Overview
What High Potassium Does
Hyperkalemia is a serum potassium concentration above 5.5 mmol/L; British Columbia guidance may flag a value above 5.2 mmol/L.
Hyperkalemia is a serum potassium concentration above 5.5 mmol/L; British Columbia guidance may flag a value above 5.2 mmol/L. The clinical danger is not the number alone. Excess extracellular potassium changes the myocardial resting membrane potential, disrupts sodium-channel availability, and slows electrical conduction. The ECG may show tall peaked T-waves and a shortened QT interval early in the process. As conduction deteriorates, the QRS widens, P-waves may disappear, and bradyarrhythmias can develop. Any of these ECG changes makes hyperkalemia a life-threatening emergency because deterioration can progress to severe conduction failure or cardiac arrest. Weakness, paresthesias, palpitations, nausea, or a sense of impending collapse may occur, but symptoms are unreliable. A patient may look relatively well while the rhythm is becoming unstable. Renal impairment increases the risk because the kidneys cannot excrete the potassium load effectively. Acute kidney injury, oliguria, acidosis, insulin deficiency, tissue breakdown, and medications that suppress aldosterone or renal potassium excretion can push a previously stable patient into danger.