A paradigmatic case of haemolysis and pseudohyperkalemia in blood gas analysis

Abstract

A 51-year old male patient was admitted to the hospital with acute dyspnea and history of chronic asthma. Venous blood was drawn into a 3.0 mL heparinized syringe and delivered to the laboratory for blood gas analysis (GEM Premier 4000, Instrumentation Laboratory), which revealed high potassium value (5.2 mmol/L; reference range on whole blood, 3.5-4.5 mmol/L). This result was unexpected, so that a second venous blood sample was immediately drawn by direct venipuncture into a 3.5 mL lithium-heparin blood tube, and delivered to the laboratory for repeating potassium testing on Cobas 8000 (Roche Diagnostics). The analysis revealed normal plasma potassium (4.6 mmol/L; reference range in plasma, 3.5-5.0 mmol/L) and haemolysis index (5; 0.05 g/L). Due to suspicion of spurious haemolysis, heparinized blood was transferred from syringe into a plastic tube and centrifuged. Potassium and haemolysis index were then measured in this heparinized plasma, confirming high haemolysis index (50; 0.5 g/L) and pseudohyperkalemia (5.5 mmol/L). Investigation of this case revealed that spurious haemolysis was attributable to syringe delivery in direct ice contact for ~15 min. This case emphasizes the importance of avoiding sample transportation in ice and the need of developing point of care analysers equipped with interference indices assessment.

A case of severe pseudohyperkalaemia due to muscle contraction

“…Familial pseudohyperkalaemia was also considered in this case, since this can also result in spurious hyperkalaemia without haemolysis (18). This can be caused by a mutation in the ABCB6 transporter (formerly called "leaky cell membrane syndrome") and by several red blood cell membrane defects such as hereditary stomato-, xero-or spherocytosis (18,19). We did, however, not find any increase after storage for 2 hours at room temperature, excluding familial pseudohyperkalaemia as cause of the spurious hyperkalaemia.…”

<p>Perspectives On Blood-Based Point-Of-Care Diagnostics</p>

“…From the perspective of this anesthesiologist, it is often difficult to load a blood specimen into the POC testing cartridge without the formation of bubbles, which may alter test results for parameters such as blood gasses, and POC devices cannot detect sample quality interferents like hemolysis, leading to uncertainty when abnormally high or low results are obtained. [10][11][12] Although central labs are known to be more analytically reliable, this clinician has observed that when sending samples to the central lab from the operating room, pre-analytical error rates can reach up to 40%, likely due to transportation issues or mislabeling of the specimen itself.…”