Neonatal Polycythemia: Definition, Causes, and Management
Neonatal polycythemia is defined as a venous hematocrit above 65%, which leads to hyperviscosity of blood and can cause symptoms of hypoperfusion affecting multiple organ systems. 1
Definition and Pathophysiology
Polycythemia in newborns refers to an abnormally high concentration of red blood cells in the blood, specifically:
- Venous hematocrit ≥65% 1, 2
- Relationship between hematocrit and blood viscosity is linear until 65%, then becomes exponential 1
- Hematocrit in newborns naturally peaks at 2 hours of age and gradually decreases thereafter 1
The increased blood viscosity from polycythemia leads to decreased blood flow to various organs, potentially causing tissue hypoperfusion and organ dysfunction 3.
Types and Causes
Neonatal polycythemia can be classified into two main categories:
Active Polycythemia - Excess production of red blood cells 4
- Chronic intrauterine hypoxia
- Placental insufficiency
- Genetic disorders
Passive Polycythemia - Increase in fetal blood volume 4
- Delayed cord clamping
- Twin-to-twin transfusion syndrome (TAPS)
- Maternal-fetal transfusion
High-Risk Groups
Certain newborns are at increased risk and should undergo screening at 2,12, and 24 hours of age 1:
- Small for gestational age (SGA) infants
- Infants of diabetic mothers (IDM)
- Multiple births (particularly monochorionic twins)
- Infants with cyanotic congenital heart disease 5
Clinical Manifestations
Polycythemia can affect multiple organ systems due to hyperviscosity and reduced blood flow:
- Neurological: Lethargy, irritability, seizures, jitteriness
- Cardiovascular: Decreased cardiac output, reduced cerebral blood flow 3, 6
- Pulmonary: Decreased pulmonary blood flow, respiratory distress 3
- Renal: Reduced renal plasma flow, decreased glomerular filtration rate 3
- Gastrointestinal: Feeding intolerance, necrotizing enterocolitis
- Hematological: Thrombocytopenia, hyperbilirubinemia
- Metabolic: Hypoglycemia
Diagnosis
- Venous hematocrit ≥65% is diagnostic 1, 2
- Capillary samples may be falsely elevated and should be confirmed with venous sampling
- Screening recommended for high-risk infants at 2,12, and 24 hours of age 1
- In twin pregnancies, middle cerebral artery Doppler peak systolic velocity can help diagnose twin anemia-polycythemia sequence (TAPS) prenatally 5
Management
Management depends on whether the infant is symptomatic:
Asymptomatic Polycythemia:
- Supportive care with close monitoring
- Adequate hydration
- Current evidence does not support partial exchange transfusion (PET) for asymptomatic infants 2
Symptomatic Polycythemia:
- Partial exchange transfusion (PET) is the definitive treatment for symptomatic infants 4
Prognosis and Long-term Outcomes
- Short-term improvements in organ function can be seen after treatment of symptomatic polycythemia
- Long-term neurodevelopmental outcomes are not clearly improved by PET 2
- Neurological abnormalities may be due to primary hypoxic events rather than reduced cerebral blood flow 3
Important Considerations
- Cerebral blood flow reduction in polycythemia appears to be a physiologic response to increased arterial oxygen content rather than a direct result of hyperviscosity 6
- In twin pregnancies with TAPS, the recipient twin may develop polycythemia and hyperviscosity, potentially leading to cerebral lesions, skin necrosis, and limb ischemia 5
- Polycythemia in cyanotic congenital heart disease occurs as a compensatory mechanism to increase tissue oxygenation in response to chronic hypoxemia 5
Screening Recommendations
For high-risk infants (SGA, IDM, multiple births), screening should be performed at:
- 2 hours of age
- 12 hours of age
- 24 hours of age 1
Early identification and appropriate management of neonatal polycythemia can help prevent complications and improve outcomes.