Pseudohyperkalemia from a Pneumatic Tube Transport System: Case Report and Literature Review

Abstract

Objective To report a case of pseudohyperkalemia due to a pneumatic tube transport system. Case Summary A 75-year-old male presented to the emergency medicine department with chest pain and intermittent vision loss over the previous 2 days. Laboratory studies revealed a potassium value of 9.6 mEq/L and a white blood cell (WBC) count of 262 × 109/L. An electrocardiogram did not reveal changes consistent with hyperkalemia. Emergent treatment for the hyperkalemia was instituted. Repeat plasma potassium values obtained after treatment for the hyperkalemia remained significantly elevated. It was eventually recognized that the hyperkalemia was due to the combination of undiagnosed leukemia causing a significantly elevated WBC count and transport of the patient's specimen to the laboratory via a pneumatic tube transport system. Manual transport of the specimen to the laboratory repeatedly revealed normal or hypokalemic values. Discussion Hyperkalemia is a potentially fatal electrolyte abnormality that must be differentiated from pseudohyperkalemia. Pseudohyperkalemia is defined as a spurious elevation of potassium levels usually due to mechanical trauma during venipuncture resulting in hemolysis and release of potassium from the cellular elements of blood. Pneumatic tube transport systems should be listed in the scientific literature as another potential cause of pseudohyperkalemia, especially in patients with high WBC and/or platelet counts. Conclusion Pharmacists and other health care providers should be aware of pneumatic tube transport systems potentially causing pseudohyperkalemia, because regular treatments for hyperkalemia for this problem may cause patient harm.