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Final FRCA - FOB > Cardiac - Fontan Circulation > Flashcards

Cardiac - Fontan Circulation Flashcards

1
Q

What is the purpose of the Fontan procedure?

A

To reroute systemic venous blood directly to the pulmonary arteries in patients with single-ventricle physiology, bypassing the heart.

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2
Q

Which conditions commonly lead to a Fontan circulation?

A

Tricuspid atresia, hypoplastic left heart syndrome, pulmonary atresia with intact septum, double inlet left ventricle, double outlet right ventricle and complete atrioventricular septal defect.

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3
Q

What are essential preconditions for a successful Fontan operation?

A

Sinus rhythm, adequate pulmonary artery size, and good ventricular function.

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4
Q

Why is the Fontan procedure staged?

A

To reduce perioperative risk, allow physiological adaptation, and accommodate pulmonary vascular resistance maturation.

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5
Q

Why is the Fontan circulation contraindicated in neonates?

A

Because neonatal pulmonary vascular resistance is physiologically high.

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6
Q

What is the main feature of a single-ventricle circulation before Fontan completion?

A

Parallel circulation with mixing of oxygenated and deoxygenated blood.

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7
Q

What did Fontan and Baudet originally develop the operation for?

A

As palliation for tricuspid atresia.

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8
Q

What is the long-term goal of Fontan physiology?

A

To separate systemic and pulmonary circulations without requiring a second ventricle.

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9
Q

What is the main functional limitation in Fontan patients?

A

Preload limitation leading to reduced cardiac output, especially during exercise.

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10
Q

What causes desaturation even after Fontan completion?

A

Right-to-left shunting via fenestration or intrapulmonary shunts.

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11
Q

What is done during Stage 1 of Fontan palliation?

A

A systemic-pulmonary shunt is created to provide controlled pulmonary blood flow.

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12
Q

What type of shunt is commonly used in Stage 1?

A

A 3–4 mm synthetic conduit between a systemic artery and the pulmonary artery.

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13
Q

What is the main goal of Stage 1 palliation?

A

Ensure adequate oxygenation while avoiding pulmonary overcirculation.

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14
Q

What is the Glenn operation in Stage 2?

A

Anastomosis of the superior vena cava to the right pulmonary artery (bidirectional Glenn).

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15
Q

When is Stage 2 typically performed?

A

At 2–6 months of age when pulmonary vascular resistance has decreased.

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16
Q

What is the function of the Glenn shunt?

A

To reduce ventricular volume load and provide passive pulmonary blood flow.

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17
Q

What is the typical result of Stage 3 (Fontan completion)?

A

Total cavopulmonary connection of both venae cavae to the pulmonary arteries.

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18
Q

What surgical method is commonly used in Stage 3?

A

Extracardiac conduit from inferior vena cava to pulmonary artery.

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19
Q

Why is a fenestration sometimes included in Stage 3?

A

To reduce venous congestion and improve cardiac output at the expense of mild desaturation.

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20
Q

What is the main cause of mortality in Fontan patients?

A

Complications during or after Stage 1 palliation.

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21
Q

Why do Fontan patients have poor exercise tolerance?

A

Due to inability to increase stroke volume and preload limitation.

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22
Q

What changes occur in the ventricle over time in Fontan physiology?

A

Dilatation, hypertrophy, and impaired systolic and diastolic function.

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23
Q

What proportion of patients show myocardial dysfunction at 10 years?

A

Around 70%.

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24
Q

Why are atrial arrhythmias common in Fontan patients?

A

Atrial dilation, surgical scarring near the sinus node, and elevated atrial pressures.

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25
What is the main risk associated with arrhythmias in these patients?
Haemodynamic collapse and increased risk of thromboembolism.
26
What is protein-losing enteropathy?
Excessive loss of proteins into the gut due to venous congestion and inflammation.
27
What are signs of protein-losing enteropathy?
Oedema, ascites, immunodeficiency, malabsorption, hypocalcaemia.
28
What is the survival after diagnosis of protein-losing enteropathy?
60% at 5 years and 20% at 10 years.
29
Why are Fontan patients at high risk of thromboembolism?
Low-flow states, atrial scarring, arrhythmias, and hypercoagulability.
30
What is the recommended thromboprophylaxis?
Warfarin or antiplatelet agents.
31
What determines pulmonary blood flow in Fontan circulation?
The pressure gradient between central venous pressure and left atrial pressure.
32
What factors increase pulmonary vascular resistance and should be avoided?
Hypoxia, hypercarbia, acidosis, pain, a-agonist drugs.
33
What drugs should be used with caution in Fontan patients?
Beta-blockers and a-agonists.
34
Why is sinus rhythm important in Fontan physiology?
It optimizes ventricular filling and atrial emptying.
35
Why must hypovolaemia be avoided in Fontan patients?
It reduces central venous pressure and pulmonary blood flow, leading to decreased cardiac output.
36
What should be included in preoperative workup?
ECG, echocardiography, coagulation status, organ function tests.
37
What monitoring is essential during major surgery?
Invasive arterial pressure, central venous pressure, and possibly transoesophageal echo.
38
Why is propofol relatively safe for induction?
It causes minimal myocardial depression if volume status is optimized.
39
Why should high concentrations of volatile agents be avoided?
They can cause arrhythmias and myocardial depression.
40
What ventilation settings are ideal for Fontan patients?
Low PEEP, short inspiratory time, low tidal volumes (5–6 ml/kg).
41
Why is pregnancy high risk in Fontan patients?
Increased blood volume and heart rate can unmask ventricular dysfunction.
42
What is the preferred method for labour analgesia?
Epidural anaesthesia with gradual dosing and careful volume control.
43
Why are assisted deliveries often recommended?
To avoid straining and increased intrathoracic pressure, which impairs pulmonary blood flow.
44
When should warfarin be converted to heparin in pregnancy?
In late pregnancy, to allow for safer neuraxial anaesthesia.
45
What causes increased thromboembolic risk in pregnancy for these patients?
Combined pro-thrombotic state of pregnancy and Fontan physiology.
46
How is fluid therapy managed during labour?
Guided by central venous pressure and slow titration to avoid overload or hypovolaemia.
47
Can Fontan patients undergo laparoscopic surgery?
Yes, if intra-abdominal pressure is <10 mmHg and ventilation is well managed.
48
What risks are specific to laparoscopic surgery in Fontan patients?
Hypercarbia, venous compression, gas embolism, increased pulmonary vascular resistance.
49
What postoperative monitoring is necessary after major surgery?
Oxygen saturation, fluid balance, and thromboprophylaxis for at least 24 hours.
50
What are the discharge criteria after day surgery for Fontan patients?
Stable saturations, no bleeding, good pain control, normal oral intake, adequate support at home.
51
In a normal heart, what drives pulmonary blood flow?
The right ventricle pumps deoxygenated blood into the pulmonary arteries.
52
How is pulmonary blood flow achieved in a Fontan circulation?
Passive flow from the systemic veins into the pulmonary arteries, driven by a central venous to atrial pressure gradient.
53
What anatomical structure is bypassed in the Fontan circulation?
The right ventricle.
54
What is the typical central venous pressure in a well-compensated Fontan patient?
Around 12 mmHg.
55
What is the typical left atrial pressure in a Fontan patient?
Around 5 mmHg.
56
What is the normal transpulmonary pressure gradient in Fontan circulation?
Around 7 mmHg.
57
Why is pulmonary vascular resistance crucial in the Fontan circulation?
Because high resistance impedes passive pulmonary blood flow, reducing preload and cardiac output.
58
What causes chronic hypoxaemia in Fontan physiology?
Incomplete separation of venous and arterial blood, residual shunts, or intrapulmonary shunting.
59
What is the role of the extracardiac conduit in Fontan completion?
It connects the inferior vena cava to the pulmonary arteries without traversing the heart.
60
What is a fenestration in the context of Fontan surgery?
A small, intentional hole between the conduit and the atrium to decompress high venous pressures.
61
How does a fenestration improve Fontan circulation?
By reducing venous congestion and increasing preload at the cost of some desaturation.
62
What happens to preload and cardiac output during exertion in Fontan patients?
They are limited due to lack of a subpulmonary ventricle and inability to significantly increase venous return.
63
What is the main circulatory limitation in Fontan physiology?
Preload dependence and lack of pulsatile pulmonary flow.
64
What organ is thought to secrete a substance promoting pulmonary vascular health, and why is this relevant?
The liver; its absence from pulmonary perfusion may contribute to arteriovenous malformations.
65
Why are intrapulmonary shunts more common in Fontan patients?
Due to non-pulsatile flow and lack of hepatic-derived factors in pulmonary circulation.
66
What is the most important goal of anaesthesia in Fontan patients?
Maintain adequate preload and minimize increases in pulmonary vascular resistance.
67
Why is spontaneous ventilation often preferred for short procedures?
It preserves negative intrathoracic pressure and enhances venous return.
68
What is the risk of positive pressure ventilation in Fontan physiology?
It increases intrathoracic pressure, reducing venous return and cardiac output.
69
What mechanical ventilation settings are recommended for Fontan patients?
Low positive end-expiratory pressure, low tidal volume (5–6 mL/kg), and short inspiratory time.
70
Why is maintaining normocapnia important in Fontan anaesthesia?
Hypercarbia increases pulmonary vascular resistance, reducing pulmonary blood flow.
71
Why should hyperoxia be avoided in some Fontan patients?
Because high oxygen can paradoxically cause pulmonary vasoconstriction in chronic hypoxaemia.
72
Why is epidural anaesthesia considered safe in many Fontan patients?
It allows controlled analgesia with minimal haemodynamic disturbance if volume is maintained.
73
What is the main concern with neuraxial blocks in Fontan patients?
Risk of vasodilation and hypotension, which may reduce pulmonary flow and preload.
74
How should fluid status be monitored intraoperatively?
Via central venous pressure trends, transoesophageal echo, or oesophageal Doppler.
75
What is the danger of even moderate hypotension in Fontan patients?
It can critically reduce the pressure gradient for pulmonary flow, impairing perfusion.
76
What types of drugs should be avoided in Fontan anaesthesia?
Negative inotropes and drugs that increase pulmonary vascular resistance.
77
What drugs are considered cardio-stable for maintenance of anaesthesia?
Low-dose volatile agents with short-acting opioids like remifentanil.
78
Why is preoxygenation important before induction in these patients?
To prevent hypoxia, which increases pulmonary vascular resistance.
79
How is intraoperative hypoxaemia managed in a Fontan patient?
Optimize ventilation, correct acidosis, increase preload, and rule out shunting or embolism.
80
What is the anaesthetic risk of an open fenestration during major surgery?
Paradoxical embolism of air or fat through the right-to-left shunt.

Final FRCA - FOB (3 decks)

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