Etiology

Causes include deficient potassium intake or excess loss of potassium due to vomiting, diarrhea, or fistulas; metabolic acidosis; diuretic therapy; aldosteronism; excess adrenocortical secretion; renal tubule disease; and alkalosis.

Symptoms

Common manifestations of mild to moderate potassium depletion include muscle aches, fatigue, or mild weakness. As potassium concentrations drop significantly below 3.0 mmol/L, ileus, paralysis, or cardiac conduction and rhythm disturbances may arise. Arrhythmias are particularly likely to affect those patients taking digoxin who become hypokalemic.

Prevention

To prevent hypokalemia, patients taking cardiac glycosides or potassium-wasting diuretics are instructed to include potassium supplements in their medical regimens. Potassium-rich foods (such as oranges, bananas, and tomatoes) are not an adequate source of the potassium that is lost by diuresis.

Treatment

Therapy consists of oral, intravenous, or combined potassium replacement.

CAUTION!

Patient care

Potassium and other electrolyte levels are monitored frequently during replacement therapy to avoid overcorrection leading to hyperkalemia. Fluid balance is monitored. A physician must be notified if the patient's urine output is less than 600 ml/day because 80% to 90% of potassium is excreted through the kidneys. Cardiac rhythm is monitored, and arrhythmias are reported immediately. Additional care is taken if the patient takes a cardiac glycoside because hypokalemia enhances its action. The patient is assessed for indications of digitalis toxicity (anorexia, nausea, vomiting, blurred vision, arrhythmias). Other signs to watch for include decreased bowel sounds, abdominal distention, and constipation.

Prescribed IV potassium replacement is administered slowly with a volumetric device if the concentration exceeds 40 mEg/L. The rate should not exceed 200-250 mEg/24 hr, and the drug should never be given as a bolus because it may precipitate cardiac arrest. If the patient is prescribed a liquid oral potassium supplement, he or she is advised to dilute it in a full glass of water or fruit juice and to sip it slowly to prevent gastric irritation. Safety measures are implemented for the patient experiencing muscle weakness due to postural hypotension. The importance of taking potassium supplements as prescribed is emphasized, particularly if the patient also is prescribed a diuretic or digitalis preparation. The patient is taught signs of potassium imbalance to report, including weakness and pulse irregularities.