Significant hyperkalaemia is defined as a serum potassium value >6.0 mmol/L (>6.0 mEq/L). Moderate hyperkalaemia is defined as serum potassium values in the 5.0 to 6.0 mmol/L (5.0-6.0 mEq/L) range. Small changes in serum potassium values can have significant muscular and cardiac effects when significant hyperkalaemia is present.
Hyperkalaemia is most commonly due either to high intake of potassium in the setting of decreased renal excretion or to extracellular redistribution of potassium from intracellular locations. There is a limited correlation between an elevated serum potassium value and an excess in total body potassium stores. Clinical manifestations of hyperkalaemia are uncommon with values <6.0 mmol/L (<6.0 mEq/L).
Common acute manifestations of significant hyperkalaemia include muscle weakness and ECG changes, with the latter having the potential to progress to a life-threatening arrhythmia.  View image Significant hyperkalaemia represents a medical emergency, and an ECG should be obtained to establish whether cardiotoxicity is present. Continuous ECG monitoring should occur until serum potassium values have been brought into a safe range and cardiotoxicity has resolved.
Whereas the treatment of significant hyperkalaemia is pre-emptive in the patient without electrocardiographic change, in the presence of electrocardiographic change significant hyperkalaemia represents a true medical emergency and requires rapid implementation of measures to reduce serum potassium concentration.