Hyponatraemia

Data gathering

  • Severity
    • Mild 125-133
    • Moderate 115-125
    • Severe Na <115 or symptomatic
  • Acute vs chronic
    • acute – rare, most often due to marked water intake – high morbidity
    • chronic – common, avoid rapid correction (to avoid osomotic demyelination syndrome)
  • Pseudohyponatraemia – high glucose, high triglycerides, high paraproteinaemia
  • Presentation
    • cognitive decline, lethargy, nausea, anorexia, seizures, coma
  • Causes
    • Hypovolaemia
      • Diuretics, D&V, AKI, Renal disease, Addison’s disease
    • Euvolaemia
      • Medications – thiazides, ACE-I, antidepressants, antiepileptics, PPIs
      • SIADH, Hypothyroidism, Hypopituitarism, Low salt intake, Chronic alcoholism, Polydipsia
    • Hypervolaemia
      • CCF, chronic liver disease, nephrotic syndrome, protein losing enteropathy

 

Clinical management

  • Investigations – urine dip (renal disease/UTI), TFTs, 9am cortisol, paired urinary/serum sodium (same day)
  • Treatment
    • Fluid overload – treat underlying condition e.g. fluid restrict/diuresis
    • Dehydration – treat underlying condition and rehydrate
    • Medications – stop causative medications and repeat Na in 1 week
  • Consider other conditions – chest infections, GI disease, CCF, liver disease, myeloma, malignancy
  • Followup / Who to admit
    • Symptomatic
    • Na < 115
    • Hypovolaemic
    • Rapid progression