Disorders of potassium homeostasis in critically ill patients.

Disorders of potassium homeostasis can be life-threatening. This is especially true in critically-ill patients, in whom concurrent disorders may exacerbate the adverse effects of both hyper- and hypokalemia. Alterations in potassium balance are usually multifunctional in origin. Four broad categories encompass the most common diseases and syndromes seen in the intensive care setting: pharmacologic agents, acid-base disturbances, hypomagnesemia, and renal insufficiency. The various influences that disturb the serum potassium concentration may either potentiate or counter-balance one another. The most important clinical manifestations of disorders of potassium homeostasis are those involving the heart: both hyper- and hypokalemia can be associated with lethal arrhythmias. Neuromuscular, renal and metabolic effects are also seen. Severe hyper- and hypokalemia, irrespective of cause, should be treated as medical emergencies.