Hyperkalaemia

Common causes of hyperkalaemia include:

• Renal due to decreased excretion or drugs ( Oliguric renal failure or K⁺sparing diuretics).
• Metabolic acidosis.
• Artefact – haemolysis of the sample.
• Adrenal Insufficiency – e.g. Addison’s.
• Drugs (ACE-inhibitors, B- blockers, NSAIDS, Iatrogenic K⁺ ).
• Rhabdomyolysis.

Hypokalaemia – overall causes are driven by inadequate potassium intake, a decrease in the total body potassium and a redistribution of electrolytes.

Prolonged decreased intake occurs with anorexia, malnutrition, dementia, extreme low calorie high protein diets for rapid weight loss, patients receiving TPN in hospital or inadequate K replacement via IV fluids.

Potassium loss: The most common causes are dependant on the source of the depletion.

• Renal causes include
  • Medications (thiazides or loop diuretics).
  • Metabolic acidosis or alkalosis.
  • Hypomagnesium.
  • Hyperaldosteronism (Conns, Cushings, renal artery stenosis).
  • Renal tubular acidosis.
  • Hypomagnesiumia.
  • Interstitial renal disease ( SLE, Sjogrens).

• GI causes
  • Severe diarrhoea.
  • vomiting.
  • Pyloric stenosis in infants.
  • Laxative abuse.
  • Structural loss: fistula.

• Dermal losses
  • excess sweating – prolonged exercise.
  • severe burns.
  • cystic fibrosis patients.

Redistribution of electrolytes is rare. It is most commonly caused by medication (insulin overdose, glucose administration, decongestants, salbutamol), alkalosis (metabolic or respiratory), MI, thyrotoxicosis, refeeding syndrome.