Pseudohyperkalaemia Induced By Blood Collection And Corrections For Hemolysis In Blood Samples From Experimental Mice

Pseudohyperkalaemia is commonly caused by improper blood collection and hemolysis in blood samples. The reported blood potassium concentrations range from 4mM to 7mM in wild-type mice of different genetic backgrounds. It is not clear whether such large differences are due to genetic background or technical problems during blood collection. In this study, we measured and compared the plasma K+ concentrations in mice with similar genetic background by using different blood collection methods and also assessed K+ concentrations in blood samples with hemolysis. Five commonly used blood collection methods were performed (via carotid artery cannulation; cardiac puncture; retro-orbital bleeding; abdominal aorta puncture; and trunk artery by decapitation) and K+ concentrations were measured from these samples. The K+ concentrations, in increasing order, were (in mM): 4.06±0.10; 4.48±0.12; 4.84±0.13; 6.00±0.18 and 6.94±0.14 respectively from blood samples collected by the above methods. We also measured the hemoglobin in these samples and found that hemoglobin concentrations are proportional to the K+ concentration and the increase in plasma potassium and changes in hemoglobin show a linear relationship with a formula of Y=0.08609 + 5.355* (X−0.08266), R2=0.9911 (where Y= change in hemoglobin; X= change in K+). These results indicate that carotid artery cannulation, cardiac puncture, and retro-orbital bleeding methods produce relatively accurate K+ values but pseudohyperkalaemia results from abdominal aorta puncture and trunk artery collections, which can be corrected by our new equation.