Management of Neonatal Polycythemia in an Infant of a Diabetic Mother
For a newborn with a venous hematocrit of 71% and plethoric appearance born to a diabetic mother, the next step is partial exchange transfusion (PET), as this level exceeds the threshold of 65% that defines polycythemia and is associated with hyperviscosity requiring intervention. 1, 2
Rationale for Partial Exchange Transfusion
Partial exchange transfusion is indicated when venous hematocrit exceeds 65%, particularly when the infant is symptomatic (plethoric appearance) or when the hematocrit is ≥70-71%. 1, 2, 3 The relationship between hematocrit and blood viscosity becomes exponential above 65%, leading to hypoperfusion of multiple organ systems. 1, 2
- Infants of diabetic mothers are at high risk for polycythemia due to chronic intrauterine hypoxia, making screening at 2,12, and 24 hours of age essential. 1, 2
- A venous hematocrit of 71% strongly indicates hyperviscosity, as 80% of neonates with hematocrit ≥63% have viscosity exceeding 3 standard deviations above normal. 3
- The plethoric appearance represents a clinical manifestation of hyperviscosity syndrome affecting multiple organ systems. 1, 2
Why Not the Other Options
Fluid resuscitation alone is inappropriate because it does not address the fundamental problem of excessive red blood cell mass and hyperviscosity. 1, 2 While hydration status should be assessed, simple fluid administration will not reduce the hematocrit to safe levels.
Urgent phototherapy is not indicated because polycythemia itself does not cause hyperbilirubinemia requiring immediate phototherapy. 4 Although polycythemic infants may develop jaundice, phototherapy thresholds are based on bilirubin levels, not hematocrit values. 4
Technical Considerations for Partial Exchange Transfusion
The goal of PET is to reduce the venous hematocrit from 71% to approximately 50-55% using isotonic saline or albumin as replacement fluid. 3 The procedure should:
- Use umbilical venous blood for confirmation of hematocrit and viscosity measurements, as peripheral venous hematocrit correlates moderately with umbilical venous values (r=0.54). 3
- Calculate exchange volume to achieve target hematocrit reduction, typically requiring removal of 10-20 mL/kg of blood with simultaneous replacement. 1, 2
- Be performed in a neonatal intensive care unit with full monitoring capabilities. 4
Important Caveats
Monitor closely for necrotizing enterocolitis (NEC) following PET, as the procedure increases NEC risk (RR 11.18,95% CI 1.49-83.64). 5 This represents the most significant complication of the intervention.
Assess for associated complications of polycythemia including hypoglycemia, hypocalcemia (9% incidence), hypomagnesemia (30% incidence), and abnormal electrocardiograms (12% incidence). 6 These metabolic derangements commonly accompany polycythemia in infants of diabetic mothers and require concurrent management. 7
Do not rely on capillary hematocrit for treatment decisions, as it correlates poorly with venous values and averages 4% higher than peripheral venous hematocrit. 3 Always confirm with venous sampling before proceeding with PET.
The evidence regarding long-term neurodevelopmental benefits of PET remains imprecise due to incomplete follow-up in studies, but the immediate risk of hyperviscosity-related organ damage at hematocrit levels of 71% justifies intervention. 5