A patient treated with a loop diuretic is monitored for acid-base/volume status. What findings are expected after treatment?

• A. Metabolic acidosis with volume contraction
• B. Metabolic alkalosis with volume contraction
• C. Metabolic acidosis without volume contraction
• D. Metabolic alkalosis without volume contraction

Answer: (B)

When a patient is treated with a loop diuretic, one of the expected findings is metabolic alkalosis combined with volume contraction. Loop diuretics, such as furosemide, inhibit sodium reabsorption in the ascending loop of Henle, leading to increased excretion of sodium, potassium, and chloride. This diuretic effect results in a reduction of extracellular fluid volume, which is often referred to as volume contraction.

The metabolic alkalosis primarily occurs due to the loss of hydrogen ions alongside the diuretic-induced electrolyte imbalances. As sodium is reabsorbed in other nephron segments to compensate for the loss, hydrogen ions are often secreted into the urine, exacerbating the alkalotic state. Additionally, hypokalemia (low potassium levels) can contribute to the development of metabolic alkalosis since low potassium can stimulate the secretion of hydrogen ions in exchange for potassium in renal tubules.

This combination of events explains why after treatment with a loop diuretic, the expectation is to observe metabolic alkalosis along with volume contraction.