Sodium imbalances

• Hyponatraemia occurs when there is a relative excess of water in the body compared to sodium. It is the most common electrolyte abnormality encountered in clinical practice.
• Hyponatraemia is a serum sodium concentration <135mmol/L, with severe hyponatraemia being a serum sodium concentration <120mmol/L
• Hypovolaemic causes of hyponatraemia:

  • Renal sodium loss - renal failure, Addison's, diuretics and osmotic diuresis (severe hyperglycaemia)
  • Non - renal sodium loss - diarrhoea and vomiting, excess sweating and burns
• Hypervolaemic causes of hyponatraemia:

  • Dilutional effect on serum sodium
  • Heart failure
  • Liver cirrhosis
  • End stage renal failure
  • Nephrotic syndrome
• SIADH is the most common cause of euvolaemic hyponatraemia - raised urine osmolality in the presence of low serum osmolality . The kidney is inappropriately producing concentrated urine
• Mild to moderate symptoms of hyponatraemia:

  • Anorexia
  • Headache
  • Nausea and vomiting
  • Lethargy
  • Confusion
• Severe symptoms of hyponatraemia:

  • Seizures
  • Coma
• The key to clinical examination in hyponatraemia is an accurate assessment of fluid/hydration status, as this will help to classify the likely cause of hyponatraemia and guide initial management.
• Acute hyponatraemia with severe neurological symptoms (seizures, severe drowsiness) is a medical emergency

  IV hypertonic saline bolus
• Hyponatraemia can lead to cerebral oedema - can lead to brain herniation and death
• Hypernatraemia is defined as serum sodium >146 mmol/L

  it is most commonly caused by dehydration - vomiting/diarrhoea
• Rarer causes of hypernatraemia:

  • Diabetes insipidus - insufficient ADH leading to excess water excretion
  • Loop-diuretics
  • Extreme levels of salt ingestion
• Thiazide like diuretics are the most common diuretic that causes hyponatraemia

  Loop diuretics are a common cause of hypernatremia
• Clinical features of hypernatraemia:

  • Mild cases usually cause excessive thirst
  • Weakness
  • Lethargy
  • Irritability
  • Confusion
  • Seizures and coma
• Hypernatraemia management:

  • Replace any fluid deficit and correct serum sodium
  • do not correct sodium too rapidly due to risk of cerebral oedema