We enjoyed the article by Gogas BD et al. reporting the electro-cardiographic consequences of a hyperkalaemia case [1]. In the same article, the authors mention briefly the condition known as pseudohy-perkalaemia. Every time the value of serum potassium (Ks) exceeds the respective value in plasma (Kp) by 0.4mEq/l, the phenomenon of pseudohyperkalaemia is present [2], The arrhythmogenic effects of hyperkalaemia, and the consequent changes of the electrocardiogram, depend upon the concentration of potassium in the plasma, not in the serum. Ks represents exclusively an in vitro condition, by definition.Several factors can affect the Ks values, creating false alarms of hyperkalaemia. In particular, several myeloproliferative haematologic diseases, with hypererythraemia, leukocytosis and thrombocytosis, are prone to provoke spectacular discrepancies between Ks and Kp values [3], Increased Ks, under those circumstances, is due to excessive in vitro release of intracellular potassium from platelets, leucocytes and erythrocytes, with Kp remaining within the normal range.
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