When is Extracorporeal Membrane Oxygenation (ECMO) indicated for patients with cardiac or respiratory failure?

ECMO Indications for Cardiac and Respiratory Failure

When to Initiate ECMO

ECMO should be considered as rescue therapy for patients with severe, potentially reversible cardiorespiratory failure when conventional medical therapies have failed, with specific thresholds including PaO₂/FiO₂ < 80 mmHg for at least 3 hours despite optimal ventilation for respiratory failure, or cardiogenic shock requiring significant inotropic support and/or norepinephrine >0.5 µg/kg/min for cardiac failure. 1, 2

Respiratory Failure: VV-ECMO Indications

Primary Criteria

• Severe hypoxemia: PaO₂/FiO₂ < 80 mmHg for ≥3 hours despite optimal ventilation strategies 1, 2
• Alternative threshold: PaO₂/FiO₂ < 70 mmHg for ≥3 hours or < 100 mmHg for ≥6 hours despite optimization of conventional treatments 1
• Severe hypercapnia: pH < 7.25 for ≥3 hours despite optimal ventilation 2
• Elevated plateau pressures: >28 cmH₂O for ≥6 hours despite lung-protective ventilation strategies 1
• Right ventricular overload: Pulmonary artery systolic pressure >40 mmHg with acute cor pulmonale on echocardiography 1

Prerequisites Before VV-ECMO

All conventional therapies must be exhausted first 1, 3:

• Lung-protective ventilation (low tidal volume, low pressure)
• Higher PEEP strategies
• Prone positioning
• Neuromuscular blockade
• Inhaled vasodilators (nitric oxide/prostacyclin)
• Corticosteroids when appropriate

Timing Considerations

• Initiate within 7 days of respiratory failure onset for optimal outcomes 1, 3
• 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

Cardiac Failure: VA-ECMO Indications

Primary Indications

• Cardiogenic shock with very low cardiac output and reduced LV ejection fraction confirmed by echocardiography 1, 4
• Hemodynamic instability requiring significant inotropic support and/or norepinephrine at dosages >0.5 µg/kg/min 1
• Postcardiotomy shock: Failure to wean from cardiopulmonary bypass 5
• Extracorporeal cardiopulmonary resuscitation (ECPR) for refractory cardiac arrest requiring rapid initiation 4
• Bridge to recovery, transplantation, or durable mechanical support 5, 6

Specific Cardiac Populations

• Postcardiotomy patients (most common indication in congenital heart disease, used in 2-5% of postoperative patients) 5
• Acute myocarditis (survival rates: 83% pediatric, 75% adult) 5
• Post-heart transplant complications 6
• Acute coronary syndrome with cardiogenic shock 6

Pediatric-Specific Indications

Consider ECMO for refractory pediatric septic shock and respiratory failure (grade 2C recommendation) 5

Pediatric Survival Data by Age

• <30 days of age: 35-40% survival 5
• 31 days to 1 year: 47-49% survival 5
• 1-16 years: 58-59% survival 5

Critical Decision Algorithm: VV vs VA-ECMO

Step 1: Assess Cardiac Function

• Perform echocardiography to evaluate cardiac output and LV ejection fraction 1
• Evaluate for right ventricular overload and acute cor pulmonale 1

Step 2: Determine ECMO Type

• VV-ECMO: Isolated severe respiratory failure with adequate cardiac function 1, 6

  • Drains and returns blood to venous system
  • Provides only respiratory support

• VA-ECMO: Combined cardiopulmonary failure or cardiogenic shock 1, 6

  • Drains from venous system, returns to arterial circulation
  • Provides both respiratory support and hemodynamic stability

Institutional Requirements (Critical)

ECMO should ONLY be performed at centers meeting these criteria 1:

• Minimum volume: >20-25 ECMO cases per year (significantly better outcomes than lower-volume centers)
• Learning curve: At least 20 cases required to establish competence
• 24/7 availability: Multidisciplinary ECMO team with quality assurance review procedures 1
• Specialized expertise: Intensivists, perfusionists, cardiac surgeons, and respiratory therapists 1

Transfer Protocols

• Hospitals without ECMO capability should establish relationships with ECMO-capable institutions for timely transfer 1
• Mobile ECMO teams should be available for retrieval of patients from centers without ECMO capability 1

Absolute Contraindications

• Contraindications to anticoagulation (bleeding risk cannot be mitigated) 1
• Irreversible underlying condition with no potential for recovery, transplant, or durable support 1

Major Complications and Monitoring

Bleeding Complications

• 42% of VV-ECMO patients experience thrombotic events, 37% bleeding events, 21% both 1
• Intracranial hemorrhage carries particularly high mortality 1
• Acquired von Willebrand syndrome (AVWS) develops in almost all ECMO patients within hours of device implantation 5, 1

Thrombotic Complications

• One-third of patients develop venous thrombus formation and systemic thromboembolic events despite anticoagulation 5
• Youngest patients are at greatest risk 5

Required Monitoring

• 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
• Regular arterial blood gas analysis 3

Anticoagulation Protocol

• Loading dose: 100 U/kg heparin before ECMO cannulation 5
• Continuous infusion: Maintain ACT between 180-220 seconds 5
• Monitoring: ACT checked every hour during support 5
• Recent data suggests improved survival with higher heparin doses 5

Critical Pitfalls to Avoid

• Do not delay optimization of conventional therapies before considering ECMO 1, 3
• Avoid ECMO at low-volume centers (<20 cases/year) due to significantly worse outcomes 1
• Do not initiate ECMO after prolonged mechanical ventilation (>9.6 days associated with worse outcomes) 1
• Weekend initiation is associated with higher mortality risk (HR 1.6) 7
• Hypothermia at initiation increases mortality risk (HR 3.8) 7
• Higher disease severity scores (SAPS III) predict worse outcomes 7