Hypoglycemia, Neonatal

Key Features

Essentials of Diagnosis

• Blood glucose < 40 mg/dL at birth to 4 h, or < 45 mg/dL at 4–24 h of age

• Large or small for gestational age (LGA/SGA), preterm, and stressed infants at risk

• May be asymptomatic

• Infants can present with lethargy, poor feeding, irritability, or seizures

General Considerations

• Blood glucose concentration in the fetus is approximately 15 mg/dL less than maternal glucose concentration

• Glucose concentration decreases in the immediate postnatal period, to as low as 30 mg/dL in many healthy infants at 1–2 hours after birth

• Concentrations below 40 mg/dL after the first feeding are considered hypoglycemic

• By 3 hours, the glucose concentration in normal full-term infants stabilizes at 45 mg/dL or greater

• Two groups of full-term newborn infants at highest risk for hypoglycemia

  • Infants of diabetic mothers (IDMs)

    • Have abundant glucose stores in the form of glycogen and fat

    • Hypoglycemia develops because of hyperinsulinemia induced by maternal and fetal hyperglycemia

  • Intrauterine growth restricted (IUGR) infants

    • Has reduced glucose stores in the form of glycogen and body fat

    • Marked hyperglycemia and a transient diabetes mellitus–like syndrome occasionally develops, particularly in the very premature infant

• Other causes

  • Disorders with islet cell hyperplasia, including Beckwith-Wiedemann syndrome, nesidioblastosis, and genetic forms of hyperinsulinism

  • Certain inborn errors of metabolism, such as glycogen storage disease and galactosemia

  • Adrenal insufficiency and hypopituitarism

  • Birth asphyxia, hypoxia, and bacterial or viral sepsis

  • Prematurity

Clinical Findings

• Lethargy, poor feeding

• Irritability

• Tremors, jitteriness

• Apnea

• Seizures

• Cardiac failure may occur in severe cases

• Hypoglycemia in hyperinsulinemic states can develop within the first 30–60 minutes of life

Diagnosis

• Blood glucose can be measured by heelstick using a bedside glucometer

• All low or borderline values should be confirmed by laboratory measurement of blood glucose concentration

Treatment

• Therapy is based on the provision of enteral or parenteral glucose

• After initial correction with a bolus of 10% dextrose in water (D₁₀W; 2 mL/kg), glucose infusion should be increased gradually as needed from a starting rate of 6 mg/kg/min, and weaned slowly when normoglycemic

Outcome

Follow-Up

• Infants with hypoglycemia requiring intravenous glucose infusions for more than 5 days should be evaluated for less common disorders, including

  • Inborn errors of metabolism

  • Hyperinsulinemic states

  • Deficiencies of counterregulatory hormones

Prognosis

• Good if therapy is prompt

• CNS sequelae are more common in infants with hypoglycemic seizures and in neonates with persistent hyperinsulinemic hypoglycemia

References