Evidence supporting early nutritional support with parenteral amino acid infusion.

Postnatal growth of extremely low birth weight (ELBW) infants remains poor and does not come close to approximating rates of in utero growth. There is good evidence that early deficiencies in protein may be an important contributor to the poor growth outcomes observed in this population. Protein losses are inversely related to gestational age, and ELBW infants lose 1% to 2% of their total endogenous body protein stores each day that they receive glucose alone. It is now abundantly clear from a variety of studies that providing intravenous amino acids to sick premature infants in early postnatal life can improve protein balance and can increase protein accretion, even at low caloric intakes. Provision of approximately 1 g/kg/day of amino acids will result in a net protein balance close to zero, whereas delivery of 3 g/kg/day will accomplish protein accretion. Although data from metabolic studies, observational studies, and even a few randomized clinical trials overwhelmingly support the short-term safety and efficacy of early amino acids in reversing protein loss, there is much less known about the effects of early amino acid administration on longer-term outcomes such as growth and neurodevelopment in extremely premature infants. Based on the sum of currently available evidence presented, providing ELBW infants with 2.5 to 3.5 g/kg/day of intravenous amino acids as soon as possible after birth is a reasonable recommendation. Future studies are required to determine whether provision of 3 to 3.5 g/kg/day of amino acids is "aggressive" enough for optimal growth and neurodevelopmental outcome of ELBW infants.