The future of nutrition for the low birth-weight infant.
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Humans↗
Biomedical subjects
P R Swyer
Publications and source records attributed to P R Swyer.
Metabolic consequences of increasing energy intake by adding lipid to parenteral nutrition in full-term infants.
The effect on energy metabolism and fuel utilization of increasing energy intake by adding intravenous lipid to a glucose and amino acid regimen was examined. Twenty fullterm, appropriate-for-gestational-age, intravenously fed neonates were entered into one of two groups: total energy intake was 261 kJ.kg-1 x d-1 (62 kcal.kg-1 x d-1) in group 1 and 355 kJ.kg-1 x d-1 (85 kcal.kg-1 x d-1) in group 2. Both groups received 2.8 g protein.kg-1 x d-1 and 14 g glucose.kg-1 x d-1. Group 2 received an additional 2 g lipid.kg-1 x d-1. Metabolic rate, respiratory gas exchange, and nonprotein substrate oxidation were similar in both groups. The addition of energy as lipid enhanced nitrogen retention (230 vs 306 mg.kg-1 x d-1; P < 0.02) and utilization (52.8% vs 66.5%; P < 0.03). Our data suggest that nitrogen utilization is improved in parenterally fed neonates by adding fat and increasing energy intake without change in metabolic rate, carbon dioxide production, oxygen consumption, and nonprotein substrate utilization. Energy expenditure does not necessarily increase with increasing energy intake independently of diet composition.
Calorimetry↗
Organisation of perinatal/neonatal care.
There is no single system, whether state run, private or mixed, that consistently produces superior perinatal results (131), although these usually emanate from jurisdictions with regionalised or centralised comprehensive antenatal and natal care, as opposed to haphazard systems of care. Again the literature is "more description than evaluation, possibly because the latter requires comparative studies or audits which have not caught up with the new technology" (132). Changes in the organisation and delivery of reproductive health care since 1960, combined with advances in treatment, have apparently had an impact on the outcome of pregnancy and newborn care, resulting in reductions in perinatal mortality, mainly through their influence on birthweight-specific mortality. The latter is a major marker of the quality of hospital reproductive health care. Changes in the distribution of weights at birth have been relatively small; consequently the proportional numbers of infants born weighing less than 1500 g, who contribute most to morbidity and mortality, has roughly tracked the birth rate and has changed little. The proportion of babies born of low weight due to prematurity and/or intrauterine growth restriction, which are mainly influenced by socioeconomic and environmental factors, has seen only a marginal reduction in most developed countries and cannot explain the fall in mortality. Many reviews (e.g. 31, 36-38, 40, 41, 43-45, 47-52, 54, 55, 66, 67, 90, 93-95) of perinatal care now accept the cause and effect relationship between enhanced perinatal care and decline in perinatal mortality. Reduction in the incidence of low birthweight between 1500 and 2500 g is attributed more to the influence of environmental and lifestyle factors, including the standard of living, housing and nutrition, the level of education and the prevalence of infections in the population. On the other hand, the incidence of infants born weighing less than 1500 g, the major contributors to perinatal morbidity and mortality in developed societies, is relatively stable across time and across different jurisdictions. It forms about 1% of all births, but is responsible for 60-75% of morbidity and mortality. It appears relatively insusceptible to improvements in standards of living and other environmental factors. It may be more dependent on biological factors controlling the onset of premature labour, the incidence of genetic or chromosomally determined disease and the prevalence of teratogens. The only way to influence these factors is through a better understanding of the mechanisms by which they operate, which should lead to the appropriate strategy for their elimination.(ABSTRACT TRUNCATED AT 400 WORDS)
Child↗
How small is too small? A personal opinion.
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Humans↗
Assumptions used in measurements of energy metabolism.
The knowledge that the chemical burning of nutrients and the oxidation of nutrients in animals were similar energy-releasing processes laid the foundations for the study of energy metabolism by direct and indirect calorimetry. The early development of calorimetry and its pioneers will be reviewed.
Animal Nutritional Physiological Phenomena↗
Effect of replacing glucose with lipid on the energy metabolism of newborn infants.
1. Indirect calorimetry and primed constant infusion of [U-13C]glucose were combined in 28 appropriate-for-gestational age newborn, parenterally fed infants, in order to measure glucose utilization and glucose oxidation and to estimate lipogenesis from glucose. 2. The infants were randomly allocated to either a group receiving glucose as the non-protein energy source or a group having one-quarter of the glucose energy replaced by intravenous fat. The energy intake (370 kJ day-1 kg-1) and protein intake (3.4 g day-1 kg-1) were similar in both groups. 3. Energy expenditure (P less than 0.005), non-protein carbon dioxide production (P less than 0.005) and non-protein oxygen consumption (P less than 0.05) were lower in the lipid-supplemented group. 4. The significant excess of glucose utilization over oxidation (P less than 0.001) can be accounted for by lipid synthesis from glucose. 5. Fat synthesis from glucose was higher in the glucose/amino acid group (P less than 0.02), but total fat storage was higher in the lipid-supplemented group (P less than 0.02). Nitrogen balance was similar in both groups. 6. As lipogenesis from glucose is an energy- and oxygen-consuming and a carbon dioxide-producing process, the data suggest that the differences between the glucose-only group and the lipid-supplemented group are due to different rates of lipogenesis from glucose.
Calorimetry↗
Evaluation of doubly labeled water for measuring energy expenditure during changing nutrition.
Change in abundance of 2H and 18O in dietary water during a doubly labeled water energy period may introduce error into the calculated carbon dioxide production rate (RCO2). To examine the accuracy of 2H2(18)O during changing nutritional regimens, we compared 2H2(18)O and periodic open-circuit respiratory gas exchange (RGE) in postsurgical infants who were changing from parenteral to alternative parenteral and/or oral nutrition. The two methods were compared before and after correction for shifts in isotopic abundance of the infant water pools during the energy-expenditure period. Baseline corrections were predicted using the difference between abundances of the initial body water and final nutrient solutions. Before isotopic correction, 2H2(18)O underestimated RCO2 in eight subjects by 11.8 +/- 20.1% (mean +/- SD). After correction, agreement between the two methods improved; the underestimate was then -8.7 +/- 12.9%. To obtain maximum precision of 2H2(18)O, subjects should be maintained on the same nutritional regimen before and during the study unless valid correction formulae are used.
Algorithms↗
New perspectives in neonatal nutrition.
Modern techniques of cardiopulmonary life support, particularly for very low birthweight infants and those suffering from major surgical conditions, has presented the neonatologist with a completely new population of infants for whom continued survival and further normal physical and mental growth and development are critically dependent on adequate nutrition. The uncertainties surrounding the definition of 'adequacy' as well as the techniques and difficulties of its attainment and assessment are exposed. This paper examines desirable goals to be aimed for in the nutrition of the neonate in relation to genetic potential for growth, development and body composition. There is discussion of current research into the intermediary metabolism and utilisation of macronutrients and certain minerals for energy production and tissue growth and of methodology for determining body composition. The editor has also allowed a certain licence for speculation concerning future directions in neonatal nutrition.
Body Composition↗
Validation of doubly labeled water for assessing energy expenditure in infants.
Previous studies show that the doubly labeled water method is accurate for measuring energy expenditure in the adult human. To validate this method in infants, carbon dioxide production rate and energy expenditure were measured for 5 to 6 days by doubly labeled water (DLW) and periodic open circuit respiratory gas exchange (RGE) in 10 blinded studies in nine infants following abdominal surgery. Infants were maintained on consistent oral or parenteral nutrition prior to and during study. This avoided diet-related changes in baseline isotopic enrichment of body water which could theoretically contribute to significant errors in calculation of carbon dioxide production rate. For DLW, insensible water loss was assumed to be proportional to respiratory volume and body surface area, where the former was predicted from carbon dioxide production rate. Insensible water loss thus calculated averaged 18% of water turnover. Rates of carbon dioxide production measured by DLW were not significantly different from that of RGE (10.4 +/- 1.1 and 10.5 +/- 0.9 l/kg/day, mean +/- SD, respectively). Energy expenditure was calculated using respiratory quotients from dietary intake (DLW:DIET) and RGE (DLW:RGE) data. There was no significant difference between energy expenditure determined by DLW (DLW:DIET and DLW:RGE) and that measured by RGE (58.5 +/- 6.1, 56.8 +/- 6.1, and 57.3 +/- 5.1 kcal/kg/day, mean +/- SD, respectively). Rate of carbon dioxide production, DLW:diet, and DLW:RGE calculated by DLW differed from corresponding RGE values by -0.9 +/- 6.2, -1.1 +/- 6.1, and 1.6 +/- 6.2%, mean +/- SD, respectively. These findings demonstrate the validity of the doubly labeled water method for determining energy expenditure in infants without concurrent water balance studies.
Absorption↗
Glucose oxidation rates in newborn infants measured with indirect calorimetry and [U-13C]glucose.
Indirect calorimetry and primed constant infusion of [U-13C]glucose were combined in 16 appropriate-for-gestational age newborn, parenterally fed infants, in order to measure glucose utilization and glucose oxidation respectively. Glucose intake ranged between 10.0 and 24.1 g day-1 kg-1 and energy intake between 156.9 and 439.3 kJ day-1 kg-1. Glucose utilization (P less than 0.001), glucose oxidation (P less than 0.001) and metabolic rate (P less than 0.005) increased significantly with rising glucose intake. The significant difference between glucose utilization and oxidation (P less than 0.001) can be accounted for by an increasing storage as fat. As lipogenesis from glucose consumes 15-24% of the original glucose energy, the increasing metabolic rate accompanying rising glucose intake is probably due to increasing lipogenesis.
Calorimetry, Indirect↗
Hypoxia associated with helium-oxygen therapy in neonates.
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Airway Obstruction↗
Myocardial ischaemia in asphyxia neonatorum. Electrocardiographic, enzymatic and histological correlations.
Serial electrocardiograms and creatine kinase (CK) isoenzyme activities were studied prospectively in 20 asphyxiated term newborn infants and 43 normal neonates. By adapting a previously described grading system for ischaemic changes, a degree of electrocardiographic ischaemia was defined which occurred almost solely in asphyxiated infants. Infants with this degree of abnormality had significantly higher mean CK-MB and MM activities than other asphyxiated infants at 0, 8 and 28 hours. Histological changes of peripartum myocardial necrosis were seen in 4 of the 5 infants on whom an autopsy was performed, and either electrocardiogram or CK-MB was abnormal in all four. It is concluded that myocardial injury in the newborn period is often associated with CK-MB release, but in view of the lack of cardiac-specificity of CK-MB in newborn infants, caution is urged in the interpretation of elevated isoenzyme activity in the neonate.
Asphyxia Neonatorum↗
The effect of energy intake and expenditure on the recovery of 13CO2 in the parenterally fed neonate during a 4-hour primed constant infusion of NAH13CO3.
The use of 13CO2 excretion to measure the oxidation of 13CO2 labeled substrates is increasing as it is both noninvasive and lacks the radiation exposure associated with the use of 14C. No standards are available for 13CO2 recovery in breath from the bicarbonate pool in the neonate. A primed constant infusion of NaH13CO3 over 4 h was used with open circuit indirect calorimetry in 15 appropriate for gestational age newborn infants (gestational age 28-39 wk; postnatal age 2-52 days), on varying amounts of intravenous feeding (37-114 kcal X kg-1 X day-1). Following a bolus of 6.9 mumol X kg-1 of NaH13CO3, a maintenance infusion of 4.6 mumol X kg-1 X h-1 was started. The 13C enrichment in breath rose rapidly to reach a plateau by 90 min with less than 5% variation of the plateau. Recovery of the tracer in breath ranged from 69.6-83.5% and was significantly correlated with 1) energy intake (37-114 kcal X kg-1 X day-1); 2) metabolic rate (34.6-56.1 kcal X kg-1 X day-1); 3) VCO2 (4.86-7.43 ml X kg X -1 X min-1). There was no correlation with the level of protein or fat intake. We provide an equation that can be used to calculate the correction factor when doing constant infusion substrate oxidation studies with a 13C label in neonates.
Bicarbonates↗
Combined noninvasive assessment of the patent ductus arteriosus in the preterm infant before and after indomethacin treatment.
Fifteen preterm infants who weighed 0.7 to 2.0 kg and had clinical evidence of a patent ductus arteriosus (PDA) were studied by combined 2-dimensional and Doppler echocardiography before and after the administration of indomethacin. In 10 patients the PDA was widely patent at the time of the study and in 5 the lumen was narrow. In this latter group, the PDA was narrow at the pulmonary artery end in 2 patients, in the middle in 2 patients and at the aortic end and the middle in 1 patient. After the administration of intravenous indomethacin, the PDA closed completely in 12 patients and constricted in 3. The patterns of closure could be documented in those in whom serial studies were performed. In 3 patients, closure occurred after a single dose of indomethacin, in 3 after 2 doses and in the rest after a full course of 3 doses. Doppler interrogation at the aortic and pulmonary artery end of the PDA demonstrated the shunting patterns and provided a reliable assessment of patency after the ductal lumen was outside the range of lateral resolution following constriction. In no case did the PDA reopen after the course of indomethacin. This combined approach is a reliable method of assessing a PDA before and after a course of indomethacin. It should provide the means to answer many of the questions regarding the effect of various manipulations on the PDA in the preterm infant.
Ductus Arteriosus, Patent↗
Metabolic consequences of intrauterine growth retardation in very low birthweight infants.
By the combination of energy and macronutrient balances, continuous open circuit computerized indirect calorimetry, and anthropometry, we have compared small for gestational age (SGA) and appropriate for gestational age (AGA) very low birthweight infants with respect to metabolizable energy intake (mean +/- SE: 125.9 +/- 2.5 versus 130.4 +/- 3.5 kcal/kg X day), energy expenditure (67.4 +/- 1.3 versus 62.6 +/- 0.9 kcal/kg X day), storage of energy and macronutrients and growth. Fourteen studies in six SGA infants (gestational age, 33.1 +/- 0.3 weeks; birthweight, 1120 +/- 30 g) and 22 studies in 13 AGA infants (gestational age, 29.3 +/- 0.4 weeks; birthweight, 1155 +/- 40 g) were performed. The SGA infants had a lower absorption of fat (68.7 +/- 3.2 versus 79.7 +/- 1.7%) and protein (69.1 +/- 3.2 versus 83.4 +/- 1.5%) and hence increased (P less than 0.001) energy loss in excreta (29.9 +/- 2.8 versus 18.2 +/- 1.5 kcal/kg X day). The significant hypermetabolism of SGA infants by 4.8 kcal/kg X day was associated with an increased fat oxidation. Despite lower energy storage, SGA infants were gaining weight (19.4 +/- 0.9 g/kg X day), length (1.25 +/- 0.14 cm/week), and head circumference (1.16 +/- 0.9 cm/week) at higher rates than the AGA group. The energy storage per g weight gain was lower (P less than 0.001) in the SGA group (3.0 +/- 0.14 versus 4.26 +/- 0.26 kcal) reflecting higher water, lower fat (22.2 +/- 1.8 versus 33.8 +/- 2.5%; P less than 0.001) and lower protein (7.7 +/- 0.5 versus 12.5 +/- 0.8%; P less than 0.001) contents of weight gain in the SGA group.
Body Weight↗
Quality of growth in premature infants fed their own mothers' milk.
With the renewed interest in the feeding of human milk to preterm infants, we have evaluated the partition of energy metabolism and of macronutrient utilization and accretion in growing very low birth weight infants fed their own mother's milk. Fifteen studies combining macronutrient balance, computerized continuous open-circuit indirect calorimetry, and anthropometric measurements were performed in 11 growing, very low birth weight (less than 1.300 gm) preterm infants. The mean milk intake of 172 ml/kg/day provided a gross energy intake of 111 kcal/kg/day. Energy losses in excreta were 11 kcal/kg/day, and the metabolic energy expenditure was 56 kcal/kg/day. The remainder (44 kcal/kg/day) represented the energy stored in the components of new tissue. The infants were gaining weight (15.3 g/kg/day), length (0.98 cm/wk), and head circumference (0.76 cm/wk) at rates approximating intrauterine growth rates. The metabolic energy expenditure was derived from the oxidation (mean +/- SE) of carbohydrate, 9.5 +/- 0.7 gm/kg/day; fat, 1.63 +/- 0.34 gm/kg/day; and protein, 0.68 +/- 0.07 gm/kg/day. The stored energy comprised 2.98 +/- 0.86 gm/kg/day as carbohydrate, 2.25 +/- 0.54 gm/kg/day as fat, and 1.97 +/- 0.1 gm/kg/day as protein. The accretion rates of fat and protein, as well as the composition of the weight gain (fat, 16.6 +/- 4.1%; protein, 13.4 +/- 0.5%), were similar to those reported for the fetus of comparable gestational age.
Anthropometry↗
Serial electrocardiographic changes in healthy and stressed neonates.
Serial changes in T-wave vector and polarity were assessed in 162 electrocardiograms, 117 from 44 healthy term neonates and 45 from 17 stressed neonates. Records were taken at 5 to 8 hours, 24 to 33 hours, and 71 to 96 hours after birth. Sequential changes in both T-wave amplitude and frontal and horizontal axes were found in both groups. A lag period was noted between healthy and stressed infants when comparing changes in T-wave amplitude, with greater flattening of T-waves for longer periods of time after birth in the stressed group. The normal changes in T-wave axis over time in the horizontal and frontal planes showed a similar lag in the stressed group. Alterations of T-wave amplitude and axis alone may be markers of myocardial ischaemia in neonates but are only reliable signs after the first 24 hours of life.
Apgar Score↗
Dietary composition and macronutrient storage in preterm infants.
A comparison has been made of the influence of feeding own mother's milk and formula on the oxidation and accretion of energy and macronutrients in the growing preterm infant of very low birth weight (less than 1,300 g) by using the combined techniques of nutrient balance and computerized indirect calorimetry. There were 22 studies in formula-fed infants and 15 studies in premature infants fed own mother's milk. Despite their lower metabolizable energy intake, the infants fed own mother's milk grew in weight, length, and head circumference at a rate approximating those of the formula-fed group. The metabolic rate was significantly lower in the infants fed own mother's milk (56.0 +/- 0.9 v 62.6 +/- 0.8 kcal/kg/d; P less than .001). The protein intake, oxidation, and accretion were similar in the two groups. The infants fed own mother's milk had a significantly lower fat intake (P less than .001), higher fat oxidation (P less than .025) and consequently lower fat accretion (P less than .001) than the formula-fed infants. The proportional fat content of the daily weight gain was lower in the infants fed own mother's milk (16% v 33%; P less than .001) but protein content was similar (13% v 12%). The accretion of energy, fat, and protein correlated with the respective metabolizable intakes in both groups (r = .81 to .98; P less than .001), suggesting that accretion rates and hence composition of weight gain are dependent on levels of energy and macronutrient intake.
Animals↗