What are the indications and contraindications for extracorporeal membrane oxygenation (ECMO)?

Indications and Contraindications for ECMO

ECMO should be initiated as rescue therapy for severe, potentially reversible cardiorespiratory failure when conventional therapies have failed, specifically when PaO₂/FiO₂ remains < 80 mmHg for ≥ 3 hours despite optimal ventilation, or when plateau pressures exceed 28 cmH₂O for ≥ 6 hours despite lung-protective strategies. 1

Pre-ECMO Optimization Requirements

Before considering ECMO, you must exhaust conventional rescue therapies to avoid premature escalation:

• Lung-protective ventilation with tidal volumes of 4–6 mL/kg ideal body weight and plateau pressure < 30 cmH₂O (ideally < 28 cmH₂O) 1
• Early prone positioning initiated within ≤ 48 hours of ARDS onset and maintained for ≥ 12–16 hours daily when PaO₂/FiO₂ < 150 mmHg 1
• Optimal PEEP titration at ≥ 12 cmH₂O based on gas-exchange and hemodynamic response 1
• Short-course neuromuscular blockade with cisatracurium for ≤ 48 hours during the first 48 hours of severe ARDS combined with deep sedation 1

Critical pitfall: High-frequency oscillatory ventilation (HFOV) should NOT be used as it increases mortality risk (relative risk ≈ 1.41) without benefit over lung-protective ventilation. 1

Specific Indications for VV-ECMO (Respiratory Support Only)

VV-ECMO is indicated for isolated severe respiratory failure when cardiac function remains adequate:

Fast-Entry (Immediate) Criteria:

• PaO₂/FiO₂ < 70 mmHg for ≥ 3 hours despite FiO₂ > 0.70 and optimal PEEP 1

Slow-Entry (Delayed) Criteria (any of the following):

• PaO₂/FiO₂ < 80 mmHg for ≥ 3 hours OR < 100 mmHg for ≥ 6 hours 1, 2
• Plateau pressure > 28 cmH₂O for ≥ 6 hours despite lung-protective ventilation 1
• Arterial pH < 7.20–7.25 for ≥ 6 hours due to uncompensated hypercapnia (PaCO₂ > 60 mmHg) 1
• Evidence of right ventricular overload with pulmonary artery systolic pressure > 40 mmHg and acute cor pulmonale on echocardiography 1

Timing is critical: VV-ECMO should be initiated within 7 days of respiratory failure onset; delays beyond 7–9 days of mechanical ventilation are associated with markedly worse survival. 1

Specific Indications for VA-ECMO (Combined Cardiopulmonary Support)

VA-ECMO is reserved for combined cardiopulmonary failure or cardiogenic shock:

• Cardiogenic shock with very low cardiac output and reduced LV ejection fraction confirmed by echocardiography 1
• Requirement for significant inotropic support and/or norepinephrine at dosages > 0.5 µg/kg/min 1
• Postcardiotomy shock following cardiac surgery (occurs in 2–5% of postoperative patients at large centers) 1
• Bridge to transplantation or durable ventricular assist device 1
• Refractory cardiac arrest requiring extracorporeal cardiopulmonary resuscitation (ECPR) 3

Key decision point: Echocardiography is mandatory to distinguish between VV and VA-ECMO candidacy. If cardiac function is adequate with norepinephrine ≤ 0.5 µg/kg/min and mean arterial pressure ≥ 65 mmHg, choose VV-ECMO. 1

Absolute Contraindications

• Contraindications to anticoagulation (ECMO requires continuous heparin infusion with ACT 180–220 seconds and hourly ACT monitoring) 1
• Irreversible cardiorespiratory failure or end-stage disease without transplant candidacy 1
• Prolonged mechanical ventilation > 9.6 days before ECMO consideration (associated with significantly worse outcomes) 1

Relative Contraindications (Unfavorable Characteristics)

• Advanced age with multiple comorbidities (young age with fewer comorbidities is favorable) 1
• Non-reversible etiology of cardiorespiratory failure 1

Institutional Requirements (Non-Negotiable)

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

• Minimum annual volume of 20–25 ECMO cases (centers with > 20–25 cases/year have significantly better outcomes) 1, 4
• 24/7 availability of multidisciplinary ECMO team including physicians, nurses, perfusionists, and ECMO specialists 1
• Nurse-to-patient ratio of at least 1:1 to 1:2 for ECMO patients 1
• Catchment area of at least 2–3 million population to maintain adequate volume 1
• Quality assurance review procedures and robust expertise in ventilatory management of severe acute respiratory failure 1
• Learning curve requirement: At least 20 cases to establish competence for optimal results 1

For hospitals without ECMO capability: Establish formal pathways with 24/7 mobile ECMO team retrieval to high-volume centers, ensuring timely transfer before clinical deterioration. Mobile teams must include experienced personnel trained in critical care transport, cannula insertion, and circuit management. 1

Monitoring During ECMO

Hemodynamic Surveillance:

• Continuous arterial blood pressure and ECMO circuit flow monitoring 1
• Repeated echocardiography, especially for VA-ECMO patients, to detect left ventricular overload 1

Metabolic and Oxygenation Tracking:

• Daily fluid balance, central venous oxygen saturation (SvO₂), and lactate measurements 1
• Hourly ACT checks during ECMO support 1

Major Complications (High-Risk Profile)

Bleeding complications are extremely common and life-threatening:

• 37% of VV-ECMO patients and 75.3% of VA-ECMO patients experience bleeding complications 1
• Acquired von Willebrand syndrome (AVWS) develops in almost all ECMO patients within hours of device implantation, contributing to bleeding risk 1, 5
• Intracranial hemorrhage carries particularly high mortality 1

Thrombotic complications occur despite anticoagulation:

• 42% of VV-ECMO patients experience thrombotic events, 37% experience bleeding events, and 21% experience both 1
• Left ventricular overload is a specific complication of VA-ECMO requiring additional mechanical unloading devices (IABP or Impella) 1

Evidence Quality and Survival Data

The overall evidence supporting ECMO for severe ARDS is conditional with low-to-moderate certainty; no randomized controlled trials have demonstrated definitive mortality benefit across all respiratory failure populations. 1 However, survival rates of 55–86% are reported in selected patients with potentially reversible causes (e.g., viral pneumonia), and > 70% survival in severe ARDS when performed at experienced centers. 1

Bottom line: ECMO is a complex, high-risk, and costly modality that should be used judiciously only at high-volume centers with comprehensive expertise, and only after exhausting conventional therapies in patients with potentially reversible disease. 4