Assessing the effect of disease on nutrition of the preterm infant

Higher versus lower protein intake in formula-fed low birth weight infants

BACKGROUND

The ideal quantity of dietary protein for formula-fed low birth weight infants is still a matter of debate. Protein intake must be sufficient to achieve normal growth without leading to negative effects such as acidosis, uremia, and elevated levels of circulating amino acids.

OBJECTIVES

To determine whether higher (≥ 3.0 g/kg/d) versus lower (< 3.0 g/kg/d) protein intake during the initial hospital stay of formula-fed preterm infants or low birth weight infants (< 2.5 kilograms) results in improved growth and neurodevelopmental outcomes without evidence of short- or long-term morbidity. Specific objectives were to examine the following comparisons of interventions and to conduct subgroup analyses if possible. 1. Low protein intake if the amount was less than 3.0 g/kg/d. 2. High protein intake if the amount was equal to or greater than 3.0 g/kg/d but less than 4.0 g/kg/d. 3. Very high protein intake if the amount was equal to or greater than 4.0 g/kg/d.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 8), in the Cochrane Library (August 2, 2019); OVID MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily, and Ovid MEDLINE(R) (to August 2, 2019); MEDLINE via PubMed (to August 2, 2019) for the previous year; and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (to August 2, 2019). We also searched clinical trials databases and the reference lists of retrieved articles for randomized controlled trials (RCTs) and quasi-randomized trials.

SELECTION CRITERIA

We included RCTs contrasting levels of formula protein intake as low (< 3.0 g/kg/d), high (≥ 3.0 g/kg/d but < 4.0 g/kg/d), or very high (≥ 4.0 g/kg/d) in formula-fed hospitalized neonates weighing less than 2.5 kilograms. We excluded studies if infants received partial parenteral nutrition during the study period, or if infants were fed formula as a supplement to human milk.

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

We identified six eligible trials that enrolled 218 infants through searches updated to August 2, 2019. Five studies compared low (< 3 g/kg/d) versus high (3.0 to 4.0 g/kg/d) protein intake using formulas that kept other nutrients constant. The trials were small (n = 139), and almost all had methodological limitations; the most frequent uncertainty was about attrition. Low-certainty evidence suggests improved weight gain (mean difference [MD] 2.36 g/kg/d, 95% confidence interval [CI] 1.31 to 3.40) and higher nitrogen accretion in infants receiving formula with higher protein content (3.0 to 4.0 g/kg/d) versus lower protein content (< 3 g/kg/d), while other nutrients were kept constant. No significant differences were seen in rates of necrotizing enterocolitis, sepsis, or diarrhea. We are uncertain whether high versus low protein intake affects head growth (MD 0.37 cm/week, 95% CI 0.16 to 0.58; n = 18) and length gain (MD 0.16 cm/week, 95% CI -0.02 to 0.34; n = 48), but sample sizes were small for these comparisons. One study compared high (3.0 to 4.0 g/kg/d) versus very high (≥ 4 g/kg/d) protein intake (average intakes were 3.6 and 4.1 g/kg/d) during and after an initial hospital stay (n = 77). Moderate-certainty evidence shows no significant differences in weight gain or length gain to discharge, term, and 12 weeks corrected age from very high protein intake (4.1 versus 3.6 g/kg/d). Three of the 24 infants receiving very high protein intake developed uremia.

AUTHORS' CONCLUSIONS

Higher protein intake (≥ 3.0 g/kg/d but < 4.0 g/kg/d) from formula accelerates weight gain. However, limited information is available regarding the impact of higher formula protein intake on long-term outcomes such as neurodevelopment. Research is needed to investigate the safety and effectiveness of protein intake ≥ 4.0 g/kg/d.

Somatic growth from birth to 6 months in low birth weight, in Bukavu, South Kivu, Democratic Republic of the Congo

BACKGROUND

Low birth weight (LBW) is one of the leading causes of perinatal and infant morbidity and mortality, as well as of impaired growth and neurocognitive development. This study aimed to evaluate the evolution of anthropometric parameters and the nutritional status of LBW infants and to analyze factors influencing the growth failure during their first 6 months of life (or adjusted age).

METHODS

This was a prospective cohort study for 6 months, including 100 infants born with LBW and 100 infants born at full-term and with normal weight. The z-scores weight for age, height for age, head circumference for age and weight for height were computed with the software Epinut and WHO Anthro 2005. Descriptive statistics, bivariate analysis and multivariable logistic regression analyses were employed to identify factors associated with growth failure. Growth failure was defined as a decrease in weight z-score (standard deviation score) of over 0.67 during one of the study's periods. The statistical significance threshold was fixed at 0.05.

FINDINGS

At 6 months of life (or adjusted age), 15.3% of LBW were underweight, 51.4% were stunted, 4.2% had an emaciation and 25% had a head circumference for age<-2 z-scores. Risk factor for growth failure was male sex (OR=1.56 [95% CI: 1.03-2.23]). The symmetrical intra-uterine growth retardation was a protector factor for growth failure (OR=0.49 [95% CI: 0.25-0.98]).

CONCLUSION

In the short term, LBW infants may have growth disorders. It is necessary to emphasize the importance of growth assessment of LBW children and proper education of their mothers about nutrition of their children for early and timely diagnosis and management of growth retardation and prevention of subsequent problems.

Higher versus lower amino acid intake in parenteral nutrition for newborn infants

BACKGROUND

Sick newborn and preterm infants frequently are not able to be fed enterally, necessitating parenteral fluid and nutrition. Potential benefits of higher parenteral amino acid (AA) intake for improved nitrogen balance, growth, and infant health may be outweighed by the infant's ability to utilise high intake of parenteral AA, especially in the days after birth.

OBJECTIVES

The primary objective is to determine whether higher versus lower intake of parenteral AA is associated with improved growth and disability-free survival in newborn infants receiving parenteral nutrition.Secondary objectives include determining whether:• higher versus lower starting or initial intake of amino acids is associated with improved growth and disability-free survival without side effects;• higher versus lower intake of amino acids at maximal intake is associated with improved growth and disability-free survival without side effects; and• increased amino acid intake should replace non-protein energy intake (glucose and lipid), should be added to non-protein energy intake, or should be provided simultaneously with non-protein energy intake.We conducted subgroup analyses to look for any differences in the effects of higher versus lower intake of amino acids according to gestational age, birth weight, age at commencement, and condition of the infant, or concomitant increases in fluid intake.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (2 June 2017), MEDLINE (1966 to 2 June 2017), Embase (1980 to 2 June 2017), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to 2 June 2017). We also searched clinical trials databases, conference proceedings, and citations of articles.

SELECTION CRITERIA

Randomised controlled trials of higher versus lower intake of AAs as parenteral nutrition in newborn infants. Comparisons of higher intake at commencement, at maximal intake, and at both commencement and maximal intake were performed.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality, and extracted data from included studies. We performed fixed-effect analyses and expressed treatment effects as mean difference (MD), risk ratio (RR), and risk difference (RD) with 95% confidence intervals (CIs) and assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

Thirty-two studies were eligible for inclusion. Six were short-term biochemical tolerance studies, one was in infants at > 35 weeks' gestation, one in term surgical newborns, and three yielding no usable data. The 21 remaining studies reported clinical outcomes in very preterm or low birth weight infants for inclusion in meta-analysis for this review.Higher AA intake had no effect on mortality before hospital discharge (typical RR 0.90, 95% CI 0.69 to 1.17; participants = 1407; studies = 14; I² = 0%; quality of evidence: low). Evidence was insufficient to show an effect on neurodevelopment and suggest no reported benefit (quality of evidence: very low). Higher AA intake was associated with a reduction in postnatal growth failure (< 10th centile) at discharge (typical RR 0.74, 95% CI 0.56 to 0.97; participants = 203; studies = 3; I² = 22%; typical RD -0.15, 95% CI -0.27 to -0.02; number needed to treat for an additional beneficial outcome (NNTB) 7, 95% CI 4 to 50; quality of evidence: very low). Subgroup analyses found reduced postnatal growth failure in infants that commenced on high amino acid intake (> 2 to ≤ 3 g/kg/day); that occurred with increased amino acid and non-protein caloric intake; that commenced on intake at < 24 hours' age; and that occurred with early lipid infusion.Higher AA intake was associated with a reduction in days needed to regain birth weight (MD -1.14, 95% CI -1.73 to -0.56; participants = 950; studies = 13; I² = 77%). Data show varying effects on growth parameters and no consistent effects on anthropometric z-scores at any time point, as well as increased growth in head circumference at discharge (MD 0.09 cm/week, 95% CI 0.06 to 0.13; participants = 315; studies = 4; I² = 90%; quality of evidence: very low).Higher AA intake was not associated with effects on days to full enteral feeds, late-onset sepsis, necrotising enterocolitis, chronic lung disease, any or severe intraventricular haemorrhage, or periventricular leukomalacia. Data show a reduction in retinopathy of prematurity (typical RR 0.44, 95% CI 0.21 to 0.93; participants = 269; studies = 4; I² = 31%; quality of evidence: very low) but no difference in severe retinopathy of prematurity.Higher AA intake was associated with an increase in positive protein balance and nitrogen balance. Potential biochemical intolerances were reported, including risk of abnormal blood urea nitrogen (typical RR 2.77, 95% CI 2.13 to 3.61; participants = 688; studies = 7; I² = 6%; typical RD 0.26, 95% CI 0.20 to 0.32; number needed to treat for an additional harmful outcome (NNTH) 4; 95% CI 3 to 5; quality of evidence: high). Higher amino acid intake in parenteral nutrition was associated with a reduction in hyperglycaemia (> 8.3 mmol/L) (typical RR 0.69, 95% CI 0.49 to 0.96; participants = 505; studies = 5; I² = 68%), although the incidence of hyperglycaemia treated with insulin was not different.

AUTHORS' CONCLUSIONS

Low-quality evidence suggests that higher AA intake in parenteral nutrition does not affect mortality. Very low-quality evidence suggests that higher AA intake reduces the incidence of postnatal growth failure. Evidence was insufficient to show an effect on neurodevelopment. Very low-quality evidence suggests that higher AA intake reduces retinopathy of prematurity but not severe retinopathy of prematurity. Higher AA intake was associated with potentially adverse biochemical effects resulting from excess amino acid load, including azotaemia. Adequately powered trials in very preterm infants are required to determine the optimal intake of AA and effects of caloric balance in parenteral nutrition on the brain and on neurodevelopment.

Higher versus lower protein intake in formula-fed low birth weight infants

BACKGROUND

The ideal quantity of dietary protein for formula-fed low birth weight infants is still a matter of debate. Protein intake must be sufficient to achieve normal growth without negative effects such as acidosis, uremia, and elevated levels of circulating amino acids.

OBJECTIVES

To determine whether higher (≥ 3.0 g/kg/d) versus lower (< 3.0 g/kg/d) protein intake during the initial hospital stay of formula-fed preterm infants or low birth weight infants (< 2.5 kilograms) results in improved growth and neurodevelopmental outcomes without evidence of short- and long-term morbidity.To examine the following distinctions in protein intake. 1. Low protein intake if the amount was less than 3.0 g/kg/d. 2. High protein intake if the amount was equal to or greater than 3.0 g/kg/d but less than 4.0 g/kg/d. 3. Very high protein intake if the amount was equal to or greater than 4.0 g/kg/d.If the reviewed studies combined alterations of protein and energy, subgroup analyses were to be carried out for the planned categories of protein intake according to the following predefined energy intake categories. 1. Low energy intake: less than 105 kcal/kg/d. 2. Medium energy intake: greater than or equal to 105 kcal/kg/d and less than or equal to 135 kcal/kg/d. 3. High energy intake: greater than 135 kcal/kg/d.As the Ziegler-Fomon reference fetus estimates different protein requirements for infants based on birth weight, subgroup analyses were to be undertaken for the following birth weight categories. 1. < 800 grams. 2. 800 to 1199 grams. 3. 1200 to 1799 grams. 4. 1800 to 2499 grams.

SEARCH METHODS

The standard search methods of the Cochrane Neonatal Review Group were used. MEDLINE, CINAHL, PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library) were searched.

SELECTION CRITERIA

Randomized controlled trials contrasting levels of formula protein intake as low (< 3.0 g/kg/d), high (≥ 3.0 g/kg/d but < 4.0 g/kg/d), or very high (≥ 4.0 g/kg/d) in formula-fed hospitalized neonates weighing less than 2.5 kilograms were included. Studies were excluded if infants received partial parenteral nutrition during the study period or were fed formula as a supplement to human milk. Studies in which nutrients other than protein also varied were added in a post-facto analysis.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Neonatal Review Group were used.

MAIN RESULTS

Five studies compared low versus high protein intake. Improved weight gain and higher nitrogen accretion were demonstrated in infants receiving formula with higher protein content while other nutrients were kept constant. No significant differences were seen in rates of necrotizing enterocolitis, sepsis, or diarrhea.One study compared high versus very high protein intake during and after an initial hospital stay. Very high protein intake promoted improved gain in length at term, but differences did not remain significant at 12 weeks corrected age. Three of the 24 infants receiving very high protein intake developed uremia.A post-facto analysis revealed further improvement in all growth parameters in infants receiving formula with higher protein content. No significant difference in the concentration of plasma phenylalanine was noted between high and low protein intake groups. However, one study (Goldman 1969) documented a significantly increased incidence of low intelligence quotient (IQ) scores among infants of birth weight less than 1300 grams who received a very high protein intake (6 to 7.2 g/kg).

AUTHORS' CONCLUSIONS

Higher protein intake (≥ 3.0 g/kg/d but < 4.0 g/kg/d) from formula accelerates weight gain. However, limited information is available regarding the impact of higher formula protein intake on long-term outcomes such as neurodevelopmental abnormalities. Available evidence is not adequate to permit specific recommendations regarding the provision of very high protein intake (> 4.0 g/kg/d) from formula during the initial hospital stay or after discharge.

Creamatocrit analysis of human milk overestimates fat and energy content when compared to a human milk analyzer using mid-infrared spectroscopy

BACKGROUND AND OBJECTIVE

Human milk (HM) is the preferred feeding for human infants but may be inadequate to support the rapid growth of the very-low-birth-weight infant. The creamatocrit (CMCT) has been widely used to guide health care professionals as they analyze HM fortification; however, the CMCT method is based on an equation using assumptions for protein and carbohydrate with fat as the only measured variable. The aim of the present study was to test the hypothesis that a human milk analyzer (HMA) would provide more accurate data for fat and energy content than analysis by CMCT.

METHODS

Fifty-one well-mixed samples of previously frozen expressed HM were obtained after thawing. Previously assayed "control" milk samples were thawed and also run with unknowns. All milk samples were prewarmed at 40°C and then analyzed by both CMCT and HMA. CMCT fat results were substituted in the CMCT equation to reach a value for energy (kcal/oz). Fat results from HMA were entered into a computer model to reach a value for energy (kcal/oz). Fat and energy results were compared by paired t test with statistical significance set at P < 0.05. An additional 10 samples were analyzed locally by both methods and then sent to a certified laboratory for quantitative analysis. Results for fat and energy were analyzed by 1-way analysis of variance with statistical significance set at P < 0.05.

RESULTS

Mean fat content by CMCT (5.8 ± 1.9 g/dL) was significantly higher than by HMA (3.2 ± 1.1 g/dL, P < 0.001). Mean energy by CMCT (21.8 ± 3.4 kcal/oz) was also significantly higher than by HMA (17.1 ± 2.9, P < 0.001). Comparison of biochemical analysis with HMA of the subset of milk samples showed no statistical difference for fat and energy, whereas CMCT was significantly higher than for both fat (P < 0.001) and energy (P = 0.002).

CONCLUSIONS

The CMCT method appears to overestimate fat and energy content of HM samples when compared with HMA and biochemical methods.

Calculating postnatal growth velocity in very low birth weight (VLBW) premature infants

OBJECTIVE

Currently, there is no standardized approach to the calculation of growth velocity (GV; g kg (-1) day(-1)) in hospitalized very low birth weight (VLBW) infants. Thus, differing methods are used to estimate GV, resulting in different medical centers and studies reporting growth results that are difficult to compare. The objective of this study was to compare actual GV calculated from infant daily weights during hospitalization in a Neonatal Intensive Care Unit (NICU) with estimated GV using two mathematical models that have been shown earlier to provide good estimated GVs in extremely low birth weight (ELBW) infants: an exponential model (EM) and a 2-Point model (2-PM).

STUDY DESIGN

Daily weights from 81 infants with birth weights (BWs) of 1000 to 1499 g were used to calculate actual GV in daily increments from two starting points: (1) birth and (2) day of life (DOL) of regaining BW. These daily GV values were then averaged over the NICU stay to yield overall NICU GV from the two starting points. We compared these actual GV with estimated GV calculated using the EM and 2-PM methods.

RESULTS

The mean absolute difference between actual and EM estimates of GV showed <1% error for 100% of infants from both starting points. The mean absolute difference between actual and 2-PM estimates showed <1% error for only 38 and 44% of infants from birth and regaining BW, respectively. The EM was unaffected by decreasing BW and increasing length of NICU stay, whereas the accuracy of the 2-PM was diminished significantly (P<0.001) by both factors.

CONCLUSION

In contrast to the 2-PM, the EM provides an extremely accurate estimate of GV in larger VLBW infants, and its accuracy is unaffected by common infant factors. The EM has now been validated for use in all VLBW infants to assess growth and provides a simple-to-use and consistent approach.

Nutritional practices and growth velocity in the first month of life in extremely premature infants

OBJECTIVES

The goals of this study were to describe nutritional practices in the first month of life for a large cohort of extremely low gestational age newborns and to determine the impact of these nutritional practices on growth velocity (GV) over the same period.

METHODS

The sample included 1187 infants born at 23 to 27 weeks of gestation, at 14 institutions, between 2002 and 2004. Inclusion criteria included survival until day 28 and weight information for days 7 and 28. GV, expressed as grams per kilogram per day, was calculated for the interval between days 7 and 28. Nutritional practices during the first week and on days 14, 21, and 28 were compared with current nutritional guidelines in the literature. Multivariable logistic regression models estimated the contribution of limited nutrition to limited GV.

RESULTS

Protein and fat delivery approximated current nutritional recommendations, whereas carbohydrate and total energy intake delivery did not. Despite this, GV of our study infants exceeded the current guideline of 15 g/kg per day. Nevertheless, we found extrauterine growth restriction (ie, weight for gestational age below the 10th centile) in 75% of the infants at 28 days, compared with only 18% at birth. A GV of 20 to 30 g/kg per day was associated with infants' maintaining or exceeding their birth weight z score, with rates in the upper range for the gestationally youngest infants. Early (day 7) nutritional practices were positively associated with GV measured between days 7 and 28.

CONCLUSION

The early provision of nutrients is an important determinant of postnatal growth. Extrauterine growth restriction remains high in extremely premature infants even when they achieve a GV rate within current guidelines.

Attenuated insulin release and storage in fetal sheep pancreatic islets with intrauterine growth restriction

We determined in vivo and in vitro pancreatic islet insulin secretion and glucose metabolism in fetuses with intrauterine growth restriction (IUGR) caused by chronic placental insufficiency to identify functional deficits in the fetal pancreas that might be caused by nutrient restriction. Plasma insulin concentrations in the IUGR fetuses were 69% lower at baseline and 76% lower after glucose-stimulated insulin secretion (GSIS). Similar deficits were observed with arginine-stimulated insulin secretion. Fetal islets, immunopositive for insulin and glucagon, secreted insulin in response to increasing glucose and KCl concentrations. Insulin release as a fraction of total insulin content was greater in glucose-stimulated IUGR islets, but the mass of insulin released per IUGR islet was lower because of their 82% lower insulin content. A deficiency in islet glucose metabolism was found in the rate of islet glucose oxidation at maximal stimulatory glucose concentrations (11 mmol/liter). Thus, pancreatic islets from nutritionally deprived IUGR fetuses caused by chronic placental insufficiency have impaired insulin secretion caused by reduced glucose-stimulated glucose oxidation rates, insulin biosynthesis, and insulin content. This impaired GSIS occurs despite an increased fractional rate of insulin release that results from a greater proportion of releasable insulin as a result of lower insulin stores. Because this animal model recapitulates the human pathology of chronic placental insufficiency and IUGR, the beta-cell GSIS dysfunction in this model might indicate mechanisms that are developmentally adaptive for fetal survival but in later life might predispose offspring to adult-onset diabetes that has been previously associated with IUGR.

Higher versus lower protein intake in formula-fed low birth weight infants

BACKGROUND

The ideal quantity of dietary protein for formula-fed low birth weight infants < 2.5 kilograms is still a matter of controversy and debate. In premature infants, the protein intake must be sufficient to achieve normal growth without negative effects such as acidosis, uremia, and elevated levels of circulating amino acids (e.g. phenylalanine levels). This systematic review evaluates the benefits and risks of higher (>= 3.0 g/kg/day) versus lower (< 3.0 g/kg/day) protein intakes during the initial hospital stay of formula-fed preterm infants < 2.5 kilograms.

OBJECTIVES

To determine whether higher (>= 3.0 g/kg/day) versus lower (< 3.0 g/kg/day) protein intakes during the initial hospital stay of formula-fed preterm infants < 2.5 kilograms result in improved growth and neurodevelopmental outcomes without evidence of short and long-term morbidity.

SEARCH STRATEGY

Two review authors searched MEDLINE (1966 - May 2005), CINAHL (1982 - May 2005), PubMed (1966 - May 2005), EMBASE (1980 - May 2005), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2005), abstracts, conferences and symposia proceedings from Society of Pediatric Research, and American Academy of Pediatrics. Cross references were reviewed independently for additional relevant titles and abstracts for articles up to fifty years old.

SELECTION CRITERIA

Randomized controlled trials contrasting levels of formula protein intakes as low (< 3.0 g/kg/day), high (=> 3.0 g/kg/day but < 4.0 g/kg/day), or very high protein intake (=> 4.0 g/kg/day) during hospitalization of neonates less than 2.5 kilograms at birth who were formula-fed. Studies were not included if infants received partial parenteral nutrition during the study period or were fed formula as a supplement to human milk. Given the small number of studies that met all inclusion criteria, studies in which nutrients other than protein also varied (> 10% relative difference) were added in a post-facto analysis.

DATA COLLECTION AND ANALYSIS

Two review authors used standard methods of the Cochrane Collaboration and of the Cochrane Neonatal Review Group to independently assess trial eligibility and quality, and extracted data. In a 3-arm trial where two groups fell within the same predesignated protein intake group, weighted means and pooled standard deviations were calculated.

MAIN RESULTS

The literature search identified 37 studies, of which five met all the inclusion criteria. All five studies compared low (< 3.0 g/kg/day) to high protein intakes (=> 3.0 g/kg/day but < 4.0 g/kg/day). The overall analysis revealed an improved weight gain (WMD 2.36 g/kg/day, 95% CI 1.31, 3.40) and higher nitrogen accretion (WMD 143.7 mg/kg/day, 95% CI 128.7, 158.8) in infants receiving formula with higher protein content while other nutrients were kept constant. None of the studies reported IQ or Bayley scores at 18 months or later. No significant differences were seen in rates of necrotizing enterocolitis, sepsis or diarrhea. Of three studies included in the post-facto analysis, only one could be included in the meta-analysis. The post-facto analysis revealed further improvement in all growth parameters in infants receiving formula with higher protein content (weight gain: WMD 2.53 g/kg/day, 95% CI 1.62, 3.45, linear growth: WMD 0.16 cm/week, 95% CI 0.03, 0.30, and head growth: WMD 0.23, 95% CI 0.12, 0.35). There was no significant difference (WMD 0.25, 95% CI -0.20, 0.70) in the concentration of plasma phenylalanine between the high and low protein intake groups. One study (Goldman 1969) in the post-facto analysis documented a significantly increased incidence of low IQ scores, below 90, in infants of birth weight less than 1300 grams who received a very high protein intake (6 to 7.2 g/kg/day).

AUTHORS' CONCLUSIONS

This systematic review suggests that higher protein intake (=> 3.0 g/kg/day but < 4.0 g/kg/day) from formula accelerates weight gain. Based on increased nitrogen accretion rates, this most likely indicates an increase in lean body mass. Although accelerated weight gain is considered to be a positive effect, increase in other outcome measures examined may represent a negative or ambivalent effect. These include elevated blood urea nitrogen levels and increased metabolic acidosis. Limited information was available regarding the impact of higher formula protein intakes on long term outcomes such as neurodevelopmental abnormalities. As determined in this review, existing research literature on this topic is not adequate to make specific recommendations regarding the provision of very high protein intake (> 4.0 g/kg/day) from formula.

Accuracy of methods for calculating postnatal growth velocity for extremely low birth weight infants

OBJECTIVE

No uniform method for calculating growth velocity (GV) (grams per kilogram per day) among extremely low birth weight (ELBW) infants has been reported. Because the calculation of actual GV is so labor intensive, investigators have estimated GV with varying approaches, making comparisons across studies difficult. This study compares the accuracy of 3 mathematical methods used for estimating average GV, namely, 2-point models using the difference between weights at 2 time points divided by time and weight (either birth weight [BW] or average weight), linear regression models that are normalized for either BW or average weight, and an exponential model. The accuracy of all models was compared with actual GVs calculated from daily weight measures for a group of ELBW infants.

METHODS

Actual GVs were calculated from daily weights for 83 ELBW infants admitted to the special care nursery and were compared with estimated GVs from each of the 5 models for the same infants.

RESULTS

The exponential model, using weights from 2 time points, ie, GV = [1000 x ln(Wn/W1)]/(Dn-D1), was extremely accurate, with mean absolute errors of 0.02% to 0.10%. The 2-point and linear models were highly inaccurate when BW was used in the denominator, with mean absolute errors of 50.3% to 96.4%. The 2-point and linear models were fairly accurate when average weight was used in the denominator, with mean absolute errors of 0.1% to 8.97%. Additional analyses showed that the accuracy of the 2-point and linear model estimates was affected significantly by the combination of BW, length of stay, and chronic lung disease, whereas the exponential model was not affected by these combined factors.

CONCLUSIONS

GV estimates calculated with 3 commonly used models varied widely, compared with actual GVs; however, the exponential model estimates were extremely accurate. The exponential model provides the accuracy and ease of use that are lacking in current methods applied to infant growth research.

Selected principles of perinatal-neonatal glucose metabolism

While the fetus is completely dependent on his/her mother for glucose and other nutrient transfer across the placenta, the adult is completely independent, especially one who is neither pregnant nor diabetic. The neonate is considered to be in a transition between the complete dependence of the fetus and the complete independence of the adult. The heterogeneity that is the hallmark of neonatal glucose metabolism is illustrated by the observation that maintenance of euglycaemia in the sick and/or low-birthweight neonate is especially difficult. This reinforces the concept that the neonate is vulnerable to carbohydrate disequilibrium. In this discussion, we shall first evaluate the definition of euglycaemia by considering the ranges for hypo- and hyperglycaemia. We shall also review the considerable literature that has been published on measurement of the rate of glucose production and the rate of glucose utilization in the neonate. This review highlights where further work is necessary to understand the developing maturation (i.e. control) of glucose homeostasis in the neonate.

Evidence-based feeding guidelines for very low-birth-weight infants

Clinical practice guidelines (CPG) for the nutritional management of premature infants are limited. This project focused on the development of a research-based enteral feeding CPG for infants of < 1,500 g. The CPG was based on an extensive literature review and developed through a process of consensus decision making by a team of clinical researchers. Infants that weigh < 1,000 g initiate minimal enteral nutrition (MEN) at 48 hours; nutritional feedings begin on day 5 to 6 of life. For infants between 1,000 and 1,500 g, nutritional feedings begin at 48 hours and are advanced at a rate of less than 30 mL/kg per day. The benefits and risks of continuous versus intermittent nasogastric tube feeding were inconclusive; therefore, the CPG does not stipulate a feeding method. Breast milk is used preferentially, and specific guidelines for the definition and management of feeding intolerance are provided. A follow-up study testing this CPG has been completed and is published in the original research section of this issue.

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.

Glucose homeostasis in the micropremie

This article evaluates the current knowledge of the kinetics of glucose homeostasis in the micropremie. Glucose production, glucose use, and glucose oxidation are reviewed in detail. This article also evaluates the developmental regulation of glucose homeostasis relative to some of the fundamental differences known to exist in the neonate compared to the adult.