Residency · Residency · Anesthesiology

The Pediatric Patient with Congenital Heart Disease for Non-Cardiac Surgery

Introduction

Approximately 1 in 100 live births is affected by congenital heart disease (CHD). Advances in surgical repair and medical management have dramatically improved survival, and these children frequently present for non-cardiac surgical procedures. The anesthesiologist must understand the underlying cardiac physiology, prior surgical interventions, and the hemodynamic goals specific to each lesion.

General Preoperative Assessment

The preoperative evaluation should begin with a review of the specific cardiac diagnosis, prior surgical repairs or palliative procedures, and current functional status. Recent echocardiography and cardiology consultation should be obtained when indicated. Current medications such as digoxin, diuretics, ACE inhibitors, anticoagulants, and prostaglandin E1 must be reviewed.

Key questions that drive the anesthetic plan include: Is there a shunt, and what is its direction (left-to-right, right-to-left, or bidirectional)? Is the circulation in series or parallel? What is the current ventricular function? Is there pulmonary hypertension? Is the child cyanotic at baseline, and what is the baseline SpO2? Are there associated syndromes such as DiGeorge/22q11 deletion or Down syndrome?

Laboratory studies should include a CBC, electrolytes, coagulation studies, and a recent ECG. Subacute bacterial endocarditis prophylaxis should be administered when indicated.

Classification of Lesions

Left-to-Right Shunts (Acyanotic)

Left-to-right shunt lesions include ventricular septal defect, atrial septal defect, patent ductus arteriosus, and atrioventricular septal defect. Blood flows from the high-pressure systemic circulation to the lower-pressure pulmonary circulation, resulting in pulmonary overcirculation, volume overload, and potential congestive heart failure.

The anesthetic goals for these lesions are to avoid further decreasing pulmonary vascular resistance (which would worsen the shunt), avoid excessive increases in SVR, and prevent hyperventilation, high FiO2, and alkalosis (all of which decrease PVR). Mild increases in PVR through slight hypoventilation or low-normal FiO2 may actually improve systemic perfusion.

Right-to-Left Shunts (Cyanotic)

Right-to-left shunt lesions include tetralogy of Fallot, transposition of the great arteries, tricuspid atresia, and severe Ebstein anomaly. Deoxygenated blood bypasses the lungs and enters the systemic circulation.

The anesthetic goals are to increase SVR to reduce the right-to-left shunt and improve pulmonary blood flow, decrease PVR to promote flow through the lungs, avoid hypovolemia, excessive depth of anesthesia, and vasodilation, and maintain adequate preload and heart rate.

Obstructive Lesions

Obstructive lesions include aortic stenosis, pulmonary stenosis, and coarctation of the aorta. The fixed obstruction limits the heart's ability to augment cardiac output. The anesthetic goals are to maintain heart rate, contractility, and preload while avoiding tachycardia (which reduces filling time) and hypotension.

Single-Ventricle Physiology

Palliation Stages

Surgical palliation for single-ventricle physiology proceeds in three stages. The Norwood procedure (Stage 1), performed in the neonatal period, creates a neoaorta from the pulmonary artery, includes an atrial septectomy, and establishes a systemic-to-pulmonary shunt (Blalock-Taussig or Sano shunt). The Glenn or Hemi-Fontan (Stage 2), performed at 4 to 6 months, connects the superior vena cava directly to the pulmonary artery and removes the volume load from the single ventricle. The Fontan (Stage 3), performed at 2 to 4 years, directs IVC flow to the pulmonary artery, completing the total cavopulmonary connection.

Anesthetic Considerations for Fontan Physiology

In the Fontan circulation, pulmonary blood flow is passive and depends on the transpulmonary gradient, which is the difference between central venous pressure and left atrial pressure. Any factor that increases PVR or decreases preload will reduce pulmonary blood flow and cardiac output.

Factors to avoid include positive pressure ventilation with high mean airway pressures, PEEP greater than 5 cmH2O, hypercarbia, acidosis, hypothermia, and dehydration. Goals include maintaining adequate preload, using spontaneous ventilation when possible, maintaining normocapnia, and ensuring adequate analgesia. These patients are exquisitely sensitive to volume depletion, and fasting times should be minimized.

Tetralogy of Fallot and Hypercyanotic Spells

Tetralogy of Fallot consists of a VSD, overriding aorta, right ventricular outflow tract obstruction, and right ventricular hypertrophy. Hypercyanotic episodes, known as "tet spells," result from dynamic infundibular spasm that worsens the RVOT obstruction. They can be triggered by crying, agitation, hypovolemia, or decreased SVR.

Acute management involves placing the child in the knee-to-chest position to increase SVR, administering phenylephrine at 5 to 10 mcg/kg IV to increase SVR and oppose right-to-left shunting, providing 100% oxygen and volume resuscitation, giving esmolol at 0.5 mg/kg IV to relax the infundibulum and slow heart rate, administering morphine at 0.1 mg/kg IV to reduce agitation and potentially reduce RVOT obstruction, and deepening anesthesia.

Intraoperative Management Principles

Monitoring

Standard ASA monitors plus an arterial line should be used for moderate-to-major procedures. Central venous access is appropriate for major surgery or patients on vasoactive infusions. Air bubbles in all IV lines must be scrupulously avoided because of the risk of paradoxical embolism through intracardiac shunts, and air filters should be used on IV tubing.

Induction

IV induction is preferred when access is available. Ketamine at 1 to 2 mg/kg maintains SVR and is useful in cyanotic lesions. Etomidate at 0.2 to 0.3 mg/kg preserves hemodynamics. Inhalational induction with sevoflurane is acceptable for acyanotic lesions but should be performed cautiously in cyanotic patients because uptake is slower due to right-to-left shunting. Conversely, IV induction is faster than expected in these patients.

Maintenance

A balanced technique with a volatile agent, opioid, and muscle relaxant is typically used. High concentrations of volatile agents should be avoided in patients with marginal ventricular function. Regional anesthesia may reduce anesthetic requirements and improve hemodynamics when appropriate. Normothermia, euvolemia, and acid-base balance should be maintained throughout.

Ventilation Strategy

Mean airway pressure should be minimized in single-ventricle physiology and Fontan patients. Low tidal volumes of 6 to 8 mL/kg with rates adjusted to maintain normocapnia are appropriate, and excessive PEEP should be avoided in passive pulmonary blood flow circuits. For patients with excessive pulmonary blood flow from large left-to-right shunts, mild hypoventilation may improve systemic perfusion.

Endocarditis Prophylaxis

AHA guidelines recommend prophylaxis for unrepaired cyanotic CHD including palliative shunts, repaired CHD with prosthetic material or device within 6 months of the procedure, repaired CHD with residual defect adjacent to prosthetic material, and cardiac transplant patients with valvulopathy. The standard regimen is amoxicillin 50 mg/kg PO or ampicillin 50 mg/kg IV within 60 minutes of incision. For penicillin allergy, clindamycin 20 mg/kg IV is used.

Postoperative Considerations

Patients with complex lesions should be monitored in a high-acuity setting. Hemodynamic monitoring and vasoactive support should be continued as needed. Adequate analgesia is critical to prevent tachycardia, hypertension, and increased PVR. Arrhythmias should be watched for, particularly in patients with prior atrial surgery such as Fontan, Mustard, or Senning procedures. Early mobilization and extubation are beneficial for Fontan patients.

Clinical Pearls

The single most important preoperative question is "What is the direction and magnitude of the shunt?" because this dictates the entire anesthetic plan. Air in IV lines can cause paradoxical systemic embolism in any patient with an intracardiac communication, making meticulous de-airing mandatory. Tet spells are treated with SVR augmentation (phenylephrine), volume, oxygen, and deepening of anesthesia, and constitute an anesthetic emergency. Fontan patients depend on passive pulmonary blood flow, and positive pressure ventilation, dehydration, and increased PVR are all poorly tolerated. Pediatric cardiology should be involved early for any patient with complex or single-ventricle CHD presenting for non-cardiac surgery.

References

1. White MC, Peyton JM. Anaesthetic management of children with congenital heart disease for non-cardiac surgery. Contin Educ Anaesth Crit Care Pain. 2012;12(1):17-22.
2. Walker A, Stokes M, Moriarty A. Anesthesia for major general surgery in neonates with complex cardiac defects. Paediatr Anaesth. 2009;19(2):119-125.
3. Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the AHA. Circulation. 2007;116(15):1736-1754.
4. Andropoulos DB, Stayer SA, Mossad EB. Anesthesia for Congenital Heart Disease. 3rd ed. Wiley-Blackwell; 2015.

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