title: Risk factors for symptomatic hyponatraemia: the role of pre-existing asymptomatic hyponatraemia.
abstract: BACKGROUND
  Hyponatraemia is associated with substantial morbidity and mortality. Identification of the risk factors associated with the development of symptomatic hyponatraemia is important in determining preventive strategies.
  
  
  METHODS
  A retrospective analysis of the risks factors associated with the development of severe, symptomatic hyponatraemia requiring hospital admission over the past 3 years at our institution was carried out.
  
  
  RESULTS
  Forty-seven patients (26 women, 21 men) with a hospital admission serum sodium <134 mmol/L were identified. Of these patients, 31 (65.9%) had associated changes in the mental status that improved with the treatment of the hyponatraemia suggesting causality. The average admission sodium level of this cohort was 118.8 mmol/L. Symptomatic hyponatraemia was associated with volume depletion (32.6%), congestive heart failure (26%), syndrome of inappropriate antidiuretic hormone (26%), thiazide diuretic use (26%) and selective serotonin re-uptake inhibitor use (26%). In 21.7% of cases, the cause was multifactorial (congestive heart failure, syndrome of inappropriate antidiuretic hormone or medication use with volume depletion). In 11% of cases, patients were taking both thiazide diuretics and serotonin re-uptake inhibitors. Most importantly, 70.9% of all patients admitted with symptomatic hyponatraemia had pre-existing hyponatraemia that was untreated and believed to be asymptomatic (P < 0.05). This was the most common risk factor identified. We next investigated the prevalence of presumed asymptomatic hyponatraemia in the outpatient setting. Out of 27 496 patients analysed, 14% had serum sodium levels less than or equal to 134 mEq/L and 4% had values less than 130 mEq/L.
  
  
  CONCLUSIONS
  Pre-existing asymptomatic hyponatraemia is a common finding and is associated with a high risk for the development of worsening hyponatraemia with altered mental status.
authors.affiliation: Department of Internal Medicine, Division of Nephrology, University of Virginia Health System, Charlottesville, Virginia, USA.
authors.forename: M
authors.initials: M
authors.lastname: Bissram
authors.forename: F D
authors.initials: FD
authors.lastname: Scott
authors.forename: L
authors.initials: L
authors.lastname: Liu
authors.forename: M H
authors.initials: MH
authors.lastname: Rosner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001834:Body Water / Q000378:metabolism; D004363:Drug Utilization; D005260:Female; D006333:Heart Failure / Q000150:complications; D006801:Humans; D007010:Hyponatremia / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology / Q000523:psychology; D007177:Inappropriate ADH Syndrome / Q000150:complications; D008297:Male; D008499:Medical Records; D008603:Mental Health; D008875:Middle Aged; D010045:Outpatients / Q000706:statistics & numerical data; D010351:Patient Discharge; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D049993:Sodium Chloride Symporter Inhibitors / Q000009:adverse effects / Q000627:therapeutic use; D014883:Water-Electrolyte Imbalance
chemical_list: D017367:Selective Serotonin Reuptake Inhibitors; D049993:Sodium Chloride Symporter Inhibitors