How do you wean a patient off VV (Veno-Venous) ECMO (Extracorporeal Membrane Oxygenation)?

VV ECMO Weaning Protocol

VV ECMO weaning should be performed through a systematic, protocol-driven approach that gradually reduces extracorporeal support while monitoring for signs of native lung recovery to minimize mortality and morbidity.

Assessment of Readiness for Weaning

Before initiating the weaning process, evaluate:

• Improvement in underlying lung pathology (radiological improvement)
• Adequate oxygenation parameters:
  • PaO2/FiO2 ratio >150-200 mmHg on moderate ventilator settings
  • SpO2 >90% with FiO2 ≤0.5 on the ventilator
• Acceptable ventilator parameters:
  • PEEP ≤10 cmH2O
  • Plateau pressure ≤30 cmH2O
  • Driving pressure ≤15 cmH2O
• Hemodynamic stability without significant vasopressor support
• Resolution of severe acidosis (pH >7.30)

Weaning Protocol

Step 1: Daily Assessment of Native Lung Function

• Perform daily trials of reduced ECMO support to assess native lung recovery 1
• Measure arterial blood gases before and after each adjustment

Step 2: Sequential Reduction of ECMO Parameters

1. Reduce ECMO Blood Flow Rate (EBFR)

   • Gradually decrease blood flow by 0.5-1 L/min increments
   • Monitor SpO2, hemodynamics, and work of breathing
   • Target minimum flow of 2 L/min before considering complete removal 2

2. Reduce Sweep Gas Flow Rate (SGFR)

   • After optimizing EBFR, gradually decrease sweep gas flow
   • This allows for assessment of native lung CO2 clearance
   • Reduce in 0.5-1 L/min increments while monitoring PaCO2 and pH

3. Reduce FdO2 on ECMO Circuit

   • Decrease the fraction of delivered oxygen on the ECMO circuit
   • Target FdO2 of 0.21 (room air) before discontinuation

Step 3: ECMO Trial Off

When the patient tolerates:

• EBFR at minimum (2 L/min)
• SGFR at minimum (0.5-1 L/min) or completely off
• FdO2 at 0.21

Perform a trial off by:

1. Clamping the sweep gas flow completely for 1-2 hours
2. Maintaining ECMO blood flow to prevent circuit thrombosis
3. Monitoring arterial blood gases at 15 minutes, 30 minutes, and hourly

Step 4: ECMO Removal

Criteria for ECMO removal:

• Successful trial off with:
  • PaO2/FiO2 >150-200 on moderate ventilator settings
  • PaCO2 <50 mmHg with acceptable pH (>7.30)
  • No significant increase in work of breathing
  • Hemodynamic stability
• Acceptable ventilator parameters:
  • FiO2 ≤0.5
  • PEEP ≤10 cmH2O
  • Plateau pressure ≤30 cmH2O

Special Considerations

Ventilator Management During Weaning

• Two approaches exist for ventilator management during weaning 3:
  1. Weaning during controlled mechanical ventilation: May allow earlier ECMO removal with shorter ICU stays
  2. Weaning during assisted ventilation/spontaneous breathing: May be preferred for patients with prolonged ECMO runs

Monitoring During Weaning

• Continuous monitoring of:
  • Arterial blood gases
  • Respiratory mechanics (compliance, driving pressure)
  • Work of breathing
  • Hemodynamic parameters
  • Near-infrared spectroscopy for tissue oxygenation 4
• Point-of-care ultrasound to assess cardiac function and volume status

Common Pitfalls to Avoid

• Weaning too rapidly, causing respiratory decompensation
• Inadequate assessment of native lung function
• Failure to recognize recurrent lung injury
• Ignoring signs of increased work of breathing
• Premature ECMO removal leading to reintubation or ECMO reinsertion

Post-ECMO Management

• Continue lung-protective ventilation
• Gradual weaning from mechanical ventilation
• Monitor for bleeding complications related to acquired von Willebrand syndrome, which typically resolves within 24-48 hours after ECMO removal 5
• Vigilant monitoring for signs of respiratory deterioration

By following this systematic approach to VV ECMO weaning, clinicians can optimize the chances of successful liberation from extracorporeal support while minimizing complications and improving patient outcomes.