Hypernatraemia

Background

  • Usually due to dehydration rather than excess of sodium
  • Symptoms
    • Headache, confusion, n&v
    • lethargy, seizures, LOC
    • nystagmus, myoclonic jerks, postural hypotension
  • Risk factors
    • Age > 65
    • Dementia, mental or physical disability
    • Residential care
  • Causes
    • Low fluid intake
    • Diabetes insipidus
      • central (lack of pituitary ADH secretion) vs nephrogenic (renal resistance to ADH)
      • polyuria, polydipsia,
      • causes of nephrogenic – lithium
      • causes of central – head injury, pituitary disease
    • Hyperosmolar Hyperglycaemic State (HHS/HONK)
      • Severe prolonged hyperglycaemia causing osmotic diuresis
    • Others – Cushing’s, Conn’s

 

Data gathering

  • Hx – polyuria, polydipsia, thirst, medications
  • Examine – neuro, L/S BP, volume status

 

Clinical Management

  • Investigations
    • Bloods – FBC, U+E, glucose, osmolality, urine Na and osmolality
    • (urine osmolality – if dehydrated, urine will be concentrated i.e. osmolality > 750mmol/kg – if inappropriately dilute, consider diabetes insipidus)
  • Treatment
    • Treat cause – likely rehydration, daily review/U+E testing, avoid rapid reduction (to avoid acute cerebral oedema)
  • Safety-net / Follow-up
    • Admit if
      • Na > 155 mmol/L
      • Na 146-155 with neurological disturbance/inability to drink adequately
      • HHS i.e. hypernatraemia plus hyperglycaemia