ECMO & MCS Course Summary: Drainage Insufficiency and Cannulation Strategies
Learning Objectives for VV ECMO Session
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Understand VV ECMO cannulation strategies.
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Explore cannula design and sizing principles.
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Recognize and manage recirculation and drainage insufficiency.
Key Concepts in VV ECMO Cannulation
🔸 ECMO Overview
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VV ECMO = “lung replacement,” supports gas exchange only.
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VA ECMO = supports both cardiac and pulmonary functions.
🔸 Venous Drainage Site Selection
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Blood can be drained from SVC or IVC; IVC is preferred (drains ~2/3 of venous return).
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Drainage cannula typically placed in R femoral vein, returning oxygenated blood via internal jugular vein.
🔸 Cannula Sizing and Flow Physics
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Based on Poiseuille’s Law: shorter, wider cannulas reduce resistance and improve drainage.
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Choose cannula size <80% of vein diameter.
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1 French = 0.33 mm (e.g., 23 Fr ≈ 7.6 mm outer diameter).
🔧 Cannulation Techniques
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Ultrasound guidance: Now standard of care to reduce vascular complications.
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Fluoroscopy (C-arm): Use in cath lab or hybrid OR to ensure correct guidewire and cannula path.
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Echocardiography (TEE/bedside): Mandatory for dual-lumen cannula placement; strongly recommended for all.
Dual Cannula Configurations
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Femoral-femoral: Drain via one femoral vein, return via contralateral femoral.
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Femoral-jugular: Drain via femoral vein, return via internal jugular vein.
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Drainage cannula: Multi-stage, 20 cm of side holes to ensure hepatic vein drainage.
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Return cannula: Short tip-focused cannula, positioned near tricuspid valve.
Single Dual-Lumen Cannula (e.g., Avalon)
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Single access via right IJ vein.
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Drainage ports in IVC and SVC, infusion directed toward tricuspid valve.
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Requires expert TEE guidance.
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Pros: Enables mobilization, fewer access sites.
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Cons: Technically challenging, risk of misdirection or cardiac injury.
🔴 Recirculation: Detection and Management
What is Recirculation?
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Occurs when oxygenated blood from return cannula is immediately sucked into drainage cannula.
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Results in inefficient oxygen delivery.
Causes:
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Cannulas too close together (<8–10 cm apart).
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Improper orientation (e.g., not facing tricuspid valve).
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Excessively high flows in circuit.
Diagnosis:
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Persistent hypoxia despite adequate ECMO flow and functioning membrane.
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High post-oxygenator saturation (>80%) with low systemic saturation.
Troubleshooting Hypoxia
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Confirm color of lines: Drain = blue, Return = red.
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Gas flow = blood flow (1:1 ratio).
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Blender set to 100% O₂.
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Ensure flow calibration completed.
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Inspect membrane for clot burden.
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Check for access insufficiency: unstable flows, swinging pressures, low inlet pressures.
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Test pre-oxygenator venous saturation:
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<60% → high oxygen consumption.
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80% → recirculation.
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✅ Summary Comparison: Dual Lumen vs Dual Cannula VV ECMO
🏁 Final Takeaways
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All cannulation strategies are valid if appropriately executed.
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Positioning and imaging are key to avoid recirculation and access insufficiency.
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Use simulation, echo, and flow monitoring to optimize patient outcomes.
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Build team competency with checklists, structured training, and interdisciplinary collaboration.