Background: In extremely preterm infants, hypoglycemia may result from insufficient hepatic glycogen stores, inadequate gluconeogenesis or both. In early postnatal life, these infants are often given parenteral glucose alone at high rates both to prevent hypoglycemia and to satisfy energy requirements. Due to diminished glucose tolerance, however, hyperglycemia accompanied by urinary loss of water and glucose calories is a frequent consequence.

Hypothesis: Substituting parenteral lipids and amino acids for a portion of administered glucose will support gluconeogenesis and maintain normoglycemia.

Subjects: 7 infants, 27 ± 1 gestational weeks(mean±SD), 973±111 grams birth weight received 3 mg/kg min glucose, 1.8 mg/kg min lipid, and 2.2 mg/kg min amino acids (corresponding to a daily intake of 51 kcal/kg) over 10-12 hours on day 5 ± 1 of life. This energy value is equivalent to the daily calorie intake of glucose given alone at a rate of 11 mg/kg min.

Methods: Gluconeogenesis was calculated using mass isotopomer distribution analysis of circulating glucose and lactate carbons during infusion of uniformly-labeled carbon-13 glucose.

Results: Between 6 and 10-12 hours, plasma glucose concentration was maintained at 57 ± 9 mg/dL. The total plasma glucose entry rate was 4.9 ± 0.3 mg/kg min and glucose production was 1.9 ± 0.3 mg/kg min. Table

Table 1
Full size table

Conclusions: In extremely preterm infants, normoglycemia is maintained in infants supplied TPN with a reduced glucose content. Glycogenolysis remains the major source of glucose production for at least 10 hours, although gluconeogenesis becomes an increasing contributor and accounts for about one-third of hepatic glucose release at 10-12 hours.