title: Sodium supply influences plasma sodium concentration and the risks of hyper- and hyponatremia in extremely preterm infants.
abstract: Hyper- and hyponatremia occur frequently in extremely preterm infants. Our purpose was to investigate plasma sodium (P-Na) concentrations, the incidence of hyper- and hyponatremia, and the impact of possible predisposing factors in extremely preterm infants.
  
  
  
  In this observational study, we analyzed data from the EXtremely PREterm (< 27 wk.) infants in Sweden Study (EXPRESS, n = 707). Detailed nutritional, laboratory, and weight data were collected retrospectively from patient records.
  
  
  
  Mean ± SD P-Na increased from 135.5 ± 3.0 at birth to 144.3 ± 6.1 mmol/l at a postnatal age of 3 d and decreased thereafter. Fifty percent of infants had hypernatremia (P-Na > 145 mmol/l) during the first week of life while 79% displayed hyponatremia (P-Na < 135 mmol/l) during week 2. Initially, the main sodium sources were blood products and saline injections/infusions, gradually shifting to parenteral and enteral nutrition towards the end of the first week. The major determinant of P-Na and the risks of hyper- and hyponatremia was sodium supply. Fluid volume provision was associated with postnatal weight change but not with P-Na.
  
  
  
  The supply of sodium, rather than fluid volume, is the major factor determining P-Na concentrations and the risks of hyper- and hyponatremia.
authors.affiliation: Department of Clinical Sciences, Pediatrics, Umeå University, Umeå, Sweden.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Späth
authors.affiliation: Department of Food and Nutrition, Umeå University, Umeå, Sweden.
authors.forename: Elisabeth Stoltz
authors.initials: ES
authors.lastname: Sjöström
authors.affiliation: Department of Women´s and Children´s Health, Uppsala University, Uppsala, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Ahlsson
authors.affiliation: Department of Women´s and Children´s Health, Uppsala University, Uppsala, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Ågren
authors.affiliation: Department of Clinical Sciences, Pediatrics, Umeå University, Umeå, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Domellöf
mesh_terms: D001835:Body Weight; D004750:Enteral Nutrition; D005260:Female; D006801:Humans; D006955:Hypernatremia / Q000097:blood*; D007010:Hyponatremia / Q000097:blood*; D062071:Infant, Extremely Premature; D008297:Male; D010288:Parenteral Nutrition; D011446:Prospective Studies; D012307:Risk Factors; D012964:Sodium / Q000097:blood*; D012965:Sodium Chloride; D013548:Sweden; D013997:Time Factors
chemical_list: D012965:Sodium Chloride; D012964:Sodium