ECMO Membrane Function Evaluation: Normal Values and Parameters
For optimal patient outcomes, ECMO membrane function evaluation should include serial arterial blood gas sampling in the first 24 hours, maintaining PaO2 >70 mmHg and avoiding severe hyperoxia (PaO2 >300 mmHg), especially in VA ECMO. 1
Key Monitoring Parameters for ECMO Membrane Function
Blood Gas Parameters
- Maintain arterial oxygenation with PaO2 >70 mmHg to prevent hypoxemia-associated acute brain injury 1
- Avoid severe arterial hyperoxia (PaO2 >300 mmHg), particularly in VA ECMO where reperfusion injury risk is high 1
- For patients with hypercapnia (PaCO2 >45 mmHg), avoid rapid changes in PaCO2 within the first 24 hours of ECMO support to prevent cerebrovascular complications 1, 2
- Target arterial oxygen saturation of 92-97% by adjusting the ECMO sweep gas FiO2 2
Flow Parameters
- Begin with a goal of 3-4 L/min ECMO flow after cannulation, gradually increasing as tolerated 2
- Maintain ECMO flow/cardiac output ratio >60% to ensure adequate blood oxygenation and oxygen transport 3
- Monitor arteriovenous O2 difference, maintaining between 3-5 cc O2/100ml of blood as a reliable parameter for setting ECMO flow goals 2
- Assess mixed venous saturation (SvO2), targeting above 66% 2
Membrane Performance Assessment
- Evaluate oxygen delivery to consumption ratio (DO2:VO2), targeting above 3 2
- Continuously monitor sweep gas flow through the membrane lung as it determines blood decarboxylation 3
- Assess membrane function by measuring oxygen uptake (VO2) and carbon dioxide removal (VCO2) on membrane lungs 4
- Monitor for signs of membrane degradation through real-time assessment of gas exchange efficiency 4
Hemodynamic Considerations
- Maintain mean arterial pressure >70 mmHg to ensure adequate cerebral and end-organ perfusion 1
- For VA ECMO, monitor for increased left ventricular afterload which can negatively impact cardiac recovery 2
- Use right radial arterial line for blood gas sampling as it best represents cerebral perfusion in peripherally cannulated patients 2
- Monitor for Harlequin syndrome in peripherally cannulated patients (occurs in approximately 10%) 2
Neurological Monitoring During ECMO
- Implement continuous cerebral oximetry to follow ongoing trends and detect acute brain injury early, especially for patients with peripheral VA ECMO at risk for differential hypoxia 1
- Use pupillometry if available to objectively evaluate pupil size and reactivity 1
- Consider intermittent EEG and somatosensory evoked potential (SSEP) monitoring, particularly in comatose patients 1
- Perform standardized neurological monitoring with clinical assessment and sedation cessation protocol to increase detection of acute brain injury 1
Temperature Management
- Continuously monitor core temperature and actively prevent fever (>37.7°C) 1
- For VA ECMO, especially ECPR, mild-moderate hypothermia (33-36°C) for 24-48 hours may be considered 1
- Hypothermia is not recommended in VV ECMO 1
Fluid Management
- Strive for daily negative fluid balance after ECMO flows are optimized and the patient is hemodynamically stable 2
- Monitor for fluid overload, which is associated with increased mortality by the third day of ECMO 2
- Consider earlier initiation of renal replacement therapy for preventing and managing fluid overload compared to non-ECMO patients 5
Common Pitfalls to Avoid
- Avoid sudden increases in ECMO flow that could precipitate hypertensive crisis 2
- Prevent excessive fluid administration, as positive fluid balance by the third day is associated with increased mortality 2
- Avoid early hyperoxia (PaO2 >300 mmHg), which is associated with mortality and poor neurological outcomes 2
- Do not neglect mechanical ventilation despite ECMO support; maintain lung expansion to prevent Harlequin syndrome 2