Polycythemia in the newborn.

Polycythemia is defined as a venous hematocrit of over 65%. The hematocrit in a newborn peaks at 2 hours of age and decreases gradually after that. The etiology of polycythemia is related either to intra-uterine hypoxia or secondary to fetal transfusion. The relationship between hematocrit and viscosity is almost linear till 65% and exponential thereafter. Increased viscosity of blood is associated with symptoms of hypo-perfusion. Clinical features related to polycythemia-hyperviscosity syndrome may affect all organ systems and this entity should be screened for in high-risk infants. Polycythemia may or may not be symptomatic and guidelines for management of both the types based on the current evidence are provided in the protocol.