Early changes in plasma amino acid concentrations during aggressive nutritional therapy in extremely low birth weight infants

Objective: To examine the changes in plasma amino acid (AA) concentrations over time when extremely low birth weight infants are provided either a standard intravenous AA supplementation (standard AA) or an early and high supplementation regimen (early and high AA). Study design: Sixty-two infants were enrolled at birth in a randomized, double-masked, prospective fashion and treated for 7 days. The infants with standard AA concentrations received intravenous AA starting at 0.5 g/kg/d and increased by 0.5 g/kg every day to a maximum of 3 g/kg/d. Infants in the early and high AA group received 2 g/kg/d of intravenous AA soon after birth and advanced by 1 g/kg every day to 4 g/kg/d. Plasma AA concentrations were determined by high-pressure liquid chromatography on days 1, 3, and 7. Results: Total AA concentrations, total essential AA concentrations, and total nonessential AA concentrations were significantly higher in the infants in the early and high AA group; essential AA concentrations and total AA concentrations were higher at 1 and 3 days, and nonessential AA concentrations were different only on day 3. There were significant differences between standard AA and early and high AA groups for all AA concentrations except the nonessential AAs Glu, Asn, Gly, Gln, Ala, and Tyr and the conditionally essential AA Cys. Conclusion: Infants who received early and higher parenteral AA had higher plasma AA concentrations.