5th April 2024

Hyperkalaemia

This is defined as serum potassium levels of greater than or equal to 5.5 mmol/L and can be divided into:

• Mild 5.5 – 5.9 mmol/L
• Moderate 6 – 6.4 mmol/L
• Severe > 6.5 mmol/L

There are various mechanisms leading to hyperkalemia, including haemolysis and release of intracellular potassium from red blood cells during difficult venepuncture, delay between venepuncture and long transit time to the laboratory and taking a blood sample from the limb receiving intravenous fluids with added potassium. Other causes of hyperkalemia include:

• Transcellular redistribution which occurs in acidosis, low insulin states, hypertonicity, rhabdomyolysis and in extreme, prolonged exercise.
• Potassium retention can occur with acute kidney injury or in advanced chronic kidney injury 
• Medications including potassium sparing diuretics (spironolactone), ACE inhibitors, beta blockers, trimethoprim, heparin and digoxin at toxic levels
• Diabetic ketoacidosis: potassium shifts from the intracellular to the extracellular space due to a lack of insulin
• Addison’s disease results in decreased aldosterone levels. Normally, aldosterone promotes the excretion of potassium via the kidneys. Decreased aldosterone levels results in reduced renal excretion of potassium thus hyperkalaemia.