Neonatal Nurse Practitioner Practice Exam

What changes occur in the body during compensation for metabolic alkalosis?

1. Decrease in HCO3 and CO2

2. Increase in HCO3 and CO2

3. Decrease in CO2 and increase in pH

4. Decrease in pH and increase in CO2

The correct answer is: Increase in HCO3 and CO2

The correct choice highlights the physiological adjustments the body makes to cope with metabolic alkalosis. During this condition, which is characterized by an elevation in blood pH due to increased bicarbonate (HCO3-) levels or loss of hydrogen ions, the body attempts to balance the elevated pH by making specific compensatory changes. In response to metabolic alkalosis, the respiratory system plays a crucial role in compensation. To decrease pH, carbon dioxide (CO2) levels must typically be increased as CO2 contributes to the production of carbonic acid when dissolved in blood, thus lowering the pH. Therefore, rather than a decrease, an increase in CO2 is expected during compensation. This occurs through decreased respiratory rate or depth (hypoventilation) to retain CO2. However, the key to understanding the changes in bicarbonate lies in that the body tends to try to restore normal pH by the nephron's ability to adjust bicarbonate excretion. Initially, in metabolic alkalosis, there is often an increase in bicarbonate. Although the kidneys may eventually excrete more bicarbonate to help correct the alkalosis, the immediate compensatory response involves retaining CO2. Recognizing this pattern is crucial. The body’s goal during metabolic alkalosis