Early postnatal calcium and phosphorus metabolism in preterm infants

Sulfate: a neglected (but potentially highly relevant) anion

Sulfate is an important anion as sulfonation is essential in modulation of several compounds, such as exogens, polysaccharide chains of proteoglycans, cholesterol or cholesterol derivatives and tyrosine residues of several proteins. Sulfonation requires the presence of both the sulfate donor 3'-phosphoadenosine-5'-phosphosulfate (PAPS) and a sulfotransferase. Genetic disorders affecting sulfonation, associated with skeletal abnormalities, impaired neurological development and endocrinopathies, demonstrate the importance of sulfate. Yet sulfate is not measured in clinical practice. This review addresses sulfate metabolism and consequences of sulfonation defects, how to measure sulfate and why we should measure sulfate more often.

Early vs late initiation of sodium glycerophosphate: Impact on hypophosphatemia in preterm infants <32 weeks

BACKGROUND & AIMS

Early electrolyte and mineral imbalances have emerged as a conspicuous problem in very preterm babies since the revision of nutrition guidelines and the eventual implementation of early aggressive parenteral nutrition (PN). We opted to carry out a study with the introduction of phosphorus as sodium glycerophosphate in PN from the first day onward to reveal the impact on serum phosphorus and calcium levels following the surge in the incidence of hypercalcemia and hypophosphatemia.

METHODS

In this single-center, prospective, observational cohort study, inborn babies <32 gestational weeks and <1500 g between August 2017 and July 2018 were enrolled consecutively. Infants born in the first 6-month of this period were initiated PN (Early phosphorus group) containing phosphorus (1 mmol P as sodium glycerophosphate/100 ml PN) immediately after birth, and in the latter six-months, mineral-free standard PN (Control group) was commenced up until 48 h of life. Parenteral nutritional prescriptions of both groups were similar in terms of macro and micronutrient intakes except for early phosphorus, calcium, and sodium. Serum mineral and electrolyte levels were measured on Days 1-3-7 and compared between the groups. The primary outcome was the presence of hypophosphatemia in the first week of life. The secondary outcome was hypercalcemia, preterm morbidity, and mortality.

RESULTS

A total of 261 infants were included in this study. There were 130 babies in Early phosphorus group and 131 in control group. Gestational ages (28.79 ± 2.1 vs 28.46 ± 2.2 weeks, respectively) and birth weights (1138 ± 273 vs 1090 ± 274 g, respectively) were similar in the groups. Mean serum phosphorus levels were higher on all days in Early phosphorus group (p < 0.001). Early phosphorus group had a lower incidence of hypophosphatemia on days 1-3 and 7 (p < 0.001). The percentage of hypercalcemic infants was significantly lower in Early phosphorus group on day 3 (p < 0.001). No difference was noted in terms of hypernatremia in the groups.

CONCLUSIONS

Adding phosphorus to PN in the first hours of life reduced the frequency of hypophosphatemia and hypercalcemia without any surge in hypernatremia or morbidity. Nutrition guidelines need to be revised accordingly in terms of early mineral/electrolyte supplementation.

Severe hypercalcemia associated with hypophosphatemia in very premature infants: a case report

BACKGROUND

Severe hypercalcemia is rare in newborns; even though often asymptomatic, it may have important sequelae. Hypophosphatemia can occur in infants experiencing intrauterine malnutrition, sepsis and early high-energy parenteral nutrition (PN) and can cause severe hypercalcemia through an unknown mechanism. Monitoring and supplementation of phosphate (PO4) and calcium (Ca) in the first week of life in preterm infants are still debated.

CASE PRESENTATION

We report on a female baby born at 29 weeks' gestation with intrauterine growth retardation (IUGR) experiencing sustained severe hypercalcemia (up to 24 mg/dl corrected Ca) due to hypophosphatemia while on phosphorus-free PN. Hypercalcemia did not improve after hyperhydration and furosemide but responded to infusion of PO4. Eventually, the infant experienced symptomatic hypocalcaemia (ionized Ca 3.4 mg/dl), likely exacerbated by contemporary infusion of albumin. Subsequently, a normalization of both parathyroid hormone (PTH) and alkaline phosphatase (ALP) was observed.

CONCLUSIONS

Although severe hypercalcemia is extremely rare in neonates, clinicians should be aware of the possible occurrence of this life-threatening condition in infants with or at risk to develop hypophosphatemia. Hypophosphatemic hypercalcemia can only be managed with infusion of PO4, with strict monitoring of Ca and PO4 concentrations.

Factors associated with early phosphate levels in preterm infants

To investigate perinatal factors and early morbidities associated with early serum phosphate (sPhos) levels in a cohort of preterm infants. Retrospective data were obtained from the medical records of a cohort of 454 infants born at < 32 weeks gestational age. Serum phosphate levels were directly associated with gestational age, body weight z-score, and Apgar scores and inversely associated with timing of enteral nutrition initiation and diet consisting of mostly breast milk. Maternal hypertension, lactate levels, early symptomatic hypotension, and total protein supplemented on days 1 to 3 were also inversely associated with sPhos. Morbidities that were found to be associated with sPhos did not persist after adjustment for confounding factors.Conclusions: We report a novel association between early sPhos and timing and content of enteral nutrition, as well as with the early neonatal hemodynamic condition of preterm infants. This information may help identify infants at risk for low sPhos and aid in the nutritional strategy utilized in these patients. This study did not identify early morbidities associated with sPhos. What is Known: • High initial amino acid intake is associated with increased risk of Refeeding like syndrome and hypophosphatemia, among preterm infants. What is New: • Early enteral nutrition, starting within the first 72 h of life, is associated with higher serum phosphate (sPhos) compared to nothing per os (NPO). • sPhos was not associated with early adverse neonatal outcomes.

Do Calcium and Potassium Levels Influence Ductal Patency in Preterm Infants?

OBJECTIVE

We investigated the relationship of serum potassium (K⁺) and ionized calcium (iCa²⁺) levels with the persistence of ductus arteriosus.

STUDY DESIGN

This retrospective cohort study included infants with birth weight < 1,500 g and gestational age < 32 weeks. Serum K⁺ and iCa²⁺ levels at the 1st and 48th hour of life were measured from samples. The difference between the two levels was calculated for both serum K⁺ (ΔK⁺) and iCa²⁺ (ΔCa²⁺). These values were compared between hemodynamically significant patent ductus arteriosus (hsPDA) and non-hsPDA.

RESULTS

Of 1,322 hospitalized preterm nonates, 1,196 were included in the study. Mean serum K⁺ levels at the 1st and 48th hour were higher and iCa²⁺ levels at the 1st and 48th hour were lower in hsPDA and non-hsPDA, respectively (p < 0.001). Ionized ΔCa²⁺ (-0.06 ± 0.13 vs. -0.02 ± 0.12 mmol/L) was higher in hsPDA (p < 0.001).

CONCLUSION

We demonstrated that serum K⁺ and iCa²⁺ level might play a role in ductal constriction.

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.

Protein intakes to optimize outcomes for preterm infants

Proteins are key structural components of all human cells and are also involved in key physiologic processes through their roles as enzymes, hormones and transport proteins. Protein requirements are substantially higher in preterm infants than those born at term, yet inadequate protein intakes are a common problem on many neonatal units. Very preterm infants (VPT, <32 weeks) commonly receive parenteral amino acid solutions which are typically commenced on admission, and increased over the next few days. Several recent studies have explored differing parenteral amino acid intakes in the first few days, and recommendations have recently been updated. Parenteral nutrition intakes are decreased as enteral feeds are tolerated, but human milk alone will not meet protein needs in most VPT and supplementation or fortification will be required. This review paper considers basic protein and amino acid physiology in the newborn period, and the evidence base for current recommendations.

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.

Early Hypophosphatemia in High-Risk Preterm Infants: Efficacy and Safety of Sodium Glycerophosphate From First Day on Parenteral Nutrition

BACKGROUND

Early hypophosphatemia is common in premature infants ≤1250 g. The aim of this study was to assess the frequency and severity of hypophosphatemia after sodium glycerophosphate supplementation from first day of life in parenteral nutrition and to address the safety of this practice.

METHODS

Prospective cohort study of infants ≤1250 g birth weight born in a tertiary-care level neonatal intensive care unit and supplied with sodium glycerophosphate from the first day of life. Primary outcome was the presence of hypophosphatemia (<4 mg/dL) on the first week. Data were compared with our 2014 prospective subcohort of infants ≤1250 g receiving phosphate after 48 hours of life and morbidity with that of our 2016 retrospective cohort of ≤1250 g.

RESULTS

Fifty-four neonates were included. The frequency of hypophosphatemia was 29.6%. Only 1 patient presented hypophosphatemia <2 mg/dL. Mild hypokalemia was found in 8 patients (50%). No cases of hypernatremia were observed. Patients with hypophosphatemia had significantly lower gestational age (27.4 vs 28.8 weeks, P = .032) and lower z-score birth weight (-1.68 vs -0.47; P = .001). When compared with the 2014 subcohort, we found a lower frequency of hypophosphatemia (29.6% vs 69.2%; P = .008) and a lower rate of samples with hypophosphatemia (20.4% vs 51.4%; P = .0002) and critical hypophosphatemia (0.68% vs 11.4%, P = .0005). No differences were found in morbidity or mortality.

CONCLUSIONS

Sodium glycerophosphate supplementation in parenteral nutrition from the first day of life significantly decreased the frequency of hypophosphatemia. No adverse events were reported.

Vitamin D in pediatric age: consensus of the Italian Pediatric Society and the Italian Society of Preventive and Social Pediatrics, jointly with the Italian Federation of Pediatricians

Vitamin D plays a pivotal role in the regulation of calcium-phosphorus metabolism, particularly during pediatric age when nutritional rickets and impaired bone mass acquisition may occur.Besides its historical skeletal functions, in the last years it has been demonstrated that vitamin D directly or indirectly regulates up to 1250 genes, playing so-called extraskeletal actions. Indeed, recent data suggest a possible role of vitamin D in the pathogenesis of several pathological conditions, including infectious, allergic and autoimmune diseases. Thus, vitamin D deficiency may affect not only musculoskeletal health but also a potentially wide range of acute and chronic conditions. At present, the prevalence of vitamin D deficiency is high in Italian children and adolescents, and national recommendations on vitamin D supplementation during pediatric age are lacking. An expert panel of the Italian Society of Preventive and Social Pediatrics reviewed available literature focusing on randomized controlled trials of vitamin D supplementation to provide a practical approach to vitamin D supplementation for infants, children and adolescents.

Effect of early nutritional intake on long-term growth and bone mineralization of former very low birth weight infants

BACKGROUND

Preterm infants are at risk for impaired bone mineralization and growth in length later in life due to inadequate nutritional intake in the early postnatal period.

OBJECTIVE

To investigate whether increased nutritional supplementation of calcium, phosphate and protein in Very Low Birth Weight (VLBW) infants during the first 14days after birth was associated with improvement in length and bone development until 9-10years of age.

DESIGN

Observational follow-up study of VLBW infants (birth weight<1500g or gestational age<32weeks) born in two consecutive years (eligible infants: 2004 n: 63 and 2005: n: 66). Cohort 2005 received higher intake of calcium, phosphate and protein with parenteral nutrition compared to Cohort 2004. Anthropometric data were collected during standard follow-up visits until five years, and additionally at 9-10years of age including measurements of bone mineral content, bone mineral density of the whole body and lumbar spine determined by dual-energy X-ray absorptiometry. Long-term growth trajectories of both cohorts were evaluated separately for participants born appropriate (AGA) and small for gestational age (SGA), stratified by gender. Multivariate linear regression was used to examine the effect of nutritional intake and clinical covariates on length and bone mineralization.

RESULTS

Both cohorts achieved a catch-up in length to SDS within the normal range by 6months (length SDS: estimated mean (95% confidence interval (CI): 6months: Cohort 2004: -0.7 (-1.1, -0.3) Cohort 2005: -0.5 (-0.8, -0.2)). Bone mineral content and density were within the normal range and not different between the cohorts. SGA children achieved a catch-up in length at 5years with bone mineralization comparable to AGA children. Only for girls birth weight was significantly associated with length SDS (per gram: β 0.001; 95% CI (0.000, 0.003); p=0.03) There was no evidence of an association between early nutritional intake and bone mineralization.

CONCLUSION

Children born as appropriate or small for gestational age preterm infants are able to catch up in length after the postnatal period, and achieve a normal length and bone mineralization at age nine-ten years. An improvement of calcium and phosphate intake during the first 14days after birth was not associated with improvement in length and bone development.

Serum Magnesium Levels in Preterm Infants Are Higher Than Adult Levels: A Systematic Literature Review and Meta-Analysis

Magnesium (Mg) is an essential mineral in the body, impacting the synthesis of biomacromolecules, bone matrix development, energy production, as well as heart, nerve, and muscle function. Although the importance of Mg is evident, reference values for serum Mg (sMg) in pediatric patients (more specifically, in neonates) are not well established. This systematic literature review and meta-analysis (using 47 eligible studies) aims to quantify normal and tolerable ranges of sMg concentrations during the neonatal period and to highlight the factors influencing Mg levels and the importance of regulating sMg levels during pregnancy and birth. In newborns without Mg supplementation during pregnancy, magnesium levels at birth (0.76 (95% CI: 0.52, 0.99) mmol/L) were similar to that of mothers during pregnancy (0.74 (95% CI: 0.43, 1.04) mmol/L), but increased during the first week of life (0.91 (95% CI: 0.55, 1.26) mmol/L) before returning to adult levels. This pattern was also seen in newborns with Mg supplementation during pregnancy, where the average was 1.29 (95% CI: 0.50, 2.08) mmol/L at birth and 1.44 (95% CI: 0.61, 2.27) mmol/L during the first week of life. Factors influencing these levels include prenatal Mg supplementation, gestational age, birth weight, renal maturity/function, and postnatal Mg intake. Elevated Mg levels (>2.5 mmol/L) have been associated with an increased risk of mortality, admission into intensive care, hypotonia, hypotension, and respiratory depression but sMg concentrations up to 2.0 mmol/L appear to be well tolerated in neonates, requiring adequate survey and minimal intervention.

Bone fracture in severe small-for-gestational-age, extremely low birth weight infants: A single-center analysis

INTRODUCTION

Bone fracture is a complication of extremely low birth weight infants (ELBWIs). This study aimed to analyze risk factors for bone fracture in a population of severe small-for-gestational-age (SGA) ELBWIs.

METHODS

We retrospectively studied data from ELBWIs with a birth weight <1000g and <-2 standard deviations (SDs) born at the National Center for Child Health and Development, Japan, from 2013 to 2015. Infants were divided into fracture and control groups. Serum calcium (Ca) and phosphorus (P) levels, perinatal factors, and previously reported risk factors were analyzed.

RESULTS

Of 25 cases of severe SGA ELBWIs, 5 cases of bone fracture were identified. Gestational age was 27.7±2.2, 29.1±2.6weeks (mean difference [MD] -1.4, 95% confidence interval [CI]: -4.0, -1.2, p=0.280), birth weight (BW) 448±105, 673±216g (MD -225, 95% CI: -433, -17, p=0.036) and BW-SD -4.1±0.1, -3.4±0.8 (MD -0.8, 95% CI: -1.5, -0.02, p=0.045) in the fracture and control groups, respectively. Minimums of serum Ca and P were 6.6±1.4, 8.1±0.8mg/dl (MD -1.5, 95% CI: -2.5, -0.6), p=0.003) and 2.3±0.6, 3.5±1.1mg/dl (MD -1.2, 95% CI: -2.2, -0.1, p=0.027) in the fracture and control groups, respectively.

CONCLUSION

Lower BW and BW-SD were possible risk factors for bone fracture. Hypocalcemia and hypophosphatemia may also contribute to the condition.

Changes in Biochemical Parameters of the Calcium-Phosphorus Homeostasis in Relation to Nutritional Intake in Very-Low-Birth-Weight Infants

Preterm infants are at significant risk to develop reduced bone mineralization based on inadequate supply of calcium and phosphorus (Ca-P). Biochemical parameters can be used to evaluate the nutritional intake. The direct effect of nutritional intake on changes in biochemical parameters has not been studied. Our objective was to evaluate the effect of Ca-P supplementation on biochemical markers as serum (s)/urinary (u) Ca and P; alkaline phosphatase (ALP); tubular reabsorption of P (TrP); and urinary ratios for Ca/creatinin (creat) and P/creatinin in Very-Low-Birth-Weight infants on Postnatal Days 1, 3, 5, 7, 10, and 14. This observational study compared two groups with High (n = 30) and Low (n = 40) intake of Ca-P. Birth weight: median (IRQ) 948 (772–1225) vs. 939 (776–1163) grams; and gestational age: 28.2 (26.5–29.6) vs. 27.8 (26.1–29.4) weeks. Daily median concentrations of biochemical parameter were not different between the groups but linear regression mixed model analyses showed that Ca intake increased the uCa and TrP (p = 0.04) and decreased ALP (p = 0.00). Phosphorus intake increased sP, uP and uP/creat ratio and ALP (p ≤ 0.02) and caused decrease in TrP (p = 0.00). Protein intake decreased sP (p = 0.000), while low gestational age and male gender increased renal excretion of P (p < 0.03). Standardized repeated measurements showed that biochemical parameters were affected by nutritional intake, gestational age and gender.

The Clinical and Biochemical Predictors of Bone Mass in Preterm Infants

BACKGROUND

Metabolic bone disease of prematurity still occurs in preterm infants, although a significant improvement in neonatal care has been observed in recent decades. Dual-energy X-ray absorptiometry (DXA) is the precise technique for assessing bone mineral content (BMC) in preterm infants, but is not widely available.

AIM

To investigate the clinical and biochemical parameters, including bone metabolism markers as potential predictors of BMC, in preterm infants up to 3 months corrected age (CA).

MATERIALS AND METHODS

Ca-P homeostasis, iPTH, 25-hydroxyvitamin D, osteocalcin, N-terminal propeptide, cross-linked C-telopeptide and amino-terminal pro C-type natriuretic peptide and the DXA scans were prospectively performed in 184 preterm infants (≤ 34 weeks' gestation) between term age and 3 mo CA. Lower bone mass was defined as BMC below or equal to respective median value for the whole study group, rounded to the nearest whole number.

RESULTS

The appropriate quality DXA scans were available for 160 infants (87%) examined at term and for 130 (71%) tested at 3 mo CA. Higher iPTH level was the only independent predictor of lower BMC at term, whereas lower BMC at 3 mo CA was associated both with lower urinary phosphate excretion and higher serum osteocalcin level. ROC analysis showed that iPTH >43.6 pg/mL provided 40% sensitivity and 88% specificity in identification of preterm infants with lower BMC at term. In turn, urinary phosphate excretion (TRP>97% or UP/Cr ≤0.74 mg/mg) and serum osteocalcin >172 ng/mL provided 40% sensitivity and 93% specificity in identification of infants with decreased BMC at 3 mo CA.

CONCLUSION

Serum iPTH might to be a simple predictor of reduced BMC in preterm infants at term age, but urinary phosphate excretion and serum osteocalcin might predict reduced BMC at 3 mo CA. These results represent a promising diagnostic tool based on simple, widely available biochemical measurements for bone mass assessment in preterm infants.

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.

Challenges in breast milk fortification for preterm infants

PURPOSE OF REVIEW

To outline new evidence published from 2013 to 2014 about breast milk fortification in preterm infants.

RECENT FINDINGS

Breast milk is the feeding choice for preterm infants because of its immunoprotective properties. However, breast milk's nutrient content is not sufficient for preterm infants, and interindividual variation is high. The variation challenges standard fortification, which assumes a standard breast milk composition. Two new fortification strategies (adjustable fortification and target fortification) optimize macronutrient intake and improve growth. Adjustable fortification uses blood urea nitrogen levels to adjust fortifier strength. Target fortification analyzes breast milk and fortifies macronutrients individually to achieve targeted intake. Its feasibility is shown in clinical routine. Current breast milk analyzers used for target fortification achieve acceptable precision for protein and fat but not for lactose and energy. Evidence of benefits for postdischarge breast milk fortification is lacking. Eliminating cow's milk products and feeding exclusively breast milk may decrease the occurrence of feeding intolerance and necrotizing enterocolitis. To facilitate exclusively breast milk diets, a collaboration of prenatal, nutrition and lactation stakeholders is key. Fortification increases osmolality; however, safety cutoffs to prevent necrotizing enterocolitis are unclear. There is also new evidence that composition and structure of various macronutrients and micronutrients affect growth and development, and might play a role in future fortification concepts.

SUMMARY

Recent research focuses on the variability of breast milk composition, its impact on postnatal growth patterns and the usefulness of target fortification. As well, diets exclusively composed of human milk are a promising approach to improve feeding tolerance. For safe fortification, osmolality cutoff levels are needed.