Diseases caused by increased number of erythrocytes

Neonatal polycythemia
Neonatal polycythemia is defined as a central venous hematocrit > 0,65. Nowever, even with a hematocrit> 0.70, only a small proportion of neonates have clinical signs of hyperviscosity. The clinical picture includes lethargy, hypotension, hyperbilirubinemia and hypoglycemia. Polycythemia may also be involved in the development of convulsions, stroke, renal venous thrombosis and necrotizing eneterocolitis.

Causes of neonatal polycythemia:
 * Fetal growth restriction (FGR, IUGR);
 * maternal hypertension;
 * maternal diabetes;
 * chromosomal defects: trisomy 21, 18, 13;
 * twin-to-twin transfusion;
 * delayed umbilical cord rupture;
 * endocrine disorders: tyreotoxicosis, congenital adrenal hyperplasia (CAH).

Treatment is controversial and may not be necessary in neonates with mild symptoms (eg borderline glycaemia, impaired peripheral blood flow). Treatment is indicated in neonates with a hematocrit> 0.65 and symptoms with a potentially severe prognosis (eg refractory hypoglycaemia, neurological symptoms). A partial exchange transfusion is performed with a crystalloid solution (eg physiological solution) with a target hematocrit of 0.55.