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

ECMO: Indications and Management

Primary Indications

ECMO should be reserved as rescue therapy for patients with severe, potentially reversible cardiorespiratory failure when conventional medical therapies have failed, with VV-ECMO indicated for isolated respiratory failure (PaO₂/FiO₂ < 80 mmHg for ≥3 hours despite optimal ventilation) and VA-ECMO for combined cardiopulmonary failure or cardiogenic shock requiring hemodynamic support. 1

Venovenous (VV) ECMO for Respiratory Failure

• Severe ARDS with PaO₂/FiO₂ < 80 mmHg for at least 3 hours despite optimal ventilation strategies is the primary indication 1, 2
• Alternative criteria include PaO₂/FiO₂ < 100 for ≥6 hours despite optimization of conventional treatments 1
• 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
• pH < 7.25 for at least 3 hours due to respiratory acidosis 2

Venoarterial (VA) ECMO for Cardiac Failure

• Severe cardiogenic shock with very low cardiac output and reduced LV ejection fraction confirmed by echocardiography 1, 3
• Requirement for significant inotropic support and/or norepinephrine at dosages >0.5 µg/kg/min 1
• Refractory ventricular arrhythmia unresponsive to conventional therapy 3
• Active cardiopulmonary resuscitation for cardiac arrest 3
• Acute or decompensated right heart failure 3

Critical Timing Considerations

VV-ECMO should be initiated within 7 days of respiratory failure onset for optimal outcomes, with early consideration recommended before irreversible end-organ damage occurs 1. A major pitfall is prolonged mechanical ventilation (>9.6 days) before ECMO consideration, which is associated with significantly worse outcomes 1.

Pre-ECMO Optimization Requirements

• Optimization of conventional treatments must always be undertaken before considering ECMO, including low-volume, low-pressure lung-protective ventilation and prone positioning 4, 1
• Ensure adequate trial of rescue therapies including neuromuscular paralysis, prone positioning, inhaled vasodilators, and high-frequency ventilation 4
• Assess cardiac function via echocardiography to determine whether VV or VA ECMO is appropriate 1

Institutional Requirements and Volume Standards

ECMO should only be performed at centers with a minimum annual volume of 20-25 ECMO cases per year, as centers with higher volumes have significantly better outcomes 1, 4. This is a critical quality threshold that directly impacts mortality and morbidity.

Essential Center Capabilities

• Multidisciplinary ECMO team available 24/7 with quality assurance review procedures 1, 4
• Robust expertise in ventilatory management of severe acute respiratory failure 1
• The learning curve requires at least 20 cases to establish competence for optimal results 1
• ECMO centers should have a catchment area of at least 2-3 million population to maintain adequate volume 1
• A minimum of 12 ECMO cases for acute respiratory failure per year is recommended 1

Staffing Requirements

• Nurse-to-patient ratio of at least 1:1 to 1:2 (one nurse for up to two patients receiving ECMO) 4
• ECMO program director should be a physician with responsibility for overall operation, training, equipment maintenance, and quality improvement 4
• ECMO team should be self-sufficient and trained to prime and set up the ECMO circuit 4
• ECMO coordinator (nurse, respiratory therapist, or perfusionist) to assist with organizing training, staffing, and quality improvement 4

Mobile ECMO Teams and Transfer Networks

Each ECMO network should create mobile ECMO teams available 24/7 to retrieve patients with critical cardiopulmonary failure refractory to conventional therapy 1, 4. This is essential for regions where not all hospitals can maintain adequate ECMO volume.

Mobile Team Composition and Capabilities

• Teams should include physicians, transport specialists, nurses, perfusionists, or ECMO specialists 1, 4
• Must be experienced in transport of critically ill patients, ECMO cannula insertion, and circuit management 1, 4
• Should have access to portable ultrasound equipment and echocardiography capability 1, 4
• Coordination runs through the tertiary ECMO referral center 4
• Hospitals without ECMO capability should establish relationships with ECMO-capable institutions for timely transfer 1

Absolute Contraindications

• Contraindications to anticoagulation are an absolute contraindication for ECMO 1
• Irreversible cardiorespiratory failure or end-stage disease 1
• Severe, irreversible neurological injury 4

Patient Selection Factors

Factors supporting ECMO use include young age with fewer comorbidities and potentially reversible etiology 1. The key is identifying patients with severe but potentially reversible conditions.

Poor Prognostic Indicators

• Prolonged mechanical ventilation (>9.6 days) before ECMO initiation 1
• Multiple significant comorbidities 1
• Advanced age (though not an absolute contraindication) 1
• Irreversible end-organ damage 1

Monitoring and Management During ECMO

Hemodynamic Monitoring

• Continuous monitoring of arterial blood pressure and ECMO flow 1
• Repeated echocardiography is essential, especially for VA-ECMO 1
• Daily monitoring of fluid balance, central venous oxygen saturation, and lactate levels 1
• VA ECMO requires more intensive hemodynamic monitoring, including continuous ECMO flow recording 1

Complication Surveillance

• Regular assessment for bleeding and thrombosis is mandatory 1
• Recent data shows 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, which may contribute to bleeding complications 1
• Intracranial hemorrhage is associated with particularly high mortality rates 1

Critical Pitfalls and Caveats

ECMO is a complex, high-risk, and costly modality that should be used judiciously 1. The most common pitfalls include:

• Initiating ECMO too late after prolonged mechanical ventilation (>9.6 days) 1
• Performing ECMO at low-volume centers without adequate expertise 1, 4
• Failing to optimize conventional therapies before ECMO initiation 4, 1
• Inadequate anticoagulation monitoring leading to thrombotic complications 1
• Failure to recognize contraindications to anticoagulation 1
• Not having clear pathways for transition to advanced therapies (durable VAD, transplantation) for VA-ECMO patients who cannot be weaned 3

Physical Facilities Required

Essential equipment and facilities include 4:

• Backup components of the ECMO system and supplies for all circuit components 4
• Uninterrupted Power System (UPS) supporting all equipment monitors and pumps for at least 45 minutes 4
• Adequate lighting to support surgical interventions 4
• Surgical instrument set for revision of cannulae or exploration for bleeding complications 4
• Doppler echocardiography machines 4
• Equipment for intrahospital transport including mobile ECMO cart 4
• Wet-primed circuit available for immediate use 4
• Emergency transport backpack with ECMO clamps and emergency drugs 4

Evidence Limitations

There is insufficient high-quality evidence to provide definitive recommendations for ECMO use in all clinical scenarios, particularly for influenza-related respiratory failure 4. The best available evidence stems from trials of ECMO for acute respiratory failure of all etiologies, among which significant heterogeneity exists 4. The ongoing EOLIA trial and future research through the International ECMO Network aim to provide more definitive evidence 4.