Influence of energy substrates on respiratory gas exchange during conventional mechanical ventilation of preterm infants

Current Nutrition Management of Infants With Chronic Lung Disease

Preterm infants with lung disease present nutrition challenges to health care providers. Malnutrition is common, develops shortly after birth, and may continue into early childhood. Although there are many studies identifying the nutrient deficiencies in infants with chronic lung disease, few randomized trials have explored the effects of nutrition support on the prevention and treatment of chronic lung disease. The purpose of this article is to review current practices and ongoing controversies in the nutrition management of infants with chronic lung disease.

Das Frühgeborene

Die nekrotisierende Enterokolitis ist die klinisch wichtigste gastrointestinale Erkrankung des Neugeborenen, vor allem des Frühgeborenen. Selbst in der leichten Form stellt sie stets eine Notfallsituation dar. Neben schweren perakuten entzündlichen Veränderungen der Darmwand entstehen Koagulationsnekrosen, z. T. mit Perforationen. Betroffen sind vor allem das terminale Ileum und das angrenzende Kolon. Es kann aber der gesamte Gastrointestinaltrakt von der Erkrankung erfasst werden. Bislang gibt es keine eindeutige ätiologische Erklärung für die NEK, gleichwohl sind eine Reihe von pathogenetischen Risikofaktoren bekannt. Die Beschwerden können von Magenentleerungsstörungen und einem ausladenden Abdomen bis hin zu foudroyanten und letalen Verläufen reichen. Das therapeutische Vorgehen richtet sich nach der Schwere der Erkrankung: Nahrungskarenz, Entlastung des Gastrointestinaltrakts, antibiotische Therapie bis zur operativen Revision des betroffenen Darmabschnitts. Die Mortalität ist hoch, insbesondere bei extrem früh Geborenen.

Nutrient supplies for optimal health in preterm infants

The most commonly recommended standard for postnatal nutrition of very preterm infants is one that meets the unique nutritional requirements of the growing human fetus and duplicates normal in utero human fetal growth (weight and body composition) and development. Normal fetal nutrition, therefore, may be a useful guide for designing postnatal nutritional strategies in very preterm infants who need to grow and develop outside the uterus. Such information indicates that normal fetal nutrition requires certain nutrients in optimal amounts and certain growth-promoting hormones in response to nutrient supply that together support optimal fetal growth and development; these include oxygen, glucose, lipids, amino acids, and insulin. Interestingly, nutrient restriction and nutrient excess in the fetus, while leading to different phenotypes, produce a similar phenotype in later life characterized as the "metabolic syndrome," consisting of obesity, insulin resistance, diabetes, and cardiovascular disease. After birth, preterm infants--who almost universally are not fed as much as normally growing fetuses receive in nutrient supply via the placenta--also end up with a higher incidence of short stature and a predisposition to the metabolic syndrome, whereas those fed excessive amounts of energy and who develop excessive growth primarily of adipose tissue in early life (rapid, positive crossing of weight-for-length centiles) also develop a higher incidence of the metabolic syndrome. It is clear, therefore, that just the right amount of the essential nutrients is required to produce optimal outcome; this is as true for the preterm infant as it is for the fetus.

Special circumstances: trophic feeds, necrotizing enterocolitis and bronchopulmonary dysplasia

There are many unresolved issues regarding how to feed the extremely-low-birth-weight (ELBW) infant. Trophic feedings of small volumes of breast milk or formula do not appear to increase the incidence of necrotizing enterocolitis (NEC). For prevention of NEC, breast milk, antenatal steroids and fluid restriction each confers a benefit. Because the incidence of NEC is relatively low, to determine if a particular prevention strategy is effective, large numbers of infants would need to be enrolled in a prospective, randomized controlled trial, and such trials are rare. Candidate therapies for NEC prevention that warrant further study include oral immunoglobulins, probiotics, long-chain polyunsaturated fatty acids and arginine. Suboptimal nutrition in ELBW infants is common in the early postnatal period. This is also the most critical time for the development of bronchopulmonary dysplasia, when even brief periods of malnutrition have significant effects on lung development and growth.

Bronchopulmonary dysplasia (chronic lung disease of infancy): an update for the pediatrician

This paper is a review of the changes that have occurred over the past 35 years in the clinical and radiologic presentation of bronchopulmonary dysplasia (BPD), now more commonly referred to as chronic lung disease of infancy (CLD). Curent thoughts on etiology are only briefly discussed. The major focus is the management of the patient with CLD by the primary care physician once the patient has been discharged from hospital. Oxygen, diuretic, bronchodilator, antiinflammatory and nutritional therapies are discussed in detail. Finally, current information on long-term prognosis and recommendations for the prevention of RSV and influenza infections are reviewed.

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 x kg(-1) x d(-1) with 35, 65, and 50% of the nonprotein energy as carbohydrate. Groups 3 and 4 received energy intake of 155 kcal x kg(-1) x d(-1) with 35 and 65% of the nonprotein energy as carbohydrate. Protein intake of all groups was 4 g x kg(-1) x 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 expenditure in infants with pulmonary insufficiency: is there evidence for increased energy needs?

The observed growth failure in infants with pulmonary insufficiency is postulated to be a consequence of elevated rates of energy expenditure. Assessment of energy expenditure by the classical technique of indirect calorimetry has yielded conflicting results. The adoption of the newer, doubly labeled water technique has provided evidence to support increased rates of energy expenditure in infants with chronic lung disease, congenital heart disease and in minimally ill, extremely low birth weight infants. The doubly labeled water technique holds great promise for the detailed study of energy expenditure in a variety of clinical conditions, including very ill as well as free-living subjects.

Chronic pulmonary insufficiency in children and its effects on growth and development

Conditions leading to chronic pulmonary insufficiency can affect infants and children. These can lead to growth failure and delayed development. Among the most common and severe of these are bronchopulmonary dysplasia (BPD) and cystic fibrosis. In addition to the respiratory consequences of these diseases, there is ample evidence that they lead to decreased growth as a result of decreased energy intake and increased energy expenditure. Furthermore, there is evidence that infants with BPD may also have delayed development, independent of the effects of their prematurity. Enhancing the long-term outlook for these conditions may therefore require consideration of both improved pulmonary management and aggressive nutritional management to limit growth failure and potentially enhance developmental outcome. Specific micronutrient supplementation, such as antioxidant therapy, may also enhance pulmonary and nutritional status.

Stability of respiratory quotient and growth outcomes of very low birth weight infants

Nutritional management of very low birth weight (VLBW) infants involves promoting growth at rates that mimic intrauterine rates. Nutritional intake at the recommended energy level to promote growth results in fat accretion at levels that exceed intrauterine rates for fat accretion. The respiratory quotient (RQ), the ratio of carbon dioxide produced to oxygen consumed during oxidation, provides a measure of the percentage of substrates used for energy. An RQ of greater than 0.9 indicates carbohydrate is used to meet energy needs, allowing the majority of fat intake to be stored as new tissue. The purpose of this study was to examine the stability of the RQ across time in relation to nutritional intake and growth in VLBW infants. Subjects were 9 enterally fed VLBW infants. Measurements to determine the RQ were obtained weekly for 3 weeks by indirect calorimetry. Nutritional intake and growth velocity were examined. There was no significant difference in the RQ across 3 weeks. The mean (+/- SD) RQs for each of the 3 weeks were 1.08 (+/- 0.04), 1.06 (+/- 0.05), and 1.06 (+/- 0.07), respectively. No significant differences were found across the 3 weeks for any of the macronutrient variables. Growth velocity for the period was 15.7 g/kg/day. By discharge from the NICU, 66% of the infants had weights less than the 10th percentile on an intrauterine growth reference. An RQ greater than 1.0 indicates VLBW infants are depositing excess fat. However, increased accretion rates of fat did not improve the growth outcomes of these VLBW infants.

Assessment of pulmonary function in resolving chronic lung disease of prematurity

AIM

To investigate the longitudinal changes of interstitial and airways disease in resolving chronic lung disease of prematurity (CLD).

METHODS

Thirty three infants were studied between 35 and 40 weeks of postconceptional age, and then at three monthly intervals throughout their first year. Measurements of mean arterial oxygen saturation (MSaO2) and its variability (delta MSaO2) were recorded. PaCO2 and PaO2 were determined while the infants breathed steady state 50% oxygen via a hood. From these, the alveolar arterial difference (A-a) DO2(50) was calculated. Airway disease was assessed by the measurement of partial forced expiratory flow volume curves (PEFC) to give Vmax Frc.

RESULTS

The cohort mean +/- 95% confidence intervals measured between 35 and 40 weeks were for MSaO2 (89.25 +/- 1.87%, range 75-96.5%) and delta MSaO2 (4.79 +/- 0.8%, range 0.16-9.64%), PaCO2 (5.89 +/- 0.56 kpa, range 4.2-10.11 kpa), (A-a) DO2(50) (22.7 +/- 2.56 kpa, range 6.67-31.4 kpa) and VmaxFrc (41.5 +/- 8.65 mls/second, range 8.5-103.7 ml/second). The most significant improvement in all measurements occurred within the first three months (P = 0.05). An MSaO2 of less than 90% in room air at 1 year of age was predicted between 35 and 40 weeks postconceptional age by an (A-a) DO2(50) of greater than 29 kpa, with a sensitivity of 0.85 and a specificity of 0.88, and a PaCO2 greater than 7 kpa predicted a specificity of 0.78 and a sensitivity of 0.88. Predictions were strengthened by combining the above criteria and these then gave a sensitivity and specificity of 1.

CONCLUSION

Measurements of (A-a) DO2(50) and PaCO2 taken between 35 and 40 weeks can be used to assess the degree of pulmonary dysfunction at 1 year. Quantification of the severity of CLD could be used as a measurable end point for early neonatal intervention studies.