Hyperkalemia
Kenneth B. Roberts MD
Potassium is the major intracellular cation; only a very small fraction of total body potassium is in the intravascular space. Increased potassium concentration in serum is infrequent in pediatrics, but it can be life-threatening because of its effect on membrane potentials, particularly of heart muscle.
The serum potassium concentration is affected primarily by the kidney. Potassium is filtered by the glomerulus, then reabsorbed and secreted by the tubule. Processes that interfere with filtration or secretion (eg, acute on chronic glomerulonephritis, interstitial nephritis) may cause hyperkalemia; processes that interfere with reabsorption may cause hypokalemia.
The most common cause of an increased serum potassium is "pseudohyperkalemia" due to hemolysis or to tissue hypoxia distal to the placement of a tourniquet.
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