Longitudinal evaluation of energy expenditure in preterm infants with birth weight less than 1000 g

Enteral Nutrition in Preterm Infants (2022): A Position Paper From the ESPGHAN Committee on Nutrition and Invited Experts

OBJECTIVES

To review the current literature and develop consensus conclusions and recommendations on nutrient intakes and nutritional practice in preterm infants with birthweight <1800 g.

METHODS

The European Society of Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) Committee of Nutrition (CoN) led a process that included CoN members and invited experts. Invited experts with specific expertise were chosen to represent as broad a geographical spread as possible. A list of topics was developed, and individual leads were assigned to topics along with other members, who reviewed the current literature. A single face-to-face meeting was held in February 2020. Provisional conclusions and recommendations were developed between 2020 and 2021, and these were voted on electronically by all members of the working group between 2021 and 2022. Where >90% consensus was not achieved, online discussion meetings were held, along with further voting until agreement was reached.

RESULTS

In general, there is a lack of strong evidence for most nutrients and topics. The summary paper is supported by additional supplementary digital content that provide a fuller explanation of the literature and relevant physiology: introduction and overview; human milk reference data; intakes of water, protein, energy, lipid, carbohydrate, electrolytes, minerals, trace elements, water soluble vitamins, and fat soluble vitamins; feeding mode including mineral enteral feeding, feed advancement, management of gastric residuals, gastric tube placement and bolus or continuous feeding; growth; breastmilk buccal colostrum, donor human milk, and risks of cytomegalovirus infection; hydrolyzed protein and osmolality; supplemental bionutrients; and use of breastmilk fortifier.

CONCLUSIONS

We provide updated ESPGHAN CoN consensus-based conclusions and recommendations on nutrient intakes and nutritional management for preterm infants.

Extreme prematurity, growth and neurodevelopment at 8 years: a cohort study

OBJECTIVE

Infants born extremely preterm (EP, <28 weeks' gestation) exhibit poorer growth and neurodevelopmental impairment in early childhood compared with their term-born peers. Whether poor growth persists and whether associations of growth with neurodevelopmental functioning have changed in the decades since the introduction of surfactant are not well described. This study aims to (1) compare growth from birth to 2 years then 8 years in children born EP between three different eras, and (2) investigate the associations of growth from birth to 2 years then 8 years with cognitive, academic, executive and motor function at 8 years, and if associations have changed over time.

DESIGN

Prospective observational cohort studies in the State of Victoria, Australia in three discrete eras: 1991-1992, 1997 and 2005. EP children had weight and head circumference measured at birth, and weight, head circumference and height at 2 and 8 years. Cognitive ability, academic performance, executive function and motor skills were assessed at 8 years, corrected for prematurity.

RESULTS

499/546 (91%) of surviving EP children were fully assessed at 8 years. Growth in children born EP did not differ substantially between eras and associations between growth and neurodevelopment did not change over time. Overall, better weight and head growth from birth to 2 years were associated with improved neurodevelopment at 8 years.

CONCLUSIONS

Growth of children born EP has not improved in more recent eras. Better early head and weight growth are associated with improved neurodevelopment in mid-childhood.

[Surviving the Lack: Natural Adaptations in Newborns]

Newborns are equipped with a number of natural adaptation mechanisms preventing them from impaired energy supply, despite their elevated (size-related) metabolic rate. These include the diving response known from aquatic mammals, which - being composed of apnea, bradycardia, and vasoconstriction - ensures an economical use of O₂ reserves and results in a subsequent influx of lactate out of peripheral tissues. From a metabolic point of view, mammalian fetuses behave "like an organ of the mother" and thus exhibit a hibernation-like deviation from the overall metabolic size relationship that adapts them to the limited intrauterine O₂/substrate availability. In case of lacking supply, they can reduce their energy demands even further by foregoing growth, with the placenta acting as a gatekeeper. Postnatal hypoxia does not only result in the suppression of non-shivering thermogenesis, but also in a hypoxic hypometabolism that otherwise has only been known from poikilothermic animals. After prolonged apnea, gasps do occur that maintain a rudimentary heart action through short elevations in pO₂ (autoresuscitation). Overall, these mechanisms postpone a critical O₂ deficit and thereby provide a "resistance" rather than a "tolerance" to hypoxia. As they are based on an (active) reduction in energy demand, they are not easy to distinguish from the (passive) breakdown of metabolism resulting from hypoxia.

A Pumpless Microfluidic Neonatal Lung Assist Device for Support of Preterm Neonates in Respiratory Distress

Premature neonates suffer from respiratory morbidity as their lungs are immature, and current supportive treatment such as mechanical ventilation or extracorporeal membrane oxygenation causes iatrogenic injuries. A non-invasive and biomimetic concept known as the "artificial placenta" (AP) would be beneficial to overcome complications associated with the current respiratory support of preterm infants. Here, a pumpless oxygenator connected to the systemic circulation supports the lung function to relieve respiratory distress. In this paper, the first successful operation of a microfluidic, artificial placenta type neonatal lung assist device (LAD) on a newborn piglet model, which is the closest representation of preterm human infants, is demonstrated. This LAD has high oxygenation capability in both pure oxygen and room air as the sweep gas. The respiratory distress that the newborn piglet is put under during experimentation, repeatedly and over a significant duration of time, is able to be relieved. These findings indicate that this LAD has a potential application as a biomimetic artificial placenta to support the respiratory needs of preterm neonates.

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.

Artificial placenta: Analysis of recent progress

The artificial placenta (AP) has for many decades captured the imagination of scientists and authors with popular fiction including The Matrix and Aldous Huxley's "Brave New World", depicting a human surviving ex-utero in an artificial uterine environment (AUE). For scientists this has fascinated as a way forward for extremely preterm infants (EPIs) born less than 28 weeks of gestation. Early successes with mechanical ventilation (MV) for infants born above 28 weeks of gestation meant that AP research lost momentum. More recently, the gestational age limit for survival now borders on 23 weeks and corresponds to the biological milestone of lung development marked by the early canalicular stage of lung morphogenesis. The so called greyzone of 23-25 weeks represents a steep increase in mortality with decreasing gestational age and current options in neonatal care are on the fringes of efficacy for this population. A shift in thinking recognizes the vitality of EPIs as a fetus rather than a 37-40 week neonate and this has reinvigorated the concept of the AP. This review will discuss the scale of extreme preterm birth with special reference to previable infants born in the greyzone. Recent AP studies using sheep models are compared, technical obstacles discussed and future research themes identified.

Early Postnatal Growth in a Subset of Convalescing Extremely-Low-Birth-Weight Neonates: Approximating the "Index Fetus" Ex Utero

OBJECTIVES

The aim of the study was to evaluate whether a subset of noncritically ill, convalescing extremely-low-birth-weight neonates who were managed using a standardized nutritional protocol could achieve the growth rate of the index fetus. We hypothesized that an aggressive nutritional protocol applied to noncritically ill, convalescing premature neonates could achieve the growth rate of the index fetus.

METHODS

This was a retrospective review of a subset of 21 premature neonates defined by 4 criteria: inborn or transferred-in within 24 hours of birth, gestational age < 30 weeks and birth weight ≤1000 g, hospitalized >35 postnatal days, and discharged between 34 and 42 weeks postconceptual age. Optimal growth at discharge was defined as weight and head circumference >10th percentile compared with comparable gestational age fetal parameters.

RESULTS

Protein intake of ≥1.4 g · kg · day and energy ≥30 kcal · kg · day were provided as of the first postnatal day. Proteins ≥3 g · kg · day and >80 kcal · kg · day were established ≥10th postnatal day. Birth weight was regained by postnatal day 10 ± 5 day (mean + standard deviation). Nutrition was predominantly enteral (ie, >50% of all calories) after the 11th postnatal day. At discharge, 71% (15/21) by weight and 76% (16/21) by head circumference were >10th percentile. After 30 weeks postconceptual age, the cohort exceeded the weight gain rate (g/wk) of a 10th-percentile fetus.

CONCLUSIONS

In a selected subset of noncritically ill, convalescing extremely-low-birth-weight neonates, after a brief period of unavoidable postnatal weight loss and body water adjustment, adequate nutrition from birth can enable a more homeostatic pattern of growth that approximates growth of the index fetus.

Relationship between energy expenditure and stress behaviors of preterm infants in the neonatal intensive care unit

PURPOSE

This research evaluated the relationship between behaviors and energy expenditure in preterm infants receiving nursing interventions.

DESIGN AND METHODS

This study was an explorative secondary data analysis from a previous study. The current study investigated energy expenditure calculated using heart rate-based energy expenditure-estimate across 500 repeated measures for 37 infants.

RESULTS

Research results indicate that preterm infants expend more energy when they show the following seven behaviors: grimace, sucking, diffusion squirm, fist, gape face, salute, and sneezing.

PRACTICE IMPLICATIONS

The interventions for preterm infants should be flexible, according to the infant's stress behaviors and conditions of energy expenditure.

Artificial Placenta - Lung Assist Devices for Term and Preterm Newborns with Respiratory Failure

Respiratory insufficiency is a major cause of neonatal mortality and long-term morbidity, especially in very low birth weight infants. Today, non-invasive and mechanical ventilation are commonly accepted procedures to provide respiratory support to newborns, but they can reach their limit of efficacy. To overcome this technological plateau and further reduce mortality rates, the technology of an “artificial placenta”, which is a pumpless lung assist device connected to the umbilical vessels, would serve to expand the therapeutic spectrum when mechanical ventilation becomes inadequate to treat neonates with severe respiratory insufficiency.

The first attempts to create such an artificial placenta took place more than 60 years ago. However, there has been a recent renaissance of this concept, including developments of its major components like the oxygenator, vascular access via umbilical vessels, flow control, as well as methods to achieve hemocompatibility in extracorporeal circuits. This paper gives a review of past and current development, animal experiments and human case studies of artificial placenta technology.

Supplementing monosodium glutamate to partial enteral nutrition slows gastric emptying in preterm pigs(1-3)

Emerging evidence suggests that free glutamate may play a functional role in modulating gastroduodenal motor function. We hypothesized that supplementing monosodium glutamate (MSG) to partial enteral nutrition stimulates gastric emptying in preterm pigs. Ten-day-old preterm, parenterally fed pigs received partial enteral nutrition (25%) as milk-based formula supplemented with MSG at 0, 1.7, 3.0, and 4.3 times the basal protein-bound glutamate intake (468 mg·kg(-1)·d(-1)) from d 4 to 8 of life (n = 5-8). Whole-body respiratory calorimetry and (13)C-octanoic acid breath tests were performed on d 4, 6, and 8. Body weight gain, stomach and intestinal weights, and arterial plasma glutamate and glutamine concentrations were not different among the MSG groups. Arterial plasma glutamate concentrations were significantly higher at birth than after 8 d of partial enteral nutrition. Also at d 8, the significant portal-arterial concentration difference in plasma glutamate was substantial (∼500 μmol/L) among all treatment groups, suggesting that there was substantial net intestinal glutamate absorption in preterm pigs. MSG supplementation dose-dependently increased gastric emptying time and decreased breath (13)CO2 enrichments, (13)CO2 production, percentage of (13)CO2 recovery/h, and cumulative percentage recovery of (13)C-octanoic acid. Circulating glucagon-like peptide-2 (GLP-2) concentration was significantly increased by MSG but was not associated with an increase in intestinal mucosal growth. In contrast to our hypothesis, our results suggest that adding MSG to partial enteral nutrition slows the gastric emptying rate, which may be associated with an inhibitory effect of increased circulating GLP-2.

Nutritional needs of the micropreterm infant

We have used an expansive definition of a micropreterm infant as <30 weeks' gestation to provide a global perspective to a "high risk" group of preterm infants for which there are little published data to guide nutritional management. Consensus nutritional guidelines for preterm infants have been developed for infants >1000 g birth weight and >28 weeks' gestational age. Micropreterm infants have greater nutritional deficits at birth than more mature preterm infants and accumulate greater postnatal deficits. Nutritional guidelines based on the needs of preterm infants born >28 weeks' gestation are unlikely, on a theoretical basis, to meet nutritional requirements of micropreterm infants. Unfortunately, very few good quality studies have addressed the nutritional requirements of this group specifically; this makes it difficult to formulate solid, evidence-based nutritional recommendations for these neonates. Nutritional management of micropreterm infants is based on recommendations established for preterm infants, which are adjusted after considering an infant's gestational age, birth weight, and clinical status. Minimal enteral feeding should commence on the first or second day of life, with incremental advancement and fortification of human milk when 100 mL/kg is tolerated. Early use of parenteral nutrition is recommended, ideally initiated within the first hours of life and enteral feeds are being established; this will help prevent the accumulation of nutritional deficits and incidence of growth failure. Fortified human milk should be given in order to meet nutritional requirements. When human milk is not available in sufficient quantity, a preterm formula should be given.

Longitudinal measurements of oxygen consumption in growing infants during the first weeks after birth: old data revisited

BACKGROUND

In a study conducted in 1966-1969, longitudinal measurements were made of the metabolic rate in growing infants. Statistical methods for analyzing longitudinal data weren't readily accessible at that time.

OBJECTIVES

To measure minimal rates of oxygen consumption (V·O2, ml/min) in growing infants during the first postnatal weeks and to determine the relationships between postnatal increases in V·O2, body size and postnatal age.

METHODS

We studied 61 infants of any birth weight or gestational age, including 19 of very low birth weight. The infants, nursed in incubators, were clinically well and without need of oxygen supplementation or respiratory assistance. Serial measures of V·O2 using a closed-circuit method were obtained at approximately weekly intervals. V·O2 was measured under thermoneutral conditions with the infant asleep or resting quietly. Data were analyzed using mixed-effects models.

RESULTS

During early postnatal growth, V·O2 rises as surface area (m(2))(1.94) (standard error, SE 0.054) or body weight (kg)(1.24) (SE 0.033). Multivariate analyses show statistically significant effects of both size and age. Reference intervals (RIs) for V·O2 for fixed values of body weight and postnatal age are presented. As V·O2 rises with increasing size and age, there is an increase in the skin-operative environmental temperature gradient (T skin-op) required for heat loss. Required T skin-op can be predicted from surface area and heat loss (heat production minus heat storage).

CONCLUSIONS

Generation of RIs for minimal rates of V·O2 in growing infants from the 1960s was enabled by application of mixed-effects statistical models for analyses of longitudinal data. Results apply to the precaffeine era of neonatal care.

Caloric intake and weight gain in a neonatal intensive care unit

The aim of this paper was to study the weight gain in very-low-birthweight (VLBW) infants by adopting earlier and higher intake of proteins and earlier intake of lipids. We studied 28 VLBW infants admitted to Neonatal Intensive Care Unit during the year 2004 (group 1) and 18 during the first semester of 2006 (group 2). Dietary intakes for group 1 were: 1 g kg(-1) day(-1) of proteins started at postnatal day 2 (P2) and 0.5-1 g kg(-1) day(-1) of lipids at P3; for group 2, 1-1.5 g kg(-1) day(-1) of proteins and 0.5-1 g kg(-1) day(-1) of lipids, both started at P1. Caloric intake was significantly higher in group 2 (p < 0.05), whereas cumulative nutritional deficit was higher in group 1 (p < or = 0.01). Weight z scores were significantly lower at discharge comparing with z scores at birth for each group (p < or = 0.01), with no differences between the two groups. Despite a higher protein intake which resulted in a lower nutritional deficit, the weight z score did not improve significantly at discharge.

Metabolic rate analysis of healthy preterm and full-term infants during the first weeks of life

BACKGROUND

Longitudinal data on resting energy expenditure (REE) in extremely immature infants and full-term neonates are scarce but are necessary to understand the energy requirements in neonatal nutrition during the first weeks of life.

OBJECTIVE

The aim of the present study was to measure REE and its main components longitudinally during the first weeks of life to quantify their significant determinants.

DESIGN

REE was investigated longitudinally over a period of 6 wk in healthy, stable, and growing preterm infants and over 5 wk in full-term neonates by means of indirect calorimetry.

RESULTS

A total of 197 infants, including 183 premature infants and 14 full-term neonates, were recruited for the study. REE values increased in all gestational age groups from the first week to 5-6 wk of postnatal age, with the most pronounced increase in the smallest infants (+140%) and the smallest increase in the full-term neonates (+47%). Univariate calculations showed that for each postnatal week, REE increased by 6.93-9.64 kcal x kg(-1) x d(-1) with each additional kcal administered, for an average increase of 0.701 kcal, and increased by 1.78 kcal for each 1 g gain in weight. Postnatal age was the strongest predictor to influence REE (r(2) = 0.727, P < 0.0001).

CONCLUSIONS

This study provides comprehensive data on longitudinally determined REE values of healthy premature and full-term infants. Results may serve as a basis for comparative studies that address various disease states as well as different nutritional protocols.

Circadian variation on oxygen consumption in preterm infants

OBJECTIVE

We investigated the diurnal variation in oxygen consumption to determine the optimal time periods of calorimetry in preterm infants.

METHODS

Oxygen consumption (VO(2)) was measured continuously for 24 h using indirect calorimetry. Twenty-two premature infants with gestational age of 27-31 (31+/-1.7) weeks were enrolled in the study. Heart rate, respiratory rate, oxygen saturation, skin and rectal temperature and physical activity were monitored continuously.

RESULTS

The averaged values of VO(2) showed a significant pattern (P<0.0001) of circadian rhythm with a peak in the afternoon and a nadir during the night with significantly differences between the mean VO(2) values. A circadian variation of VO(2) was found in more than 80% of preterm infants and was unrelated to gestational age, physical activity or environmental stress. The infants spent 90.4% of their time sleeping.

CONCLUSIONS

These findings indicate the possible existence of an endogenous circadian rhythm of VO(2) in preterm infants beginning shortly after birth. Day-night variations of VO(2) should be considered when VO(2) values are extrapolated from short measurement periods to prevent overestimation of values.

Randomized trial of very low birth weight infants receiving higher rates of infusion of intravenous fat emulsions during the first week of life

OBJECTIVE

The goal was to determine whether very low birth weight infants could tolerate higher rates of infusion of intravenous fat emulsion during the first week of life and maintain their serum triglyceride levels at <or=200 mg/dL.

METHODS

This was a randomized, controlled trial of 110 infants who were classified as appropriate for gestational age and had birth weights between 750 g and 1500 g. The primary clinical outcome was serum triglyceride levels; secondary outcomes also were monitored.

RESULTS

One hundred infants completed the study (experimental group: N = 48; control group: N = 52). Infants in the experimental group had significantly higher energy intake for the entire 7-day study period and achieved 90 kcal/kg per day (1 kcal = 4.184 kJ) significantly sooner (7.38 +/- 3.381 days vs 9.44 +/- 3.578 days). Triglyceride levels for infants in the experimental group remained significantly higher for the first 5 days of life. Fifteen percent of infants in the experimental group but only 4% of infants in the control group developed hypertriglyceridemia. Ten percent of infants in the control group but no infants in the experimental group required insulin therapy. Forty-two percent of infants in the experimental group and 17% of infants in the control group remained at >or=10th percentile for weight for age. Fourteen percent of infants in the control group but no infants in the experimental group developed necrotizing enterocolitis. Twenty-three percent of infants in the control group but only 6% of infants in the experimental group developed retinopathy of prematurity. There were no significant differences in other outcomes.

CONCLUSIONS

Very low birth weight infants can tolerate higher rates of infusion of intravenous fat emulsion solutions during the first week of life without significant adverse events.

Dynamic coordination of macronutrient balance during infant growth: insights from a mathematical model

BACKGROUND

Complex dynamic changes in body composition, dietary intake, energy expenditure, and macronutrient oxidation occur during infant growth. Although previous investigators have focused on energy requirements for normal growth, little is known about the dynamic coordination of macronutrient balance.

OBJECTIVE

Our objective was to develop a mathematical model of the dynamic relations between diet, macronutrient oxidation, and energy expenditure during normal infant growth.

DESIGN

We developed a mathematical model that integrates longitudinal data on changes of body composition and carbon dioxide production determined with the doubly labeled water method to calculate both energy intake requirements and macronutrient oxidation rates during normal infant growth.

RESULTS

The calculated fat oxidation rate was initially <20 kcal x kg(-1) x d(-1), despite the consumption of >60 kcal x kg(-1) x d(-1) of dietary fat. This discrepancy was maintained until approximately 6 mo, after which fat intake was only slightly greater than fat oxidation. Nonfat oxidation closely followed nonfat dietary intake for the duration of the period studied. Model calculations of the energy intake requirements for normal growth were slightly lower than previous estimates. The calculations were robust to variations of body weight, body composition, and diet composition input data, but depended sensitively on variations of carbon dioxide production data.

CONCLUSIONS

Our model presents a dynamic picture of how macronutrient oxidation adapts in concert with dietary changes and energy expenditure to give rise to normal tissue deposition. The model integrates a variety of data in a self-consistent way, simulating the complex metabolic adaptations occurring during normal growth while extracting important physiologic information from the data that would otherwise be unavailable.

Effect of high volume intake of mother's milk with an individualized supplementation of minerals and protein on early growth of preterm infants <28 weeks of gestation

OBJECTIVE

A prospective study was designed to evaluate the effects of high volume intake of mother's milk fortified (FMM) with an individualized supplementation of minerals and protein on tolerance, short-term somatic growth, serum concentrations of calcium, phosphorus, alkaline phosphatase, and total plasma protein in healthy preterm infants below 28 weeks of gestation.

METHODS

Sixty preterm infants were included in the FMM group, for having received >80% or more of the milk volume as their own mother's milk at 3 weeks of postnatal age to 38 weeks of corrected gestational age. This group was compared with 60 preterm infants fed exclusively preterm formula milk (PF). Intended fluid volume of the FMM group was approximately 200 and 150-170 mL/kg/d in the PF group. Mother's milk was supplemented with the goal of a daily protein intake of 3.5-4 g/kg/d. Phosphorus was supplemented from 15.5 to 31 mg per 100mL mother's milk.

RESULTS

Both feeding regimes were well tolerated. At the end of the study, nutritional management in both groups resulted in a body weight between the 25th and 50th percentiles of intrauterine growth expectations. Serum values of electrolytes, alkaline phosphatase, plasma protein, blood urea nitrogen, and urinary mineral excretion did not differ significantly between the two groups at study entry as well as at the end of the investigation.

CONCLUSIONS

Mother's milk fed at higher volumes with an individualized fortification of minerals and protein provides sufficient nutrients to allow adequate growth of preterm infants <28 weeks of gestation.

Effect of late-onset sepsis on energy expenditure in extremely premature infants

The purpose of this study was to compare total energy expenditure (TEE) in extremely premature infants during and after an episode of sepsis. We hypothesized that TEE in the sepsis group (SEP) would be higher during the septic period and higher than an age-matched control group (CTL). We further hypothesized that the TEE of the SEP group during the recovery period would be similar to that of the CTL group. The doubly labeled water method was used to determine TEE in both groups. Infant characteristics were as follows: SEP group, n = 10, gestation = 26 +/- 1 wk, birth weight = 854 +/- 218 g; CTL group, n = 10, gestation = 26 +/- 1 wk, birth weight = 880 +/- 158 g. TEE of the SEP group during the septic period was significantly greater than during the recovery period (96 +/- 25 kcal/kg/d versus 55 +/- 17 kcal/kg/d) and significantly greater than the CTL group during the first study period (96 +/- 25 kcal/kg/d versus 67 +/- 12 kcal/kg/d). TEE in the SEP group during the recovery period was similar to the CTL group. These increases in TEE may contribute to impaired growth and need to be considered when providing nutritional support for extremely premature infants.

Enteral intake for very low birth weight infants: what should the composition be?

Providing optimal nutrition to satisfy the growth needs of very low birth weight infants is critical. The available preterm formulas and fortified human milk diets provide protein intakes of approximately 3.5 to 3.6 g/kg/d when volumes sufficient to provide 120 kcal/kg/d are fed to these infants. These intakes support growth and protein accretion at about or slightly greater than intrauterine rate and lead to relatively increased fat deposition. However, most very low birth infants fed these diets remain below the 10th percentile of the intrauterine growth standards at discharge. There is clear evidence that, with respect to growth, very low birth infants are likely to benefit from a higher protein intake; however, there is no clear evidence that energy intakes greater than 120 kcal/kg/d are needed. Although the upper limit of protein intake and the ideal protein:energy ratio remain controversial, there is enough evidence to support the beneficial and safe use of formulas providing protein:energy ratio of 3.2 to 3.3 g/100 kcal.

Energy requirements

The determination of the appropriate energy and nutritional requirements of a newborn infant requires a clear goal of the energy and other compounds to be administered, valid methods to measure energy balance and body composition, and knowledge of the neonatal metabolic capacities. Providing an appropriate amount of energy to newborn infants remains a challenge considering the great number of newborn infants who suffer in-hospital growth retardation. The energy requirements of a newborn infant are influenced by several factors - basal metabolism, growth, energy expenditure, and energy losses - which change continuously during development. Calculating the energy requirements of preterm infants is subject to error if general recommendations are applied without recognition of the large variation in factors that influence, for example, energy expenditure. Therefore, energy recommendations should be individualized and preferably based on measurements of energy expenditure. In particular, extremely low birth-weight and very low birth-weight infants are prone to develop negative energy and nutrient balances, due to low energy intake, low energy reserves and high energy demands. Early energy accretion is not only essential for growth but also influences neurodevelopmental outcome and physical health in the long term, thereby underlining the importance of adequate neonatal nutrition.

Oxygen consumption monitoring by oxygen saturation measurements in mechanically ventilated premature neonates

PURPOSE

To assess oxygen consumption VO2) with arterial and venous oxygen saturation SaO2 and SvO2) from blood measurements for continuous monitoring of mechanically ventilated preterm neonates.

METHOD

Twelve preterm neonates with gestational ages ranging from 27 to 34 weeks at birth, who were mechanically ventilated and had umbilical arterial and venous lines in place, were investigated. Analyses were performed with blood samples and continuous monitoring of VO2 from SaO2 and SvO2 measurements.

RESULTS

Mean VO2 from blood samples was 3.3 mL/(kg min) (+/-2.49), and that from monitor readings was 8.8 (+/-4.49). Using curve fit analysis to predict the stability of monitor reading, the period from 8 to 28 hours following blood validation was most stable for SvO2 (cubic curve, R=0.5, P<.001). There is a considerable mix of arterial blood in the venous blood, which increased SvO2 and decreased VO2 in the blood samples during first 8 hours of monitoring following blood draws. A multivariate linear mixed model was established for VO2 measurements including related parameters. Ventilatory weaning was associated with decreased VO2.

CONCLUSIONS

These findings warrant caution against interpreting VO2 from blood SvO2 and subsequent monitoring readings during mechanical ventilation for preterm neonates.

Energy expenditure and plasma catecholamines in preterm infants with mild chronic lung disease

The present study examined the hypothesis that the energy expenditure (EE) increases during the development of chronic lung disease (CLD) together with serum catecholamines as indicator of stress. Sixteen spontaneously breathing infants with gestational age of 28-34 weeks and birth weight of 870-1920 g were studied. Eight patients were at risk for CLD, eight were healthy controls. Measurements of indirect calorimetry were done weekly at postnatal ages of 2, 3, 4 and 5 weeks. Serum concentrations of adrenaline and noradrenaline were measured by means of a high-pressure liquid chromatography (HPLC) method. The eight CLD risk infants developed mild CLD with FiO(2) of 0.27-0.31 and characteristic radiographic signs at 28 days. Compared to the healthy controls, preterm infants with mild CLD showed increases in EE from week 3 (+67%) to week 5 (+46%). Plasma noradrenaline was increased significantly in the CLD infants when compared to the controls at week 3 (0.7+/-0.3 vs. 0.5+/-0.1 ng/ml; P<0.05) and more pronounced at week 4 (1.4+/-0.2 vs. 0.6+/-0.2 ng/ml; P<0.001) and 5 (1.1+/-0.3 vs. 0.7+/-0.2 ng/ml; P<0.01). Plasma adrenaline was markedly higher in the CLD risk group (mean overall value: 0.64+/-0.1 ng/ml) than in the controls (<0.1 ng/ml in all controls) from week 2 to 5. Regression analysis for the combined values of the infants with and without CLD showed that EE was directly correlated with heart rate, noradrenaline and adrenaline concentration at each of the four study weeks and with respiratory rate at weeks 2 and 3. Increased plasma catecholamine concentrations in preterm infants with CLD suggest that these infants experienced marked stress during the early stages of the disease. Increased EE may in part be a result of this stress.