Hyponatraemia

• Sodium levels <120 mmol/l

  • between 115-120 can get headaches, lethargy

  • 110-115 severe risk of seizure, coma

    • post-menopausal women most at risk and may fit at higher levels

• Is mostly due to defective renal water excretion

Types

• Isotonic - pseudohyponatraemia due to abnormally high lipids, protein in sample

• Hypertonic -hyperglycaemia or excess mannitol treatment

• Hypotonic -Then decide on water volume in patient

Hypervolaemic

• usually manifested with clinical oedema

• if low urine sodium (<10mmol/l) then plasma volume lost to 3rd space and kidney attempting to compensate for reduced effective volume

  • congestive cardiac failure

  • cirrhosis with ascites

  • nephrotic syndrome

• if high urine sodium (>20mmol/l) then there is a kidney problem

  • acute tubular necrosis

  • end stage renal failure

Hypovolaemic

• patient shocked, appropriate water retention by kidney

• low urine sodium (<10 mmol/l) due to extra-renal loss of sodium

  • GI tract fistula

  • pancreatitis

  • exercise

  • sweating

  • burns

• high urine sodium - kidney inappropriately excreting sodium

  • diuretics

  • osmotic diuresis

  • diabetic ketoacidosis

  • renal tubular acidosis

  • salt losing nephropathy

  • adrenal insufficiency

  • hyporeninaemia

  • hypoaldosteronism

Normovolaemic

• usually no oedema

• high urine sodium

  • SIADH
  • hypothyroidism
  • hypopituitarism
• renal failure drugs
  • chlorpropamide
  • cyclophosphamide

Management

• History

  • medication

• Examination

  • volume status

  • neurological

• Investigations

  • Plasma

    •  electrolytes - sodium , potassium

    • urea, glucose

    • creatinine

    • osmolality - direct and/or calculated

  • urine

    • electrolyte

    • osmolality

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