[Disturbances of the Potassium Homeostasis]

Potassium is a key cation in the human organism and largely responsible for the resting membrane potential of excitable cells. 98% of the potassium pool resides within the cells and only 2% in the extracellular space. Thus, blood sample measurements of potassium do not necessarily reflect the total potassium state. The extracellular potassium concentration however is tightly regulated, either through potassium elimination via the kidney or shift between the intra- or extracellular compartment. Changes in the blood serum potassium concentration are defined as hypokalemia (< 3,5 mmol/l) or hyperkalemia (> 5,0 mmol/l). Hypokalemia is caused by a low-potassium diet, gastrointestinal losses or polyuric renal failure. Hyperkalemia can follow excessive intake, severe tissue damage or oliguric or anuric renal failure. Acute alteration of the extracellular potassium concentration should spark immediate action by the perioperative physician. In particular, hyperkalemic states require immediate attention and therapeutic interventions. In this review, we give an overview of the pathophysiology of potassium changes and provide a practical approach to their management.