Ratio of non-protein calories to grams of amino acids and amino acid blood levels in preterm infants receiving parenteral nutrition.

Abstract

Background: Studies evaluating the optimal intake of amino acids for preterm infants have often not considered the effect of the non-protein calorie to grams of amino acids ratio (NPKcal:g AA) in parenteral nutrition solutions. The objectives of this study were to document the ratio in a group of preterm infants and explore any associations of the ratio to AA and acylcarnitine levels.

Methods: This was descriptive cohort study of data collected from a previously published prospective study evaluating the influence that gestational age had on amino acid and acylcarnitine profiles in preterm infants ≤31 weeks postmenstrual age. Acylcarnitine and AA levels on day of life 7 of three study groups, based upon terciles of the NPKcal:g AA, who were receiving minimal enteral feedings and an enterally fed comparison group were measured. Growth velocities and changes in z-scores were also evaluated.

Results: NPKcal:g AA terciles were: 6.3-17.6:1 (low, N = 153), 17.7-21.2:1 (mid, N = 150), and 21.3-36.2:1 (high, N = 159). Higher levels of ornithine, citrulline, blood urea nitrogen, isovalerylcarnitine + methylbutyrylcarnitine, and octenoylcarnitine were found in the low versus the high group. From day 1-42 of life, the low group had a lower head circumference (HC) growth velocity and the low and mid groups had more negative HC changes in z-scores versus the enteral group.

Conclusions: This study suggests that preterm infants may receive parenteral nutrition solutions containing inadequate energy to prevent oxidation of administered AA. The impact of inadequate non-protein caloric intake needs to be considered when evaluating growth and outcomes in nutritional studies of VLBW infants.