title: Hypervolemic hypernatremia is the most common type of hypernatremia in the intensive care unit.
abstract: BACKGROUND
  A high incidence of hypervolemic hypernatremia has been described in patients recovering from acute kidney injury (AKI) in intensive care units. However, this has been limited to only a few cases.
  
  
  METHODS
  One hundred fifty adult patients recovering from AKI in the intensive care unit of a single institution during a 6-year period, who developed hypernatremia during the course of their illness, were investigated. Serum and urine electrolytes, osmolality, urea nitrogen and creatinine were measured. The weights of these patients at the time of hypernatremia development and at presentation to the hospital were also measured.
  
  
  RESULTS
  Even though the hypernatremia was mild in most patients (146-160 mEq/L), the average rise in serum sodium concentration was 14.5 ± 7.1 mEq/L. Of the 34 patients who had all urinary studies available, the average urine osmolality was 436 ± 128 mmol/kg of which 172 ± 54 mmol/L was contributed by sodium, potassium and their accompanying anion. Another 204 ± 96 mmol/L was accounted for by urea and creatinine (mainly urea). Almost all the patients had hypervolemia as evidenced by the presence of edema and an average weight gain of more than 9 ± 11 kg between the time of presentation and the onset of hypernatremia despite likely having lost muscle mass from being in the intensive care unit for several days. The weight data were available in 54 patients, and only eight of these patients had lost weight at the time of the development of hypernatremia.
  
  
  CONCLUSIONS
  Hypervolemic hypernatremia is by far the most common cause of hypernatremia in patients in the intensive care unit. Even though the patients are in negative fluid balance at the time of the development of the hypernatremia, earlier saline administration has caused massive volume overload despite the ongoing losses. Post-AKI diuresis in the face of inability to maximally concentrate the urine because of renal failure often leads to mainly mild elevations in serum sodium concentration. The urine solute is mainly urea because of the often high serum urea concentrations with little electrolytes being present in the urine.
authors.affiliation: Division of Nephrology, San Francisco General Hospital and the University of California-San Francisco, 1001 Potrero Ave, Building 100, Rm 342, San Francisco, CA, 94110-1341, USA.
authors.forename: Sanaz
authors.initials: S
authors.lastname: Sarahian
authors.affiliation: Division of Nephrology, San Francisco General Hospital and the University of California-San Francisco, 1001 Potrero Ave, Building 100, Rm 342, San Francisco, CA, 94110-1341, USA.
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Pouria
authors.affiliation: Department of Medicine, Loyola University Chicago, Maywood, IL, USA.
authors.forename: Todd S
authors.initials: TS
authors.lastname: Ing
authors.affiliation: Division of Nephrology, San Francisco General Hospital and the University of California-San Francisco, 1001 Potrero Ave, Building 100, Rm 342, San Francisco, CA, 94110-1341, USA. ramin.sam@ucsf.edu.
authors.forename: Ramin
authors.initials: R
authors.lastname: Sam
mesh_terms: D058186:Acute Kidney Injury / Q000150:complications / Q000628:therapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001810:Blood Volume; D003404:Creatinine / Q000097:blood / Q000652:urine; D004573:Electrolytes / Q000652:urine; D005260:Female; D006801:Humans; D006955:Hypernatremia / Q000209:etiology / Q000503:physiopathology*; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011188:Potassium / Q000652:urine; D012189:Retrospective Studies; D012964:Sodium / Q000097:blood*; D014508:Urea / Q000652:urine; D015430:Weight Gain; D015431:Weight Loss
chemical_list: D004573:Electrolytes; D014508:Urea; D012964:Sodium; D003404:Creatinine; D011188:Potassium
keywords: Electrolyte-free water clearance; Hypernatremia; Hypervolemia