In metabolic alkalosis, which compensation mechanism is used?

• A. Hyperventilation
• B. Hypoventilation
• C. Increased bicarbonate secretion
• D. Renal compensation

Answer: (B)

In metabolic alkalosis, the body seeks to compensate for the increased blood pH through a variety of mechanisms. One of the primary compensatory responses is hypoventilation. When metabolic alkalosis occurs, the blood becomes more alkaline due to an excess of bicarbonate or loss of hydrogen ions. To counteract this alkalinity, the respiratory system may decrease the rate of breathing (hypoventilation), which leads to a buildup of carbon dioxide (CO2) in the blood. The increased levels of CO2 can contribute to the formation of carbonic acid, which helps lower the pH back toward normal.

This hypoventilation response is a quick, acute compensatory mechanism that helps the body to mitigate the effects of metabolic alkalosis. Over the longer term, the renal system also plays a role by adjusting bicarbonate levels through secretion or reabsorption, but the immediate respiratory response is hypoventilation.

In contrast, increased bicarbonate secretion and renal compensation typically are more relevant in response to different acid-base disturbances, such as metabolic acidosis, rather than directly countering metabolic alkalosis.