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Influence of postnatal age on nitrogen metabolism in very low birth weight infants appropriate for gestational age
G Boehm1, M D Müller, H Senger
1Department of Paediatrics, Karl-Marx-University, Leipzig, GDR.
Insights
Nutrient absorption improves in very low birth weight (VLBW) infants with age. However, metabolic adaptation, not digestion, limits their nutritional status, highlighting the need for metabolic monitoring.
Area of Science:
- Neonatal Nutrition
- Pediatric Gastroenterology
- Infant Metabolism
Background:
- Very low birth weight (VLBW) infants require specialized nutritional support.
- Assessing nutrient absorption and metabolic adaptation is crucial for optimizing growth in VLBW infants.
Purpose of the Study:
- To evaluate nitrogen and energy balance in VLBW infants fed a human milk formula.
- To investigate the changes in nutrient absorption and retention during early postnatal development.
Main Methods:
- Studied 14 VLBW infants at 8 days and 6 weeks of postnatal age.
- Infants were fed a human milk formula enriched with freeze-dried human milk.
- Measured nitrogen and fat absorption rates and analyzed urinary nitrogen excretion patterns.
Main Results:
- Nitrogen and fat absorption rates significantly increased with postnatal age, remaining high even at 8 days.
- Despite increased absorption, total nitrogen excretion decreased by the 6th week.
- Urinary nitrogen composition shifted from alpha-amino- and ammonium-nitrogen towards urea-nitrogen with age.
Conclusions:
- VLBW infants demonstrate significant postnatal development in both digestive and metabolic capacities.
- Metabolic adaptation to utilize nitrogen appears to be a stronger nutritional limitation than digestive/absorptive capacity.
- Metabolic monitoring, particularly via urine analysis, is essential for individualizing nutrition in VLBW infants during early postnatal life.
Abstract:
In 14 very low birth weight (VLBW) infants appropriate for gestational age the absorption and retention of nitrogen and the energy balance were studied on the 8th day and the 6th week of postnatal age. All infants were fed with a human milk formula composed by fresh mother's milk enriched with 6 g freeze-dried human milk/100 ml. The absorption rates of nitrogen and fat increase significantly with postnatal age but even on the 8th day of life they are on high levels (nitrogen absorption: 86.9 +/- 3.2% of intake; fat absorption: 85.7 +/- 4.3% of intake). Despite the higher nitrogen absorption during the 6th week of life the excretion of total nitrogen is lower in comparison to the 8th day of life. Similarly, the percentages of alpha-amino-nitrogen and of ammonium-nitrogen of the total nitrogen excretion in the urine decrease whereas the percentage of urea-nitrogen increases with postnatal age. The results indicate a postnatal development of both the digestive, as well as the metabolic capacity. The postnatal adaptation of the metabolic capacity to utilize nitrogen seems to be the stronger limiting factor for nutrition than the functional capacity of digestion and absorption. Thus, metabolic monitoring is essential for the individual nutrition of VLBW-infants during the first weeks of postnatal life. Urine analysis data are very sensitive for evaluating the metabolic state of these infants.