Potassium - what an intensive care specialist should know

Potassium is the most important intra-cellular cation and essential for physio-logical cellular function. Deviations in potassium regulation can lead to neuro-muscular, gastrointestinal, and cardiac pathologies. Both hypo-and hyper-kalaemia can cause potentially fatal arrhythmias, cardiac dysfunction, and other complications. Hypokalaemia, hyperkalaemia, and potassium variability are very common in critically ill patients and independently associated with in-creased mortality; therefore, adequate monitoring in the ICU is essential. The clinical manifestation of symptoms of dyskalaemia essentially depends on the temporal dynamics. In clinical management, it is important to correct concomitant electrolyte disturbances at the same time, as they can reinforce each other. A transcellular ,,potassium shift" is of particular importance and may play a decisive role both in the development and in the therapy of dyskalaemia. Patients with heart failure, renal impairment or diabetes mellitus are particularly vulnerable to hyperkalaemia. Diagnostically, in addition to the clinic and a blood gas analysis, an electrocardiogram should always be made. Full electrolyte solutions are the infusion therapy of choice in case of hyperkalaemia. Cardiac arrhythmias re-present the classic indication for acute therapy in hyperkalaemia. Therapeutic measures include cardiac membrane stabilisation by calcium administration, an induction of intracellular potassium uptake (,,potassium shift"), and the finally elimination of potassium by forced diuresis or extracorporeal procedures (renal replacement therapy, acute dialysis). It is clinically relevant that renal replacement therapy will usually not be necessary if diuresis is preserved. Hypokalaemia, which is frequently accompanied by hypovolaemia and hypotension, is clinically characterised by physical weakness and cardiac arrhythmias. In the therapy of hypokalaemia, it should be noted that the repletion of the total body po-tassium deficit takes significantly more time than the short-term correction of serum potassium.