What are the indications for Extracorporeal Membrane Oxygenation (ECMO)?

Indications for ECMO

ECMO is indicated as rescue therapy for severe, potentially reversible cardiorespiratory failure when conventional medical therapies have failed, with specific criteria including VV-ECMO for respiratory failure with PaO₂/FiO₂ < 80 mmHg for ≥3 hours despite optimal ventilation, and VA-ECMO for cardiogenic shock requiring significant inotropic support (norepinephrine >0.5 µg/kg/min) with reduced LV ejection fraction. 1

VV-ECMO: Respiratory Failure Indications

VV-ECMO provides isolated pulmonary support when cardiac function remains adequate. 1 The specific criteria include:

• PaO₂/FiO₂ < 80 mmHg for at least 3 hours despite optimal mechanical ventilation and rescue therapies 1, 2
• PaO₂/FiO₂ < 100 mmHg for ≥6 hours despite optimization of conventional treatments 1
• Plateau pressure > 28 cmH₂O for ≥6 hours despite lung-protective ventilation strategies 1
• pH < 7.25 for at least 3 hours indicating severe hypercapnia 2
• Evidence of right ventricular overload with pulmonary artery systolic pressure > 40 mmHg and acute cor pulmonale on echocardiography 1
• Persistent hypoxemia (PaO₂ < 55 mmHg) despite optimal mechanical ventilation including prone positioning 3, 4

Critical Prerequisite: Failure of Conventional Therapies

Before initiating VV-ECMO, you must document failure of all conventional treatments 1, 3:

• Lung-protective ventilation with tidal volumes 4-8 mL/kg predicted body weight 3
• Plateau pressures maintained < 30 cmH₂O 3
• Prone positioning for 12-16 hours daily in patients with PaO₂/FiO₂ < 150 mmHg 3
• Optimization of PEEP and FiO₂ 1

VA-ECMO: Cardiac Failure Indications

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

• Severe cardiogenic shock with very low cardiac output and reduced LV ejection fraction confirmed by echocardiography 1, 5
• Requirement for significant inotropic support and/or norepinephrine at dosages >0.5 µg/kg/min 1
• Refractory ventricular arrhythmias unresponsive to conventional therapies 5
• Active cardiopulmonary resuscitation for cardiac arrest (extracorporeal CPR/ECPR) 5, 6
• Acute or decompensated right heart failure 5
• Post-cardiotomy shock, post-heart transplant failure, severe myocarditis, or acute coronary syndrome with cardiogenic shock 7

Timing Considerations

VV-ECMO should be initiated within 7 days of respiratory failure onset for optimal outcomes. 1 Critical timing factors include:

• Early consideration is recommended before irreversible end-organ damage occurs 1
• Prolonged mechanical ventilation (>9.6 days) before ECMO is associated with worse outcomes 1
• For VA-ECMO in cardiac arrest (ECPR), rapid initiation is essential to prevent further decompensation and improve neurologic outcomes 6

Patient Selection Criteria

ECMO should only be considered in patients with potentially reversible cardiorespiratory failure. 1 Favorable selection factors include:

• Young age with fewer comorbidities 1
• Potentially reversible etiology of failure 1, 2
• Absence of contraindications to anticoagulation 1

Absolute Contraindications

• Contraindications to anticoagulation 1
• Irreversible organ failure without transplant candidacy 1

Institutional Requirements for ECMO Centers

ECMO should only be performed at centers with sufficient experience, volume, and expertise. 1 Specific requirements include:

• Minimum annual volume of 20-25 ECMO cases per year for the entire center, with significantly better outcomes at higher-volume centers 8, 1
• At least 12 ECMO cases for acute respiratory failure per year 8
• Learning curve requires at least 20 cases to establish competence for optimal results 8, 1
• Catchment area of at least 2-3 million population to maintain adequate volume 8
• Multidisciplinary ECMO team available 24/7 with quality assurance review procedures 1
• Robust expertise in ventilatory management of severe acute respiratory failure 8

Mobile ECMO Teams

Each ECMO network should create mobile ECMO teams available 24/7 to retrieve patients with critical cardiopulmonary failure refractory to conventional therapy. 8 These teams should:

• Employ experienced personnel trained in transport of critically ill patients 8
• Be capable of ECMO cannula insertion and circuit management 8
• Include physicians, transport specialists, nurses, perfusionists, or ECMO specialists 8
• Have access to portable ultrasound equipment and echocardiography capability 8

Common Pitfalls and Caveats

ECMO is a complex, high-risk, and costly modality that should be used judiciously. 1 Key warnings include:

• Bleeding complications are common and associated with high mortality rates, particularly intracranial hemorrhage 1
• 42% of VV-ECMO patients experience thrombotic events, 37% experience bleeding events, and 21% experience both 1
• Almost all ECMO patients develop acquired von Willebrand syndrome (AVWS) within hours of device implantation, contributing to bleeding complications 1
• Thrombotic and thromboembolic complications can occur despite anticoagulation 1
• Failure to optimize conventional therapies before ECMO initiation leads to inappropriate use 1, 3
• Delaying ECMO consideration in appropriate candidates with refractory hypoxemia despite optimal management worsens outcomes 3

Referral Pathways

Hospitals without ECMO capability should establish relationships with ECMO-capable institutions for timely transfer. 1, 3, 4 The emergency clinician is uniquely positioned to affect timeliness of referrals and transport to an ECMO center. 6