ONE of the most common disorders encountered in clinical medicine is abnormal potassium metabolism resulting in either hyperkalemia or hypokalemia. In a healthy person, potassium balance is a function of oral intake and renal excretion. On a normal daily oral intake of 40 to 100 mEq, the urinary potassium excretion varies between 40 and 90 mEq/24 hr. Only small amounts of potassium are normally excreted through sweating and fecal excretion; however, substantial potassium wasting can occur in cases of severe sweating or gastrointestinal disease (usually diarrhea, vomiting, or fistulae).
The regulation of potassium excretion is dependent on renal function, total body potassium content, acid-base balance, delivery of sodium to the distal nephron, and mineralocorticoid secretion. Acidosis, decreased total body potassium content, decreased sodium delivery to the distal tubule, and mineralocorticoid insufficiency are associated with decreased potassium excretion. In contrast, alkalosis, increased total body potassium content, increased urinary sodium excretion, and