Multi-institution comparison of whole blood potassium hemolysis rates

Hemolysis causes falsely elevated potassium results and if undetected, can lead to misidentification of hypokalemia or hyperkalemia causing delayed or inappropriate treatment. The prevalence of hemolysis in whole blood samples submitted for potassium or blood gas analysis remains unknown due to historical limitations in blood gas analyzer hemolysis detection. This study aimed to compare hemolysis rates in whole blood potassium samples measured by blood gas analyzers at four different academic medical centers. Further, we compared rates among differing blood sources and hospital settings, and potassium results among different hemolysis flags.

Potassium results and hemolysis flags measured on the GEM Premier 7000 at four different academic medical centers were compiled for six months at each location.

A total of 37,944 samples with hemolysis flags were obtained from four academic medical centers with an overall hemolysis rate of 10.0 % (hemolysis flags corresponding to > 50 mg/dL plasma free hemoglobin). Hemolysis rates varied by institution ranging from 9.2-14.6 %. Hemolysis rates were similar between arterial (8.6 %) and venous (10.6 %) samples but were substantially higher for capillary (17.7 %) samples. Samples collected in the emergency department showed greater hemolysis rates (17 %) compared to those samples originating in intensive care units (8.1 %) and all other (10.2 %) departments.

This study demonstrates high hemolysis rates for whole blood potassium samples measured by blood gas analyzers, particularly for the emergency department setting and capillary specimens. This study demonstrates the importance of hemolysis detection for improving laboratory quality and patient safety.