Protein balance in the first week of life in ventilated neonates receiving parenteral nutrition

Early versus late administration of amino acids in preterm infants receiving parenteral nutrition

BACKGROUND

Observational studies in preterm newborns suggest that delay in administering amino acids (AA) could result in a protein catabolic state and impact on growth and development.

OBJECTIVES

The objective of this review was to compare the efficacy and safety of early versus late administration of intravenous AA in neonates born at < 37 weeks of gestation.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, and trial registries in March 2023. We checked the reference lists of included studies and studies/systematic reviews where subject matter related to the intervention or population examined in this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing early administration of AA with late administration in premature newborn infants. We defined early administration of AA solution as the administration of AA in isolation or with total parenteral nutrition within the first 24 hours of birth, and late administration as the administration of AA in isolation or with total parenteral nutrition after the first 24 hours of birth.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

Nine studies (383 participants) were eligible for inclusion in the review. All study participants were born at < 37 weeks of gestation and were inpatients in neonatal intensive care units. No studies reported growth during the first months of life as assessed by difference in weight. Early administration of AA may have little or no effect on growth in the first month of life as measured by length (mean difference (MD) 0.00, 95% confidence interval (CI) -0.41 to 0.41; 1 study; 21 participants; low-certainty evidence) and head circumference (MD 0.05, 95% CI -0.03 to 0.14; 2 studies; 87 participants; low-certainty evidence). No studies reported the discharge weight outcome. Early administration of AA may result in little to no difference in neurodevelopmental outcome assessed by Mental Developmental Index (MDI) of < 70 at two years of age (odds ratio 0.83, 95% CI 0.21 to 3.28; 1 study; 111 participants; low-certainty evidence). No studies reported all-cause mortality at 28 days and before discharge. Early administration of AA may result in a large increase in positive nitrogen balance in the first three days of life (MD 250.42, 95% CI 224.91 to 275.93; 4 studies; 93 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

Low-certainty evidence suggests that there may be little to no difference between early and late administration of AA in growth (measured by length and head circumference during the first month after birth) and neurodevelopmental outcome (assessed by MDI of < 70). No RCTs reported on weight in the first month of life, mortality (all-cause mortality at 28 days and before discharge), or discharge weight. Low-certainty evidence suggests a large increase in positive nitrogen balance in preterm infants who received AA within 24 hours of birth. The clinical relevance of this observation is unknown. The number of infants in the RCTs included in the review was small, and there was clinical heterogeneity amongst trials. Adequately powered trials in infants < 37 weeks' gestation are required to determine optimal timing of initiation of AA. We identified two ongoing studies. Both studies will be recruiting infants ≥ 34 weeks of gestation and may or may not add to the outcome data for this review.

Nutritional Support Strategies for the Preterm Infant in the Neonatal Intensive Care Unit

The goal of nutrition of the preterm infant is to "provide nutrients to approximate the rate of growth and composition of weight gain for a normal fetus of the same postmenstrual age and to maintain normal concentrations of blood and tissue nutrients" (American Academy of Pediatrics 2014). Failure to provide the necessary amounts of all of the essential nutrients to preterm infants has produced not only growth failure, but also increased morbidity and less than optimal neurodevelopment. This continues to be true despite many efforts to increase nutrition of the preterm infants. In contrast, enhanced nutrition of very preterm infants, both intravenous and enteral, beginning right after birth, promotes positive energy and protein balance and improves longer term neurodevelopmental outcomes. The benefits are long lasting too, particularly for prevention of later life chronic diseases.

Preterm formula use in the preterm very low birth weight infant

Whereas human milk is the recommended diet for all infants, preterm formulas are indicated for enteral feeding of preterm very low birth weight infants when sufficient maternal breast milk and donor human milk are not available. Feeding with preterm formulas helps to ensure consistent delivery of nutrients. The balance of risks and benefits of feeding preterm formulas versus supplemented maternal and donor breast milk for preterm infants, however, is uncertain. Numerous studies and extensive practice have shown improved growth with preterm formulas, but there is concern for increased risks of necrotizing enterocolitis, possibly from cow milk antigen in the formulas or from different gut microbiomes, increased duration of total parenteral nutrition, and increased rates of sepsis in infants receiving preterm formulas. Furthermore, whereas preterm formulas improve neurodevelopmental outcomes compared to term formulas and unfortified donor milk, they do not produce neurodevelopmental outcomes better than fortified human milk, again indicating that maternal milk has unique properties that formulas need to mimic as closely as possible.

When Is Parenteral Nutrition Appropriate?

Parenteral nutrition (PN) represents one of the most notable achievements of modern medicine, serving as a therapeutic modality for all age groups across the healthcare continuum. PN offers a life-sustaining option when intestinal failure prevents adequate oral or enteral nutrition. However, providing nutrients by vein is an expensive form of nutrition support, and serious adverse events can occur. In an effort to provide clinical guidance regarding PN therapy, the Board of Directors of the American Society for Parenteral and Enteral Nutrition (ASPEN) convened a task force to develop consensus recommendations regarding appropriate PN use. The recommendations contained in this document aim to delineate appropriate PN use and promote clinical benefits while minimizing the risks associated with the therapy. These consensus recommendations build on previous ASPEN clinical guidelines and consensus recommendations for PN safety. They are intended to guide evidence-based decisions regarding appropriate PN use for organizations and individual professionals, including physicians, nurses, dietitians, pharmacists, and other clinicians involved in providing PN. They not only support decisions related to initiating and managing PN but also serve as a guide for developing quality monitoring tools for PN and for identifying areas for further research. Finally, the recommendations contained within the document are also designed to inform decisions made by additional stakeholders, such as policy makers and third-party payers, by providing current perspectives regarding the use of PN in a variety of healthcare settings.

Nutritional practices and postnatal growth restriction in preterm newborns

OBJECTIVE

to assess the nutritional practices in neonatal intensive care units (NICU) associated with growth retardation in premature (preterm) infants.

METHODS

retrospective study of preterm infants weighing between 500 and 1,499 g admitted to NICU. Evolution of growth and parenteral (PN) and enteral (EN) nutrition practices were analyzed.

RESULTS

among 184 preterm infants divided into G1 (500 to 990 g; n=63) and G2 (1000 to 1499 g; n=121), 169 received PN (G1=63, G2=106). Compared with the recommendations, PN was started late, its progress was slow and the maximum glucose, amino acid, lipid and energy supplies were low in both groups. The initial supply of amino acid and lipid and initial and maximum glucose and energy were lower in G1. The onset of EN was early (1-2 days), the time to reach exclusive EN was appropriate (11-15 days) and the use of human milk was possible in a reasonable amount of time (7-13 days). The multivariate analysis showed that respiratory distress syndrome and obtaining a supply of 120 kcal/kg/day too late increased the chance of weight loss greater than 10%. Sepsis, maximum energy supply for PN <60 kcal/kg/day and obtaining a supply of 120 kcal/kg/day too late increased the chance of regaining birth weight after 14 days, while small for gestational age (SGA) at birth reduced this chance. SGA at birth, sepsis and achieving exclusive enteral nutrition after 14 days increased the chance of being SGA at post-conceptual age of term.

CONCLUSION

improving nutritional practices in the NICU can reduce the growth deficit in premature infants of very low birth weight.

Administering different levels of parenteral phosphate and amino acids did not influence growth in extremely preterm infants

AIM

When a new high amino acid parenteral nutrition (PN) solution was introduced to our hospital, a design error led to decreased phosphate levels. This prompted us to examine the effect of three different PN solutions on plasma phosphate, plasma calcium and weight increases on extremely preterm infants.

METHOD

This was a retrospective study of 186 infants with a gestational age of <28 weeks during their first month of life. They were divided into three groups based on the PN they received during hospitalisation. Group one received high levels of phosphate and low levels of amino acids. Group two received low levels of phosphate and high levels of amino acids. Group three received high levels of both phosphate and amino acids.

RESULTS

The lowest plasma phosphate values varied significantly between groups one (1.80 ± 0.46 mmol/L), two (1.05 ± 0.48 mmol/L) and three (1.40 ± 0.37 mmol/L) (p < 0.001), but no significant difference in weight increase was seen (p = 0.497).

CONCLUSION

The phosphate content of the PN influenced plasma phosphate and plasma calcium levels, but increasing the levels of both phosphate and amino acids did not improve weight gain during the first month of life.

The present challenges of parenteral nutrition in preterm infants and children

The goal of pediatricians involved in the nutritional management of preterm infants is to mimic intrauterine growth and to obtain a functional outcome comparable to that for infants born at term. Appropriate administration of nutrients in the first few days to weeks of life will reduce the growth restriction that is frequently observed. Existing guidelines advise providing preterm infants with both amino acids and lipids from birth onward. Despite this knowledge, many hospital units do not comply with these guidelines. Further improvement of the quality of the composition of parenteral solutions for both neonates as well as older children should be the subject of further research.

Early amino acid administration in very preterm infants: Too little, too late or too much, too soon?

Early postnatal growth failure is well described in very preterm infants. It reflects the nutritional deficits in protein and energy intake that accumulate in the first few weeks after birth. This coincides with the period of maximum parenteral nutrition (PN) dependency, so that protein intake is largely determined by intravenous amino acid (AA) administration. The contribution of PN manufacture, supply, formulation, prescribing and administration to the early postnatal nutritional deficit is discussed, focusing on total AA intake. The implications of postnatal deficits in AA and energy intake for growth are reviewed, with particular emphasis on early head/brain growth and long-term neurodevelopmental outcome. The rationale for maximising AA acid intake as soon as possible after birth is explained. This includes the benefits for very early postnatal nutritional intake and metabolic adaptation after birth. These benefits relate to total AA intake and so have to be interpreted with some caution, given the very limited evidence base surrounding the balance of individual AAs in neonatal PN formulations. This work mostly predates current nutritional recommendations and therefore may not provide a true reflection of individual AA utilisation in current clinical practice.

Feeding extremely low birth weight infants

CME EDUCATIONAL OBJECTIVES: 1.List the indications for parenteral nutrition in the preterm infant.2.Estimate protein and calories required by a preterm infant to support appropriate fetal weight gain.3.Discuss the calcium and phosphorus needs of preterm infants. The patient presented as a 5-week-old 26 week preterm infant, with a birth weight of 686 g. Her mother was 25 years old. The child's Apgar scores were 6 and 7 at 1 and 5 minutes. The infant was intubated after birth and placed on the high-frequency oscillator on day of life (DOL) 3 because of worsening respiratory failure. She was placed back on conventional mechanical ventilation on DOL 7, extubated on DOL 15, and placed on 40% oxygen via nasal cannula. She was discharged home on DOL 84 without mechanical ventilation.

Plasma arginine levels and blood glucose control in very preterm infants receiving 2 different parenteral nutrition regimens

BACKGROUND

Improving parenteral nutrition (PN) amino acid (AA) intake in very preterm infants is associated with less hyperglycemia. AAs stimulate newborn insulin secretion with arginine, demonstrating a specific effect. We hypothesized that low arginine levels would be associated with increased insulin-treated hyperglycemia and higher mean daily blood glucose levels in very preterm infants.

METHODS

We performed a secondary analysis on previous study data comparing high-protein/calorie PN (HPC-PN) and control groups in infants <29 weeks' gestation. Infants were substratified (within original groups) according to high (highARG) and low (lowARG) plasma arginine levels on days 8-10 using a reference population-derived threshold for high/low arginine (57 µmol/L). Daily protein, arginine, carbohydrate intake, mean daily blood glucose, and insulin treatment data from the first 15 days of life were collected.

RESULTS

Control group infants (n = 60) were stratified into lowARG (n = 41) and highARG (n = 19) groups. There were no differences in basic demographic data or carbohydrate intake. LowARG infants had higher mean daily blood glucose levels ( P .05) and a trend to more insulin treatment on days 610. HPC-PN group infants (n = 55) were stratified into lowARG (n = 33) and highARG (n = 22) GROUPS. LowARG infants had lower gestation and birth weight and were sicker than highARG infants. There were no differences in carbohydrate intake. LowARG infants had higher mean daily blood glucose levels (p .01) and more insulin treatment (p .01) on days 15 and 610. Insulin-treated hyperglycemia was also associated with low plasma glutamine levels.

CONCLUSION

Low plasma arginine levels (≤57 µmol/L) in very preterm infants are associated with poorer blood glucose control.

Parenteral amino acid intakes: possible influences of higher intakes on growth and bone status in preterm infants

OBJECTIVE

To study the possible influences of amino acid (AA) intakes on growth and bone status in preterms.

STUDY DESIGN

Newborns, weighing <1250 g, received standard (S) or higher (H) parenteral AA intakes (3 or 4 g kg(-1) per day). Anthropometry, biochemistry and quantitative ultrasound (metacarpus bone transmission time (mcBTT), in μs) were measured prospectively.

RESULT

A total of 55 patients in group S and 60 in group H were studied. Significantly better growth rate was found in the H group during the study without signs of intolerance. We found a significant decrease in mcBTT from birth to 21 days in the H group; nonetheless, mcBTT at 36 weeks of gestational age significantly positively correlated with early AA and energy intakes. A significant positive correlation between mcBTT and lower limb length (LLL) at 21 days was found.

CONCLUSION

Early higher AA intakes improved growth without short-term AA intolerance. Nutritional parameters could influence bone growth. LLL was the anthropometric parameter that best correlated to bone status.

Impact of early and high amino acid supplementation on ELBW infants at 2 years

OBJECTIVE

The aim of the present study was to examine the effects of early and high intravenous (IV) amino acid (AA) supplementation on growth, health, and neurodevelopment of extremely-low-birth-weight (ELBW) infants throughout their first 2 years of life.

METHODS

Infants were prospectively randomized in a double-masked fashion and treated for 7 days with either IV AA starting at 0.5 g · kg (-1) · day(-1) and increased by 0.5 g · kg(-1) every day to 3 g · kg(-1)· day(-) or starting at 2 g · kg (-1) · day(-1) of IV AA and advanced by 1 g · kg(-1) every day to 4 g · kg (-1) · day(-1). Plasma AA concentrations were determined by reverse-phase high-performance liquid chromatography. Survivors were longitudinally assessed with Bayley II Scales of Infant Development and physical, social, and global health.

RESULTS

Forty-three of 51 survivors were studied. Mental Developmental Index (MDI) and Psychomotor Developmental Index were similar between groups; however, the early and high AA group had a lower MDI at 18 months. This difference disappeared at 2 years of age. The early and high AA group z score means for weight, length, and head circumferences were significantly lower than the standard AA group at most visits. Cumulative and single plasma AA concentrations correlated negatively with MDI and postnatal growth.

CONCLUSIONS

ELBW infants who received early and high IV AA during the first week of life were associated with poor overall growth at 2 years.

Increasing early protein intake is associated with a reduction in insulin-treated hyperglycemia in very preterm infants

BACKGROUND

Impaired early protein intake in very preterm infants contributes to early growth failure and may affect long-term neurocognitive development. The authors have previously shown that a standardized concentrated neonatal parenteral nutrition (scNPN) formulation can improve the efficiency of early protein administration. They recognized that very early protein intake could be improved further by modifying the original scNPN regimen and starting PN within 4 hours.

AIM

To demonstrate that the new scNPN regimen could improve very early protein intake in infants <29 weeks' gestation without causing clinically important PN intolerance and complications.

METHODS

All eligible infants <29 weeks' gestation, receiving the modified scNPN regimen and born between October 2009 and December 2010, were studied (group scNPN2). These were compared with previously studied infants, <29 weeks' gestation and receiving the original scNPN regimen and born between June 2006 and December 2006 (group scNPN1). Infant details, actual nutrition intake, and metabolic/infection data were recorded.

RESULTS

Thirty-eight infants <29 weeks' gestation (group scNPN2) were compared with the 38 infants previously studied (group scNPN1). PN was started earlier in group scNPN2, leading to increased mean (95% confidence interval) total protein intake (first 7 days) of 15.3 (14.5-16.1) g/kg in group scNPN2 vs 11.8 (11.0-12.6) g/kg in group scNPN1. There were no differences in calorie, lipid, and carbohydrate intake. Infants receiving insulin for hyperglycemia fell from 20 (53%) in group scNPN1 to 10 (26%) in group scNPN2.

CONCLUSION

Increasing early protein intake is associated with a reduction in insulin-treated hyperglycemia in infants <29 weeks' gestation.

Reduction in postnatal cumulative nutritional deficit and improvement of growth in extremely preterm infants

AIM

To evaluate the influence of gestational age (GA) on cumulative nutritional deficit and postnatal growth in extremely preterm (EPT) infants after optimizing nutritional protocol as recently recommended.

METHODS

A prospective, nonrandomized, observational study in extremely preterm (EPT, <28 weeks) and very preterm (VPT, 28-30 weeks) infants.

RESULTS

Eighty-four infants were included (BW: 978 ± 156 g, GA: 27.8 ± 1.3 weeks). Cumulative nutritional deficit increased during first week of life to -290 ± 84 and -285 ± 117 kcal/kg and -4.2 ± 3.1 and -4.8 ± 3.9 g/kg of protein in EPT and VPT groups, respectively. After 6 weeks, only cumulative energy deficit in EPT group remained significant (p < 0.05) even when 96% of theoretical energy intakes were provided. Weight z score decreased during first 3 days in average with initial weight loss, and then, the z score increased during the first 6 weeks of life in the majority (75%) of infants. Cumulative protein deficit during the first week of life was the major determinant of the postnatal growth during the first 6 weeks of life.

CONCLUSION

Cumulative nutritional deficit may be drastically reduced in both EPT and VPT infants after optimizing nutritional policy during the first weeks of life, and the postnatal growth restriction could even be prevented.

Optimizing early nutritional support based on recent recommendations in VLBW infants and postnatal growth restriction

OBJECTIVE

The aim of this study was to evaluate postnatal growth up to discharge in very low birth weight infants after optimizing nutritional support based on recent nutritional recommendations.

PATIENTS AND METHODS

A prospective, nonrandomized, consecutive, and observational study in infants weighing <1250 g.

RESULTS

One hundred two infants were included during a 2-year period (birth weight 1005 ± 157 g, gestational age 28.5 ± 1.9 weeks). First-day nutritional intake was 38 ± 6 kcal/kg/day with 2.4 ± 0.3 g/kg/day of protein. Mean intake during the first week of life was 80 ± 14 kcal/kg/day with 3.2 ± 0.5 g/kg/day of protein. On average from birth to discharge, 122 ± 10 kcal/kg/day and 3.7 ± 0.2 g/kg/day of protein were administered. Postnatal weight loss was limited to the first 3 days of life, and birth weight was regained after 7 days in average. Catch-up occurred after the second week in all groups of very low birth weight infants. Small-for-gestational age infants demonstrated an earlier and higher weight gain, allowing a rapid catch-up growth. The same proportion of infants was small-for-gestational age at birth and at discharge (20%, P = 0.74).

CONCLUSIONS

This study confirmed that the first week of life is a critical period to promote growth and that early nutrition from the first day of life is essential. Postnatal weight loss may be limited and subsequent growth may be optimized with a dramatic reduction of postnatal growth restriction.

Effect of low versus high early parenteral nutrition on plasma amino acid profiles in very low birth-weight infants

OBJECTIVE

To study the efficacy of early high doses parenteral nutrition (PN) versus early low dose with progressive increments PN regimens, we performed a prospective randomized study in very low birth-weight infants.

STUDY DESIGN

Forty-one appropriate gestational age preterm infants with birth weights ranging from 750-1500 g were randomly assigned into two groups. In Group 1, infants started on 3.0 g/kg/day amino acids (AA) and 3 g/kg/day of 20% lipid; in Group 2, AA and lipid were started on 1 g/kg/day, and advanced over 3 days to a maximum 3 g/kg/day. Blood samples were obtained for AA concentrations before starting of the PN, and at the 7th and 14th days.

RESULTS

The mean (±SD) birth weight was 1335 g (240), gestational age was 29.7 weeks (1.7) of the study group. The mean body weight and head circumference was similar in the Group 1 and Group 2 at the 14th postnatal days. There was no difference in the blood levels of triglyceride, blood urea nitrogen, creatinine, ammonia, lactat and bicarbonate in the two groups. There was no significant difference in the concentrations of AA except for arginine and asparagine. On day 14, the mean arginine concentrations were significantly higher and asparagine concentrations were lower in Group 2.

CONCLUSION

Although earlier more aggressive administration of AA and fat is not associated with any significant metabolic abnormalities, growth rates and plasma AA concentrations of the infants were similar to infants who AA and lipid given lower in the first day of life.

SCAMP: standardised, concentrated, additional macronutrients, parenteral nutrition in very preterm infants: a phase IV randomised, controlled exploratory study of macronutrient intake, growth and other aspects of neonatal care

Background

Infants born <29 weeks gestation are at high risk of neurocognitive disability. Early postnatal growth failure, particularly head growth, is an important and potentially reversible risk factor for impaired neurodevelopmental outcome. Inadequate nutrition is a major factor in this postnatal growth failure, optimal protein and calorie (macronutrient) intakes are rarely achieved, especially in the first week. Infants <29 weeks are dependent on parenteral nutrition for the bulk of their nutrient needs for the first 2-3 weeks of life to allow gut adaptation to milk digestion. The prescription, formulation and administration of neonatal parenteral nutrition is critical to achieving optimal protein and calorie intake but has received little scientific evaluation. Current neonatal parenteral nutrition regimens often rely on individualised prescription to manage the labile, unpredictable biochemical and metabolic control characteristic of the early neonatal period. Individualised prescription frequently fails to translate into optimal macronutrient delivery. We have previously shown that a standardised, concentrated neonatal parenteral nutrition regimen can optimise macronutrient intake.

Methods

We propose a single centre, randomised controlled exploratory trial of two standardised, concentrated neonatal parenteral nutrition regimens comparing a standard macronutrient content (maximum protein 2.8 g/kg/day; lipid 2.8 g/kg/day, dextrose 10%) with a higher macronutrient content (maximum protein 3.8 g/kg/day; lipid 3.8 g/kg/day, dextrose 12%) over the first 28 days of life. 150 infants 24-28 completed weeks gestation and birthweight <1200 g will be recruited. The primary outcome will be head growth velocity in the first 28 days of life. Secondary outcomes will include a) auxological data between birth and 36 weeks corrected gestational age b) actual macronutrient intake in first 28 days c) biomarkers of biochemical and metabolic tolerance d) infection biomarkers and other intravascular line complications e) incidence of major complications of prematurity including mortality f) neurodevelopmental outcome at 2 years corrected gestational age

Trial registration

Current controlled trials: ISRCTN76597892; EudraCT Number: 2008-008899-14

The effects of early parenteral amino acids on sick premature infants

OBJECTIVES

To study the effects of early parenteral amino acid administration on body weight, fluid compartments and metabolic parameters during the first week of life in sick premature infants.

METHODS

Appropriate for gestational age, sick premature infants were randomized into two groups. Group A infants (n=8, birth weight 1258±339 g) were supplemented with amino acids starting within 24 h of birth and advanced to 2.5 g/kg per day by day 3. Group G infants (n=9, birth weight 1182±214 g) received amino acids starting on day 4 of life. Energy intake was comparable in the 2 groups. Amino acid concentrations and nitrogen balance studies were performed on day 3 of life. Total body water and extracellular water were measured on day 1 and 8 and change in intracellular volume was calculated.

RESULTS

There was no significant difference between the 2 groups in terms of weight, intracellular volume change from day 1 to day 8 of life, despite a significant (P<0.01) difference in protein intake. Plasma ammonia levels were comparable in the 2 groups, but plasma urea levels were significantly higher in group A vs. group G infants (7.2±3.4 mmol/L vs. 3.2±1.2 mmol/L respectively, P<0.01). Nitrogen balance was positive in all group A infants and negative in group G infants. Nitrogen loss was inversely correlated with energy intake in group G infants (P<0.05). The mean plasma amino acid concentrations in group A infants (compared to those of group G) were within previously reported ranges in older premature infants.

CONCLUSIONS

There was no significant effect on body weight and redistribution of body fluid compartments in infants receiving amino acids early during the first week of life. Serum urea concentrations were significantly higher in infants receiving early amino acids. Nitrogen losses in infants who did not receive amino acids were inversely correlated with energy intake during the first 3 days of life.

Protein for preterm infants: how much is needed? How much is enough? How much is too much?

Preterm infants require considerably more protein to achieve normal intrauterine growth rates than is commonly fed to them during their first postnatal days. Continuing protein nutrition to maintain normal growth rates often is not achieved until several weeks after birth. Most very preterm infants do not receive the protein necessary to produce the 2-3 kilograms of body mass over a 12-16 week period of NICU care and, as a result, end up growth restricted by term, in lean body mass more than fat. This article reviews the requirements for protein and amino acids necessary to achieve normal growth and development of preterm infants. Protein requirements at 24-30 weeks' gestation are as high as 4 g/kg/day, decreasing to 2-3 g/kg/day by term. Individual amino acids are important not just as building blocks for protein synthesis and net protein balance, but also as essential signalling molecules for normal cellular function. Perhaps most importantly, brain growth and later life cognitive function are directly related to protein intake during the neonatal period in preterm infants. Data are reviewed that document successful increase in protein balance in preterm infants achieved with higher than usual rates of amino acid and protein nutrition, noting that positive protein balance requires at least 1.5 g/kg/day, but there still is increased protein balance up to 4 g/kg/day. Further research is necessary to determine optimal amounts and mixtures of protein and amino acids for both intravenous and enteral feeding to improve growth, development, and functional capacity of preterm infants.

Initial nutritional management of the preterm infant

Postnatal nutrition has a large impact on long-term outcome of preterm infants. Evidence is accumulating showing even a relationship between nutrient supply in the first week of life and later cognitive development in extremely low birth weight infants. Since enteral nutrition is often not tolerated following birth, parenteral nutrition is necessary. Yet, optimal parenteral intakes of both energy and amino acids are not well established. Subsequently, many preterm infants fail to grow well, with long-term consequences. Early and high dose amino acid administration has been shown to be effective and safe in very low birth weight infants, but the effect of additional lipid administration needs to be defined.

Early amino acids and the metabolic response of ELBW infants (< or = 1000 g) in three time periods

OBJECTIVE

To evaluate early amino-acid (AA) administration in extremely low birth weight (ELBW) infants over three time periods, beginning with the initiation of this strategy.

STUDY DESIGN

This was a retrospective study of ELBW infants between 2000 and 2007. Nutritional intake and laboratory results were monitored during the first 5 days of life. Growth rates and complications were followed until discharge.

RESULT

Infants were similar in birth weight (BW), gestational age (GA) and severity of illness. The age at initiation of AA decreased significantly over time. Age at weight nadir, return to BW and percent postnatal weight loss decreased in epoch 3. There were modest increases in blood urea nitrogen (BUN), but no significant metabolic disturbances were observed. Cholestasis was more prevalent in epoch 2.

CONCLUSION

AA administration within the first hours of life appears to be safe and beneficial for ELBW infants. Absent signs of renal dysfunction, a modest rise in BUN is consistent with the neonate's utilization of AAs for energy.

Early amino-acid administration improves preterm infant weight

OBJECTIVE

Premature infants, especially those born less than 1500 g, often exhibit slow overall growth after birth and lack of early nutritional support may be an important element. We tested the hypothesis that early administration of amino acids (within the first few hours of life) to infants born at less than 1500 g would be associated with fewer infants that were less than the 10th percentile at 36 weeks post-conceptual age than infants that received amino acids after the first 24 h of life.

STUDY DESIGN

A prospective intervention of early amino-acid (EAA) supplementation, began before 24 h of life, in preterm infants, <1500 g, was compared to a retrospective cohort of preterm infants receiving late amino-acid (LAA) supplementation, began after 24 h of life. The primary outcome variable was the proportion of infants at less than the 10th percentile at 36 weeks post-conceptual age.

RESULT

Fewer infants fell below the 10th percentile (P<0.001) in the EAA group. Furthermore, infants in the EAA groups had significantly greater weight gains than did the LAA group (P<0.003) after adjusting for gestational age and time from birth to discharge. In addition, shorter duration of parenteral nutrition was associated with EAA supplementation (P<0.001).

CONCLUSION

A prospective strategy of EAA in preterm infants <1500 g was associated with an improved weight gain, suggesting that nutrition that included amino acids may be critical during the first 24 h of life.

First-week protein and energy intakes are associated with 18-month developmental outcomes in extremely low birth weight infants

OBJECTIVE

We sought to evaluate the association between early protein and energy intake and neurodevelopment and growth of extremely low birth weight (<1000 g) infants.

STUDY DESIGN

Daily protein and energy intakes were collected by chart review for the first 4 weeks of life on 148 extremely low birth weight survivors. A total of 124 infants (84%) returned for evaluation at 18 months' corrected age. Bivariate analysis tested correlations between weekly protein or energy intakes and Bayley Mental Development Index, Psychomotor Development Index, or growth at 18 months. Separate regression models evaluated contributions of protein (grams per kilogram per day) and energy intake (kilojoules per kilogram per day) to the Mental Development Index, Psychomotor Development Index, and growth, while controlling for known confounders.

RESULTS

After adjusting for confounding variables, week 1 energy and protein intakes were each independently associated with the Mental Development Index. During week 1, every 42 kJ (10 kcal)/kg per day were associated with a 4.6-point increase in the Mental Development Index and each gram per kilogram per day in protein intake with an 8.2-point increase in the Mental Development Index; higher protein intake was also associated with lower likelihood of length <10th percentile.

CONCLUSIONS

Increased first-week protein and energy intakes are associated with higher Mental Development Index scores and lower likelihood of length growth restrictions at 18 months in extremely low birth weight infants. Emphasis should be placed on providing more optimal protein and energy during this first week.

Optimizing growth in the preterm infant

Most very low birth weight preterm infants experience postnatal growth failure in the neonatal ICU. In an attempt to minimize this phenomenon, the nutritional support of these infants has tended to become more aggressive in recent years and has become a focus of much study. Despite this attention, many questions remain unresolved. This article examines several of these issues, including the controversies regarding optimal postnatal growth velocity, early aggressive nutritional support, and the transition to enteral nutrition in preterm infants.

Improved growth and decreased morbidities in <1000 g neonates after early management changes

OBJECTIVE

To test the hypothesis that three changes in the early management of extremely low birth weight (ELBW) neonates would decrease the incidence of extra-uterine growth restriction (EUGR) by 25%. The three early management practice changes (EMPC) included surfactant at delivery followed by immediate extubation to nasal continuous positive airway pressure (CPAP), decreased oxygen exposure and early parenteral amino acids.

STUDY DESIGN

Historical cohort study of preterm infants<or=1000 g birth weight (BW) born at the University of Texas Medical Branch between January 2001 and June 2002 (pre-EMPC, before changes, n=87) and July 2004 to December 2005 (post-EMPC, after changes, n=76). Outcomes measured included feeding and growth parameters, morbidities and interventions. Statistical analysis included chi2-analysis, Student's t-test, and analysis of variance.

RESULT

Infants in the post-EMPC cohort regained BW more quickly, maintained appropriate size for weight at 36 weeks and had less morbidity associated with poor long-term outcome. Predictors of EUGR included BW<750 g and surgical necrotizing enterocolitis.

CONCLUSION

The introduction of surfactant at delivery followed by immediate extubation to CPAP, decreased oxygen exposure and early parenteral amino acids in ELBW infants is possible, safe and associated with improvements in growth and morbidity.

Protein metabolism in preterm infants with particular reference to intrauterine growth restriction

There is growing evidence that neonatal and long-term morbidity in preterm infants, particularly those born before 32 weeks' gestation, can be modified by attained growth rate in the neonatal period. Guidelines for optimal growth and the nutritional intakes, particular of protein, required to achieve this are not well defined. Due to delays in postnatal feeding and a lack of energy stores developed in the last trimester of pregnancy, preterm infants often suffer early postnatal catabolism until feeding is established. There are indications that infants born with intrauterine growth restriction have perturbations in protein metabolism. Therefore, they may have different protein requirements than appropriate for gestational age infants. This review summarises what is known about protein requirements and metabolism in the fetus and preterm infant, with particular emphasis on the distinct requirements of the growth-restricted infant.

Enhancing parenteral nutrition therapy for the neonate

The neonate receiving parenteral nutrition (PN) therapy requires a physiologically appropriate solution in quantity and quality given according to a timely, cost-effective strategy. Maintaining tissue integrity, metabolism, and growth in a neonate is challenging. To support infant growth and influence subsequent development requires critical timing for nutrition assessment and intervention. Providing amino acids to neonates has been shown to improve nitrogen balance, glucose metabolism, and amino acid profiles. In contrast, supplying the lipid emulsions (currently available in the United States) to provide essential fatty acids is not the optimal composition to help attenuate inflammation. Recent investigations with an omega-3 fish oil IV emulsion are promising, but there is need for further research and development. Complications from PN, however, remain problematic and include infection, hepatic dysfunction, and cholestasis. These complications in the neonate can affect morbidity and mortality, thus emphasizing the preference to provide early enteral feedings, as well as medication therapy to improve liver health and outcome. Potential strategies aimed at enhancing PN therapy in the neonate are highlighted in this review, and a summary of guidelines for practical management is included.

Albumin synthesis in preterm infants on the first day of life studied with [1-13C]leucine

Albumin is the major binding protein in the human neonate. Low production of albumin will lower its transport and binding capacity. This is especially important in preterm infants, in whom albumin binds to potentially toxic products such as bilirubin and antibiotics. To study the metabolism of plasma albumin in preterm infants, we administered a 24-h constant infusion of [1-(13)C]leucine to 24 very low birth weight (VLBW) infants (28.4 +/- 0.4 wk, 1,080 +/- 75 g) on the first day of life. The caloric intake consisted of glucose only, and therefore amino acids for albumin synthesis were derived from proteolysis. The fractional synthesis rate (FSR) of plasma albumin was 13.9 +/- 1.5%/day, and the absolute synthesis rate was 148 +/- 17 mg x kg(-1) x day(-1). Synthesis rates were significantly lower (P<0.03) in infants showing intrauterine growth retardation. Albumin synthesis increased with increasing SD scores for gestation and weight (P<0.05). The FSR of albumin tended to increase by 37% after administration of antenatal corticosteroids to improve postnatal lung function (P=0.09). We conclude that liver synthetic capacity is well developed in VLBW infants and that prenatal corticosteroids tend to increase albumin synthesis. Decreased weight gain rates in utero have effects on protein synthesis postnatally.

Parenteral amino acid and energy administration to premature infants in early life

After birth, the nutritional supply through the umbilical cord ceases. Premature infants do not immediately tolerate full enteral feedings, yet they retain high nutritional needs for both growth and metabolic maintenance. Parenteral nutrition should therefore be initiated as quickly as possible after premature birth, thereby reducing the dependence on endogenous substrates. Intrauterine studies show very high amino acid uptake, clearly exceeding accretion rates. Studies covering the early neonatal period demonstrate that the initiation of high-dose amino acid administration directly after birth is safe and effective, even at low energy intakes. Future research should reveal whether usage could be improved through better amino acid solutions or by providing more energy via lipids from birth onwards as well.

Extremely low birthweight infants: issues related to growth

While survival rates are increasing in the extremely low birthweight (ELBW) group of preterm infants, the most common morbidity among these infants is inadequate growth. By the time of discharge from the neonatal intensive care unit, many ELBW infants develop extrauterine growth restriction. Several issues related to improving the growth of ELBW infants, including defining adequate growth and developing evidence-based nutritional strategies, are discussed in this article. Suggestions for future research are also presented.

Oxalate and phytate concentrations in seeds of soybean cultivars [Glycine max (L.) Merr.]

This study analyzed soybean seeds from 116 cultivars for total, insoluble, and soluble oxalate (Ox), phytate (InsP6), calcium (Ca), and magnesium (Mg) because of their potential beneficial or harmful effects on human nutrition. These cultivars were divided into four groups (A-D) on the basis of the year and geographic location where they were grown. Oxalate concentration ranged from about 82 to 285 mg/100 g of dry seed. The InsP6 concentration ranged from 0.22 to 2.22 g/100 g of dry seed. There was no correlation between Ox and InsP6 within or among the four groups of cultivars. There was a significant correlation between total Ox and Ca, but not Mg, in group D cultivars (r = 0.3705; p < 0.0005). No significant relationship was found in the group A-C cultivars. Eleven group D cultivars had InsP6 less than 500 mg/100 g, but all had total Ox of 130 mg/100 g or greater. Five cultivars from groups A-C had relatively low InsP6 (group B; < or =1.01 g/100 g) and low Ox (<140 mg/100 g). These cultivars could be useful for producing soy foods beneficial to populations at risk for kidney stones and for improved mineral bioavailability. The Ox and InsP6 concentrations of the cultivars indicate that choosing specific parents could generate seeds in succeeding generations with desirable Ox and InsP6 concentrations.

Amino acid administration to premature infants directly after birth

OBJECTIVES

To test the hypothesis that the administration of 2.4 g amino acids (AA)/(kg.d) to very low birth weight infants is safe and results in a positive nitrogen balance.

STUDY DESIGN

We conducted a randomized, clinical trial. Preterm infants with birth weights <1500 g received either glucose and 2.4 g AA/(kg.d) from birth onward (n=66) or solely glucose during the first day with a stepwise increase in AA intake to 2.4 g AA/(kg.d) on day 3 (n=69). Blood gas analysis was performed daily during the first 6 postnatal days; blood urea nitrogen levels were determined on days 2, 4, and 6; AA plasma concentrations and nitrogen balances were determined on days 2 and 4. Student t tests, Mann-Whitney tests, and chi2 tests were performed to compare groups.

RESULTS

Infants supplemented with AA had no major adverse side effects. Their blood urea nitrogen levels were higher, nitrogen balance turned positive upon AA administration, and more AA concentrations were within reference ranges.

CONCLUSIONS

High-dose AA administration to very low birth weight infants can be introduced safely from birth onward and results in an anabolic state.

Pragmatic approach to in-hospital nutrition in high-risk neonates

Extremely low birth weight infants may experience periods of moderate to severe undernutrition during the acute phase of their respiratory problems. This undernutrition contributes to early growth deficits in these patients and may have long-lasting effects, including poor neurodevelopmental outcome. Early postnatal intravenous amino-acid administration and early enteral feeding strategies will minimize the interruption of nutrient intake that occurs with premature birth. These two strategies will prevent intracellular energy failure, allow the administration of more non-protein energy, as well as enhance overall nutritional health, as evidenced by less postnatal weight loss and earlier return to birth weight, and improved overall postnatal growth and outcome.

Blood urea nitrogen concentration as a marker of amino-acid intolerance in neonates with birthweight less than 1250 g

OBJECTIVE

Currently blood urea nitrogen (BUN) is commonly used as a marker of protein intolerance in very preterm infants. The purpose of this study was to evaluate the relationship between amino-acid intakes and BUN concentrations during the early neonatal period in preterm neonates.

STUDY DESIGN

Retrospective review of BUN concentration data from 121 infants with birthweight <or=1250 g receiving exclusive parenteral nutrition over the first 72 hours of life.

RESULTS

There were 136 separate BUN concentration values. Amino-acid intake range was 0 to 3.7 g kg-1 day-1 and nonprotein calorie intake range was 15 to 45 kcal kg-1 d-1. There was no correlation between BUN concentration and amino-acid intake (p=0.2 and r2=0.01).

CONCLUSIONS

In parenterally nourished preterm neonates amino-acid intake is not correlated with BUN concentration in the first days of life. Therefore, limiting amino-acid intake based on BUN concentration is not warranted in this patient population.

Can an alternative umbilical arterial catheter solution and flush regimen decrease iatrogenic hemolysis while enhancing nutrition? A double-blind, randomized, clinical trial comparing an isotonic amino acid with a hypotonic salt infusion

OBJECTIVE

In the process of sampling blood through an umbilical arterial catheter (UAC), infant blood comes into stagnant contact with infusion solution in the "waste syringe" before being reinfused. We have previously demonstrated in vitro that this process is associated with less hemolysis of red blood cells (RBCs) with use of an isotonic solution compared with a hypotonic 0.25 normal saline (NS) solution. The objective of this study was to compare the in vivo effect on hemolysis of 2 UAC infusion/flush regimens (an isotonic regimen vs a hypotonic regimen) and to assess the early nutritional benefit of an amino acid solution as the isotonic UAC infusion solution.

METHODS

Infants who had a birth weight of < or =1.5 kg and were expected to have a UAC for > or =3 days were enrolled within 24 hours of life into this prospective, double-blind, randomized, clinical trial of 2 UAC infusion solution/flush regimens. Power analysis demonstrated that 40 infants were needed to determine differences in hemolysis quantified by plasma-free hemoglobin (PFH) level. Nutrition from glucose was evaluated by measurement of daily dextrose calories. C-peptide was measured to evaluate endogenous insulin production. Adverse events and protein tolerance were tracked.

RESULTS

Twenty-two infants (mean gestational age: 27 weeks; 945 g birth weight) were enrolled in each group, for an average of 4.2 days (range: 2.5-8 days). There were no group differences in demographics. PFH levels were lower for infants who received isotonic amino acid (IAA) in comparison with 0.25 NS (33 +/- 14 mg/dL vs 62 +/- 27 mg/dL, respectively). C-peptide was higher in those who received IAA, as were nonprotein calories received on days 4 to 6 of the study (51 +/- 11 kcal/kg/day vs 44 +/- 12 kcal/kg/day, IAA vs 0.25 NS, respectively).

CONCLUSIONS

Lower PFH levels in IAA versus 0.25 NS group were consistent with our hypothesis of decreased hemolysis with an isotonic infusion/flush regimen. IAA use may also allow greater early glucose nutrition, as indicated by the higher level of endogenous insulin production and improved glucose tolerance. IAA seems to be a superior UAC solution to 0.25 NS in that it is associated with less hemolysis and improved nutrition.

Effect of low versus high intravenous amino acid intake on very low birth weight infants in the early neonatal period

Greater protein intakes are required than have been commonly used to achieve fetal in utero protein accretion rates in preterm neonates. To study the efficacy and safety of more aggressive amino acid intake, we performed a prospective randomized study in 28 infants [mean wt, 946 +/- 40 g (SEM)] of 1 (low amino acid intake, LAA) versus 3 g.kg(-1).d(-1) (high amino acid intake, HAA) at 52.0 +/- 3.0 h of life. After a minimum of 12 h of parenteral nutrition, efficacy was determined by protein balance and was significantly lower in the LAA versus HAA groups by both nitrogen balance (-0.26 +/- 0.11 versus 1.16 +/- 0.15 g.kg(-1).d(-1), p < 0.00005) and leucine stable isotope (0.184 +/- 0.17 versus 1.63 +/- 0.20 g.kg(-1).d(-1), p < 0.0005) methods. Leucine flux and oxidation and nonoxidative leucine disposal rates were all significantly higher in the HAA versus LAA groups (249 +/- 13 versus 164 +/- 8, 69 +/- 5 versus 32 +/- 3, and 180 +/- 10 versus 132 +/- 8 micro mol.kg(-1).h(-1), respectively, p < 0.005), but leucine appearance from protein breakdown was not (140 +/- 15 in HAA versus 128 +/- 8 micro mol.kg(-1).h(-1)). In terms of possible toxicity with HAA, there were no significant differences between groups in the amount of sodium bicarbonate administered, degree of acidosis as determined by base deficit, or blood urea nitrogen concentration. Parenteral HAA versus LAA intake resulted in increased protein accretion, primarily by increasing protein synthesis versus suppressing protein breakdown, and appeared to be well tolerated by very preterm infants in the first days of life.

Aggressive nutrition of the very low birthweight infant

We propose an approach to nutrition of the VLBW infant that aims at minimizing the interruption of nutrient uptake engendered by premature birth. Our approach is aggressive in that it goes beyond current practice in several key aspects. The gap in nutrient intakes between the proposed aggressive approach and current practice will most likely disappear over the next few years as today's aggressive practice becomes tomorrow's standard practice. As the gap diminishes, so will the threat that nutritional deprivation poses to growth and development of VLBW infants.

Parenteral nutrition-associated liver complications in children

Parenteral nutrition is a life-saving therapy for patients with intestinal failure. It may be associated with transient elevations of liver enzyme concentrations, which return to normal after parenteral nutrition is discontinued. Prolonged parenteral nutrition is associated with complications affecting the hepatobiliary system, such as cholelithiasis, cholestasis, and steatosis. The most common of these is parenteral nutrition-associated cholestasis (PNAC), which may occur in children and may progress to liver failure. The pathophysiology of PNAC is poorly understood, and the etiology is multifactorial. Risk factors include prematurity, long duration of parenteral nutrition, sepsis, lack of bowel motility, and short bowel syndrome. Possible etiologies include excessive caloric administration, parenteral nutrition components, and nutritional deficiencies. Several measures can be undertaken to prevent PNAC, such as avoiding overfeeding, providing a balanced source of energy, weaning parenteral nutrition, starting enteral feeding, and avoiding sepsis.

Growth patterns of extremely low-birth-weight hospitalized preterm infants

OBJECTIVE

To characterize the growth of extremely low-birth-weight (ELBW) infants during hospitalization in terms of weight gain, growth velocity, and relative change in weight.

DESIGN

Retrospective, descriptive design.

SETTING

Two neonatal intensive-care units located in the midwestern United States.

PATIENTS

Thirty-five ELBW infants with a birth weight less than 1,000 g and appropriate for gestational age.

MAIN OUTCOME MEASURES

Clinical data related to the infant's growth and nutrition were obtained from a chart review. Birth weight and discharge weight were compared following conversion of the weights to z scores. The discharge weight was compared to the median weight of a fetus of comparable gestational age based on an intrauterine growth reference. Growth velocity was determined (grams/day).

RESULTS

Weight-for-age z scores decreased significantly between birth and discharge. By discharge, 89% of the infants had discharge weights less than the 10th percentile. The mean discharge weight was significantly less than the median weight of a fetus of comparable gestational age. Days to regain birth weight significantly affected growth outcomes.

CONCLUSION

ELBW infants develop a growth deficit during the first few weeks of life that not only persists but also worsens during hospitalization. Potential causes of this growth deficit include the medical and nutritional management that are part of the usual care of ELBW infants. Because these infants are discharged with this growth deficit, catch-up growth will have to occur at home.

Early aggressive nutrition in preterm infants

Increasingly, neonatologists are realizing that current feeding practices for preterm infants are insufficient to produce reasonable rates of growth, and earlier and larger quantities of both parenteral and enteral feeding should be provided to these infants. Unfortunately, there is very little outcome data to recommend any particular nutritional strategy to achieve better growth. Instead, the rationale for feeding regimens in many nurseries has been quite variably extrapolated from animal data and human studies conducted in gestationally more mature and/or stable neonates. Additionally, there are no well-controlled, prospective studies that validate any nutritional regimen for the very preterm and or sick, unstable neonate. The goal of this review is to present available data to help define the risks and benefits of early parenteral and enteral nutrition, particularly in very preterm neonates, concluding with a more aggressive approach to feeding these infants than has been customary practice.

Early feeding strategies in preterm and critically ill neonates

This two-part article presents feeding strategies for the NICU population over the first several weeks of life. It focuses primarily on the theory and approach to feeding extremely low birth weight (ELBW) infants, but also addresses some issues pertinent to larger, ill infants. The premise for these recommendations is that avoiding early malnutrition in ELBW and ill infants has both short- and long-term benefits. Many practitioners may consider our approach to be somewhat aggressive. In this strategy, total parenteral nutrition (TPN) is initiated in the first hours after birth and is given together with initially small, and then increasing, enteral feedings beginning on the first or second day of life. The role of the TPN is to provide rapid, maximal nutrition and that of the early enteral feedings is to "prime" the gut and stimulate normal gastrointestinal tract activity.

Effects of parenteral cysteine and glutathione feeding in a baboon model of severe prematurity

BACKGROUND

The availability of cysteine for glutathione synthesis is low in premature infants with respiratory distress.

OBJECTIVE

The effects of gestational age, oxygen delivery, and cysteine infusion or glutathione infusion, or both, on plasma total cysteine and other methionine metabolites were studied in a baboon model of severe premature birth with respiratory distress.

DESIGN

Premature baboons were studied as part of the multiinvestigator National Institutes of Health Collaborative Project on Bronchopulmonary Dysplasia. Premature baboons, 125 d (69% of term) or 140 d (78% of term) of gestational age, were maintained in neonatal intensive care units for </=14 d. Parenteral feeding with or without supplemental cysteine and glutathione infusions was given. Plasma total cysteine, methionine, N:-methylglycine, cystathionine, and the other methionine metabolites were monitored by capillary gas chromatography-mass spectrometry.

RESULTS

Cord blood plasma total cysteine was the lowest in the 125-d-old premature baboons. Plasma total cysteine decreased in the first 3 d after delivery in the 125-d-old (but not in the 140-d-old) premature baboons even when cysteine was infused. Supplementation with glutathione from the first day of life raised plasma total cysteine markedly. Plasma cystathionine increased in all animals after birth but increased 4-fold in 125-d-old animals with glutathione infusion. At 6 and 10 d postdelivery, the arterial-alveolar oxygen gradient was significantly higher in the 125-d-old animals that received glutathione infusions.

CONCLUSIONS

Glutathione, but not supplemental cysteine, infusions prevented the postdelivery decline in plasma cysteine concentrations in premature baboons. Glutathione infusions resulted in marked elevations of plasma cystathionine concentration.

Current total parenteral nutrition solutions for the neonate are inadequate

The amino acid requirements of the parenterally fed neonate are poorly defined. Newborn infants are at risk for amino acid deficiency and toxicity, due to lack of small intestinal metabolism and metabolic immaturity. We discuss recent evidence that identifies inadequacies of commercial amino acid solutions with respect to the balance and quantity of aromatic amino acids, and sulphur amino acids. We present data demonstrating that impaired small intestinal metabolism (or lack of first pass metabolism) alters the whole body requirement for methionine, threonine, and arginine, and discuss the potential adverse effects of excess or inadequate parenteral amino acid intake.