Weaning from VV-ECMO
To wean VV-ECMO, reduce the oxygen concentration in the ECMO air-oxygen mixer to 21%, decrease air flow to zero, and maintain minimal ventilator support for 2-3 hours; if the patient maintains SpO2 >92%, respiratory rate <25 breaths/min, and normal PaCO2, proceed with decannulation. 1
Stepwise Weaning Protocol
Initial Assessment Phase
- Perform a sweep gas-off trial (SGOT) by turning off the sweep gas flow while maintaining blood flow to assess native lung recovery 2, 3
- Monitor continuously for 2-3 hours during the trial period 1
- Ensure ventilator settings remain at non-injurious levels throughout the assessment 3
Critical Parameters to Monitor During Weaning
Respiratory Parameters:
- SpO2 must remain >92% throughout the trial 1
- Respiratory rate should stay ≤25 breaths/min 1
- PaCO2 must normalize without ECMO support 1
- Tidal volume per predicted body weight should remain low - higher tidal volumes during SGOT predict unsafe liberation (OR 1.58,95% CI 1.05-2.40) 3
Hemodynamic Parameters:
- Heart rate should remain stable - elevated heart rate during SGOT predicts unsafe liberation (OR 1.07,95% CI 1.022-1.15) 3
- Monitor for hemodynamic instability as a contraindication to proceeding 3
Ventilatory Effort:
- Esophageal pressure swings should be <13 cm H2O if monitoring is available - higher inspiratory efforts (18 cm H2O vs 9 cm H2O) are associated with unsafe liberation 3
- Excessive inspiratory effort indicates the patient is not ready for decannulation 3
Staged Approach to Weaning
Step 1: Optimize ECMO Blood Flow Rate (EBFR)
- Perform daily assessments of native lung function to determine appropriate blood flow requirements 2
- Reduce EBFR based on improving native lung function rather than maintaining unnecessarily high flows 2
- This allows for more restrictive fluid balance and lighter sedation as recovery progresses 2
Step 2: Optimize Sweep Gas Flow Rate (SGFR)
- After optimizing blood flow, adjust sweep gas flow to match physiologic CO2 removal needs 2
- This staged approach utilizes the "decoupling" of oxygenation and decarboxylation unique to ECMO support 2
Step 3: Reduce FiO2 in Sweep Gas
- Decrease the fraction of delivered oxygen (FdO2) in sweep gas to 21% as the final step before trial off 1, 2
Criteria for Safe Liberation
Safe liberation is defined as avoiding all of the following within 48 hours post-decannulation: 3
- ECMO recannulation
- Increased mechanical ventilation support requirements
- Need for rescue therapy (prone positioning, inhaled pulmonary vasodilators)
- Hemodynamic instability
Patients who fail to meet these criteria have significantly worse outcomes including longer mechanical ventilation duration, ICU length of stay, and hospital length of stay 3
Common Pitfalls to Avoid
Do not proceed with decannulation if: 3
- Tidal volumes are escalating during the trial (indicates inadequate native lung recovery)
- Heart rate is rising (suggests cardiovascular stress)
- Ventilatory ratio is worsening (indicates impaired CO2 clearance)
- Patient demonstrates high inspiratory effort with excessive esophageal pressure swings
Avoid maintaining unnecessarily high ECMO flows once native lung function begins recovering, as this requires deeper sedation and less restrictive fluid management, both potentially harmful during ARDS recovery 2
Post-Decannulation Considerations
- Acquired von Willebrand syndrome (AVWS) develops in nearly all ECMO patients but resolves rapidly within 12-48 hours after weaning 1, 4
- Perform neurological assessment before and after weaning to evaluate for acute brain injury 4
- Continue monitoring for 48 hours post-decannulation to ensure sustained safe liberation 3