When caring for a patient on multiple cardiac medications, the nurse notices signs of hypokalemia. Which medication is most likely contributing?

Choice A rationale Furosemide is a potent loop diuretic that acts on the loop of Henle in the kidneys, inhibiting the reabsorption of sodium, chloride, and potassium. This action leads to a significant increase in the excretion of potassium, making hypokalemia a very common and expected side effect. The normal potassium range is 3.5 to 5.0 mEq/L, and values below this range can lead to serious cardiac arrhythmias, muscle weakness, and fatigue. Therefore, this medication is the most likely culprit. Choice B rationale Spironolactone is a potassium-sparing diuretic that acts as an aldosterone antagonist, promoting sodium and water excretion while retaining potassium. Instead of causing hypokalemia, it can lead to hyperkalemia, especially when used with other potassium-retaining drugs or in patients with impaired renal function. The normal potassium range is 3.5 to 5.0 mEq/L. Therefore, it would counteract, not contribute to, hypokalemia. Choice C rationale Lisinopril is an ACE inhibitor that blocks the conversion of angiotensin I to angiotensin II, leading to decreased aldosterone secretion. Aldosterone promotes sodium and water retention and potassium excretion. By reducing aldosterone levels, lisinopril causes potassium retention, and therefore, its use is associated with a risk of hyperkalemia. Normal potassium range is 3.5 to 5.0 mEq/L. Thus, it would not be the cause of hypokalemia. Choice D rationale Metoprolol is a beta-blocker that primarily affects the heart rate and blood pressure by blocking beta-adrenergic receptors. It does not directly impact the renal excretion of potassium in the same manner as diuretics. While metabolic side effects can occur, they are generally not a primary cause of significant electrolyte imbalances like hypokalemia. Its main effect is on the cardiovascular system.