Normal value of resting energy expenditure in healthy neonates

Evolution of Resting Energy Expenditure, Respiratory Quotient, and Adiposity in Infants Recovering from Corrective Surgery of Major Congenital Gastrointestinal Tract Anomalies: A Cohort Study

This cohort study describes the evolution of resting energy expenditure (REE), respiratory quotient (RQ), and adiposity in infants recovering from corrective surgery of major congenital gastrointestinal tract anomalies. Energy and macronutrient intakes were assessed. The REE and RQ were assessed by indirect calorimetry, and fat mass index (FMI) was assessed by air displacement plethysmography. Longitudinal variations over time are described. Explanatory models for REE, RQ, and adiposity were obtained by multiple linear regression analysis. Twenty-nine infants were included, 15 born preterm and 14 at term, with median gestational age of 35.3 and 38.1 weeks and birth weight of 2304 g and 2935 g, respectively. In preterm infants, median REE varied between 55.7 and 67.4 Kcal/kg/d and median RQ increased from 0.70 to 0.86–0.92. In term infants, median REE varied between 57.3 and 67.9 Kcal/kg/d and median RQ increased from 0.63 to 0.84–0.88. Weight gain velocity was slower in term than preterm infants. FMI, assessed in a subset of 15 infants, varied between a median of 1.7 and 1.8 kg/m² at term age. This low adiposity may be related to poor energy balance, low fat intakes, and low RQ¸ that were frequently recorded in several follow-up periods.

Energy expenditure, growth, and nutritional therapy in appropriate and small for gestational age preterm infants

OBJECTIVE

To evaluate the resting energy expenditure, growth, and quantity of energy and macronutrients intake in a group of preterm newborns.

METHODS

The cohort study was performed with appropriate and small for gestational age preterm infants (birth weight lower than 1500g or gestational age<32 weeks). Resting energy expenditure was measured using indirect calorimetry on the 7th, 14th, 21st, and 28th days of life, and at discharge. Length, head circumference and body weight were assessed weekly. Nutritional therapy was calculated during the hospital stay and the information for each type of food was recorded in software that calculates the total amount of energy and macronutrients.

RESULTS

61 preterm infants were followed; 43 appropriate and 18 small for gestational age infants. There was no statistical difference for resting energy expenditure between the groups, and it increased from the first to the fourth week of life (appropriate: 26.3% and small: 21.8%). Energy intake in the first two weeks of life was well below the energy requirement.

CONCLUSION

Considering that the results demonstrate high energy expenditure during the first weeks of life, there is an evident need to provide the best quality of nutrition for each child in the first weeks of life so that preterm infants with or without intrauterine growth restriction can achieve their maximum potential for growth and development.

Resting energy expenditure in infants with congenital diaphragmatic hernia without respiratory support at time of neonatal hospital discharge

BACKGROUND

Infants with congenital diaphragmatic hernia (CDH) are at risk for growth failure because of inadequate caloric intake and high catabolic stress. There is limited data on resting energy expenditure (REE) in infants with CDH.

AIMS

To assess REE via indirect calorimetry (IC) in term infants with CDH who are no longer on respiratory support and nearing hospital discharge with advancing post-conceptional age and to assess measured-to-predicted REE using predictive equations.

METHODS

A prospective cohort study of term infants with CDH who were no longer on respiratory support and nearing hospital discharge was conducted to assess REE via IC and caloric intake. Baseline characteristics and hospital course data were collected. Three day average caloric intake around time of IC testing was calculated. Change in REE with advancing post-conceptional age and advancing post-natal age was assessed. The average measured-to-predicted REE was calculated for the cohort using predictive equations [22].

RESULTS

Eighteen infants with CDH underwent IC. REE in infants with CDH increased with advancing postconceptional age (r2 = 0.3, p < 0.02). The mean REE for the entire group was 53.2 +/- 10.9 kcal/kg/day while the mean caloric intake was 101.2 +/- 17.4 kcal/kg/day. The mean measured-to-predicted ratio for the cohort was in the normal metabolic range (1.10 +/- 0.17) with 50% of infants considered hypermetabolic and 11% of infants considered hypo-metabolic.

CONCLUSIONS

Infant survivors of CDH repair who are without respiratory support at time of neonatal hospital discharge have REE, as measured by indirect calorimetry, that increases with advancing post-conceptional age and that is within the normal metabolic range when compared to predictive equations.

LEVEL OF EVIDENCE

III.

Predicting growth of the healthy infant using a genome scale metabolic model

An estimated 165 million children globally have stunted growth, and extensive growth data are available. Genome scale metabolic models allow the simulation of molecular flux over each metabolic enzyme, and are well adapted to analyze biological systems. We used a human genome scale metabolic model to simulate the mechanisms of growth and integrate data about breast-milk intake and composition with the infant's biomass and energy expenditure of major organs. The model predicted daily metabolic fluxes from birth to age 6 months, and accurately reproduced standard growth curves and changes in body composition. The model corroborates the finding that essential amino and fatty acids do not limit growth, but that energy is the main growth limiting factor. Disruptions to the supply and demand of energy markedly affected the predicted growth, indicating that elevated energy expenditure may be detrimental. The model was used to simulate the metabolic effect of mineral deficiencies, and showed the greatest growth reduction for deficiencies in copper, iron, and magnesium ions which affect energy production through oxidative phosphorylation. The model and simulation method were integrated to a platform and shared with the research community. The growth model constitutes another step towards the complete representation of human metabolism, and may further help improve the understanding of the mechanisms underlying stunting.

Resting energy expenditure, macronutrient utilization, and body composition in term infants after corrective surgery of major congenital anomalies: A case-study

INTRODUCTION

Knowledge on the metabolic changes and nutritional needs during the postsurgical anabolic phase in infants is scarce. This analysis explores the associations of resting energy expenditure (REE) and macronutrient utilization with body composition of full-term infants, during catch-up growth after corrective surgery of major congenital anomalies.

METHODS

A cohort of full-term appropriate for-gestational-age neonates subjected to corrective surgery of major congenital anomalies were recruited after gaining weight for at least one week. REE and macronutrient utilization, measured by respiratory quotient (RQ), were assessed by indirect calorimetry using the Deltatrac II Metabolic Monitor ®. Body composition, expressed as fat-free mass (FFM), fat mass (FM) and adiposity defined as percentage of FM (% FM), was measured by air displacement plethysmography using the Pea Pod ®.

RESULTS

Four infants were included at 3 to 5 postnatal weeks. Recommended energy and macronutrient intakes for healthy term infants were provided. Through the study, the median (min-max) REE (Kcal/Kg FFM/d) was 70.8 (60.6-96.1) and RQ was 0.99 (0.72-1.20). Steady increases in both body weight and FFM were associated with initial decrease in FM and adiposity followed by their increase. Low RQ preceded decrease in adiposity.

CONCLUSION

The marked adiposity depletion, not expected during steady weight gain in the postsurgical period, prompts us to report this finding. The subsequent adiposity catch-up was associated with relatively high REE and RQ, suggesting preferential oxidation of carbohydrates and preservation of lipids for fat storage.

Accurate estimation of energy requirements of young patients

The provision of optimal nutritional care is based on accurate estimations of patients' resting energy expenditure. The latter can be calculated with the use of predictive equations or measured with indirect calorimetry (IC). Owing to their ease of use, mathematical equations have largely replaced IC in clinical practice. This article examines the limitations and predictive inaccuracy of commonly used equations in pediatrics, which may contribute to the provision of poor nutritional care and directly affect patient outcomes. In addition, the role of IC is discussed and the physiology of nutrient metabolism, in terms of energy expenditure, is reviewed.