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A description of the changing body composition of the growing premature infant
D W Spady1, D Schiff, W A Szymanski
1Department of Pediatrics, University of Alberta, Edmonton, Canada.
Insights
This study details the body composition of premature infants, providing reference data for water, protein, and fat content as they grow. These findings offer crucial insights into infant nutrition and development.
Area of Science:
- Pediatrics
- Neonatology
- Human Physiology
Background:
- Premature infants require precise nutritional support to ensure healthy growth and development.
- Understanding the changing body composition of premature infants is essential for optimizing feeding strategies.
- Existing data on premature infant body composition is limited, particularly for infants fed breast milk.
Purpose of the Study:
- To describe the body composition of a typical premature infant aged 3-4 weeks, gaining weight from 1,200 to 2,000 g.
- To establish reference equations for estimating total body water, extracellular fluid, and total body potassium based on body weight.
- To provide detailed estimates of major body components (water, protein, fat, ash, carbohydrate) at specific body weights.
Main Methods:
- Utilized data from two groups of premature infants (n=17 and n=23) with serial measurements of total body water, extracellular fluid, nitrogen balance, and total body potassium.
- Derived regression equations relating body composition parameters to body weight for infants between 1,200 and 2,000 g.
- Estimated protein content using total body potassium and nitrogen:potassium ratios, with subsequent calculations for other components based on accretion data and reference values.
Main Results:
- Established reference body composition for premature infants at 1,200 g (72.1% water, 10.7% protein, 14.9% fat) and 2,000 g (67.8% water, 11.6% protein, 18.2% fat).
- Developed equations to estimate total body water, extracellular fluid, and total body potassium in premature infants within the studied weight range.
- Provided estimates for body cell mass, intracellular fluid, and the relationship of potassium to these compartments, alongside energy balance data.
Conclusions:
- The study provides a comprehensive description of premature infant body composition during a critical growth phase.
- The derived equations and reference data can aid clinicians in assessing and managing the nutritional status of premature infants.
- This research contributes valuable data for understanding the physiological changes and nutritional requirements of growing premature infants.
Abstract:
Data from studies of two similar groups of premature infants were used to describe the changing body composition (BC) of a "typical" premature infant, 3 to 4 weeks old, gaining weight from 1,200 to 2,000 g and being fed its mother's expressed breast milk at a metabolizable energy intake of 93.6 kcal/kg/day. Serial measurements had been made of total body water (TBW), the extracellular fluid space (ECF), nitrogen balance, and gross energy balance in one group of premature (n = 17) infants and of total body potassium (TBK) in another group (n = 23); all infants studied weighed between 900 and 2,300 g. Equations relating TBW, ECF, and TBK to body weight were derived for estimating the content of these substances at body weights between 1,200 and 2,000 g. Protein content at 1,200 g body weight was estimated from measured TBK and N:K ratio (determined from the reference fetus) at this weight. Subsequent protein content was determined from average N accretion, determined from data of N balance, and carbohydrate and ash content were estimated from reference data. The remainder of the body weight was assumed to be fat. At 1,200 g, the proposed BC of the premature infant is 72.1% water, 10.7% protein, 14.9% fat, 1.9% ash, and 0.4% carbohydrate. At 2,000 g comparable figures are 67.8% water, 11.6% protein, 18.2% fat, 1.9% ash, and 0.5% carbohydrate. The description also provides estimates of the body cell mass (BCM) and intracellular fluid (ICF), the relationship of K to the BCM and ICF, and the energy balance of the growing premature infant.