Which is a common cause of metabolic alkalosis?

Which is a common cause of metabolic alkalosis?

• A. Vomiting
• B. Hyperkalemia
• C. Excessive diuresis
• D. Lactic acidosis

Answer: (C)

Metabolic alkalosis arises when there is a net gain of bicarbonate or loss of hydrogen ions, often reinforced by volume depletion. Excessive diuresis causes contraction alkalosis: diuretics increase sodium delivery to the distal nephron and, with resulting volume loss, activate the renin-angiotensin-aldosterone system. Aldosterone promotes sodium reabsorption in exchange for hydrogen and potassium secretion in the collecting ducts, so hydrogen ions are lost in the urine and bicarbonate is retained, raising blood bicarbonate and pH. Chloride loss from diuretics also reduces the kidney’s ability to buffer bicarbonate, worsening the alkalosis. Vomiting can cause alkalosis through H+ loss, but the diuretic-related contraction mechanism is a classic, very common cause in clinical settings. Hyperkalemia and lactic acidosis, by contrast, tend toward acidosis rather than alkalosis.

Metabolic alkalosis arises when there is a net gain of bicarbonate or loss of hydrogen ions, often reinforced by volume depletion. Excessive diuresis causes contraction alkalosis: diuretics increase sodium delivery to the distal nephron and, with resulting volume loss, activate the renin-angiotensin-aldosterone system. Aldosterone promotes sodium reabsorption in exchange for hydrogen and potassium secretion in the collecting ducts, so hydrogen ions are lost in the urine and bicarbonate is retained, raising blood bicarbonate and pH. Chloride loss from diuretics also reduces the kidney’s ability to buffer bicarbonate, worsening the alkalosis. Vomiting can cause alkalosis through H+ loss, but the diuretic-related contraction mechanism is a classic, very common cause in clinical settings. Hyperkalemia and lactic acidosis, by contrast, tend toward acidosis rather than alkalosis.