When a client is prescribed digitalis medication, the nurse should closely monitor the potassium levels when caring for the client, because a key concern associated with digoxin therapy is digitalis toxicity. Clinical manifestations of toxicity include anorexia, nausea, visual disturbances, confusion, and bradycardia. The serum potassium level is monitored because the effect of digoxin is enhanced in the presence of hypokalemia and digoxin toxicity may occur.