What are the anesthetic considerations for non‑cardiac surgery in patients with Fontan physiology?

Anesthetic Considerations for Non-Cardiac Surgery in Fontan Patients

Specialized anesthesia and perioperative management, including cardiac and nutritional optimization, is crucial in Fontan patients, with the primary anesthetic goal being preservation of adequate central venous pressure (CVP), avoidance of systemic hypotension, and ensuring proper flow through the pulmonary circulation 1.

Core Hemodynamic Principles

The Fontan circulation is fundamentally different from normal physiology—it relies on elevated, nonpulsatile venous pressure to drive passive blood flow through the pulmonary vascular bed without a subpulmonary ventricle 2. This creates chronically elevated CVP, decreased preload to the systemic ventricle, and impaired cardiac output augmentation during stress.

Critical Hemodynamic Goals:

• Maintain adequate CVP to ensure pulmonary blood flow
• Avoid systemic hypotension (reduces preload further)
• Prevent increases in pulmonary vascular resistance (tachycardia, hypoxia, hypercarbia, acidosis)
• Preserve sinus rhythm (atrial arrhythmias are poorly tolerated)
• Maintain preload while avoiding volume overload

Risk Stratification and Surgical Setting

Fontan patients should undergo non-cardiac surgery at specialized centers with expertise in adult congenital heart disease (ACHD), particularly for intermediate to high-risk procedures 3, 4. The ACC/AHA guidelines explicitly state that patients with prior Fontan procedure are select high-risk populations requiring management at ACHD centers under all circumstances unless the operation is an absolute emergency 3.

Risk Assessment:

• Low composite risk: Standard monitoring may suffice 4
• Intermediate/high composite risk: Requires invasive monitoring and ICU admission 4
• Ejection fraction <30%: Associated with significantly worse outcomes; one study showed patients with EF 22-28% had non-resolving complications including death 5

Monitoring Requirements

For intermediate to high-risk procedures, continuous invasive arterial pressure monitoring and regular measurement of PaO₂ and PaCO₂ are essential, with addition of continuous central venous pressure monitoring specifically for Fontan circulation 4.

Specific Monitoring:

• Central venous catheter: Continuous CVP monitoring 1
• Transesophageal echocardiogram: Monitor cardiac contractility and ventricular function 1
• Invasive arterial line: Continuous blood pressure and arterial blood gas sampling 4, 5
• Meticulous IV line management: Use filters to prevent paradoxical air embolism in patients with residual shunts 3

Anesthetic Technique Selection

The anesthetic strategy should prioritize minimizing hemodynamic and ventilatory variations, with peripheral locoregional anesthesia preferred over general anesthesia when feasible, and titrated neuraxial techniques over non-titrated approaches 4.

General Anesthesia Considerations:

• Choose agents that maintain hemodynamic stability
• Avoid agents causing significant systemic vasodilation or myocardial depression
• Maintain sinus rhythm and normotension 6
• Phenylephrine or norepinephrine can increase blood pressure in patients without significant coronary disease 6

Regional Anesthesia:

• Preferred when appropriate for the surgical procedure 4, 7
• Neuraxial techniques should use high-dilution local anesthetics combined with opioids to avoid rapid systemic pressure changes 6
• Peripheral nerve blocks successfully used (e.g., supraclavicular brachial plexus block) 7
• No studies demonstrate increased risk from local anesthetics in CHD patients 4

Laparoscopic vs. Open Surgery:

For abdominal procedures, laparoscopic approach appears safer with fewer postoperative complications, though pneumoperitoneum can modify abdominal and intrathoracic pressures, hindering cardiac preload 1. Open abdominal surgeries carry high risk of bleeding and cardiac decompensation 1.

Perioperative Management

Preoperative Optimization:

• Cardiac function assessment (echocardiography, consider cardiac MRI)
• Evaluation for arrhythmias (common in 25% of patients) 8
• Assessment of ventricular function and atrioventricular valve regurgitation
• Nutritional status optimization 1
• Review anticoagulation status (many require warfarin for atrial arrhythmias or thrombus) 3

Intraoperative Management:

• Fluid balance is critical: Judicious administration to maintain adequate preload without causing pulmonary edema 3
• Avoid tachycardia: Reduces diastolic filling time and increases CVP
• Prevent hypoxemia and hypercarbia: Both increase pulmonary vascular resistance
• Maintain normothermia
• Use of inotropes: Associated with reduced odds of same-day discharge (OR 0.48) 9, suggesting these patients require closer monitoring

Postoperative Care:

Patients with intermediate or high composite risk scores should be systematically managed in a critical care unit postoperatively 4. This is crucial because 60% of complications in ACHD patients occur during the postoperative period 4.

• ICU admission for 24-72 hours for intermediate/high-risk procedures 6
• Continued invasive monitoring
• Close attention to fluid balance
• Early detection of arrhythmias, hypotension, or hypoxemia
• Overnight admission appropriate for most cases 5

Common Pitfalls and Complications

Major Concerns:

1. Bleeding risk: Elevated CVP increases surgical bleeding, particularly in hepatic procedures 1
2. Cardiac decompensation: From fluid shifts, blood loss, or increased afterload
3. Arrhythmias: Atrial tachyarrhythmias cause serious hemodynamic compromise 3
4. Hypoxemia and hypotension: Integrally linked in Fontan physiology 4
5. Thromboembolism: 19% incidence of thrombotic complications in long-term follow-up 8

Specific Complications:

• Perioperative complications occurred in 31% of non-cardiac surgeries in one series 5
• One study showed 36.3% same-day discharge rate, with major surgical procedures (OR 0.17) and inotrope use (OR 0.48) reducing likelihood 9
• Mortality risk exists, particularly with EF <30% 5

Special Populations

Fontan with Liver Disease:

Fontan-associated liver disease (FALD) is increasingly common. For hepatic procedures, extraordinary surgical maneuvers (Pringle maneuver, reverse Trendelenburg position, veno-venous bypassing) may be needed due to massive bleeding risk from high CVP 1.

Pregnancy and Delivery:

Requires specialized planning with ACHD experts, though this is beyond the scope of non-cardiac surgery 3.

Contraindications to Same-Day Discharge

Based on evidence, same-day discharge is reduced by:

• Increased chronic condition index (OR 0.91 per additional condition) 9
• Major surgical procedures (OR 0.17) 9
• Intraoperative inotrope use (OR 0.48) 9
• Preoperative admission status (OR 0.24) 9

Well-selected patients with Fontan physiology can undergo anesthesia without complications and be discharged same day 9, but this requires careful patient selection and low-risk procedures.

Consultation Requirements

Consultation with ACHD experts regarding risk assessment is recommended for all Fontan patients undergoing non-cardiac surgery, and consultation with a cardiac anesthesiologist is recommended for moderate- and high-risk patients 3. Electrophysiology consultation is vital for arrhythmia management 3.