What is the management approach for a patient on Veno-Arterial (VA) Extracorporeal Membrane Oxygenation (ECMO) with elevated lactate levels and unwashed blood?

Management of Elevated Lactate with Unwashed Blood on VA ECMO

When a patient on VA ECMO develops elevated lactate levels in the context of unwashed blood, immediately assess for hemolysis as the primary cause, while simultaneously evaluating for inadequate tissue perfusion, and prioritize serial lactate measurements over single values to guide management decisions.

Understanding the Clinical Context

The use of unwashed blood products during VA ECMO support can contribute to elevated lactate through multiple mechanisms:

• Hemolysis from unwashed blood releases free hemoglobin and cellular contents that can falsely elevate lactate measurements and contribute to actual metabolic derangements 1
• Inadequate ECMO flow causing tissue hypoperfusion remains the most critical reversible cause of true hyperlactatemia 1
• Circuit-related complications including cannula malposition, "suctioning," or "chatter" can reduce effective blood flow and cause hemolysis 1

Immediate Assessment Protocol

Hemolysis Evaluation

• Check plasma-free hemoglobin levels immediately to quantify degree of hemolysis 1
• Inspect ECMO circuit for signs of mechanical hemolysis including dark discoloration of tubing, excessive negative pressures, or cannula vibration 1
• Monitor for cannula "suctioning" and "chatter" which indicate venous collapse and can cause both flow reduction and hemolysis 1

Hemodynamic Assessment

• Maintain continuous monitoring of MAP, ECMO flow, and echocardiography as recommended for all VA ECMO patients 1
• Target MAP ≥ 65-70 mmHg to ensure adequate tissue perfusion 1
• Assess pulse pressure, as values < 20 mmHg in the first 24 hours are associated with acute brain injury and poor outcomes 1
• Evaluate for differential hypoxia using continuous cerebral oximetry, particularly with peripheral VA ECMO 1

Serial Lactate Monitoring Strategy

Absolute lactate levels outperform lactate clearance for prognostication and should be prioritized:

Critical Time Points and Thresholds

• At 12 hours post-ECMO: Lactate > 8.2 mmol/L predicts mortality with 86.8% accuracy (AUROC: 0.868) 2
• At 24 hours post-ECMO: Lactate > 2.6 mmol/L predicts mortality with 89.6% accuracy (AUROC: 0.896) 2
• Peak lactate: Values > 14.35-14.65 mmol/L predict mortality with 81.7-82.8% sensitivity 2, 3

Lactate Clearance as Secondary Marker

• At 12 hours: Clearance < 21.94% indicates poor prognosis (adjusted HR: 2.73) 2
• At 24 hours: Clearance < 40.3% indicates poor prognosis (adjusted HR: 1.98) 2
• Note: Absolute lactate levels demonstrate better performance than clearance percentages at identical time points 2

Management Algorithm

Step 1: Optimize ECMO Circuit Function

• Increase ECMO flow if inadequate (typically 60-80 mL/kg/min for adults) to improve tissue perfusion 1
• Correct hypovolemia carefully, as it can induce venous collapse and worsen hemolysis, but avoid volume overload which independently predicts poor outcomes 1
• Reposition cannulas if malpositioned based on echocardiographic assessment 1

Step 2: Address Hemolysis

• Discontinue unwashed blood products and switch to washed or leukoreduced products 1
• Reduce circuit-related hemolysis by optimizing flow rates and eliminating mechanical causes 1
• Monitor for acquired von Willebrand syndrome (AVWS) which develops in nearly all ECMO patients and contributes to bleeding complications 4, 5

Step 3: Optimize Oxygen Delivery

• Avoid arterial hypoxemia (PaO₂ < 70 mmHg) especially in the first 24-48 hours, as this is associated with acute brain injury 1
• Maintain adequate hemoglobin to optimize oxygen-carrying capacity despite hemolysis 1
• Monitor central venous oxygen saturation (SvO₂) continuously as part of hemodynamic assessment 1

Step 4: Temperature Management

• Actively prevent fever through continuous core temperature monitoring 1
• Consider mild-moderate hypothermia (33-36°C) for VA ECMO patients, particularly post-cardiac arrest (ECPR), though not recommended for VV ECMO 1

Step 5: Fluid Balance Optimization

• Maintain meticulous fluid balance records, as positive fluid balance is an independent predictor of mortality in ECMO patients 1
• Implement fluid-conservative strategy once shock resolves 1

Prognostic Implications

High-Risk Features Requiring Escalation

• Progressive hyperlactatemia despite adequate ECMO support (OR: 1.427 for mortality) 3
• Lactate > 3.25 mmol/L at 24 hours (88.3% sensitivity, 97.8% specificity for mortality) 3
• Increasing SOFA score at 48 hours (OR: 1.819 for mortality) 3
• Atrial fibrillation (OR: 6.17 for mortality in post-cardiotomy ECMO) 2

Neurological Risk Assessment

• Peak lactate ≥ 15.15 mmol/L predicts cerebral strokes with 70.8% sensitivity 3
• Lactate ≥ 3.25 mmol/L at 24 hours predicts cerebral strokes with 79.2% sensitivity 3
• Implement standardized neuromonitoring including continuous cerebral oximetry and serial neurological examinations 1

Critical Pitfalls to Avoid

• Do not rely on single lactate measurements - serial measurements at 12 and 24 hours provide superior prognostic information 2, 3
• Do not assume all elevated lactate is from hemolysis - inadequate tissue perfusion must be ruled out first 1, 2
• Do not use continuous thermodilution or pulse contour cardiac output monitoring as these are unreliable in ECMO patients 1
• Do not delay neuroimaging if lactate remains elevated with neurological concerns, as hyperlactatemia predicts cerebrovascular complications 1, 3
• Avoid excessive vasopressor doses (norepinephrine > 0.5 µg/kg/min) which may indicate need for VA ECMO rather than VV ECMO 1

When to Consider ECMO Modification or Withdrawal

• Lactate > 8.2 mmol/L at 12 hours despite optimization suggests poor prognosis and warrants multidisciplinary discussion 2
• Failure to achieve lactate clearance > 21.94% by 12 hours indicates significantly increased mortality risk 2
• Progressive hyperlactatemia with rising SOFA scores suggests multi-organ failure and poor salvageability 2, 3
• Neurological prognostication should employ multimodal assessment including clinical examination, electrophysiological tests, and neuroimaging - never rely on single factors 1