ECMO Cannulation Techniques and Strategies 3 — Questions and Answers
Question 1: In neonatal ECMO, the right internal jugular vein is the preferred venous access site primarily because:
- It has the highest flow capacity relative to size
- It provides the most direct path to the right atrium (Correct answer)
- It avoids the risk of pneumothorax
- It is easiest to compress for hemostasis
Correct answer: It provides the most direct path to the right atrium
The right internal jugular vein offers the most direct, shortest course to the right atrium, optimizing drainage cannula positioning in neonates.
Question 2: What is 'chattering' of the ECMO circuit, and which cannula is most often implicated?
- Arterial cannula vibration causing hemolysis
- Intermittent venous line collapse due to inadequate preload at the drainage cannula (Correct answer)
- Oxygenator membrane flutter from high sweep gas flows
- Pump head vibration from air in the circuit
Correct answer: Intermittent venous line collapse due to inadequate preload at the drainage cannula
Chattering refers to cyclical collapse and re-expansion of the venous drainage line when the cannula cannot provide sufficient blood to the pump.
Question 3: During cannulation for VV-ECMO using a bicaval dual-lumen cannula (e.g., Avalon), the return lumen is designed to direct oxygenated blood toward:
- The pulmonary artery
- The tricuspid valve (Correct answer)
- The coronary sinus
- The left atrium via a patent foramen ovale
Correct answer: The tricuspid valve
The return lumen of a bicaval dual-lumen cannula is angled to direct flow across the tricuspid valve into the right ventricle, reducing recirculation.
Question 4: Why is systemic anticoagulation typically administered before the first dilator is placed during ECMO cannulation?
- To prevent clot formation on instrumentation and in the cannula (Correct answer)
- To lower blood pressure for easier vessel access
- To reduce vasospasm at the puncture site
- To increase cardiac output during the procedure
Correct answer: To prevent clot formation on instrumentation and in the cannula
Heparin is given prior to dilation to prevent thrombus formation on the guidewire, dilators, and cannula surfaces during insertion.
Question 5: In a patient undergoing right internal jugular VV-ECMO cannulation, the drainage cannula tip should ideally rest at:
- The right atrium-IVC junction (Correct answer)
- The right atrium-SVC junction (cavoatrial junction)
- The right ventricle
- The hepatic vein ostium
Correct answer: The right atrium-IVC junction
The drainage tip at the IVC-RA junction maximizes venous return from both the IVC and RA while avoiding right ventricular irritation.
Question 6: What is the Seldinger technique in the context of ECMO cannulation?
- Direct surgical cutdown and cannula insertion under direct visualization
- Needle puncture followed by guidewire insertion, then cannula advancement over the wire (Correct answer)
- Cannula insertion using a sheath-based rapid deployment system
- Two-stage dilation using balloon angioplasty
Correct answer: Needle puncture followed by guidewire insertion, then cannula advancement over the wire
The Seldinger technique involves placing a guidewire through an introducer needle, then advancing dilators and ultimately the cannula over the wire.
Question 7: Which factor most increases the risk of acute aortic dissection during femoral arterial cannulation for ECMO?
- Use of wire-reinforced cannulas
- Pre-existing aortic aneurysm or dissection (Correct answer)
- High ECMO flow rates above 5 L/min
- Use of ultrasound guidance for access
Correct answer: Pre-existing aortic aneurysm or dissection
Pre-existing aortic pathology such as an aneurysm or dissection greatly increases the risk of propagation or injury during retrograde arterial cannulation.
ECMO Cannulation Techniques and Strategies 3
In neonatal ECMO, the right internal jugular vein is the preferred venous access site primarily because: