Acid-Base and Electrolyte Disorders: Potassium Disorders

A normal serum potassium level of 3.5 to 5.0 mEq/L is maintained via potassium ingestion, excretion, and distribution between intra- and extracellular fluid. Potassium balance is essential for maintenance of normal resting cell membrane potential in excitatory tissues. Abnormalities in serum potassium, whether low or high, can cause life-threatening complications due to cardiac, respiratory, or neurologic compromise. Hypokalemia results from renal or gastrointestinal losses, or transcellular shifts. In the absence of an identified cause, evaluation of urinary potassium excretion and acid-base status can help determine the etiology. Patients with severe (ie, serum potassium less than 2.5 mEq/L) or symptomatic hypokalemia should be admitted to the hospital for intravenous potassium replacement and cardiac monitoring. Patients with mild to moderate hypokalemia are often asymptomatic and can be treated with oral potassium while the underlying cause is addressed. Hyperkalemia is usually due to low urinary excretion, and less often to cellular release and transcellular shifts. Patients with acute hyperkalemia with associated electrocardiography findings and those with potassium levels 6.5 mEq/L or greater require inpatient treatment with calcium gluconate and other measures. Asymptomatic patients with chronic mild to moderate hyperkalemia can be managed as outpatients with dietary modification, diuretics, and medication adjustments.