A patient presenting with a history of hypertension

A patient presenting with a history of hypertension, dyspnea, orthopnea, lung crackles, and bilateral pitting edema likely has an exacerbation of congestive heart failure (CHF). This patient is experiencing volume overload.⁣
Diuretics, furosemide in particular, are a mainstay of treatment for CHF exacerbations. Furosemide is a loop diuretic that inhibits the sodium-potassium-chloride cotransporter. At maximal dosage, it can cause excretion of about 25% of filtered sodium. The reabsorption of calcium in the loop of Henle is primarily passive, being driven by the gradient created by sodium and chloride transport. With furosemide, this gradient is destroyed. Because it promotes the excretion of calcium, furosemide is used to treat hypercalcemia, but it is contraindicated for a patient experiencing hypocalcemia.⁣

In addition to treating CHF exacerbations and hypercalcemia, furosemide and other loop diuretics can be used to treat edema associated with nephrotic syndrome. Although loop diuretics can be used to lower blood pressure, they are not a first-line treatment for hypertension.