Helen M Towers

Effects of quality of energy intake on growth and metabolic response of enterally fed low-birth-weight infants

Carbohydrate and fat may vary in their ability to support protein accretion and growth. If so, variations in the source of nonprotein energy might be used to therapeutic advantage in enterally fed low-birth-weight infants. To test the hypothesis that high-carbohydrate diets are more effective than isocaloric high-fat diets in promoting growth and protein accretion, low-birth-weight infants weighing 750–1600 g at birth were randomized in a double blind study to receive one of five formulas differing only in the quantity and quality of nonprotein energy. Groups 1, 2, and control received 130 kcal·kg−1·d−1 with 35, 65, and 50% of the nonprotein energy as carbohydrate. Groups 3 and 4 received energy intake of 155 kcal·kg−1·d−1 with 35 and 65% of the nonprotein energy as carbohydrate. Protein intake of all groups was 4 g·kg−1·d−1. Growth and metabolic responses were followed weekly, and macronutrient balances including 6-h indirect calorimetry were performed biweekly. Greater rates of weight gain and nitrogen retention were observed at high-carbohydrate intake compared with high-fat intake at both gross energy intakes. Greater rates of energy storage and an increase in skinfold thickness were observed in group 4 (high-energy high-carbohydrate diet) despite higher rates of energy expenditure. These data support the hypothesis that at isocaloric intakes, carbohydrate is more effective than fat in enhancing growth and protein accretion in enterally fed low-birth-weight infants. However, a diet with high-energy and high-carbohydrate content also results in increased fat deposition.

Energy expended by low birth weight infants in the deposition of protein and fat

One hundred twenty low birth weight infants were enterally fed diets containing fixed differences in protein and energy content. Serial, biweekly measurements were made of metabolizable energy intake, energy expenditure, nitrogen balance, and distribution of states of sleep, from the time the infants were receiving full enteral intakes (180 mL/kg·d) until weight reached 2200 g. Using multiple regression analysis of energy expenditure against protein stored, and metabolizable energy, the energy expended in the deposition of protein was calculated to be 5.5 kcal/g ± 1.1 kcal/g (SE) and the energy cost of fat deposited was 1.6 kcal/g ± 0.3 kcal/g (SE). Estimated maintenance energy expenditure of the nongrowing low birth weight infant was 42.3 ± 3.2 kcal/kg/d. Variations in distribution of sleep state, an assessment of the activity state of the infant, did not explain additional variability in energy expenditure, after adjusting for protein and energy storage.

The Effects of Prone vs Supine Body Position on Metabolic and Thermal Measurements in Growing Low Birth Weight (LBW) Infants † 1737

Objectives: To determine the effects of prone vs supine positioning on the metabolic gas exchange and surface temperature profile of healthy growing enterally nourished LBW infants.

Effects of Variations in Carbohydrate (CHO) Intake on Postprandial Gas Exchange, and Respiratory Frequency of Low Birth Weight (LBW) Infants

Effects of Variations in Carbohydrate (CHO) Intake on Postprandial Gas Exchange, and Respiratory Frequency of Low Birth Weight (LBW) Infants

Blood Pressure and Urinary Catecholamine Excretion Vary Inversely with Rate of Weight Gain in Low Birth Weight (LBW) Infants

Blood Pressure and Urinary Catecholamine Excretion Vary Inversely with Rate of Weight Gain in Low Birth Weight (LBW) Infants

Postural Differences in Cardiac Dynamics during Quiet and Active Sleep in Low Birth Weight Infants † 74

To study the effects of body position (supine versus prone) on changes in cardiac inter-beat interval during quiet and active sleep, 6-h continuous electrocardiographic recordings and simultaneous minute-by-minute behavioural activity state assignments were made in 61 healthy, growing, low birthweight infants. The infants weighed 795-1600 g at birth and ranged between 30-38 wk in postconceptual age. Infants were randomly assigned to the supine or prone position for the first 3 h of each study; the position was reversed for the second 3 h. Higher heart rates and lower time and frequency domain measures of inter-beat interval variability were observed in the prone position as compared to the supine position, during both quiet and active sleep. In addition, an analysis of consecutive increases and decreases in the instantaneous heart rate revealed a lower incidence of sustained accelerations or decelerations in the prone position. Although consistent findings concerning inter-beat interval variability and sleeping position were obtained from all analytic techniques, the differences derived from analysis of consecutive inter-beat changes were the most robust. These differences in multiple measures of cardiac rate and rhythm between prone and supine positions suggest that autonomic control of the heart is altered by body position, the net effect on heart rate being increased sympathetic dominance.

Maturational Changes in Heart Rate Variability Dynamics during Quiet and Active Sleep in Low Birth Weight Infants 303

Objectives: To examine the maturational changes in cardiac interbeat interval variability during quiet (QS) and active sleep (AS) in low birth weight (LBW) infants.

Effects of Quality of Energy (E) on Protein (P), Fat (F) and Carbohydrate (C) Oxidation in Enterally Fed Low Birth Weight (LBW) Infants |[bull]| 1532

Objective: To determine the effects of fixed variations in the quantity and quality of dietary energy at constant P intake (Pin) on the rate of C and F oxidation (Cox, Fox) as estimated from indirect calorimetry and the rate of P oxidation (Pox) as determined from urinary nitrogen excretion.

The Effect of Dietary Composition on Ventilation in Low Birth Weight Infants• 1579

Introduction: As the caloric value for CO2 is greater for fat (F) than carbohydrate (C), it has been suggested that high F, low C diets would benefit patients with respiratory insufficiency by reducing the amount of CO2 produced per kcal of energy expended.

POSTURAL DIFFERENCES IN CARDIORESPIRATORY ACTIVITY DURING QUIET AND ACTIVE SLEEP IN LOW BIRTH WEIGHT INFANTS. † 293

Objectives: The objectives of this study were to determine the effects of body position (supine vs prone) on cardiorespiratory activity during quiet and active sleep in growing low birth weight (LBW) infants.