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Worsening hypoxemia is not uncommon upon initiation of VV ECMO for severe ARDS as tidal volumes drop to double digits (often <20cc) after transition to “lung rest” ventilator settings. The following are strategies to improve peripheral oxygenation:
1. Increase the blood’s oxygen content
- Ensure FIO2 of ECMO sweep gas is 1
- Increase ECMO blood flow
o Limited by cannula size and configuration – may require placement of additional venous drainage cannula
o Also limited by greater risk of recirculation and hemolysis
- Increase blood oxygen-carrying capacity
o Transfuse PRBCs – some advocate for goal hemoglobin 12-14, though institutional practices vary significantly
2. Minimize recirculation
- Maximize distance between drainage and return cannulae
3. Reduce oxygen consumption
- Optimize sedation and neuromuscular blockade. (This is not the appropriate scenario for awake ECMO.)
- Consider therapeutic hypothermia
4. Decrease cardiac output and intrapulmonary shunt
- Consider beta blocker (esmolol) infusion
- Prone positioning (only if staff are experienced with proning on ECMO as this poses significant risk of cannula displacement)
5. Consider switching to hybrid configuration (VVA – continued venous drainage cannula and venous return cannula with addition of arterial return cannula)
References
Montisci A, Maj G, Zangrillo A, Winterton D, Pappalardo F. Management of Refractory Hypoxemia During Venovenous Extracorporeal Membrane Oxygenation for ARDS. ASAIO J. 2015;61(3):227-236. doi:10.1097/MAT.0000000000000207.