Renal Functions of Low Birth Weight Infants with Hyperglycemia and Glucosuria Produced by Glucose Infusions

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Abstract
Hyperglycemia and glucosuria, which may lead to an osmotic diuresis, are often seen in low birth weight infants receiving glucose infusions during parenteral alimentation. This study was designed to examine the degree of glucose tolerance and the renal handling of glucose, solute, and water during intravenous glucose infusions in low birth weight infants. Twenty infants (mean birth weight, 1,170 gm; gestational age, 30 weeks) were studied between 1 and 20 days of age. At similar glucose infusion rates, 12 of 20 infants of lower gestational ages (29 ± 0.6 weeks, mean ± SEM) had higher plasma glucose concentrations and developed glucosuria while the remaining eight of 20 infants of higher gestations (31.4 ± 0.5 weeks, P < .05) did not. In the glucosuric infants, there were significant increments in the filtered glucose load on the basis of increased plasma glucose concentrations and slightly higher glomerular filtration rates, although the changes of the latter were not statistically significant. The percentage of tubular reabsorption of glucose decreased and urinary excretion of glucose increased significantly with increased plasma glucose. Although urine flow remained unchanged, significant increments occurred in osmolar and sodium excretions. Exogenous glucose infusions in low birth weight infants resulted in a greater degree of hyperglycemia in the less mature infants and produced significant changes in the renal handling of glucose and sodium associated with significant, although slight, increments in solute excretion. In this series of six-hour glucose infusions, untoward effects of an osmotic diuresis (significant urine loss) were not observed.