Venovenous Extracorporeal Membrane Oxygenation for Refractory Hypoxemia in Acute Respiratory Distress Syndrome: Pathophysiology and Evidence-Based Management

Venovenous Extracorporeal Membrane Oxygenation for Refractory Hypoxemia in Acute Respiratory Distress Syndrome: Pathophysiology and Evidence-Based Management https://www.academia.edu/166076628/Venovenous_Extracorporeal_Membrane_Oxygenation_for_Refractory_Hypoxemia_in_Acute_Respiratory_Distress_Syndrome_Pathophysiology_and_Evidence_Based_Management --- https://hopefuldreamily78fc58b8fc-kgrjb.wordpress.com/2026/04/29/venovenous-extracorporeal-membrane-oxygenation-for-refractory-hypoxemia-in-acute-respiratory-distress-syndrome-pathophysiology-and-evidence-based-management/ https://www.scribd.com/document/1032484837/Venovenous-Extracorporeal-Membrane-Oxygenation-for-Refractory-Hypoxemia-in-Acute-Respiratory-Distress-Syndrome

Dr Indunil Karunarathna © Uva Clinical Research Lab 2026 © Uva Clinical Anaesthesia and Intensive Care ISSN 2827-7198, 2026

Refractory hypoxemia represents a critical, life-threatening complication that may develop in a subset of patients with acute respiratory distress syndrome (ARDS) despite the optimization of conventional mechanical ventilation, including lung-protective strategies, prone positioning, and neuromuscular blockade. The absence of a universally accepted definition, though clinically challenging, does not diminish the urgency of recognition: refractory hypoxemia generally denotes persistent arterial oxygen desaturation (e.g., PaO₂/FiO₂ ratio ≤ 100 or oxygenation index > 40) despite high inspired oxygen concentrations and elevated levels of positive end-expiratory pressure. When conventional rescue interventions fail, venovenous extracorporeal membrane oxygenation (VV ECMO) provides a physiological bridge that maintains systemic oxygen delivery while permitting "ultraprotective" ventilation, thereby mitigating ventilator-induced lung injury. This comprehensive review examines the etiology, epidemiology, and pathophysiology of refractory hypoxemia, with particular emphasis on intrapulmonary shunting as the dominant mechanism. The evidence base for VV ECMO, derived from the pivotal CESAR and EOLIA trials and reinforced by large-scale COVID-19 observational data, is critically appraised, acknowledging both the strengths and limitations of existing studies. Key clinical considerations-including patient selection, timing of initiation, cannulation strategies, anticoagulation management, and weaning protocols-are systematically addressed. Major complications, including bleeding (30-50%), thrombosis, infection, hemolysis, and neurologic injury, are analyzed within the context of risk mitigation and interprofessional management. The review concludes that while VV ECMO is not without substantial risk, it confers a survival advantage in carefully selected patients with severe, refractory hypoxemia when deployed early, within high-volume expert centers, and under the auspices of a coordinated, multidisciplinary team. Prognosis depends critically on patient-specific factors, timing, and institutional experience; long-term functional and cognitive recovery, though often achievable, requires structured rehabilitation and follow-up.