ICU · Resuscitation

Vasoplegic and vasopressor-refractory shock: methylene blue, vasopressin, adjuncts

Also known as Vasoplegic shock · Vasopressor-refractory shock · Catecholamine-resistant shock · Methylene blue · Vasopressin · Refractory septic shock

Vasoplegic shock = distributive shock refractory to catecholamine vasopressors (noradrenaline) — profound NO-mediated vasodilation. Causes: septic shock (most common), post-cardiac surgery vasoplegia, anaphylaxis, post-reperfusion, drug-induced (ACEi, PDE inhibitors, protamine), adrenal insufficiency. PATHOPHYSIOLOGY: excessive nitric oxide (NO) production (iNOS induction in sepsis) → cGMP accumulation → vascular smooth muscle relaxation → vasodilation unresponsive to catecholamines. MANAGEMENT ESCALATION: (1) Adequate volume (but not over-resuscitate). (2) Noradrenaline (first-line alpha-1 agonist). (3) ADD VASOPRESSIN (V1 agonist — 0.03 U/min — catecholamine-sparing, different receptor). (4) ADD STEROIDS (hydrocortisone 200 mg/day — for CIRCI/adrenal insufficiency). (5) METHYLENE BLUE (1.5 mg/kg IV in the landmark RCT — inhibits NO-cGMP pathway — emerging for refractory vasoplegia). (6) Adjuncts: angiotensin II (ATHOS-3). High-dose vitamin C is not recommended (LOVIT). ALWAYS: treat cause, source control, exclude adrenal insufficiency/hypovolaemia.

Checked against its sources on 2 Sept 2026