What are the anesthetic considerations for a patient with tetralogy of Fallot?

Anesthetic Considerations for Tetralogy of Fallot

Critical Preoperative Assessment

All patients with TOF—whether repaired or unrepaired—require comprehensive hemodynamic evaluation before any anesthetic, as residual lesions are nearly universal and directly impact anesthetic tolerance. 1

Mandatory Imaging and Functional Studies

• Obtain comprehensive echocardiography to assess RV size and function, severity of pulmonary regurgitation, residual RVOT obstruction, tricuspid regurgitation, and aortic root dilation 1
• Review cardiac MRI for precise RV volume quantification and pulmonary regurgitation severity, as echocardiography commonly underestimates these parameters 1
• Analyze 12-lead ECG specifically for QRS duration >180 ms, which indicates significantly increased risk of ventricular tachycardia and sudden cardiac death 2, 1
• Assess exercise tolerance objectively through formal exercise testing to evaluate functional capacity and detect exertional arrhythmias 1

Key Residual Pathology Requiring Identification

• Pulmonary regurgitation (present in 40-85% of repaired patients 5-10 years post-repair) leading to progressive RV dilation and dysfunction 2, 1
• Residual RVOT obstruction with RV systolic pressure >50 mmHg or RV/LV pressure ratio >0.7 1
• RV dysfunction from chronic volume overload, which limits cardiac reserve even in asymptomatic patients 1, 3
• Tricuspid regurgitation secondary to RV dilation 1
• Arrhythmias including atrial flutter, atrial fibrillation, and ventricular tachycardia related to surgical scarring and hemodynamic abnormalities 2, 1
• Coronary artery anomalies, particularly anomalous left anterior descending coronary arteries crossing the RVOT 2, 4

Intraoperative Hemodynamic Management

Primary Goals for RV Function Preservation

Maintain RV function by optimizing preload, reducing afterload, and supporting contractility throughout the anesthetic. 1

• Optimize preload carefully: Decreased preload reduces RV filling and cardiac output, potentially worsening cyanosis in patients with residual shunts 5
• Minimize pulmonary vascular resistance by avoiding hypoxia, hypercarbia, acidosis, hypothermia, and excessive positive pressure ventilation 1
• Prevent tachycardia, which reduces diastolic filling time and coronary perfusion, potentially triggering arrhythmias 5, 1
• Maintain systemic vascular resistance to prevent right-to-left shunting if residual ASD/VSD is present 1

Monitoring Requirements

• Use transesophageal echocardiography to continuously monitor RV function intraoperatively 3
• Have defibrillator immediately available and antiarrhythmic medications prepared given the high arrhythmia risk 1
• Monitor for signs of hypercyanotic spells in unrepaired or palliated patients, as hypovolemia and decreased systemic vascular resistance increase right-to-left shunting 6, 7

Pharmacologic Strategy

• Administer inotropic vasodilators and alpha-adrenergic agents as appropriate to maintain RV contractility while managing systemic vascular resistance 3
• Treat underlying hemodynamic causes of arrhythmias including hypovolemia, hypoxia, acidosis, and electrolyte abnormalities immediately 1

Special Considerations by Patient Type

Repaired TOF Patients

• Do not assume repaired TOF patients are "normal"—residual hemodynamic abnormalities are common and significantly affect tolerance to volume loss and anesthetic stress 5, 1
• Patients with significant residual lesions (moderate-to-severe RV dysfunction or enlargement) have limited cardiac reserve and require lower thresholds for intervention 5
• Excessive positive pressure ventilation increases RV afterload and impairs venous return, risking decompensation 1

Unrepaired or Palliated TOF Patients

• These patients maintain a delicate hemodynamic balance that is highly sensitive to volume status 5
• The degree of cyanosis is determined by RVOT obstruction severity and resultant right-to-left shunting 5
• Hypotension can precipitate right-to-left shunting if residual septal defects exist 5
• Right-to-left shunting and hyperviscosity predispose to brain abscess and neurological complications 6

Perioperative Complications and Management

Arrhythmias (Most Critical Complication)

• Ventricular tachycardia related to surgical scarring and hemodynamic abnormalities is a significant risk, particularly with QRS >180 ms 2, 1
• Atrial arrhythmias (flutter and fibrillation) occur due to atrial dilation 1
• Arrhythmias reflect severe hemodynamic difficulties and mandate immediate evaluation 2

Bleeding Complications

• Vascular injury during removal of adhesions during re-sternotomy is frequent 3
• Bleeding from collateral vessels is a common complication in re-operative cases 3

Non-Cardiac Surgery Considerations

• Maintain normothermia to prevent increased pulmonary vascular resistance 1
• Ensure adequate pain control to prevent tachycardia and increased oxygen consumption 1

Critical Pitfalls to Avoid

• Never underestimate RV dysfunction even in asymptomatic patients, as decompensation can occur rapidly under anesthesia 1
• Inadequate preoperative assessment (lacking recent echocardiography and knowledge of residual lesions) significantly increases risk 1
• Never ignore QRS duration >180 ms, which significantly increases arrhythmia risk and mandates enhanced monitoring 1
• Avoid tachycardia, which reduces diastolic filling time and coronary perfusion 5, 1
• Never ignore signs of decompensation such as worsening cyanosis, syncope, or palpitations, which mandate immediate evaluation 5