The effect of parenteral nitrogen and energy intake on electrolyte balance in the preterm infant

Fluid and electrolyte management in the neonate and what can go wrong

PURPOSE OF REVIEW

This review highlights recent advances in understanding fluid and electrolyte homeostasis during the newborn period, including heightened recognition of fluid overload and acute kidney injury contributing to poor clinical outcomes. Particular attention is given towards the care of extremely preterm infants.

RECENT FINDINGS

Emerging data demonstrate (i) disproportionally large transepidermal water loss in the extremely preterm population, (ii) the relationship between postnatal weight loss (negative fluid balance) and improved outcomes, (iii) the frequency and negative effects of dysnatremias early in life, (iv) the role of sodium homeostasis in optimizing postnatal growth, and (v) the deleterious effects of fluid overload and acute kidney injury.

SUMMARY

As clinicians care for an increasing number of preterm infants, understanding progress in approaches to fluid and electrolyte management and avoidance of fluid overload states will improve the care and outcomes of this vulnerable population. Further translational and clinical studies are needed to address remaining knowledge gaps and improve current approaches to fluid and electrolyte management.

High protein intake can lead to serious hypophosphatemia and hypokalemia in growth restricted preterm newborns

Objectives

High protein parenteral nutrition (HPPN) in the early postnatal period is a recommended strategy for very low birth weight (VLBW) infants. However, limited data is available on electrolyte changes when HPPN strategy is utilized. We investigated the impact of HPPN on the development of hypophosphatemia and hypokalemia in preterm VLBW newborns.

Methods

A retrospective, single-center study investigated the levels of phosphate and potassium in VLBW infants who received HPPN (amino acids intake up to 3.5 g/kg/day) during the first week of life. Preterm infants were divided into two subgroups: appropriate for gestational age (AGA) and small for gestational age (SGA) newborns. Clinical data were obtained from hospital database and medical records.

Results

Overall, 170 VLBW infants were included for the study analysis: 41 SGA (mean birth weight 752 ± 39 g) and 129 AGA infants (mean birth weight 994 ± 23 g). Phosphate and potassium levels were significantly lower in the SGA infants compared to AGA infants (Phosphate: 0.97 ± 0.07 mmol/l vs. 1.44 ± 0.04 mmol/l, p < 0.001; Potassium: 3.0 ± 0.1 mmol/l vs. 3.6 ± 0.1 mmol/l, p < 0.001).

Conclusions

Repeated measurement of serum phosphate and potassium is recommended when HPPN strategy is utilized in preterm SGA infants where significant hypophosphatemia and hypokalemia might have serious clinical consequences.

Quality improvement project in a neonatal intensive care unit reduced the prevalence and duration of hypophosphatemia with significant and sustainable results

BACKGROUND

Hypophosphatemia is associated with prolonged mechanical ventilation and may affect growth, bone mineralization, nephrocalcinosis, and mortality in preterm infants. Optimal nutrition practices may decrease risk for hypophosphatemia and improve outcome.

METHODS

A quality improvement project was established to improve parenteral and enteral phosphorus intake with the goal to decrease prevalence and duration of hypophosphatemia in the first 14 days in infants <32 weeks' gestation.

RESULTS

Among 406 preterm infants, the prevalence of moderate hypophosphatemia decreased from 44% to 19% (P < 0.01) over 4 years. The median duration of moderate hypophosphatemia decreased from 72 h (48-128) to 24 (24-53) (P < 0.01). Daily intakes of parenteral calcium and phosphorus on the fourth day of life increased from 1.5 to 2.5 mEq/kg/day (P < 0.01) and 0.6 to 1.3 mmol/kg/day (P < 0.01), respectively. The median postnatal age of first serum phosphorus concentration assessment decreased from 53 h (41-64) to 32 (24-40) (P < 0.01).

CONCLUSION

During this quality improvement project, reduced prevalence and duration of hypophosphatemia in infants <32 weeks' gestation in the first 14 days of life was achieved through the optimization of parenteral and enteral phosphorus intake and improved response to acute hypophosphatemia.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Higher Parenteral Electrolyte Intakes in Preterm Infants During First Week of Life: Effects on Electrolyte Imbalances

OBJECTIVES

This study aimed to investigate the effects of a higher intake of electrolytes from parenteral nutrition (PN) on plasma electrolyte concentrations in very low birth weight (VLBW, <1500 g) infants.

METHODS

This was a single-center cohort study including all VLBW infants born before (n = 81) and after (n = 53) the implementation of a concentrated PN regimen. Daily nutritional intakes and plasma concentrations of sodium, chloride, potassium, phosphate, and calcium were collected from clinical charts.

RESULTS

During the first postnatal week, electrolyte intakes were higher in infants who received concentrated PN compared with infants who received original PN. Infants who received concentrated PN had a lower incidence of hypokalemia (<3.5 mmol/L; 30% vs 76%, P < 0.001) and severe hypophosphatemia (<1.0 mmol/L; 2.2% vs 17%, P = 0.02). While the relatively high prevalence of severe hypophosphatemia in infants who received original PN can be explained by a phosphorus intake below the recommendation, the potassium intake during the first 3 postnatal days (mean ± SD: 0.7 ± 0.2 mmol/kg/d) was within the recommendation. The prevalence of early hypernatremia was not affected by the different sodium intake in the 2 groups.

CONCLUSIONS

In VLBW infants, a sodium-containing PN solution (about 2.7 mmol/100 mL) does not cause hypernatremia during the first days of life. Furthermore, providing at least 1 mmol potassium/kg/d during the first 3 postnatal days might be necessary to prevent early hypokalemia.

Macronutrients and Micronutrients in Parenteral Nutrition for Preterm Newborns: A Narrative Review

Preterm neonates display a high risk of postnatal malnutrition, especially at very low gestational ages, because nutritional stores are less in younger preterm infants. For this reason nutrition and growth in early life play a pivotal role in the establishment of the long-term health of premature infants. Nutritional care for preterm neonates remains a challenge in clinical practice. According to the recent and latest recommendations from ESPGHAN, at birth, water intake of 70-80 mL/kg/day is suggested, progressively increasing to 150 mL/kg/day by the end of the first week of life, along with a calorie intake of 120 kcal/kg/day and a minimum protein intake of 2.5-3 g/kg/day. Regarding glucose intake, an infusion rate of 3-5 mg/kg/min is recommended, but VLBW and ELBW preterm neonates may require up to 12 mg/kg/min. In preterm infants, lipid emulsions can be started immediately after birth at a dosage of 0.5-1 g/kg/day. However, some authors have recently shown that it is not always possible to achieve optimal and recommended nutrition, due to the complexity of the daily management of premature infants, especially if extremely preterm. It would be desirable if multicenter randomized controlled trials were designed to explore the effect of early nutrition and growth on long-term health.

The influence of parenteral protein intake on electrolyte disturbances in premature infants

INTRODUCTION

Aggressive parenteral nutrition with delivery of high amino acid and energy doses is used to improve growth and neurodevelopmental outcomes in very low birth weight (VLBW) preterm infants. Recent findings, however, suggest that this approach may cause electrolyte imbalances. The aim of our study was to compare the prevalence of hypercalcaemia, hypophosphataemia, and hypokalaemia in 2 groups of preterm infants that received parenteral nutrition with different amounts of amino acids and to analyse perinatal and nutritional variables associated with the development of electrolyte imbalances.

METHODS

We conducted a retrospective observational study comparing 2 groups of preterm infants born before 33 weeks' gestation with birth weights of less than 1500 g managed with parenteral nutrition. One of the groups received less than 3 g/kg/day of amino acids and the other received 3 g/kg//day of amino acids or more. We analysed the prevalence of electrolyte imbalances and possible associations with aggressive parenteral nutrition, adjusting for potential confounders.

RESULTS

We studied 114 infants: 60 given less than 3 g/kg/day of amino acids (low-intake group) and 54 given at least 3 g/kg/day (high-intake group). The prevalence of electrolyte imbalances was similar in both groups. The prevalence of hypercalcaemia was 1.67% in the low-intake group and 1.85% in the high-intake group (P > .99), the prevalence of severe hypophosphataemia 11.7% vs 9.3%, and the prevalence of hypokalaemia 15.0% vs 11.1% (P > .99). A calcium to phosphorus ratio greater than 1.05 had a protective effect against hypophosphataemia (P = .007).

CONCLUSIONS

We did not find an association between hypercalcaemia, hypophosphataemia, and hypokalaemia and the amino acid dose delivered by PN in the high-intake group of preterm infants.

Total body water in full-term and preterm newborns: systematic review and meta-analysis

BACKGROUND

Total body water (TBW) is one component of fat-free mass and changes in TBW are influenced by fluid shifts (especially during transition to postnatal life), electrolyte balance and nutritional status. Normal values for term-born neonates and preterm infants at birth have not been defined in large cohorts, limiting investigation into its monitoring and use in clinical practice.

OBJECTIVE

To systematically review the evidence base for percentage of TBW in term-born infants, quantify the effect of prematurity on TBW at birth, and describe normal progression of TBW over time in preterm infants.

METHODS

Systematic review of Medline, Web of Science Core Collection and EBSCO-CINAHL (January 1946 to January 2020). Included articles used dilutional methods to assess TBW.

RESULTS

Searches identified 2349 articles of which 22 included data suitable for analysis. Mean TBW in term-born newborns was 73.8% (95% CI 72.47% to 75.06%, 15 studies, 433 infants). Meta-regression showed that TBW was higher in preterm infants (up to 90% at 26 weeks gestation, dropping to 75% at 36 weeks corrected gestation) and was negatively correlated with gestation at birth, falling 1.44% per week (95% CI 0.63% to 2.24%, 9 studies, 179 infants). Analysis of TBW over time during the ex utero growth of preterm infants was not possible due to paucity of data.

CONCLUSION

This review defines the normal TBW percentage in term-born infants and confirms and quantifies previous findings that preterm infants have a higher TBW percentage.

Neonatal Refeeding Syndrome and Clinical Outcome in Extremely Low-Birth-Weight Babies: Secondary Cohort Analysis From the ProVIDe Trial

BACKGROUND

Refeeding syndrome (RS) following preterm birth has been linked to high intravenous (IV) protein intake in the presence of low electrolyte supply. In extremely low-birth-weight (ELBW) babies, we aimed to determine the incidence of RS and associations with birth characteristics and clinical outcomes.

METHOD

Prospective cohort study of ELBW ProVIDe Trial participants in 6 New Zealand neonatal intensive care units. RS was defined as serum phosphate < 1.4 mmol.L^-1 and total calcium > 2.8 mmol.L^-1 . Relationships between RS and other factors were explored using 2-sample tests and logistic regression adjusted for sex, gestation, and birth-weight z-score.

RESULTS

Of 338 babies (mean [SD] birth-weight, 780 (134) g, gestational age, 25.9 [1.7] weeks), 68 (20%) had RS. Mortality was greater in babies with RS (32% vs 11%; P < .0001). More small- than appropriate-for-gestational-age babies developed RS (22% vs 8%; P = .001). Growth from birth to 36 weeks' corrected age was not different between babies who did and did not have RS. In logistic regression, the odds of RS decreased by 70% for each 1 mmol per kg^-1 .d^-1 IV phosphate intake (odds ratio [OR], 0.3; CI, 0.1-0.6; P = .002) and increased by 80% for each 1 g.kg^-1 .d^-1 IV protein intake (OR, 1.8; CI, 1.3-2.7; P = .002).

CONCLUSIONS

Neonatal RS is common in this cohort of ELBW babies and is associated with increased morbidity and mortality. Optimizing phosphate and calcium intakes in IV nutrition solutions may reduce RS and its consequences.

Attainment Targets for Protein Intake Using Standardised, Concentrated and Individualised Neonatal Parenteral Nutrition Regimens

Neonatal parenteral nutrition (NPN) regimens that are individualised (iNPN) or standardised concentrated NPN (scNPN) are both currently used in preterm clinical practice. Two recent trials (one iNPN and one scNPN) each compared standard (control) and high (intervention) parenteral protein and energy dosage regimens and provided data about actual protein intake. We hypothesised that scNPN regimens would achieve a higher percentage of the target parenteral protein intake than their corresponding iNPN regimens. We calculated the daily individual target parenteral protein intake and used the daily parenteral protein intake to calculate the target attainment for protein intake in each infant for the two control (iNPN: n = 59, scNPN: n = 76) and two intervention (iNPN: n = 65; scNPN: n = 74) groups. The median (IQR) target attainment of high-dose protein was 75% (66-85) versus 94% (87-97) on days 1-15 for iNPN and scNPN regimens respectively (p < 0.01). The median (IQR) target attainment of standard dose protein was 77% (67-85) versus 94% (91-96) on days 1-15 for iNPN and scNPN regimens, respectively (p < 0.01). This was associated with improved weight gain (p = 0.050; control groups only) and head growth (p < 0.001; intervention groups only). scNPN regimens have better target attainment for parenteral protein intakes than iNPN regimens.

Increased risk of refeeding syndrome-like hypophosphatemia with high initial amino acid intake in small-for-gestational-age, extremely-low-birthweight infants

BACKGROUND

Recent nutrition guidelines for extremely-low-birth-weight infants (ELBWIs) recommend implementation of high initial amino acid (AA) supplementation in parenteral nutrition.

OBJECTIVE

We sought to evaluate the influence of AA intake on refeeding syndrome-like electrolyte disturbances including hypophosphatemia in ELBWIs.

STUDY DESIGN

Medical records of 142 ELBWIs were reviewed. Demographic, nutritional, outcome, and electrolyte data were compared between ELBWIs with initial low (1.5 g/kg/day) and high (3 g/kg/day) AA intake. Multivariate analysis was conducted to determine the odds ratio of hypophosphatemia with high AA intake and small-for-gestational-age (SGA) ELBWIs.

RESULTS

The incidence of hypophosphatemia and severe hypophosphatemia increased from 51% and 8% in period I to 59% and 20% in period II, respectively (p = 0.36 and < 0.01). Specifically, SGA ELBWIs showed higher incidence of hypophosphatemia than appropriate-for-gestational age (AGA) ELBWIs in period II, whereas there was no difference in period I. For severe hypophosphatemia, SGA ELBWIs presented a 27% incidence versus a 2% incidence in AGA ELBWIs, even with low initial AA intake. Despite no difference in phosphate intake between infants with and without hypophosphatemia, serum phosphate level reached a nadir at the sixth postnatal day and gradually recovered over the second week in infants with hypophosphatemia. In multivariate analyses, the odds ratios for severe hypophosphatemia were 3.6 and 6.6 with high AA intake and SGA status, respectively, with the highest being 18.0 with combined high AA intake and SGA status.

CONCLUSIONS

In summary, high initial AA intake significantly increased the risk of refeeding syndrome-like electrolyte dysregulations including severe hypophosphatemia in ELBWIs. In SGA ELBWIs, the risk of electrolyte disturbance was significantly higher, even with low initial AA intake. Therefore, new tailored parenteral nutrition protocols starting with lower energy intake and a gradual increase over the first week may be warranted for application in high-risk SGA ELBWIs.

Parenteral nutrition for preterm infants: Issues and strategy

Due to transient gut immaturity, most very preterm infants receive parenteral nutrition (PN) in the first few weeks of life. Yet providing enough protein and energy to sustain optimal growth in such infants remains a challenge. Extrauterine growth restriction is frequently observed in very preterm infants at the time of discharge from hospital, and has been found to be associated with later impaired neurodevelopment. A few recent randomized trials suggest that intensified PN can improve early growth; whether or not such early PN improves long-term neurological outcome is still unclear. Several other questions regarding what is optimal PN for very preterm infants remain unanswered. Amino acid mixtures designed for infants contain large amounts of branched-chain amino acids and taurine, but there is no consensus on the need for some nonessential amino acids such as glutamine, arginine, and cysteine. Whether excess growth in the first few weeks of life, at a time when very preterm infants receive PN, has an imprinting effect, increasing the risk of metabolic or vascular disease at adulthood continues to be debated. Even though uncertainty remains regarding the long-term effect of early PN, it appears reasonable to propose intensified initial PN. The aim of the current position paper is to review the evidence supporting such a strategy with regards to the early phase of nutrition, which is mainly covered by parenteral nutrition. More randomized trials are, however, needed to further support this type of approach and to demonstrate that this strategy improves short- and long-term outcome.

Standardized Parenteral Nutrition for the Transition Phase in Preterm Infants: A Bag That Fits

The optimal composition of standardized parenteral nutrition (SPN) is not yet known, contributing to nutrient deficit accrual and growth failure, with the period of parenteral nutrition weaning, i.e., transition (TN) phase, being identified as particularly vulnerable. We created a comprehensive nutrition database, representative of the nutritional course of a diverse range of preterm infants (n = 59, birth weight ≤ 1500 g, gestation < 34 weeks) by collecting hourly macronutrient intake data as part of a prospective, observational study over 19 months. Using a nutrient modeling technique for the TN phase, various amino acid (AA) concentrations of SPN were tested within the database, whilst acknowledging the nutritional contribution from enteral feeds until target AA intakes were consistently achieved. From the modeling, the AA composition of SPN was determined at 3.5 g/100 mL, which was the maximum to avoid exceeding target intakes at any point in the TN phase. However, in order to consistently achieve target AA intakes, additional nutritional strategies were required, which included increasing the exclusion of enteral feeds in fluid and nutrient calculations from <20 mL/kg/day to <40 mL/kg/day, and earlier fortification of breastmilk at 80 mL/kg/day. This data-driven nutrient modeling process supported the development of an improved SPN regimen for our preterm population in the TN phase.

Transition Phase Nutrition Recommendations: A Missing Link in the Nutrition Management of Preterm Infants

BACKGROUND

Despite the availability of international nutrition recommendations, preterm infants remain vulnerable to suboptimal nutrition. The standard approach of assessing nutrient intakes chronologically may make it difficult to identify the origin of nutrient deficits and/or excesses.

OBJECTIVE

To develop a "nutrition phase" approach to evaluating nutrition support, enabling analysis of nutrient intakes during the period of weaning from parenteral nutrition (PN) to enteral nutrition (EN), called the transition (TN) phase, and compare the data with those analyzed using the standard "chronological age" approach to assess whether the identification of nutrient deficits and/or excesses can be improved.

METHODS

Analysis of a comprehensive nutrition database developed using actual nutrient intake data collected on an hourly basis in 59 preterm infants (birth weight ≤1500 g, gestation <34 weeks) over the period of PN delivery (range, 2-21 days).

RESULTS

The nutrition phase analysis approach revealed substantial macronutrient and energy deficits during the TN phase. In particular, deficits were identified as maximal during the EN-dominant TN phase (enteral feeds ≥80 mL/kg/d) of the infant's nutrition course. In contrast, the chronological age analysis approach did not reveal a corresponding pattern of deficit occurrence but rather intakes that approximated or exceeded recommendations.

CONCLUSION

Actual intakes of nutrients, analyzed using a nutrition phase approach to evaluating nutrition support, enabled a more infant-driven rather than age-driven application of nutrition recommendations. This approach unmasked nutrient deficits occurring during the transition phase. Overcoming nutrient deficits in this nutrition phase should be prioritized to improve the nutrition management of preterm infants.

Early optimal parenteral nutrition and metabolic acidosis in very preterm infants

BACKGROUND

It is currently recognized that an optimized nutritional approach, consisting of an early and substantial supply of protein and energy by parenteral route, may be beneficial for very low birth weight infants and recent guidelines endorse this strategy. However, the impact of the enhanced parenteral nutrition (PN) on acid-basic balance has never been investigated. The aim of the present study is to assess the effect of nutrient intake on acid-base homeostasis in a large population of preterm infants on PN.

METHODS

This observational study described the acid-base profile of very preterm infants (≤29 week's gestation) receiving PN during the first week of life. For this purpose three different cohorts of infants who received increasing (group 1 to group 3) nutritional intakes were considered. Nutrition data were recorded daily and correlated to acid-base data (pH, base excess, and lactate). The outcome measure to assess metabolic acidosis was the base excess (BE).

RESULTS

161 infants were included. 1127 daily nutritional records and 795 blood gas data were analyzed. The three groups were different with regard to nutritional intravenous intakes. Group 3 in particular had a higher mean intake of both amino acids (3.3 ± 0.8 g/kg/d) and lipids (2.8 ± 1.4 g/kg/d) during the first week of life. Metabolic acidosis was more severe in the group with the highest parenteral intake of amino acids and lipids: mean BE = -8.7 ± 3.4 (group 3); -6.4 ± 3.4 (group 2); -5.1 ± 3.0 (group 1)]. At the multivariate analysis the significant risk factors for metabolic acidosis were: gestational age, initial base excess, amino acid and lipid intravenous intakes.

DISCUSSION

Acid-base homeostasis was influenced by the nutritional intake. Earlier and higher intravenous amino acid and lipid intakes particularly increased the risk of metabolic acidosis. The nutritional tolerance was different depending on gestational age, and the smaller infants (24-26 week's gestation) displayed greater acidotic disequilibrium and a higher need of bicarbonate.

Risk Factors for the Development of Refeeding Syndrome-Like Hypophosphatemia in Very Low Birth Weight Infants

Background

Refeeding syndrome is characterized by metabolic disturbance including hypophosphatemia and hypokalemia upon reinstitution of nutrition in severely malnourished patients.

Objective

The present study sought to identify the risk factors for the development of refeeding syndrome-like metabolic disturbance in very low birth weight infants.

Methods

The correlations of severe hypophosphatemia with the serum levels of potassium and ionized calcium, daily calorie and phosphate intake, and umbilical cord blood flow on ultrasonography were analyzed in 49 very low birth weight infants.

Results

Fifteen infants (36%) presented with hypophosphatemia during the first postnatal week. Hypophosphatemia was significantly associated with birth weight z score (odds ratio, 1.60; 95% confidence interval, 1.04-2.47; p = 0.034) and umbilical artery resistance index (odds ratio, 7.72E-04; 95% confidence interval, 1.14E-06-0.523; p = 0.031). Multiple regression analysis revealed that umbilical artery resistance index was independently associated with hypophosphatemia.

Conclusions

Umbilical artery resistance index may serve as a useful marker for future development of refeeding syndrome-like hypophosphatemia in very low birth weight infants. Close monitoring of serum phosphorus and potassium levels and early intervention are important for the management of very low birth weight infants with intrauterine growth restriction due to placental dysfunction.

Optimising preterm nutrition: present and future

The goal of preterm nutrition in achieving growth and body composition approximating that of the fetus of the same postmenstrual age is difficult to achieve. Current nutrition recommendations depend largely on expert opinion, due to lack of evidence, and are primarily birth weight based, with no consideration given to gestational age and/or need for catch-up growth. Assessment of growth is based predominately on anthropometry, which gives insufficient attention to the quality of growth. The present paper provides a review of the current literature on the nutritional management and assessment of growth in preterm infants. It explores several approaches that may be required to optimise nutrient intakes in preterm infants, such as personalising nutritional support, collection of nutrient intake data in real-time, and measurement of body composition. In clinical practice, the response to inappropriate nutrient intakes is delayed as the effects of under- or overnutrition are not immediate, and there is limited nutritional feedback at the cot-side. The accurate and non-invasive measurement of infant body composition, assessed by means of air displacement plethysmography, has been shown to be useful in assessing quality of growth. The development and implementation of personalised, responsive nutritional management of preterm infants, utilising real-time nutrient intake data collection, with ongoing nutritional assessments that include measurement of body composition is required to help meet the individual needs of preterm infants.

Biological Impact of Recent Guidelines on Parenteral Nutrition in Preterm Infants

OBJECTIVES

Recent guidelines for preterm neonates recommend early initiation of parenteral nutrition (PN) with high protein and relatively high caloric intake. This review considers whether these changes could influence homeostasis in very preterm infants during the first few postnatal weeks.

METHODS

This systematic review of relevant literature from searches of PubMed and recent guidelines was reviewed by investigators from several perinatal centers in France.

RESULTS

New recommendations for PN could be associated with metabolic acidosis via the increase in the amino acid ion gap, hyperchloremic acidosis, and ammonia acidosis. The introduction of high-intake amino acids soon after birth could induce hypophosphatemia and hypercalcemia, simulating a "repeat feeding-like syndrome" and could be prevented by the early intake of phosphorus, especially in preterm infants born after fetal growth restriction. Early high-dose amino acid infusions are relatively well tolerated in the preterm infant with regard to renal function. Additional studies, however, are warranted to determine markers of protein intolerance and to specify the optimal composition and amount of amino acid solutions.

CONCLUSIONS

Optimal PN following new guidelines in very preterm infants, despite their demonstrated benefits on growth, may induce adverse effects on ionic homeostasis. Clinicians should implement appropriate monitoring to prevent and/or correct them.

Extremely preterm infants who are small for gestational age have a high risk of early hypophosphatemia and hypokalemia

AIM

Electrolyte balances have not been sufficiently evaluated in extremely preterm infants after early parenteral nutrition. We investigated the risk of early hypophosphatemia and hypokalemia in extremely preterm infants born small for gestational age (SGA) who received nutrition as currently recommended.

METHODS

This prospective, observational cohort study included all consecutive extremely preterm infants born at 24-27 weeks who received high amino acids and lipid perfusion from birth. We evaluated the electrolyte levels of SGA infants and infants born appropriate for gestational age (AGA) during the first five days of life.

RESULTS

The 12 SGA infants had lower plasma potassium levels from Day One compared to the 36 AGA infants and were more likely to have hypokalemia (58% vs 17%, p = 0.001) and hypophosphatemia (40% vs 9%, p < 0.01) during the five-day observation period. After adjusting for perinatal factors, SGA remained significantly associated with hypophosphatemia (odds ratio 1.39, confidence intervals 1.07-1.81, p = 0.01).

CONCLUSION

Extremely preterm infants born SGA who were managed with currently recommended early parenteral nutrition had a high risk of early hypokalemia and hypophosphatemia. Potassium and phosphorus intakes should be set at sufficient levels from birth onwards, especially in SGA infants.

Electrolyte and Mineral Homeostasis After Optimizing Early Macronutrient Intakes in VLBW Infants on Parenteral Nutrition

OBJECTIVES

The aim of the present study was to evaluate electrolyte and mineral homeostasis in very-low-birth-weight (VLBW) infants who received high protein and energy intakes with a unique standardized parenteral nutrition solution containing electrolytes and minerals from birth onward.

METHODS

Prospective cohort study in 102 infants with birth weight <1250 g. The evolution of plasma biochemical parameters was described during the first 2 weeks of life.

RESULTS

During the first 3 days of life, mean parenteral intakes were 51 ± 8 kcal · kg · day with 2.7 ± 0.4 g · kg · day of protein, 1.1 ± 0.2 mmol · kg · day of sodium and potassium, and 1.3 ± 0.2 mmol · kg · day of calcium and phosphorus. Afterwards, most nutritional intakes (parenteral and enteral) met growth requirements. No infant developed a hyperkalemia >7 mmol/L, and a hypernatremia >150 mmol/L occurred only in 15.7% of the infants. In contrast, hyponatremia <130 mmol/L and hypokalemia <3 mmol/L occurred in 30.4% and 8.8% of the infants, respectively. The initial neonatal metabolic acidosis rapidly resolved in most infants and only 2.0% developed a base deficit >10 mmol/L after day 3 of life. Early hypocalcemia <1.8 mmol/L occurred in 13.7% of the infants. In contrast, hypophosphatemia <1.6 mmol/L occurred in 37.3% and hypercalcemia >2.8 mmol/L occurred in 12.7% of the infants.

CONCLUSIONS

Increasing early protein and energy intakes in VLBW infants in the first week of life improves electrolyte homeostasis. It also increases the phosphorus requirements with a calcium-to-phosphorus ratio ≤1.0 (mmol/mmol) and the potassium and sodium requirements to avoid the development of a refeeding-like syndrome. These data suggest that the parenteral nutrition guidelines for VLBW infants for the first week of life need to be revised.

Nutritional strategy of early amino acid administration in very low birth weight infants

Relative to a fetus of the same gestational age, very low birth weight (VLBW) infants are more likely to be underfed and to undergo growth restriction during their early hospital stay. The current trend towards "early and aggressive" nutritional strategies in VLBW infants aims to overcome the early nutritional deficiency and thereby boost postnatal catch-up growth, simultaneously improving long-term neurodevelopmental outcomes. Although the minimum starting amino acid (AA) dose to prevent negative nitrogen balance is well established, the upper limit and the rate of increase of early AA doses are controversial. Most randomized controlled trials show that early and high-dose (target, 3.5 to 4.9 g/kg/day) AA regimens, with or without high nonprotein calories, do not improve long-term growth and neurodevelopment. High-dose AA supplementation may lead to early metabolic disturbances and excessive or disproportionate plasma AA levels, particularly in infants of very low gestational age. Further large studies are needed to clarify the optimal strategy for early administration of parenteral AA doses in VLBW infants.

Responses of Preterm Pigs to an Oral Fluid Supplement During Parenteral Nutrition

BACKGROUND

Nutrients and electrolytes in amniotic fluid swallowed by fetuses are important for growth and development. Yet, preterm infants requiring parenteral nutrition (PN) receive minimal or no oral inputs. With the limited availability of amniotic fluid, we evaluated the responses of preterm pigs receiving PN to an oral fluid supplement (OFS) based on the electrolyte and nutrient composition of amniotic fluid.

MATERIALS AND METHODS

Preterm pigs (92% of term) received a combination of PN (6 mL/kg-h) and 4 mL/kg-h of supplemental fluid as an experimental OFS (n = 9), lactated Ringer's either enterally (n = 10) or intravenously (n = 8). Outcome measures after 96 hours were weight gain, blood chemistry, organ weights, and small intestine mass and brush-border membrane carbohydrases.

RESULTS

The OFS did not improve weight gain compared with providing lactated Ringer's orally or intravenously, or increase serum urea nitrogen values, but resulted in higher serum total and low-density lipoprotein cholesterol, as well as improved glucoregulation and heavier intestines, livers, kidneys, and brains and lighter lungs.

CONCLUSIONS

Providing supplemental fluid and electrolytes during PN either intravenously or orally increases weight gain after preterm birth. An oral fluid supplement based on amniotic fluid may accelerate development and maturation of organs critical for extrauterine life after preterm birth and may enhance neurodevelopment.

Current status of parenteral nutrition and enteral nutrition application: an assessment of nutritional prescriptions from 59 hospitals in the People's Republic of China

Purpose

The aim of the study reported here was to assess the use of parenteral nutrition (PN) and enteral nutrition (EN), and the prevalence of PN and EN formulas, in the People’s Republic of China.

Methods

Fifty-nine hospitals in the People’s Republic of China participated in a nutrition survey. The resulting information on nutritional support was analyzed.

Results

We received 379,584 nutritional-support prescriptions over 40 days in 2013. PN provided approximately 63.2% and EN provided approximately 36.8% of nitrogen intake. PN provided 63.5% and EN provided 36.5% of lipid intake. There were obvious differences in nitrogen and lipid intake between PN and EN in different regions, departments, and diseases. The percentage of nourishment provided by PN in different regions was highest in Chengdu, followed by the Beijing, Guangzhou, and Hangzhou areas. The percentage of nourishment provided by PN in different departments was highest in general surgery, followed by gastroenterology and the intensive care unit. The percentage of nourishment provided by PN in different diseases/conditions was highest in acute pancreatitis, followed by cancer, and burns. The main source of nitrogen in PN was balanced amino-acid preparations, and in EN, it was protein. The main source of lipids in PN was long- and medium-chain triglyceride lipid emulsion injection.

Conclusion

Despite recent improvements in the application of nutritional support in the People’s Republic of China, a much higher percentage of nitrogen and lipids is delivered through PN than through EN. Furthermore, there are marked regional, departmental, and disease-based differences in the selection of PN versus EN. The rationale for use of nutritional support needs to be improved.

Urinary metabolite profiles in premature infants show early postnatal metabolic adaptation and maturation

Objectives: Early nutrition influences metabolic programming and long-term health. We explored the urinary metabolite profiles of 48 premature infants (birth weight < 1500 g) randomized to an enhanced or a standard diet during neonatal hospitalization. Methods: Metabolomics using nuclear magnetic resonance spectroscopy (NMR) was conducted on urine samples obtained during the first week of life and thereafter fortnightly. Results: The intervention group received significantly higher amounts of energy, protein, lipids, vitamin A, arachidonic acid and docosahexaenoic acid as compared to the control group. Enhanced nutrition did not appear to affect the urine profiles to an extent exceeding individual variation. However, in all infants the glucogenic amino acids glycine, threonine, hydroxyproline and tyrosine increased substantially during the early postnatal period, along with metabolites of the tricarboxylic acid cycle (succinate, oxoglutarate, fumarate and citrate). The metabolite changes correlated with postmenstrual age. Moreover, we observed elevated threonine and glycine levels in first-week urine samples of the small for gestational age (SGA; birth weight < 10th percentile for gestational age) as compared to the appropriate for gestational age infants. Conclusion: This first nutri-metabolomics study in premature infants demonstrates that the physiological adaptation during the fetal-postnatal transition as well as maturation influences metabolism during the breastfeeding period. Elevated glycine and threonine levels were found in the first week urine samples of the SGA infants and emerged as potential biomarkers of an altered metabolic phenotype.

Standardised neonatal parenteral nutrition formulations - an Australasian group consensus 2012

Standardised parenteral nutrition formulations are routinely used in the neonatal intensive care units in Australia and New Zealand. In 2010, a multidisciplinary group was formed to achieve a consensus on the formulations acceptable to majority of the neonatal intensive care units. Literature review was undertaken for each nutrient and recommendations were developed in a series of meetings held between November 2010 and April 2011. Three standard and 2 optional amino acid/dextrose formulations and one lipid emulsion were agreed by majority participants in the consensus. This has a potential to standardise neonatal parenteral nutrition guidelines, reduce costs and prescription errors.

Intrauterine-like growth rates can be achieved with premixed parenteral nutrition solution in preterm infants

Growth failure in neonatal intensive care units is a major challenge for pediatricians and neonatologists. The use of early "aggressive" parenteral nutrition (PN), with >2.5 g/(kg ·d) of amino acids and at least 40 kcal/(kg ·d) of energy from the first day of life, has been shown to provide nutritional intakes in the range recommended by international guidelines, reducing nutritional deficit and the incidence of postnatal growth restriction in preterm infants. However, nutritional practices and adherence to recommendations may vary in different hospitals. Two ready-to-use (RTU), premixed parenteral solutions (PSs) designed for preterm infants have been prospectively evaluated: a binary RTU premixed PS from our hospital pharmacy and a commercially premixed 3-chamber bag (Baxter Healthcare). These premixed PSs provide nitrogen and energy intakes in the range of the most recent recommendations, reducing or eliminating the early cumulative nutritional deficit in very-low-birth-weight infants, and avoiding the development of postnatal growth restriction. A further rationale for RTU premixed PSs is that preterm infants require balanced PN that contains not only amino acids and energy but also minerals and electrolytes from the first day of life in order to reduce the incidence of metabolic disorders frequently reported in extremely-low-birth-weight infants during the early weeks of life.

Safety and efficacy of early parenteral lipid and high-dose amino acid administration to very low birth weight infants

OBJECTIVE

To assess the efficacy and safety of early parenteral lipid and high-dose amino acid (AA) administration from birth onwards in very low birth weight (VLBW, birth weight <1500 g) infants.

STUDY DESIGN

VLBW infants (n = 144; birth weight 862 ± 218 g; gestational age 27.4 ± 2.2 weeks) were randomized to receive 2.4 g of AA kg(-1) · d(-1) (control group), or 2.4 g AA kg(-1) · d(-1) plus 2-3 g lipids kg(-1) · d(-1) (AA + lipid group), or 3.6 g AA kg(-1) · d(-1) plus 2-3 g lipids kg(-1) · d(-1) (high AA + lipid group) from birth onwards. The primary outcome was nitrogen balance. The secondary outcomes were biochemical variables, urea rate of appearance, growth rates, and clinical outcome.

RESULTS

The nitrogen balance on day 2 was significantly greater in both intervention groups compared with the control group. Greater amounts of AA administration did not further improve nitrogen balance compared with standard AA dose plus lipids and was associated with high plasma urea concentrations and high rates of urea appearance. No differences in other biochemical variables, growth, or clinical outcomes were observed.

CONCLUSIONS

In VLBW infants, the administration of parenteral AA combined with lipids from birth onwards improved conditions for anabolism and growth, as shown by improved nitrogen balance. Greater levels of AA administration did not further improve the nitrogen balance but led to increased AA oxidation. Early lipid initiation and high-dose AA were well tolerated.

Initial amino acid intake influences phosphorus and calcium homeostasis in preterm infants--it is time to change the composition of the early parenteral nutrition

BACKGROUND

Early aggressive parenteral nutrition (PN), consisting of caloric and nitrogen intake soon after birth, is currently proposed for the premature baby. Some electrolyte disturbances, such as hypophosphatemia and hypercalcemia, considered unusual in early life, were recently described while using this PN approach. We hypothesize that, due to its impact on cell metabolism, the initial amino acid (AA) amount may specifically influence the metabolism of phosphorus, and consequently of calcium. We aim to evaluate the influence of AA intake on calcium-phosphorus metabolism, and to create a calculation tool to estimate phosphorus needs.

METHODS

Prospective observational study. Phosphate and calcium plasma concentrations and calcium balance were evaluated daily during the first week of life in very preterm infants, and their relationship with nutrition was studied. For this purpose, infants were divided into three groups: high, medium and low AA intake (HAA, MAA, LAA). A calculation formula to assess phosphorus needs was elaborated, with a theoretical model based on AA and calcium intake, and the cumulative deficit of phosphate intake was estimated.

RESULTS

154 infants were included. Hypophosphatemia (12.5%) and hypercalcemia (9.8%) were more frequent in the HAA than in the MAA (4.6% and 4.8%) and in the LAA group (0% and 1.9%); both p<0.001.

DISCUSSION

Calcium-phosphorus homeostasis was influenced by the early AA intake. We propose to consider phosphorus and calcium imbalances as being part of a syndrome, related to incomplete provision of nutrients after the abrupt discontinuation of the placental nutrition at birth (PI-ReFeeding syndrome). We provide a simple tool to calculate the optimal phosphate intake. The early introduction of AA in the PN soon after birth might be completed by an early intake of phosphorus, since AA and phosphorus are (along with potassium) the main determinants of cellular growth.

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.

Standardised parenteral nutrition

Parenteral nutrition (PN) has become an integral part of clinical management of very low birth weight premature neonates. Traditionally different components of PN are prescribed individually considering requirements of an individual neonate (IPN). More recently, standardised PN formulations (SPN) for preterm neonates have been assessed and may have advantages including better provision of nutrients, less prescription and administration errors, decreased risk of infection, and cost savings. The recent introduction of triple-chamber bag that provides total nutrient admixture for neonates may have additional advantage of decreased risk of contamination and ease of administration.

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.