This manifests as poor flow or sludging of blood, which predisposes the infant to the development of microthrombi and decreased tissue oxygenation. Blood viscosity is determined by multiple factors. As previously mentioned, viscosity increases as hematocrit rises. Plasma volume, plasma proteins, platelets, and endothelial factors also contribute to viscosity. The central nervous, cardiopulmonary, gastrointestinal, and renal systems are at risk.
Metabolic derangements are common.
Coagulation also can be affected. The hematocrit peaks 2 hours after birth and then declines until the infant is aged 6 hours, at which time it equals the cord blood hematocrit. Priapism may be observed in males. Central nervous system CNS manifestations are the most common problems observed with polycythemia and hyperviscosity. Symptoms include lethargy, irritability, jitteriness, tremors, seizures, and cerebrovascular accidents.