Effect of amino acids on glucose tolerance and hyperkalemia in very low birth weight infants

The purpose of the study was to investigate alimentation of very low birth weight (VLBW) infants and its effect on blood concentration of glucose, urea nitrogen, creatinine and potassium.

The subjects were 100 VLBW infants born between 1993-1999. The gestational age ranged from 23 to 32 weeks and the birth weight from 443 to 1470 g. Intravenous glucose infusions were begun shortly after birth, amino acids on day 3 and lipids on day 4. Blood samples were drawn for determinations of urea nitrogen, creatinine and potassium.

Mean caloric intake of glucose rose from 24.7 kcal/kg/day on day 1 to 58.1 kcal/kg/day on day 8 (p < 0.0001) and of amino acids from 1.1 g/kg/day on day 3 to 1.9 g/kg/day on day 8 (p < 0.0001). Potassium administration increased from 1 mq/kg/day on day 2 to 1.9 mq/kg/day on day 8. Urea nitrogen was at a mean level of 21.4 mg/dl on day 4 and declined afterwards (p < 0.0001). Serum potassium levels declined from 5.9 mmol/L on day 2 to 4.1 mmol/L on day 8 (p < 0.0001), while creatinine levels remained stable.

Our findings suggest that a catabolic state in VLBW infants begins to be reversed when the caloric intake of 40-50 kcal/kg/day is achieved.