musings of a salt whisperer
Last week I posted a tweetorial on pseudohyperkalemia due to CLL and a high white blood cell count.
This case peaked with a potassium of 9.5. Pretty frightening, but that was nothing compared to the potassium of 15.5 I saw in 2014. Details here.
I had another case of pseudohyperkalemia in 2011. That one was due to thrombocytosis.
In response to my Tweetorial, Yash Chivate shared a case of pseudohyperkalemia of his own.
I had the honor of being invited back to the Curbsiders to discuss hyperkalemia. I am not all the way through the episode yet, but so far I have not heard any embarrassing mistakes. But I’ll be sure to post any retractions and corrections here when I come across one.
The highest potassium I have ever seen? That would be 15.5 mEq/L.
It’s not real. It was pseudohyperkalemia from leukocytosis. The patient had chronic lymphocytic leukemia with a white count of 300,000. If you are not familiar with this condition, check out these posts on Renal Fellow Network: Westervelt and Nate. Nice full text references here and here (pdf).
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| The pseudohyperkalemia merit badge |
The first time I saw this was when I was senior resident. I was sleeping in the call room my pager buzzed. It was the oncology floor with a potassium of 9. The patient had CML and was in a blast crisis. His leukocyte count around 100,000. I immediately suspected pseudohyperkalemia and ordered a whole blood potassium from the ABG lab. It was normal so I went back to sleep. The next morning I received an angry call from the Hemo-Onc fellow. The patient was coding and he was furious that I only ordered an ABG instead of treating the hyperkalemia.
I don’t know if the patient coded from hyperkalemia, but I wish that I had gotten out of bed and evaluated the patient. I solved the problem the nurses alerted me to, but if I assessed him, maybe I could of averted an arrest.
Regrets…
A patient came to the hospital with a swollen arm. The ED suspected a DVT and ordered a doppler ultrasound which confirmed their suspicion. The admission labs included a chem-7 which revealed a potassium of 7. Her creatinine was 1 and she wasn’t taking an ACEi, ARB, aldactone, ketoconazole, or potassium supplements. The ER was surprised and repeated the study and checked an EKG:
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| Narrow QRS and unimpressive T-waves |
The EKG gave no hint of hyperkalemia, though EKG changes are not a sensitive marker for hyperkalemia. The ED gave insulin, glucose and Kayexalate for the lab finding of hyperkalemia. We were consulted to determine the cause of the hyperkalemia. The patient’s past medical history was significant for primary thrombocytosis and during the hospital stay her platelet count rose to over a million.
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| dats a lot o’platelets |
We presumed that his hyperkalemia was actually pseudohyperkalemia due to the high platelet count. Platelets release potassium when they clot and the risk of pseudohyperkalemia rises as the platelet count approaches a million.
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| You remember this classic NEJM article from 1962. |
We then sent the patients blood to the ABG lab in a heparinized syringe rather than a red top and the potassium normalized. Platelets release potassium when they are activated. By measuring the potassium in whole blood rather than serum, the contribution of platelet activation is prevented. The ABG results are the electrolytes to the far left in the screen-grab below (click to enlarge).
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