Case Report: Patient With Hyponatremia and Fontan-Associated Cardiac Cirrhosis

The management of patients with hyponatremia in cardiac cirrhosis is challenging. Palliative care for patients with single ventricle congenital heart lesions includes Fontan surgery that diverts blood from the great veins to the pulmonary arteries, bypassing the right ventricle. Managing patients who develop elevated central venous pressure and cardiac cirrhosis with hyponatremia commonly includes a combination of loop diuretics and mineralocorticoid receptor antagonists.

During a poster session at ASN Kidney Week 2024, Prashant N. Bhenswala, MD, and colleagues at Northwell Health, New Hyde Park, New York, presented a case report of a patient with refractory fluid overload and hyponatremia requiring treatment with tolvaptan. The poster was titled Low-Dosage Tolvaptan for Refractory Hyponatremia in Fontan-Associated Cardiac Cirrhosis.

The male patient was 45 years of age and had undergone Fontan procedure complicated by Fontan-associated liver disease that required paracenteses every 3 weeks. He presented to the emergency department with serum sodium concentration of 122 mEq/L. He was being treated with water restriction and maximally tolerated diuretics (40 mg furosemide and 25 mg spironolactone daily), but the hyponatremia persisted and required more frequent paracenteses and hospitalizations.

Results of physical examination revealed blood pressure of 85/48 mm Hg and ascites and anasarca. His serum osmolality was 266 mosmol/kg. Results of laboratory urine testing showed sodium 7 mmol/L, potassium 45 mmol/L, and osmolality 628 mosm/kg, suggesting antidiuretic hormone-mediated hyponatremia. Low dose tolvaptan was administered despite his history of cirrhosis.

Over four days, the patient’s serum sodium level appropriately increased from 125 mEq/L to 135 mEq/L. He was discharged on tolvaptan 7.5 mg once a week in combination with his home diuretics. He has remained stable with a serum sodium concentration of 130 to 133 mEq/L. The need for hospitalizations and paracenteses has decreased, and serum creatinine remains stable at 1.2 mg/dL.

Due to the risk of liver failure and variceal bleed, recommendations for the use of tolvaptan suggest avoiding use in patients with cirrhosis. In this case, due to the refractory nature of the patient’s hyponatremia and limited therapeutic alternatives, low dose tolvaptan was initiated. The treatment resulted in controlled and sustained correction of serum sodium level and reduction in hospitalizations.

The researchers said, “Tolvaptan should be considered as an alternative therapy for refractory hyponatremia in cirrhosis. Altered pharmacokinetics of the drug in cirrhosis may enable use of a lower dose and frequency for the same effect with no appreciable adverse events.”

Source: Bhenswala P, Upadrista PK, Sharma PD. Low-dosage tolvaptan for refractory hyponatremia in Fontan-associated cardiac cirrhosis. Th-PO340. Abstract of a poster presented at the American Society of Nephrology Kidney Week 2024; October 24, 2024; San Diego, California.