Which action should be added to a patient's treatment with furosemide who has developed hypokalemia?

To address hypokalemia in a patient receiving furosemide, it is essential to consider how potassium is typically managed within the nephron. Furosemide is a loop diuretic that acts on the ascending loop of Henle, leading to increased excretion of sodium, chloride, and potassium. This can result in a significant loss of potassium, especially because the collecting duct, where potassium is also handled, may not effectively reabsorb it when sodium concentration is high due to preceding diuretic therapy.

The correct action to add in this scenario, which enhances potassium retention, involves decreasing the luminal permeability to Na+ in the collecting duct. By decreasing sodium reabsorption in the collecting duct, this action helps to retain potassium. When sodium levels in the lumen decrease, the driving force for potassium secretion (which normally occurs in exchange for sodium reabsorption) is also diminished. Therefore, the action that results in decreased luminal permeability to sodium helps maintain potassium levels by preventing its excessive loss.

In the treatment of diuretic-induced hypokalemia, it is critical to prevent potassium loss while managing the patient's fluid and electrolyte balance, hence the importance of decreasing sodium reabsorption at this point in the nephron.