{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T11:46:04Z","timestamp":1789731964435,"version":"4.0.1"},"reference-count":24,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2025,2,13]],"date-time":"2025-02-13T00:00:00Z","timestamp":1739404800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Children"],"abstract":"<jats:p>Background\/Objectives: Sodium regulation is critical in extremely low birth weight (ELBW, &lt;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\u2013control studies (n = 2, Tegaderm application yes\/no, gestational age &lt; 24 or 24\u201328 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\u201392.2%) and hyponatremia (0\u201352.9%). Peak sodium values were observed on days 2\u20134 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, \u22120.6 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.<\/jats:p>","DOI":"10.3390\/children12020231","type":"journal-article","created":{"date-parts":[[2025,2,13]],"date-time":"2025-02-13T12:06:32Z","timestamp":1739448392000},"page":"231","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Hypo- and Hypernatremia in Extremely Low Birth Weight Infants in the First 10 Days of Life: A Review"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-6919-1736","authenticated-orcid":false,"given":"Myrna","family":"Pace","sequence":"first","affiliation":[{"name":"Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-7894-5804","authenticated-orcid":false,"given":"Stijn","family":"van Sas","sequence":"additional","affiliation":[{"name":"Faculty of Medicine, KU Leuven, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas","family":"Salaets","sequence":"additional","affiliation":[{"name":"Pediatric Cardiology, University Hospitals, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1371-442X","authenticated-orcid":false,"given":"Annouschka","family":"Laenen","sequence":"additional","affiliation":[{"name":"Leuven Biostatistics and Statistical Bioinformatics Center (L-BioStat), KU Leuven, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8846-1650","authenticated-orcid":false,"given":"Anke","family":"Raaijmakers","sequence":"additional","affiliation":[{"name":"Department of Paediatric Nephrology, Sydney Children\u2019s Hospital Randwick, Sydney Children\u2019s Hospital Network, Randwick, NSW 2031, Australia"},{"name":"School of Women\u2019s and Children\u2019s Health, Randwick Clinical Campus, University of New South Wales, Randwick, NSW 2033, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9921-5105","authenticated-orcid":false,"given":"Karel","family":"Allegaert","sequence":"additional","affiliation":[{"name":"Department of Development and Regeneration, KU Leuven, 3000 Leuven, Belgium"},{"name":"Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, 3000 Leuven, Belgium"},{"name":"Department of Hospital Pharmacy, Erasmus MC, 3000 Rotterdam, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,2,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1111\/j.1442-200X.2008.02577.x","article-title":"Fluid and electrolyte balance in extremely preterm infants < 24 weeks of gestation in the first week of life","volume":"50","author":"Wada","year":"2008","journal-title":"Pediatr. 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