The effect of feeding on oxygen consumption, RQ and plasma levels of glucose, FFA, and D-beta-hydroxybutyrate in newborn infants of diabetic mothers and small for gestational age infants.

Eight infants of strictly controlled diabetic mothers (IDM), 8 infants of gestational diabetic mothers (IGDM) and 6 small for gestational age infants (SGA) were studied before the first feeding and during an early feeding regimen. In IDMs and IGDMs continuous monitoring from 2 hours up to 7 1/2 hours after birth before feeding revealed no consistent changes of VO2 and RQ. The groups of infants were studied on 4 different occasions: (I) 2 to 16 hours, (II) 1 to 2 days, (III) 3 to 4 days, and (IV) 7 to 11 days. Prefeeding VO2-values were not significantly different between each of the groups, but mean RQ was higher in IGDMs than in IDMs. Age of the infant and prefeeding RQ were inversely correlated (r = -0.537, p less than 0.02). With increasing age and milk intake VO2 increased significantly in all groups. RQ decreased during the first 24 to 48 hours in all groups and rose thereafter with highest values at 7 to 11 days. Plasma levels of glucose, FFA, and D-beta-hydroxybutyrate were not significantly different between each of the group. The highest values for D-beta-hydroxybutyrate were found at 1-2 days when the lowest RQ values were also recorded. D-beta-hydroxybutyrate concentrations and RQ values (r = 0.648, p less than 0.001) were inversely correlated suggesting increasing oxidation of fat. Feeding resulted in a marked rise in RQ to values around unity, which preceded a distinct increase in VO2 that reached a maximum at 1 to 1 1/2 hour after the feed, then slowly returned to pretest values. The rise in VO2 was accompanied by an increase in rectal temperature (0.4 to 1.5 degrees C). VO2, RQ, and plasma levels of glucose, FFA, and D-beta-hydroxybutyrate, were almost identical for each of the groups. We suggest: 1) That differences in feeding practice is the most likely explantation for the discrepancy between reported values for VO2, RQ, and circulating substrates in normal and low birth weight newborns. 2) That the rise in VO2 during the neonatal period, caused by feeding, reflects the cost of growth.