ECMO & MCS Course Summary: Drainage Insufficiency and Cannulation Strategies

 Learning Objectives for VV ECMO Session

  • Understand VV ECMO cannulation strategies.

  • Explore cannula design and sizing principles.

  • Recognize and manage recirculation and drainage insufficiency.

 Key Concepts in VV ECMO Cannulation

🔸 ECMO Overview

  • VV ECMO = “lung replacement,” supports gas exchange only.

  • VA ECMO = supports both cardiac and pulmonary functions.

🔸 Venous Drainage Site Selection

  • Blood can be drained from SVC or IVC; IVC is preferred (drains ~2/3 of venous return).

  • Drainage cannula typically placed in R femoral vein, returning oxygenated blood via internal jugular vein.

🔸 Cannula Sizing and Flow Physics

  • Based on Poiseuille’s Law: shorter, wider cannulas reduce resistance and improve drainage.

  • Choose cannula size <80% of vein diameter.

  • 1 French = 0.33 mm (e.g., 23 Fr ≈ 7.6 mm outer diameter).

🔧 Cannulation Techniques

  • Ultrasound guidance: Now standard of care to reduce vascular complications.

  • Fluoroscopy (C-arm): Use in cath lab or hybrid OR to ensure correct guidewire and cannula path.

  • Echocardiography (TEE/bedside): Mandatory for dual-lumen cannula placement; strongly recommended for all.

Dual Cannula Configurations

  • Femoral-femoral: Drain via one femoral vein, return via contralateral femoral.

  • Femoral-jugular: Drain via femoral vein, return via internal jugular vein.

  • Drainage cannula: Multi-stage, 20 cm of side holes to ensure hepatic vein drainage.

  • Return cannula: Short tip-focused cannula, positioned near tricuspid valve.

Single Dual-Lumen Cannula (e.g., Avalon)

  • Single access via right IJ vein.

  • Drainage ports in IVC and SVC, infusion directed toward tricuspid valve.

  • Requires expert TEE guidance.

  • Pros: Enables mobilization, fewer access sites.

  • Cons: Technically challenging, risk of misdirection or cardiac injury.

🔴 Recirculation: Detection and Management

What is Recirculation?

  • Occurs when oxygenated blood from return cannula is immediately sucked into drainage cannula.

  • Results in inefficient oxygen delivery.

Causes:

  • Cannulas too close together (<8–10 cm apart).

  • Improper orientation (e.g., not facing tricuspid valve).

  • Excessively high flows in circuit.

Diagnosis:

  • Persistent hypoxia despite adequate ECMO flow and functioning membrane.

  • High post-oxygenator saturation (>80%) with low systemic saturation.

Troubleshooting Hypoxia

  1. Confirm color of lines: Drain = blue, Return = red.

  2. Gas flow = blood flow (1:1 ratio).

  3. Blender set to 100% O₂.

  4. Ensure flow calibration completed.

  5. Inspect membrane for clot burden.

  6. Check for access insufficiency: unstable flows, swinging pressures, low inlet pressures.

  7. Test pre-oxygenator venous saturation:

    • <60% → high oxygen consumption.

    • 80% → recirculation.

✅ Summary Comparison: Dual Lumen vs Dual Cannula VV ECMO

🏁 Final Takeaways

  • All cannulation strategies are valid if appropriately executed.

  • Positioning and imaging are key to avoid recirculation and access insufficiency.

  • Use simulation, echo, and flow monitoring to optimize patient outcomes.

  • Build team competency with checklists, structured training, and interdisciplinary collaboration.

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