<prompt> Pseudohyperkalemia can result fromProlonged use of tourniquetHemolysisMarked leukocytosisTumor lysis syndrome  <response>: Hyperkalemia should be distinguished from factitious hyperkalemia or pseudohyperkalemia, an aifactual increase in serum K due to the release of K during or after venipuncture. Pseudohyperkalemia can occur in the setting of excessive muscle activity during venipuncture e.g., fist clenching, a marked increase in cellular elements thrombocytosis, leukocytosis, andor erythrocytosis within vitro efflux of K, and acute anxiety during venipuncture with respiratory alkalosis and redistributive hyperkalemia. Cooling of blood following venipuncture is another cause, due to reduced cellular uptake; the converse is the increased uptake of K by cells at high ambient temperatures, leading to normal values for hyperkalemic patients andor to spurious hypokalemia in normokalemic patients. Finally, there are multiple genetic subtypes of hereditary pseudohyperkalemia, caused by increases in the passive K permeability of erythrocytes. For example, mutations in the red cell anion exchanger AE1, encoded by the SLC4A1 gene Ref: Harrison 19e pg: 309 