 water retention (HYPONATRAEMIA at high or prolonged doses; taught mapping), with decreased cardiac output from increased afterload and reflex bradycardia (taught). Against noradrenaline, vasopressin is non-adrenergic (no tachyarrhythmia, effective when adrenergic receptors are downregulated) where noradrenaline is alpha-plus-beta-1 adrenergic — the two are used TOGETHER in septic shock (Hiroto 2026). Against adrenaline the mechanism differs entirely (peptide versus catecholamine; taught). Built on the septic-shock norepinephrine-and-vasopressin timing review (Hiroto 2026, sparing frame only, no dose-tier ownership), the neonatal fluid-refractory septic shock systematic review (Yahya 2026, 4-RCT neonatal scope only), the vasopressor-and-delirium null study (Dong 2026, null scope only; vasopressin not studied), the desmopressin-in-ICU review (Vinjamuri 2025, DDAVP scope), and the cardiac-surgery vasoplegia review (Torre 2026, adjunct scope).

Checked against its sources on 11 Sept 2026