CVP CVP Cannulation Techniques and Circulatory Support 2 — Questions and Answers
Question 1: What is the purpose of a left ventricular vent during CPB?
- To administer medications directly into the LV cavity
- To prevent LV distension by draining bronchial and thebesian venous return (Correct answer)
- To continuously monitor left ventricular pressure
- To deliver retrograde cardioplegia into the LV
Correct answer: To prevent LV distension by draining bronchial and thebesian venous return
The LV vent drains non-coronary collateral blood (from bronchial and thebesian veins) that continues to enter the arrested LV during bypass, preventing distension and subendocardial injury.
Question 2: Which is the most important consideration when selecting arterial cannula size?
- Patient age and gender
- Achieving required pump flow at acceptable pressure gradient without excessive velocity (Correct answer)
- Surgeon preference and habit
- Cannula color coding for identification
Correct answer: Achieving required pump flow at acceptable pressure gradient without excessive velocity
Arterial cannula selection must balance achieving required flow rates within acceptable pressure gradients; undersized cannulas cause excessive velocity, hemolysis, and jetting injury to the aortic wall.
Question 3: What is the standard method to confirm correct venous cannula placement before initiating full bypass?
- Chest X-ray confirmation in the OR
- Observing adequate venous drainage combined with TEE visualization of cannula position (Correct answer)
- Serial blood gas analysis
- Venous pressure measurement alone
Correct answer: Observing adequate venous drainage combined with TEE visualization of cannula position
Transesophageal echocardiography directly visualizes cannula tip position while observation of adequate gravity or vacuum-assisted venous drainage confirms functional placement.
Question 4: Which complication results from advancing a two-stage venous cannula too deeply into the IVC?
- Inadequate SVC drainage with superior vena cava hypertension and facial edema (Correct answer)
- Aortic regurgitation
- Pulmonary embolism
- Ventricular fibrillation
Correct answer: Inadequate SVC drainage with superior vena cava hypertension and facial edema
Excessive IVC advancement positions the atrial drainage holes below the tricuspid valve, blocking right atrial drainage and causing SVC hypertension, facial plethora, and cerebral edema.
Question 5: For which clinical scenario is axillary artery cannulation most commonly selected?
- Routine primary CABG procedures
- Aortic dissection repair requiring antegrade cerebral perfusion when the aorta is unsafe (Correct answer)
- Elective pediatric congenital repairs
- Off-pump coronary artery bypass
Correct answer: Aortic dissection repair requiring antegrade cerebral perfusion when the aorta is unsafe
Axillary artery cannulation provides safe arterial inflow in aortic dissection and allows antegrade cerebral perfusion via the innominate artery during circulatory arrest.
Question 6: What is the function of a purse-string suture at a cannulation site?
- To secure ECG monitoring leads
- To create a hemostatic seal around the cannula insertion site that prevents bleeding (Correct answer)
- To ligate venous collateral vessels
- To anchor the cannula to the pericardium
Correct answer: To create a hemostatic seal around the cannula insertion site that prevents bleeding
Purse-string sutures placed concentrically around the cannulation site are cinched with a tourniquet to form a blood-tight seal around the cannula during bypass.
CVP CVP Cannulation Techniques and Circulatory Support 2
What is the purpose of a left ventricular vent during CPB?