Epidemiology & Risk Factors

Definition: Peripheral venous hematocrit (Hct) > 65% or Hb > 22 g/dL.
Pathophysiologic Mechanisms:
- Increased Erythropoiesis (Chronic Intrauterine Hypoxia):
  - Maternal conditions: Maternal DM (↑ fetal O2 consumption), preeclampsia/maternal HTN, maternal smoking.
  - Fetal/Placental conditions: SGA / IUGR, LGA, placental insufficiency, post-term gestation (> 42 weeks).
  - Genetic/Endocrine: Trisomy 13, 18, 21; Beckwith-Wiedemann syndrome; congenital adrenal hyperplasia (CAH); neonatal thyrotoxicosis.
- Erythrocyte Transfusion (Passive/Excess Volume):
  - Delayed umbilical cord clamping (> 2–3 min).
  - Twin-twin transfusion syndrome (TTTS) (recipient twin).
  - Maternal-fetal hemorrhage.

Clinical Features

Often asymptomatic.
Derm: Plethora (“ruddy” complexion), cyanosis.
CNS: Lethargy, irritability, jitteriness, poor feeding, seizures.
Cardiopulmonary/GI: Tachypnea, respiratory distress, abdominal distension/vomiting.

Initial / Screening: Capillary heel stick (high sensitivity, frequent false positives due to stasis/poor peripheral perfusion).
Confirmatory / Gold Standard: Peripheral venous blood draw (must confirm any capillary Hct > 65%).
Key Labs:
- Glucose: Screen for hypoglycemia (↑ consumption by RBC mass).
- Bilirubin: Screen for hyperbilirubinemia (↑ RBC breakdown).
- Ca2+: Screen for hypocalcemia (common in IDM).

Neonatal Sepsis: Diff by fever/hypothermia, ↑ inflammatory markers, positive cultures, normal Hct.
Dehydration: Diff by excessive weight loss (> 10%), ↑ Na+/BUN, normalizes rapidly with IVF.
Cyanotic CHD: Diff by failed hyperoxia test, cardiac murmur/abnormal echo, normal Hct.

Asymptomatic:
- Hct 65%–75%: IV hydration or increased feeds; monitor glucose/Hct q4–6h.
- Hct > 75%: Consider PET to prevent thrombotic events.
Symptomatic (Venous Hct > 65%):
- First-line / Definitive: Partial Exchange Transfusion (PET) with 0.9% NS (goal: Hct < 55%).
Supportive: IV dextrose (for hypoglycemia), phototherapy (for hyperbilirubinemia).

GI: Necrotizing enterocolitis (NEC) (mesenteric sludging/ischemia).
Renal: Renal vein thrombosis (RVT) (hematuria, flank mass, thrombocytopenia).
Metabolic/CNS: Refractory hypoglycemia, seizures, stroke, kernicterus.

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