Protein/amino acid metabolism and nutrition in very low birth weight infants

Early amino acids and the metabolic response of ELBW infants (< or = 1000 g) in three time periods

OBJECTIVE

To evaluate early amino-acid (AA) administration in extremely low birth weight (ELBW) infants over three time periods, beginning with the initiation of this strategy.

STUDY DESIGN

This was a retrospective study of ELBW infants between 2000 and 2007. Nutritional intake and laboratory results were monitored during the first 5 days of life. Growth rates and complications were followed until discharge.

RESULT

Infants were similar in birth weight (BW), gestational age (GA) and severity of illness. The age at initiation of AA decreased significantly over time. Age at weight nadir, return to BW and percent postnatal weight loss decreased in epoch 3. There were modest increases in blood urea nitrogen (BUN), but no significant metabolic disturbances were observed. Cholestasis was more prevalent in epoch 2.

CONCLUSION

AA administration within the first hours of life appears to be safe and beneficial for ELBW infants. Absent signs of renal dysfunction, a modest rise in BUN is consistent with the neonate's utilization of AAs for energy.

Protein and amino acid metabolism in the human newborn

Birth and adaptation to extrauterine life involve major shifts in the protein and energy metabolism of the human newborn. These include a shift from a state of continuous supply of nutrients including amino acids from the mother to cyclic periodic oral intake, a change in the redox state of organs, thermogenesis, and a significant change in the mobilization and use of oxidative substrates. The development of safe, stable isotopic tracer methods has allowed the study of protein and amino acid metabolism not only in the healthy newborn but also in those born prematurely and of low birth weight. These studies have identified the unique and quantitative aspects of amino acid/protein metabolism in the neonate, thus contributing to rational nutritional care of these babies. The present review summarizes the contemporary data on some of the significant developments in essential and dispensable amino acids and their relationship to overall protein metabolism. Specifically, the recent data of kinetics of leucine, phenylalanine, glutamine, sulfur amino acid, and threonine and their relation to whole-body protein turnover are presented. Finally, the physiological rationale and the impact of nutrient (amino acids) interventions on the dynamics of protein metabolism are discussed.

Nutrition in the neonatal intensive care unit: how do we reduce the incidence of extrauterine growth restriction?

Extrauterine growth restriction is a major clinical problem for prematurely born neonates, especially critically ill preterm neonates, and malnutrition in the neonatal intensive-care unit remains common. There are numerous perceived risks to initiation of adequate nutritional support. How many of these factors pose a real risk to health outcomes is less clear. Current nutritional support does not prevent extrauterine growth restriction and the consequences of malnutrition are both acute and delayed. Our clinical approach to providing nutritional support impacts neonatal morbidity and long-term neuro developmental outcomes. While more and better evidence is needed to help guide best practices, this gap should not prevent neonatologists from using the observations in this review to improve their current practice. There is evidence that changes in nutritional support can have a positive influence on growth. These include early administration of intravenous amino acids and lipids, minimal enteral nutrition, and supplemented formula and human milk. Simply recognizing the degree of growth failure by monitoring weight and focusing on the accruing deficit should encourage clinicians to increase nutritional support to enhance recovery growth. Continued research is needed to define the efficiency of early feeding, more rapid advancements in nutritional support, protein needs, the optimal composition of breast-milk supplements, the etiology of necrotizing enterocolitis, and perhaps most importantly, the health consequences of extrauterine growth restriction.