Hyperkalemia Differential Diagnoses

Updated: Jun 20, 2018
  • Author: Eleanor Lederer, MD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Diagnostic Considerations

Pseudohyperkalemia is the term applied to the clinical situation in which in vitro lysis of cellular contents leads to measurement of a high serum potassium level that does not reflect the true in vivo level. It occurs most commonly with red blood cell hemolysis during the blood draw (eg, when the tourniquet is too tight or left on too long or the blood is left sitting too long). With intravascular hemolysis (eg, from a transfusion reaction, hemolytic sickle crisis, or drug-induced hemolytic reaction), in contrast, the measured potassium level reflects the actual level.

In pediatric patients, factitious hyperkalemia can occur because of “milking” of extremities (which can introduce a significant amount of interstitial fluid into the blood sample) during phlebotomy, especially with heel-poke and finger-stick phlebotomy, which are commonly performed in infants and small children. Hemolysis can also be caused by fist clenching during phlebotomy, which can also lead to an acidotic sample with resultant hyperkalemia.

Blood sampled “upstream” of an intravenous (IV) line infusing potassium-containing fluid (or from a multiple-lumen central venous catheter in which the sampling lumen is near the lumen containing potassium-rich infusate) can have falsely elevated levels of potassium that do not reflect circulating levels.

Thrombocytosis can also lead to false elevations of serum potassium levels. The normal serum potassium level is 0.4 mEq/L higher than the plasma level because of potassium release during clot formation. For every 100,000/µL elevation in the platelet count, the serum potassium increases by approximately 0.15 mEq/L. This can easily be corrected on the basis of a measurement of whole blood potassium level. A similar effect on serum, but not plasma, potassium can also be seen with leukocytosis.

Differential Diagnoses