Pseudohyperkalemia secondary to postsplenectomy thrombocytosis.

Hyperkalemia is a regularly encountered electrolyte abnormality. Less commonly recognized is pseudohyperkalemia. In vitro clotting results in the release of potassium from the formed elements of blood; this falsely elevates the serum potassium concentration. Usually attributed to thrombocytosis, leukocytosis, or hemolysis it is rarely reported in the postsplenectomy trauma patient. A 49-year-old man underwent splenectomy for a grade IV splenic injury. He developed an elevated serum potassium on postoperative day 16. His renal function remained normal, and an active search for causes of hyperkalemia failed to delineate a source for his elevated potassium. Pseudohyperkalemia was proposed as an etiology and confirmed by analyzing simultaneous serum (5.9 mEq/L) and plasma potassium levels (3.9 mEq/L). The serum potassium showed a concomitant rise with the evolution of the patient's postsplenectomy thrombocytosis. This is a case report of our patient and a literature review of this rarely reported and underestimated cause of a potentially serious electrolyte abnormality. We found through our patient that pseudohyperkalemia does occur in the postsplenectomy population and that this should be included in the differential diagnosis of any patient with an elevated serum potassium level and thrombocytosis.