Pseudohyperkalemia secondary to postsplenectomy thrombocytosis

Hyperkalemia is a regularly encountered electrolyte abnormality. Less commo nly recognized is pseudohyperkalemia. In vitro clotting results in the rele ase of potassium from the formed elements of blood; this falsely elevates t he serum potassium concentration. Usually attributed to thrombocytosis, leu kocytosis, or hemolysis it is rarely reported in the postsplenectomy trauma patient. A 49-year-old man underwent splenectomy for a grade IV splenic in jury. He developed an elevated serum potassium on postoperative day 16. His renal function remained normal, and an active search for causes of hyperka lemia failed to delineate a source for his elevated potassium. Pseudohyperk alemia 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 potass ium showed a concomitant rise with the evolution of the patient's postsplen ectomy thrombocytosis. This is a case report of our patient and a literatur e review of this rarely reported and underestimated cause of a potentially serious electrolyte abnormality. We found through our patient that pseudohy perkalemia does occur in the postsplenectomy population and that this shoul d be included in the differential diagnosis of any patient with an elevated serum potassium level and thrombocytosis.