Tricky cases - Pseudohyperkalemia

An elderly patient with hypertension was found to have hyperkalemia in a routine check up. His hypertension was well controlled with amlodipine. Initial potassium (K) value was 5.9mmol/l. He was seen by a general practitioner and was asked to avoid fruits and king coconut juice and repeat a serum electrolyte in 3 days. Repeat K value was still 5.7mmol/l. As the ECG did not show any significant hyperkalemic changes he was asked to continue avoiding high K containing food and beverages. A week later he presented again with a K value of 6.1mmol/l. He was so annoyed that he had to avoid fruits as he used to have a fruit platter each morning.

The GP decided to admit him for further investigations.

He was admitted to medical casualty ward.

Investigations revealed

  • WBC - 16.67 
    • N - 60%
    • L - 36%
  • Hb - 16.8 g/dl
  • Plt - 570

  • S. Cr - 73umol/l

  • Na - 138mmol/l
  • K - 6.1mmol/l

  • ECG 



The consultant made a spot diagnosis and an hour later the patient was seen eating a full platter of fruits.

Lesson

~ Elevated potassium with normal ECG should raise the suspicion of pseudohyperkalemia.

~ Common causes include
  • Anything which predispose hemolysis. Eg: Shear stress on red cells due to tourniquet. True intravascular hemolysis.
  • Movement of potassium out of cells while the sample is in the tube. Eg: When theres thrombocytosis or leucocytosis.
~ There are many other causes which you will read tonight!

~ Read about ECG changes in hyperkalemia and the emergency management of hyperkalemia.

~ The ultimate diagnosis of this patient was Polycythemia Rubra Vera.





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