Significant hyperkalemia is defined as a serum potassium value >6.0 mEq/liter (>6.0 mmol/L). Moderate hyperkalemia is defined as serum potassium values in the 5.0 to 6.0 mEq/liter (5.0-6.0 mmol/L) range. Small changes in serum potassium values can have significant muscular and cardiac effects when significant hyperkalemia is present.
Hyperkalemia 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 hyperkalemia are uncommon with values <6.0 mEq/liter (<6.0 mmol/L).
Common acute manifestations of significant hyperkalemia include muscle weakness and ECG changes, with the latter having the potential to progress to a life-threatening arrhythmia.  Significant hyperkalemia 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 hyperkalemia is pre-emptive in the patient without electrocardiographic change, in the presence of electrocardiographic change significant hyperkalemia represents a true medical emergency and requires rapid implementation of measures to reduce serum potassium concentration.
The University of Kansas Medical Center
SGY declares that she has no competing interests.
Dr Sri G. Yarlagadda would like to gratefully acknowledge Dr Domenic Sica, a previous contributor to this monograph. DS declares that he has no competing interests.
Department of Internal Medicine
Division of Nephrology
University of Iowa Hospital and Clinics
MS declares that he has no competing interests.
Royal London Hospital
RT declares that he has no competing interests.
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