Parenteral aminoacid strategies for nutritional optimization in low birth weight infants

Parenteral amino acid (AA) supplementation is vital for appropriate nutrition in preterm infants. Amino acids and proteins are essential components of growth, development, and regulation of metabolism. Growth restriction during this vulnerable time has been negatively associated with short-/longterm outcomes. In order to improve postnatal growth to that which parallels a healthy, growing fetus, it is important to mimic AA accretion by the fetus. Early loss of protein stores can be prevented or minimized by provision of as little as 1-1.5 g/kg/day of parenteral AA. The minimum AA requirement necessary to approximate intrauterine rates of protein accretion is Â3 g/kg/day, but the placenta serves as a metabolic organ in utero; premature infants may not have mature metabolic pathways and therefore, may not tolerate the same protein load ex-utero. Although BUN may correlate with AA plasma levels, it cannot effectively be utilized to assess protein accretions, but a level >60 mg/dL may suggest immature metabolic pathways in the absence of renal disease. With the current data available, Parenteral AA supplementation should be started shortly after birth at a minimum dose of 1-1.5 g/kg/day to prevent catabolism in all VLBW infants. A maximum of 3.5 g/kg/day is recommended until enteral nutrition is established for VLBW infants. Higher doses of protein supplementation have not shown additional benefits and may cause deleterious effects in overall growth and neurodevelopment. Additional glutamine and/or higher L-cysteine or arginine supplementation does not provide additional benefits.