The aim of the present work was to study whole body protein synthesis and breakdown, as well as energy metabolism, in very low birth weight premature infants (less than 1500 g) during their rapid growth phase. Ten very low birth weight infants were studied during their first and second months of life. They received a mean energy intake of 114 kcal/kg X day and 3 g protein/kg X day as breast milk or milk formula. The average weight gain was 15 g/kg X day. The apparent energy digestibility was 88%, i.e. 99 kcal/kg X day. Their resting postprandial energy expenditure was 58 kcal/kg X day, indicating that 41 kcal/kg X day was retained. The apparent protein digestibility was 89%, i.e. 2.65 g/kg X day. Their rate of protein oxidation was 0.88 g/kg X day so that protein retention was 1.76 g/kg X day. There was a linear relationship between N retention and N intake (r = 0.78, p less than 0.001). The slope of the regression line indicates a net efficiency of N utilization of 67%. Estimates of body composition from the energy balance, coupled with N balance method, showed that 25% of the gain was fat and 75% was lean tissue. Whole body protein synthesis and breakdown were determined using repeated oral administration of 15N glycine for 60-72 h, and 15N enrichment in urinary urea was measured. Protein synthesis averaged 11.2 g/kg X day and protein breakdown 9.4 g/kg X day. Muscular protein breakdown, as estimated by 3-methylhistidine excretion, contributed to 12% of the total protein breakdown.(ABSTRACT TRUNCATED AT 250 WORDS)
Non‐invasive methods, including stable isotope techniques, indirect calorimetry, nutritional balance and skinfold thickness, have given a new insight into early postnatal growth in neonates. Neonates and premature infants in particular, create an unusual opportunity to study the fluid and metabolic adaptation to extrauterine life because their physical environment can be controlled, fluid and energy balance can be measured and the link between metabolism and the energetics of their postnatal growth can be assessed accurately. Thus the postnatal time course of total body water, heat production, energy cost of growth and composition of weight gain have been quantified in a series of “healthy” low‐birth‐weight premature infants. These results show that total body water is remarkably stable between postnatal days 3‐21. Energy expenditure and heat production rates increase postnatally from mean values of 40 kcal/kg/day during the first week to 60 kcal/kg/day in the third week. An apparent energy balance deficit of 180 kcal/kg can be ascribed to premature delivery. The cost of protein metabolism is the highest energy demanding process related to growth. The fact that nitrogen balance becomes positive within 72 h after birth places the newborn in a transitional situation of dissociated balance between energy and protein metabolism during early postnatal growth: skinfold thickness, dry body mass and fat decrease, while there is a gain in protein and increase in supine length. This particular situation ends during the second postnatal week and soon thereafter the rate of weight gain matches statural growth. The goals of the following review are to summarize data on total body water and energy metabolism in premature infants and to discuss how they correlate with physiological aspects of early postnatal growth
Twenty-five asphyxiated term babies were investigated in order to evaluate the prediction of their neurodevelopmental outcome by means of computerized tomography (CT) as compared to neurological symptoms during the neonatal period. Low density (LD) areas, thought to represent hypoxicischaemic lesions, were assessed quantitatively by means of a LD score based on the extent and degree of LD, the total score ranging from 0-36. Neonatal scans were defined according to the time span elapsed between asphyxia and CT as (1) early CT (day 1-7, n = 15), and (2) intermediate CT (day 9-23: n = 14; day 29: n = 1). The newborns were classified according to the neonatal neurological findings as having mild (n = 8, 32%), moderate (n = 9, 36%), and severe (n = 8, 32%) encephalopathy, following the definition of Sarnat and Sarnat (1976). Among the twenty-two survivors, the follow-up (mean age 19.2 +/- 6.0 mts) revealed fourteen (56%) with normal outcome, two (8%) with transient neurodevelopmental anomalies during the first year, and nine (36%) with permanent abnormalities such as cerebral palsy and/or retardation (mainly global) and/or epilepsy. Early CT scans had no predictive value. Intermediate CT, however, showed distinct variations of LD areas which resulted in an LD score well correlated with the later outcome. In particular, a LD score below 14 characterized every baby who developed normally; a prediction not possible in a reliable way be means of neonatal neurological signs. For all abnormal children, the score correlated with the severity of the later neurodevelopmental disorder, except for one with the latest intermediate CT (day 29).
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