Hyperkalaemia

• Hyperkalaemia refers to a raised serum potassium level.
• The main complication of hyperkalaemia is cardiac arrhythmias, such as ventricular fibrillation, which can lead to cardiac arrest.
• Normal serum potassium levels are 3.5 – 5.3 mmol/L.
• Mild hyperkalaemia is defined as a serum potassium level of 5.4 – 6 mmol/L.
• Moderate hyperkalaemia is defined as a serum potassium level of 6 – 6.5 mmol/L.
• Severe hyperkalaemia is defined as a serum potassium level over 6.5 mmol/L.
• Conditions that can cause hyperkalaemia include acute kidney injury, chronic kidney disease (stage 4 or 5), rhabdomyolysis, adrenal insufficiency, and tumour lysis syndrome.
• Medications that can cause hyperkalaemia include aldosterone antagonists (e.g., spironolactone and eplerenone), ACE inhibitors (e.g., ramipril), Angiotensin II receptor blockers (e.g., candesartan), NSAIDs (e.g., naproxen), and haemolysis (rupture of blood cells) during sampling can create a falsely elevated potassium (pseudohyperkalaemia).
• Each hospital will have a policy and protocol to follow for hyperkalaemia.
• Oral calcium resonium reduces potassium absorption in the GI tract, but this is slow and causes constipation.
• Tall peaked T-waves, flattening or absence of P waves, prolonged PR interval, broad QRS complexes are ECG changes associated with hyperkalaemia.
• Insulin drives potassium from the extracellular space to the intracellular space.
• Severe hyperkalaemia requires input from experienced seniors, including the intensive care team.
• Calcium gluconate stabilises the cardiac muscle cells and reduces the risk of arrhythmias.
• Management of serum potassium below 6.5 mmol/L without ECG changes is aimed at the underlying cause, for example, treating acute kidney injury and stopping medications such as spironolactone or ACE inhibitors.
• Dextrose is required to prevent hypoglycaemia while on insulin.
• Patients require urgent treatment for hyperkalaemia if they have either ECG changes or serum potassium above 6.5 mmol/L.
• The mainstay of treatment for hyperkalaemia is an insulin and dextrose infusion and IV calcium gluconate.
• Haemodialysis may be required in severe or persistent cases of hyperkalaemia.
• Nebulised salbutamol temporarily drives potassium into cells.
• Sodium bicarbonate (in acidotic patients on renal advice) drives potassium into cells as it corrects the acidosis.