What are the indications and management strategies for Extracorporeal Membrane Oxygenation (ECMO) therapy?

ECMO: Indications and Management

Primary Indications

ECMO should be initiated for severe, potentially reversible cardiorespiratory failure when conventional therapies have failed, with distinct indications based on ECMO type. 1

Venovenous (VV) ECMO for Respiratory Failure

VV ECMO is indicated when patients meet the following criteria 1:

• PaO₂/FiO₂ < 80 mmHg for ≥3 hours despite optimal ventilation strategies 1
• PaO₂/FiO₂ < 70 for ≥3 hours or < 100 for ≥6 hours after optimization of conventional treatments 1
• Plateau pressure > 28 cmH₂O for ≥6 hours despite lung-protective ventilation 1
• Evidence of right ventricular overload with pulmonary artery systolic pressure > 40 mmHg and acute cor pulmonale on echocardiography 1

VV ECMO drains blood from the venae cavae via femoral or internal jugular venous cannula, pumps it through a membrane oxygenator, and returns it to the venous system, providing high blood flow (up to full pulmonary support) 2

Venoarterial (VA) ECMO for Cardiac Failure

VA ECMO is indicated for 1, 3:

• Severe cardiogenic shock with very low cardiac output and reduced LV ejection fraction requiring significant inotropic support and/or norepinephrine >0.5 µg/kg/min 1
• Cardiac arrest requiring extracorporeal cardiopulmonary resuscitation (ECPR) 3
• Post-cardiotomy shock and post-heart transplant failure 4
• Refractory ventricular tachycardia 3
• Acute complications of invasive cardiac procedures 3

VA ECMO drains blood from venous system and returns it to the arterial system (femoral, subclavian, or directly into aorta), providing up to 7 L/min flow for full or partial cardiopulmonary support 2

Timing of Initiation

VV-ECMO should be initiated within 7 days of respiratory failure onset for optimal outcomes, before irreversible end-organ damage occurs 1. Prolonged mechanical ventilation (>9.6 days) before ECMO is associated with worse outcomes 1. Optimization of conventional treatments including low-volume, low-pressure lung-protective ventilation and prone positioning must always be undertaken before considering ECMO 1.

Absolute Contraindications

• Contraindications to anticoagulation 1
• Unsalvageable patients without potential for recovery, bridge to transplant, or durable device 3

Institutional Requirements

ECMO should only be performed at centers with sufficient experience and volume. 1

• Centers caring for >20-25 ECMO cases per year have significantly better outcomes than lower-volume centers 2, 1
• Minimum recommended annual volume is 20 cases per year for the entire center, with at least 12 ECMO cases for acute respiratory failure 2, 1
• Learning curve requires at least 20 cases for optimal competence 2, 1
• A multidisciplinary ECMO team available 24/7 with quality assurance review procedures is essential 1
• Hospitals without ECMO capability should establish relationships with ECMO-capable institutions for timely transfer, with mobile ECMO teams available for patient retrieval 1

Critical Management Parameters

Oxygenation and Ventilation

• Maintain PaO₂ >70 mmHg to prevent hypoxemia-associated acute brain injury 5
• Avoid severe arterial hyperoxia (PaO₂ >300 mmHg), particularly in VA ECMO where reperfusion injury risk is high 5
• Target arterial oxygen saturation 92-97% by adjusting ECMO sweep gas oxygen percentage 5
• Avoid rapid changes in PaCO₂ within the first 24 hours of ECMO support to prevent cerebrovascular complications 5. Rapid early decrease in PaCO₂ (ΔPaCO₂ >50%) is independently associated with increased risk of intracranial hemorrhage 2
• Perform serial ABG sampling in the first 24 hours of ECMO 2, 5

Hemodynamic Management

• Maintain mean arterial pressure (MAP) >70 mmHg to ensure adequate cerebral and end-organ perfusion 2, 5
• Target ECMO flow of 3-4 L/min after cannulation, gradually increasing as tolerated 5
• Monitor arteriovenous oxygen difference, maintaining between 3-5 cc oxygen/100ml of blood 5
• Continuous monitoring of arterial blood pressure and ECMO flow is essential 1
• Repeated echocardiography is critical, especially for VA-ECMO, to assess left ventricular afterload which can negatively impact cardiac recovery 1, 5

Temperature Management

• Continuously monitor core temperature and actively prevent fever (>37.7°C) 2, 5
• Consider mild-moderate hypothermia (33-36°C) for 24-48 hours in VA ECMO patients, especially those undergoing ECPR 2, 5
• Hypothermia is not recommended in VV ECMO patients 2

Fluid Management

• Strive for daily negative fluid balance after ECMO flows are optimized and the patient is hemodynamically stable 5
• Monitor for fluid overload, which is associated with increased mortality by the third day of ECMO 5
• Daily monitoring of fluid balance, central venous oxygen saturation, and lactate levels 1

Neurological Monitoring

Standardized neuromonitoring and neurological expertise are recommended for ECMO patients at high risk of developing acute brain injury (ABI). 2

Essential Monitoring Tools

• Continuous cerebral oximetry (rSO₂) to follow trends and detect ABI early, especially for peripheral VA ECMO patients at risk for differential hypoxia 2, 5
• Pupil assessment with pupillometry if available for objective evaluation 2, 5
• Intermittent EEG and somatosensory evoked potential (SSEP) monitoring, particularly in comatose patients 2, 5
• Continuous EEG if available to detect non-convulsive seizures in comatose patients 2
• Early neuroimaging (preferably MRI) for patients at risk of ABI based on physical examination and neuromonitoring tools 2
• Neurological consultation for acute neurological changes 2

Blood Pressure Goals for Neuroprotection

• After acute ischemic stroke: permissive hypertension (BP ≤220/120 mmHg) is reasonable to maintain adequate cerebral perfusion 2
• After intracranial hemorrhage: lower BP targets (systolic BP <140 mmHg, MAP <90 mmHg) are preferred due to anticoagulation-associated bleeding risk 2
• Avoid low pulse pressure (<20 mmHg) in the first 24 hours of VA ECMO, as this is associated with ABI 2

Anticoagulation Management

Anticoagulation is required for cannulation and to prevent clot formation in the circuit and oxygenator, but carries high bleeding and thrombotic risk. 2

• 42% of VV-ECMO patients experience thrombotic events (mostly ECMO circuit thrombosis) 2
• 37% experience bleeding events (including cannulation/surgical site and medical bleeding) 2
• 21% experience both complications while on ECMO 2
• Acquired von Willebrand Syndrome (AVWS) develops in almost all ECMO patients within hours of device implantation and may contribute to bleeding complications 1
• Regular assessment for bleeding and thrombosis complications is essential 1

Major Complications and Pitfalls

Intracranial hemorrhage (ICH) while anticoagulated during ECMO carries extremely high mortality and morbidity. 2

Common Complications

• Bleeding complications are common and associated with high mortality rates, particularly intracranial hemorrhage 1
• Thrombotic and thromboembolic complications can occur despite anticoagulation 1
• Vascular access complications including leg ischemia 2
• Circuit-related complications including oxygenator failure 2

Critical Pitfalls to Avoid

• Avoid arterial hypoxemia (PaO₂ <70 mmHg) for 24-48 hours in VA ECMO, especially for patients at high risk of reperfusion injury 2, 5
• Do not use ECMO on unsalvageable patients without potential for recovery or bridge to definitive therapy 3
• Recognize that ECMO is a bridge-to-recovery, bridge-to-bridge, bridge-to-definitive treatment, or bridge-to-decision, not destination therapy 3

Long-Term Outcomes and Follow-Up

Pre-discharge clinical examination using the modified Rankin Scale is recommended, with neuroimaging (preferably MRI) for those with neurological or cognitive dysfunction. 2

• Long-term MRI found cerebral infarction or hemorrhage in 37-52% of adult ECMO survivors 2
• Cognitive impairment is associated with neuroradiologic findings 2
• Outpatient care planning with visits at 3,6, and 12 months after discharge is recommended 2
• Serial neurological assessments and quality of life assessments are essential 2
• Follow-up with disease-specific specialists (pulmonologist, cardiologist, neurologist, nephrologist) tailored to underlying disease and comorbidities 2