Summary: Hypokalemia is defined as a decrease in the serum potassium level below 3.8 mmol/l. Numerous data from retrospective analyses of the causes of sudden arrhythmic deaths indicate that one of the most common direct causes of aggravation or occurrence of arrhythmias is overlooked or recognized but uncorrected hypokalemia. Low potassium concentration, approximately 3.5‒3.8 mmol/l, frequently does not imply any therapeutic decisions and is regularly seen in the documentation of patients discharged from hospital emergency wards. Adequately correcting a potassium deficiency is crucial in reducing the risk of life-threatening arrhythmias. In practice, this is often done intuitively, which may result in both the risk of hyperkalemia and the recurrence of hypokalemia after transient normalization, due to incomplete correction of potassium deficiency. Hence, a rational solution would be the precise estimation of potassium deficiency in a specific case, as well as the unequivocal determination of the cause of its occurrence, thus minimizing the risk of recurrence.
The paper briefly summarizes the most common causes of hypokalemia with a simplified diagnostic algorithm. Further on, it discusses the pathophysiological consequences of potassium homeostasis disorders resulting from the decrease in serum concentration, the target values of potassium levels optimal for the electrical stability of the heart, as well as presenting a simple method of calculating the demand for potassium and quantifying the deficit.