What are the indications for Extracorporeal Membrane Oxygenation (ECMO) in patients with severe cardiac or respiratory failure?

Indications for Extracorporeal Membrane Oxygenation (ECMO)

ECMO is indicated as rescue therapy for severe, potentially reversible cardiorespiratory failure when conventional medical therapies have failed, with distinct indications for venovenous (VV) ECMO in isolated respiratory failure and venoarterial (VA) ECMO in cardiogenic shock or combined cardiopulmonary failure. 1

VV-ECMO: Respiratory Failure Indications

VV-ECMO provides isolated pulmonary support for patients with adequate cardiac function but severe respiratory failure. 1

Specific criteria for VV-ECMO initiation:

• PaO₂/FiO₂ < 80 mmHg for ≥3 hours despite optimal ventilation with FiO₂ > 70% and optimal PEEP 1, 2, 3
• PaO₂ < 55 mmHg on optimal mechanical ventilation 2
• pH < 7.25 for ≥3 hours due to uncompensated hypercapnia with PaCO₂ > 60 mmHg 1, 2, 3
• Plateau pressure > 28 cmH₂O for ≥6 hours despite lung-protective ventilation strategies 1
• Evidence of right ventricular overload with pulmonary artery systolic pressure > 40 mmHg and acute cor pulmonale on echocardiography 1

Critical prerequisite: All conventional therapies must be exhausted before ECMO consideration, including lung-protective ventilation (tidal volume 4-6 mL/kg ideal body weight, plateau pressure < 30 cmH₂O), prone positioning for 12-16 hours daily when PaO₂/FiO₂ < 150 mmHg, neuromuscular blockade within 48 hours of moderate-to-severe ARDS, and optimized PEEP. 1, 2

Timing matters: VV-ECMO should be initiated within 7 days of respiratory failure onset for optimal outcomes, before irreversible end-organ damage occurs. 1, 4 Prolonged mechanical ventilation (>9.6 days) before ECMO is associated with worse outcomes. 1

VA-ECMO: Cardiac and Combined Cardiopulmonary Failure Indications

VA-ECMO provides both hemodynamic support and respiratory support by actively pumping oxygenated blood into the arterial circulation. 1

Specific criteria for VA-ECMO initiation:

• Cardiogenic shock with very low cardiac output and reduced LV ejection fraction confirmed by echocardiography 1, 5, 6
• Requirement for significant inotropic support and/or norepinephrine at dosages >0.5 µg/kg/min 1
• Postcardiotomy shock following cardiac surgery (used in 2-5% of postoperative patients at large centers) 7, 5, 6
• Cardiac arrest with active cardiopulmonary resuscitation 5, 6
• Refractory ventricular arrhythmias 5, 6
• Bridge to transplantation or durable ventricular assist device 7, 5, 6
• Acute graft failure following heart or lung transplantation 8

Key decision point: Echocardiography is crucial to determine whether VA or VV ECMO is appropriate—if cardiac function is preserved, VV-ECMO suffices; if cardiac output is severely compromised, VA-ECMO is required. 1

Absolute Contraindications

• Contraindications to anticoagulation (ECMO requires continuous heparin infusion with ACT 180-220 seconds) 7, 1
• Irreversible underlying condition with no potential for recovery, bridge to transplant, or durable device 1, 5

Institutional Requirements: Non-Negotiable Standards

ECMO should only be performed at high-volume centers meeting these criteria:

• Minimum 20-25 ECMO cases per year for the entire center (centers with higher volumes have significantly better outcomes) 1, 2, 4
• 24/7 availability of multidisciplinary ECMO team including intensivists, pulmonologists, nurses, perfusionists, and ECMO specialists 1, 2
• Nurse-to-patient ratio of 1:1 to 1:2 for ECMO patients 1
• Quality assurance review procedures with regular training 1, 2
• Catchment area of at least 2-3 million population to maintain adequate volume 1

For hospitals without ECMO capability: Establish relationships with ECMO-capable institutions and mobile ECMO teams for timely transfer. Mobile teams should be available 24/7 with experienced personnel capable of cannula insertion and circuit management. 1, 4

Complications and Monitoring Requirements

Bleeding complications are extremely common and life-threatening:

• 37% of VV-ECMO patients and 75.3% of VA-ECMO patients experience bleeding 1
• 42% experience thrombotic events despite anticoagulation 1
• Almost all ECMO patients develop acquired von Willebrand syndrome within hours of device implantation 1
• Intracranial hemorrhage carries particularly high mortality 1

VA-ECMO specific complication: Left ventricular overload requiring additional unloading with IABP or Impella. 1

Mandatory monitoring includes:

• Continuous arterial blood pressure and ECMO flow monitoring 1
• Repeated echocardiography (especially for VA-ECMO) 1
• Daily fluid balance, central venous oxygen saturation, and lactate levels 1
• Hourly ACT checks during ECMO support 7

Evidence Quality and Clinical Application

The American Thoracic Society provides only a conditional recommendation with low certainty of evidence for VV-ECMO in severe ARDS, largely due to limitations of the CESAR trial (which compared transfer to specialized centers rather than pure ECMO vs. conventional ventilation). 2, 4 Despite this, survival rates of >70% have been reported in selected patients with refractory respiratory failure, and 35-40% survival in neonates with cardiac ECMO, improving to 58-59% in older children. 7, 9

The fundamental premise: ECMO is a bridge—to recovery, to more durable support, to definitive treatment, or to decision. It should never be used on unsalvageable patients. 5