A physiological approach to fluid and electrolyte management of the preterm infant: Review

Sodium Patterns and Their Variables in a Cohort of ELBW Infants in the First 10 Days of Life

Background: Sodium regulation is critical in extremely low-birth-weight (ELBW, <1000 g) infants. In a recent systematic review, a sodium pattern over postnatal age and its variables (care factors, fluid regimens, and maturational factors) has been summarized. However, this systematic review also illustrated the shortages and limitations of reported cohorts, and the need to report on additional datasets. This study therefore aims to describe the postnatal sodium patterns and their variables in a cohort of ELBW neonates in the first 10 days of postnatal life. Methods: Data on 1704 serum sodium observations in the first 10 days of life from 211 ELBW infants hospitalized in a single neonatal intensive care unit were available to explore associations between serum sodium and perinatal variables. Multivariate linear models with sodium as a response variable and postnatal day as a factor were hereby applied. Baseline and treatment characteristics were included as variables, applying an unstructured covariance matrix to account for the longitudinal data. Results: Gestational age, birth weight, and length showed variable correlations with serum sodium concentrations over postnatal age. Interestingly, the analysis of sodium patterns in this ELBW cohort also revealed significant associations between prenatal betamethasone use, delivery mode, ibuprofen, or the use of inotropes and the postnatal serum sodium concentrations patterns. Multivariate analyses confirmed that gestational age and birth weight independently impacted sodium concentration patterns, and that ibuprofen use remained a significant variable after adjusting for these variables. Conclusions: Gestational age and birth weight complexities emphasize the need for nuanced understanding and standardized methodologies. Sodium patterns in the current ELBW cohort provide support for previously published sodium reference patterns in this population. New variables associated with sodium levels include ibuprofen administration and the use of inotropic agents.

Hypo- and Hypernatremia in Extremely Low Birth Weight Infants in the First 10 Days of Life: A Review

BACKGROUND/OBJECTIVES

Sodium regulation is critical in extremely low birth weight (ELBW, <1000 g) infants. This study aimed to provide a comprehensive overview of sodium dynamics and related variables in ELBW infants in their first 10 days of life through a structured literature review.

METHODS

Applying PRISMA guidelines, six databases were searched (1 August 2023) on sodium measurements in ELBW cohorts, with quality assessment (RoB2, ROBINS-1, Newcastle Ottawa scale) of retained papers, and subsequent data extraction in line with these PRISMA guidelines to describe findings.

RESULTS

Only eight heterogeneous studies could be retained, including observational cohort studies (n = 5), case-control studies (n = 2, Tegaderm application yes/no, gestational age < 24 or 24-28 weeks), and only one randomized trial (sodium restriction versus no sodium restriction). Definitions of hyper- or hyponatremia were also heterogeneous, with incidence ranges for hyper- (8-92.2%) and hyponatremia (0-52.9%). Peak sodium values were observed on days 2-4 in the individual studies. When pooled and compared to the cohort mean sodium values, the highest increases in mean serum sodium values were observed on day 3 (+4, range, -0.6 to +8.6 mEq). Variables of sodium values were related to care factors [incubator settings (open/closed, double-/not double-walled, humidity), fluid regimens (water volume, sodium supplementation), occlusive skin care], as well as related maturational factors (postnatal age, gestational age, small versus appropriate for gestational age, SGA/AGA).

CONCLUSIONS

Based on a structured literature review, patterns of sodium changes over postnatal age in ELBW cases were documented. Besides incubator settings, fluid regimens, or occlusive skin care, these patterns also depend on maturational factors of the ELBW infant (gestational age, postnatal age, SGA/AGA). These complexities emphasize the need for nuanced interpretation, the relevance of standardizing clinical practices and research definitions, and the need to report on additional datasets.

Fluid Management in ELGANs: Striking the Perfect Balance!

Managing fluid and electrolytes in extremely low gestational age neonates (ELGANs) is often challenging because of their distinctive fluid physiology. Most of the fluid loss in the first week of life is trans-epidermal due to the immature barrier function of the skin. ELGANs also have a developmental tendency for exaggerated diuresis and natriuresis. Allowing an initial weight loss of 6-12% promotes physiological extracellular contraction. Also, restricted fluid intake in the first week of life may decrease the incidence of bronchopulmonary dysplasia, patent ductus arteriosus, and necrotizing enterocolitis. A protocol-based approach for fluid management in ELGANs, developed based on physiology and available evidence, is the best strategy. Based on the estimated dermal and renal losses and desired weight change, the authors recommend initiating total fluids on the first day of life at 100 mL/kg/d in neonates at 26-27 wk gestation and 110 mL/kg/d at 24-25 wk gestation. The subsequent fluid rate is determined based on rigorous monitoring of weight, urine output, and serum sodium, with a typical daily increment in fluids of 10-20 mL/kg and a maximum fluid rate of 150-160 mL/kg/d in 26-27 wk and 160-180 mL/kg/d in 24-25 wk gestation neonates by day 7 of life. Fluid strategy should ideally be revised every 12 h in the first few days of life. A humidified incubator is the ideal care environment to minimize trans-epidermal losses. Since most of these recommendations are not based on concrete evidence from trials, it is advisable to periodically audit the outcomes and devise a unit-specific fluid strategy.

Thermal equilibrium as a predictor of growth efficiency in preterm infants

Introduction

Providing adequate nutrition to preterm infants to achieve postnatal growth similar to intrauterine growth remains challenging due to the unpredictability of individual determinants.

Material and methods

We used a calculation program for infant incubators to compare the estimated heat balance with the caloric intake and growth rate in Very Low Birth Weight Infants (VLBWI).

Results and discussion

A group of 32 VLBWI was studied over a period of 14-28 days. An interrelationship between thermal equilibrium and growth rate was observed, with standardized incubator settings being unable to avoid periods of negative thermal balance and concomitantly poor growth rate.

Conclusion

Determining personalized incubator settings by means of a calculation program could help improve nutrition and growth in preterm infants.

Actual electrolyte intake during the first week of life and morbidity in very-low-birthweight infants

AIM

To describe sodium and potassium intake, their sources and plasma concentrations, and the association between intake and morbidity in very-low-birthweight (VLBW, <1500 g) infants during the first week of life.

METHODS

This retrospective cohort study comprised 951 VLBW infants born at <32 weeks. Infants were divided into three groups according to gestational age: 23-26 (n = 275), 27-29 (n = 433) and 30-31 (n = 243) weeks. Data on fluid management and laboratory findings were acquired from an electronic patient information system.

RESULTS

The median sodium intake was highest in the 23-26 week group, peaking at 6.4 mmol/kg/day. A significant proportion of sodium derived from intravascular flushes; it reached 27% on day 1 in the 23-26 week group. High cumulative sodium intake in the first postnatal week was associated with weight gain from birth to day 8 in the 23-26 week group. High intake of sodium associated with an increased risk of surgically ligated patent ductus arteriosus (PDA), bronchopulmonary dysplasia and intraventricular haemorrhage, whereas low intake of potassium associated with an increased risk of PDA.

CONCLUSION

Sodium intake in the most premature infants exceeded recommendations during the first postnatal week. Saline flushes accounted for a significant proportion of the sodium load.

Precision Nutrition: The Hype Is Exceeding the Science and Evidentiary Standards Needed to Inform Public Health Recommendations for Prevention of Chronic Disease

As dietary guidance for populations shifts from preventing deficiency disorders to chronic disease risk reduction, the biology supporting such guidance becomes more complex due to the multifactorial risk profile of disease and inherent population heterogeneity in the diet-disease relationship. Diet is a primary driver of chronic disease risk, and population-based guidance should account for individual responses. Cascading effects on evidentiary standards for population-based guidance are not straightforward. Precision remains a consideration for dietary guidance to prevent deficiency through the identification of population subgroups with unique nutritional needs. Reducing chronic disease through diet requires greater precision in (a) establishing essential nutrient needs throughout the life cycle in both health and disease; (b) considering effects of nutrients and other food substances on metabolic, immunological, inflammatory, and other physiological responses supporting healthy aging; and (c) considering healthy eating behaviors. Herein we provide a template for guiding population-based eating recommendations for reducing chronic diseases in heterogenous populations.

Positive fluid balance and diuretic therapy are associated with mechanical ventilation and mortality in preterm neonates in the first fourteen postnatal days

BACKGROUND

Fluid overload leads to poor neonatal outcomes. Diuretics may lower the rates of mechanical ventilation (MV) and mortality in neonates with fluid overload.

METHODS

This is a retrospective study of preterm neonates ≤ 36 weeks of gestational age (GA) in the first 14 postnatal days in a level IV NICU in 2014-2020. We evaluated the epidemiology of fluid balance in the first 14 postnatal days and its association with MV and mortality and studied the association of diuretics with fluid balance, MV, and mortality.

RESULTS

In 1383 included neonates, the overall median lowest and peak fluid balances were - 7.8% (IQR: - 11.7, - 4.6) and 8% (3, 16) on days 3 (2, 5) and 13 (5, 14), respectively. Fluid balance distribution varied significantly by GA. Peak fluid balance of ≥ 10% was associated with increased odds of MV on days 7 and 14 with highest odds ratios (OR) of MV in neonates with fluid balance ≥ 15%. Peak fluid balance of ≥ 15% was associated with the greatest odds of mortality. Diuretics were used more frequently in neonates with younger GA, smaller birthweight, positive fluid balance, and those on MV.

CONCLUSIONS

Positive fluid balance negatively impacts pulmonary status. The odds of MV and death increase significantly as peak fluid balance percentage increases in all GA groups. The impact of diuretics on MV and death in preterm neonates needs further evaluation. A higher resolution version of the Graphical abstract is available as Supplementary information.

Neonatal fluid overload-ignorance is no longer bliss

Excessive accumulation of fluid may result in interstitial edema and multiorgan dysfunction. Over the past few decades, the detrimental impact of fluid overload has been further defined in adult and pediatric populations. Growing evidence highlights the importance of monitoring, preventing, managing, and treating fluid overload appropriately. Translating this knowledge to neonates is difficult as they have different disease pathophysiologies, and because neonatal physiology changes rapidly postnatally in many of the organ systems (i.e., skin, kidneys, and cardiovascular, pulmonary, and gastrointestinal). Thus, evaluations of the optimal targets for fluid balance need to consider the disease state as well as the gestational and postmenstrual age of the infant. Integration of what is known about neonatal fluid overload with individual alterations in physiology is imperative in clinical management. This comprehensive review will address what is known about the epidemiology and pathophysiology of neonatal fluid overload and highlight the known knowledge gaps. Finally, we provide clinical recommendations for monitoring, prevention, and treatment of fluid overload.

Children's water intake and hydration: a public health issue

Optimal hydration is required for all physiologic functions and cognition. Children, especially younger ones, are particularly susceptible to dehydration, given their physiological specificities, in particular, their renal immaturity and relatively large skin surface in early life, but also their dependence on adults and their greater propensity to develop digestive diseases leading to fluid losses. Mild dehydration consequences are dominated by their impact on cognitive functions, whereas more severe dehydration may endanger the health outcome. Studies on this subject in children are scarce; in particular, the long-term consequence on renal function remains questionable. This review considers how children's water intake including fluid intake and water content of food, are worrying. The findings show that, worldwide, most children do not meet adequate water intake recommendations. The main problems likely to explain insufficient water intake are access to safe water, availability of drinking water at school, and healthy-hydration education, which are all points that need to be improved within health policy.

Association of early dysnatremia with mortality in the neonatal intensive care unit: results from the AWAKEN study

OBJECTIVE

To determine the association of dysnatremia in the first postnatal week and risk of acute kidney injury (AKI) and mortality.

STUDY DESIGN

A secondary analysis of 1979 neonates in the AWAKEN cohort evaluated the association of dysnatremia with (1) AKI in the first postnatal week and (2) mortality, utilizing time-varying Cox proportional hazard models.

RESULT

Dysnatremia developed in 50.2% of the cohort and was not associated with AKI. Mortality was associated with hyponatremia (HR 2.15, 95% CI 1.07-4.31), hypernatremia (HR 4.23, 95% CI 2.07-8.65), and combined hypo/hypernatremia (HR 6.39, 95% CI 2.01-14.01). In stratified models by AKI-status, hypernatremia and hypo/hypernatremia increased risk of mortality in neonates without AKI.

CONCLUSION

Dysnatremia within the first postnatal week was associated with increased risk of mortality. Hypernatremia and combined hypo/hypernatremia remained significantly associated with mortality in neonates without AKI. This may reflect fluid strategies kidney injury independent of creatinine and urine-output defined AKI, and/or systemic inflammation.

Fluid and Electrolyte Management in the Neonate: Potassium and Phosphorus

Maintenance of electrolyte balance in the neonate is challenging in the context of illness or prematurity. Imbalances in potassium and phosphorus can occur in neonates, ranging from benign and clinically insignificant to those that can be life-threatening. An individualized approach to fluid and electrolyte management is based on the neonate's gestational age, day of life, maintenance needs, deficits, and ongoing losses. This article reviews normal and abnormal potassium and phosphorus values along with management strategies. Using a case scenario, the reader can apply concepts outlined in this article to management of critically ill neonates with electrolyte disturbances.

Fluid and Electrolyte Management in the Neonate: Sodium and Chloride

Maintenance of electrolyte balance in the neonate is a challenge in the context of illness or prematurity. Neonatal providers' approach to fluid management changes and adapts based on the newborn's age, maintenance needs, deficits, and ongoing losses. Understanding the total body water content of the fetus and newborn is foundational to management of electrolyte disturbances. This article reviews common imbalances of sodium and chloride, identifies causes of imbalances, and discusses current evidence-based treatment options.

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.

Association of Weight Changes by Three Days after Birth and Mortality and/or Severe Neurological Injury in Preterm Infants < 29 Weeks Gestational Age: A Multicenter Cohort Study

OBJECTIVE

This study aimed to determine the range of weight loss, at 3 days postnatal age, associated with the lowest risk of mortality/short-term morbidity in preterm infants <29 weeks gestational age (GA).

STUDY DESIGN

This multicenter retrospective cohort study employed data from the Canadian Neonatal Network database. The primary outcome was a composite of mortality and/or severe neurological injury. Multivariable quadratic and linear regression models which adjusted for potential confounders were built.

RESULTS

A total of 9275 preterm infants (median GA 26, IQR 25, 28 weeks) were included. The optimal weight change range at day three, after adjustment for potential confounders for the primary outcomes, was -15 to -8.9%.

CONCLUSIONS

There is a 'U'-shaped relationship between weight change from birth to day three and mortality and/or severe neurological injury. Interventional studies, which target weight loss within the range found in this study and evaluate the impact on neonatal outcomes, are needed to corroborate our findings.

Fluid management considerations in extremely preterm infants born at 22-24 weeks of gestation

Emerging data regarding the encouraging outcomes of extremely preterm infants from centers taking active approaches to the care of these infants have prompted dialogue regarding optimal medical management. Among the multitude of decisions providers make in caring for extremely premature infants is the prescribing of parenteral fluids. Surprisingly, there are limited data to guide evidenced-based approaches to fluid and electrolyte management in this population. Immaturity of renal function and skin barriers contribute to the impaired capacity of the preterm infant to maintain salt and water homeostasis. This perspective paper highlights developmental physiological properties of the kidney and skin, which the provider needs to understand to provide parenteral fluid therapy. Additionally, we provide recommendations for initial fluid and electrolyte management of the preterm infant based on novel data as well as the published literature.

Fluid Balance in the Critically Ill Child Section: "How Bad Is Fluid in Neonates?"

Fluid overload (FO) in neonates is understudied, and its management requires nuanced care and an understanding of the complexity of neonatal fluid dynamics. Recent studies suggest neonates are susceptible to developing FO, and neonatal fluid balance is impacted by multiple factors including functional renal immaturity in the newborn period, physiologic postnatal diuresis and weight loss, and pathologies that require fluid administration. FO also has a deleterious impact on other organ systems, particularly the lung, and appears to impact survival. However, assessing fluid balance in the postnatal period can be challenging, particularly in extremely low birth weight infants (ELBWs), given the confounding role of maternal serum creatinine (Scr), physiologic weight changes, insensible losses that can be difficult to quantify, and difficulty in obtaining accurate intake and output measurements given mixed diaper output. Although significant FO may be an indication for kidney replacement therapy (KRT) in older children and adults, KRT may not be technically feasible in the smallest infants and much remains to be learned about optimal KRT utilization in neonates. This article, though not a meta-analysis or systematic review, presents a comprehensive review of the current evidence describing the effects of FO on outcomes in neonates and highlights areas where additional research is needed.

Dissociable effects of dietary sodium in early life upon somatic growth, fluid homeostasis, and spatial memory in mice of both sexes

Postnatal growth failure is a common morbidity for preterm infants and is associated with adverse neurodevelopmental outcomes. Although sodium (Na) deficiency early in life impairs somatic growth, its impact on neurocognitive functions has not been extensively studied. We hypothesized that Na deficiency during early life is sufficient to cause growth failure and program neurobehavioral impairments in later life. C57BL/6J mice were placed on low- (0.4), normal- (1.5), or high- (3 g/kg) Na chow at weaning (PD22) and continued on the diet for 3 wk (to PD40). Body composition and fluid distribution were determined serially by time-domain NMR and bioimpedance spectroscopy, and anxiety, learning, and memory were assessed using the elevated plus maze and Morris water maze paradigms in later adulthood (PD63-PD69). During the diet intervention, body mass gains were suppressed in the low- compared with normal- and high-Na groups despite similar caloric uptake rates across groups. Fat mass was reduced in males but not in females fed low-Na diet. Fat-free mass and hydration were significantly reduced in both males and females fed the low-Na diet, although rapidly corrected after return to normal diet. Measures of anxiety-like behavior and learning in adulthood were not affected by diet in either sex, yet memory performance was modified by a complex interaction between sex and early life Na intake. These data support the concepts that Na deficiency impairs growth and that the amount of Na intake which supports optimal somatic growth during early life may be insufficient to fully support neurocognitive development.