So a couple of weeks ago we got a lovely gentleman through our doors who had a medical problem. He was mid 60s and had a pneumonia, but was tolerating it pretty well. He had HTN, and CLL.
What irked our collective team noodle was his K+ of 8.9, his ECG was normal, and he wasn’t in renal failure.
No tenting, sineing, PR prolongation, or P wave abnormality, or weird block.
“No, the sample isn’t haemolysed” the lab told us.
The repeat came back 8.7. – not haemolysed (this time written in block capitals).
The VBG we did, and ran to ICU to analyse gave us a value of 8.2.
So we turned to google, pubmed, and litfl, and all learnt about pseudohyperkalaemia:
The commonest cause is sloppy venepuncture, but it can also occur in patients with thrombocytosis, or leucocytosis. Effectively it is a measurement error that occurs if you have tonne of cells in the sample all gently, slowly lysing.
Our gentleman’s WCC was 200
Pseudohypokalaemia has also been reported with leucocytosis as well. As always I suppose we should always interpret lab results in light of what the patient looks like in front of us.
I’ll start by sharing a little mistake I made…
I saw a 72 year old lady who attended the ED 36 hours after sudden onset right 4th and 5th finger motor weakness, flexion 2/5 extension 3/5. Coordination in the rest of the hand was normal, her radial and median nerve had no sensory or motor deficits. Apart from the weakness, of the 4th and 5th digit, she had no other symptoms.
No history of trauma, carpal tunnel, or diabetes. Past medical history was high blood pressure, which she was on Enalapril for.
I wasn’t really sure what was going on here so along with the consultant we sent this lady to the plastic surgeons for ?ulnar nerve entrapment. She was reviewed the next day by the plastic surgery team, who referred her to the Neurology department, the neurology registrar diagnosed her with a “hand knob” stroke, a rare but well documented stroke syndrome.
So yes, I sent a lady with a stroke to plastics.
- Nerve entrapment was unlikely because the symptoms came on suddenly, and were at their most severe immediately.
- There was no involvement of any modality other than power, if this was a peripheral nerve lesion, sensation should also be affected.