ICU · Resuscitation

Extracorporeal membrane oxygenation (ECMO)

Also known as ECMO · Extracorporeal life support (ECLS) · VV-ECMO (venovenous) · VA-ECMO (venoarterial) · ECPR (extracorporeal CPR) · Extracorporeal CO2 removal (ECCO2R) · Centrifugal pump ECMO · Avalon dual-lumen cannula · North-south syndrome (Harlequin) · EOLIA trial

Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass that provides temporary support for refractory cardiac and/or respiratory failure outside the operating theatre. VA-ECMO (venoarterial) drains venous blood from the right atrium via a femoral vein, pumps it through a membrane oxygenator and returns oxygenated blood to the femoral artery — providing BOTH circulatory (cardiac output) and respiratory (oxygenation/CO2 removal) support; indications: cardiogenic shock refractory to inotropes/IABP, ECPR, fulminant myocarditis, post-cardiotomy failure, severe drug toxicity with cardiac depression. VV-ECMO (venovenous) drains from the IVC (femoral vein) and returns oxygenated blood to the right atrium (IJ vein or dual-lumen single cannula) — provides RESPIRATORY support only (the heart must work); indications: severe ARDS (PaO2/FiO2 <80 despite optimised ventilation), bridge to lung transplant, near-fatal asthma (all 16 patients survived in one published adult case series), massive PE as bridge. Circuit: centrifugal (non-occlusive) pump → polymethylpentene hollow-fibre membrane oxygenator → heat exchanger. Percutaneous Seldinger femoro-femoral cannulation is standard. Systemic anticoagulation required: unfractionated heparin is the first-line agent (77% of patients in the largest prospective VV-ECMO study), monitored most often with aPTT (median 52 s in that cohort). Complications: bleeding (1 — major bleeding 40.8% pooled in VA-ECMO), haemolysis, thrombosis, infection, limb ischaemia (16.9% pooled in VA-femoral — reduced by prophylactic distal perfusion cannula, OR 0.31), Harlequin/north-south syndrome (differential hypoxia in VA-femoral), LV distension (afterload). Weaning: VV by reducing sweep gas; VA by echo-guided stepwise flow reduction. EOLIA trial (Combes, NEJM 2018): VV-ECMO for very severe ARDS did not significantly reduce 60-day mortality (35% vs 46%, RR 0.76, P=0.09), but 28% of controls crossed over to ECMO and a post-hoc Bayesian reanalysis estimated an 88–99% posterior probability of mortality benefit. CESAR trial (Peek, Lancet 2009): transfer to an ECMO centre improved survival in severe reversible adult respiratory failure (63% vs 47% alive without disability at 6 months).