Hypernatremia in a patient with cyanotic congenital heart disease

Cyanotic congenital heart disease produces blood hyperviscosity secondary to increased hemoglobin. Hyperviscosity can alter microvascular renal circulation hemodynamics and can induce both glomerular damage with proteinuria and tubular disturbances altering sodium reabsorption. We report a woman with complex cyanotic congenital heart disease who was referred to us for hypernatremia. The highest sodium concentration coincided with maximum hemoglobin concentration and with a significant hypererythropoietinemia. After surgery, erythropoietin, hemoglobin and sodium concentration became normal. We propose erythropoietin-induced sodium reabsorption as the etiology of hypernatremia in this patient.