Glucose Production Rate in Extremely Immature Neonates (<28 Weeks) Studied by Use of Deuterated Glucose

ABSTRACT: Neonatal hypoglycemia is a frequent complication in immature infants. This may be due to small substrate stores, a high brain:body weight ratio, and immature enzyme systems. The purpose of the present study was to investigate the rate of glucose production in newborn infants with gestational ages of less than 28 wk. The subjects were 10 newborn infants delivered after 25 to 26 gestational wk. Their mean birth weight was 772 g (range 588–1000 g), and their mean postnatal age at the time of the study was 15 h (range 4–24 h). An isotopic compound (d-6,6-2H2-glucose) was given as a constant-rate i.v. infusion. In addition to dideuteroglucose, eight of the infants also received an i.v. infusion of unlabeled glucose at a rate of 1.4–2.6 mg·kg−1·min−1. Blood samples for determination of the concentration and isotopic enrichment of plasma glucose were obtained every 15 min in a 2-h period. Isotopic enrichment, measured by gas chromatography/mass spectrometry, was used for calculating the glucose production rate. The mean glucose production rate related to body weight (± SD) was 6.1 ± 1.5 mg·kg−1·min−1. The results show that infants born at <28 gestational wk have a capacity to produce glucose on their 1st d of life at rates close to or even exceeding those reported in term infants.