title: Severe hyponatraemia in medical in-patients: aetiology, assessment and outcome.
abstract: BACKGROUND
  Hyponatraemia is the most commonly identified electrolyte abnormality. Published data on severe hyponatraemia in general medical in-patients is lacking.
  
  
  OBJECTIVE
  To determine the aetiology, adequacy of assessment, and outcome of severe hyponatraemia in general medical in-patients.
  
  
  METHODS
  Retrospective case-note review.
  
  
  METHODS
  All general medical in-patients (n = 108) with serum sodium < or =125 mmol/l were identified from the clinical chemistry database, over a six-month period. A full review of notes and computer records was undertaken at the index date and a pre-determined follow-up date.
  
  
  RESULTS
  Follow-up data were available in 105 patients. There was a wide range of aetiologies: diuretic therapy (loop and thiazide), congestive cardiac failure and liver disease were the most common, and 75.3% of patients had multiple causes. None of the 48% of patients whose history suggested a possible diagnosis of the syndrome of inappropriate anti-diuretic hormone (SIADH) met the generally accepted diagnostic criteria. Overall mortality was 20% during the index admission and 44.6% at follow-up, vs. 7.1% and 22%, respectively, for other patients admitted to the same directorate over the same time period (p < 0.001). Mortality was linked to aetiology, but not to reduced absolute serum sodium concentration at admission.
  
  
  CONCLUSIONS
  Severe hyponatraemia in general medical patients is associated with a complex, multifactoral aetiology and a very poor prognosis. Outlook is governed principally by aetiology, and not by serum sodium level. Assessment of patients with hyponatraemia requires a practical clinical algorithm for diagnosing SIADH.
authors.affiliation: Division of Therapeutics and Molecular Medicine, Queen's Medical Centre, Nottingham NG7 2UH. jennifer.marshall@nottingham.ac.uk
authors.forename: J A
authors.initials: JA
authors.lastname: Clayton
authors.forename: I R
authors.initials: IR
authors.lastname: Le Jeune
authors.forename: I P
authors.initials: IP
authors.lastname: Hall
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004812:Epidemiologic Methods; D005260:Female; D006760:Hospitalization; D006801:Humans; D007010:Hyponatremia / Q000175:diagnosis / Q000209:etiology*; D007177:Inappropriate ADH Syndrome / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011379:Prognosis