Fontan

Fontan

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Estimated around 70,000 patients worldwide with Fontan circulation. Performed in patients where biventricular repair not possible; conditions such as tricuspid atresia, pulmonary atresia with intact ventricular septum, double inlet left ventricle, hypoplastic left heart syndrome, double outlet right ventricle, and complete atrioventricular septal defects. Fontan is usually the final of 3 stages of palliative surgery (first being Norwood, second being Glenn); staged approach to allow the body to adapt. Patients tend to demonstrate gradual decline over time.

Fontan circulation dependent on systemic venous pressure, PVR, AV valve function, cardiac rhythm, and ventricular function. Driving force of blood through pulmonary circuit is dependent on the different between the central venous pressure and the atrial pressure (passive process). CVP is mainly determined by intravascular volume, thus hypovolemia is poorly tolerated. Also important to maintain sinus rhythm and competent AV valve for optimal atrial emptying and ventricular filling. Additionally avoid agents that decrease myocardial contractility, as well avoid increases in PVR.

Anesthetic implications

Preoperative optimization

Detailed history and physical examination

Baseline labs, ECG, Echo.

Intraoperative management

If undergoing major surgery with fluid shifts, monitor with arterial line and CVP. Young patient with well compensated Fontan physiology with CVP (mPAP) of 12 mmHg, and atrial pressure of 5 mmHg (transpulmonary pressure gradient of 7 mmHg).

Avoid hypotension from anesthetic agents (such as high concentration volatiles, or induction agents that drop SVR). Avoid increased in PVR (such as hypercarbia, acidosis, increased intrathoracic pressure, inadequate analgesia/anesthesia)

Spontaneous ventilation may be beneficial for short procedures if able to avoid hypercarbia. If needing invasive ventilation, need to avoid increased in intrathoracic pressure (which would decrease venous return, and in turn reduce pulmonary blood flow); thus low respiratory rates, short inspiratory times, low PEEP, tidal volumes 5-6 mL/kg. Plan for early extubation.

Postoperative management

Monitor oxygen saturation, volume status. Address anticoagulation needs. Adequate pain management to facilitate normal breathing patterns.

Related surgical procedures

Norwood (stage 1)

Glenn (stage 2)

Heart transplant (as treatment for failing Fontans)

Pathophysiology

Abnormal cardiorespiratory response to exercise: blunted heart rate response, limited ability to increase stroke volume (impaired ventricular function and difficulty increasing preload)

Restrictive respiratory physiology in up to 89% of patients, due to both extrinsic and intrinsic causes; can also experience recurrent pneumonias, pleural effusions, pulmonary embolisms, and in rare cases plastic bronchitis.

45% of patients with atrial arrhythmias in 10 years following surgery, related to multiple suture lines near sinus node, atrial enlargement, and elevated atrial pressure.

Left to right shunts may be present due to aorto-pulmonary collaterals, or incomplete occlusion of prior artificial shunts; may result in increases in PVR and volume overload of ventricle

Protein losing enteropathy in 13% of patients in a 10 year follow up after surgery. Manifests as edema, ascites, malabsorption of fat, hypercoagulopathy, hypocalcemia, hypomagnesemia, immunodeficiency

In 10-year follow-up studies, about 30% of patients with thromboembolic events. Patients usually with anticoagulation or antiplatelet agents.

Fontan associated liver disease causing congestion, fibrosis, and cirrhosis; usually progressive.

Diagnosis

Assess Fontan function with Echo, CT and MRI.

Treatment

Medication

Pertaining to complications arising from failing Fontan: heart failure medications, anticoaguation, anti-arrhythmic, pulmonary vasodilators

Surgery

Fontan final stage usually performed around 1-5 years of age. Blood from IVC is directed to pulmonary circuit via extracardiac conduit (usual), or intra-atrial baffle. Some patients require a small fenestration between right atrium and conduit to limit caval pressures, as well as increase preload to ventricle.

Prognosis

After Fontan surgery, 30-year survival of >80%. After diagnosis of PLE, 60% 5-year and 20% 10-year survival.

References

Lei SY. FONTAN PHYSIOLOGY. In: Houck PJ, Haché M, Sun LS. eds. Handbook of Pediatric Anesthesia. McGraw Hill; 2015. Accessed June 04, 2023. https://accesspediatrics.mhmedical.com/content.aspx?bookid=1189&sectionid=70364339

McNamara JR, McMahon A, Griffin M. Perioperative Management of the Fontan Patient for Cardiac and Noncardiac Surgery. J Cardiothorac Vasc Anesth. 2022 Jan;36(1):275-285. doi: 10.1053/j.jvca.2021.04.021. Epub 2021 Apr 20. PMID: 34023201.

Sandeep Nayak, MBBS MD FRCA , P.D. Booker, MBBS MD FRCA, The Fontan circulation, Continuing Education in Anaesthesia Critical Care & Pain, Volume 8, Issue 1, February 2008, Pages 26–30, https://doi.org/10.1093/bjaceaccp/mkm047