Hypokalemia: causes, consequences and correction.

Hypokalemia poses a common diagnostic challenge with many potential etiologies. Multiple factors may contribute to this electrolyte deficiency in any given patient. Gastrointestinal potassium wasting usually is identifiable by an associated increase in fluid losses via biliary tract or bowel. A urinary potassium excretion of 20 mEq or more per day in the presence of a low serum potassium (less than 3.5 mEq/L) suggests inappropriate potassium wasting. Although diuretic therapy (loop diuretics, thiazides) undoubtedly is the most common cause of a potassium deficit, one also must consider abnormalities of the pituitary-adrenal axis, renal disorders including tumors, other drugs, and a variety of less well-defined entities. Potassium deficiency may produce both functional and structural defects in the kidneys, myocardium, skeletal muscle, central nervous system, and gastrointestinal tract. Treatment is aimed at replacing potassium intravenously or orally or preventing further potassium loss (spironolactone, triamterene); when associated with a metabolic alkalosis (chloride deficiency), the replacement should be potassium chloride.