Anesthesia Considerations 

Fontan Physiology 

 

 

Background 

 

• Fontan is a palliative procedure for patients with functional univentricular physiology

• Selection criteria for performance of Fontan are: adequately sized pulmonary arteries; low PVR; good LV function & the presence of sinus rhythm

• The driving force for blood flow through the pulmonary circulation is the difference between central venous pressure (CVP) & atrial pressure

  • There is no active pumping of blood through the lungs

  • Cardiac output is essentially completely dependent on pulmonary blood flow

  • Therefore, hypovolemia is tolerated very poorly

 

 

Considerations 

 

• Congenital heart disease patient with altered cardiac anatomy & potentially other congenital anomalies 

• Hemodymanic & ventilatory goals of Fontan circulation (see below) 

• High risk cardiac patient:

  • Consider surgery at tertiary cardiac centre 

  • Consultation with cardiology 

  • Perioperative TEE invaluable 

• Single ventricle pathophysiology:

  • Venous congestion: protein loosing enteropathy, kidney disease, hepatic failure, failure to thrive 

  • Arrhythmias, embolic stroke, anticoagulation

  • LV dysfunction

  • Hypoxemia & hyperviscosity

• Medication management (possible beta blockers, ACE inhibitors, anticoagulants, diuretics) 

• Consideration of bacterial endocarditis prophylaxis if applicable 

• Possible ↑ risk of bleeding 

• Postoperative monitoring in HAU/ICU 

 

 

Anesthetic Principles 

 

• Hemodynamic principles:

  • Systemic venous pressure: keep full/avoid dehydration  

  • Pulmonary vascular resistance (PVR) = keep low:

    • Avoid hypercarbia, hypoxemia, acidosis, stress, pain, high intra-thoracic pressures 

  • Cardiac rhythm: strict sinus

  • Ventricular function: maintain 

  • Systemic vascular resistance: maintain 

• Fluid management: guided by CVP or TEE (TEE very useful)

  • Vascular capacitance is ↑ in the Fontan patient; more fluid may be required than anticipated based on the formula commonly used to calculate fluid requirements.

• Ventilatory strategy:

  • Spontaneous ventilation is best as it enhances venous return & pulmonary blood flow 

  • For PPV:  limit peak inspiratory pressure (< 20 cmH2O), use low respiratory rates (< 20 bpm), short inspiratory times, avoid excessive PEEP, moderately elevated tidal volumes (10–15 mL/kg), ensure adequate intravascular volume.

• ↑ bleeding potential: coagulation factor deficiencies, antithrombotic therapy, venous collaterals, & venous hypertension

• Postoperative concerns:

  • Maintaining volume status, acid-base balance, & cardiac output are essential in the postoperative period: ensure adequate hydration & aggressively manage low cardiac output with IV hydration & inotropes

  • Adequate analgesia improves pulmonary mechanics & oxygenation; enhanced vigilance is required to avoid the effects of hypercapnia secondary to opioids

  • Treat postoperative nausea & vomiting to permit adequate hydration, prevent dehydration & electrolyte loss, & allow the patient to resume their medication regimen 

 

 

Pregnancy Considerations 

 

• Case reports exist 

• Titrated epidural is probably the safest technique as it does not worsen PVR; caution with ↓ in preload so ensure well-hydrated, reduction in afterload is probably desirable

• Labor is NOT contraindicated, but needs to occur in a cardiac centre with invasive monitoring (arterial line) & with assisted 2nd stage 

• If cearean section: best to use epidural technique 

• If GA required, use strategies mentioned above 

 

 

Laparoscopy Considerations 

 

• Case reports exist 

• Detailed discussion with surgeon ahead of time 

• Minimize insufflation pressures or do staged insufflation & see effects

• Avoid high intrathoracic pressures, ↓ preload, & hypercarbia 

• If cannot tolerate, may need an open technique