Rosh Internal Medicine Boost Practice Exam

Which scenario is most likely to result in metabolic acidosis?

1. Bacterial pneumonia with underlying chronic obstructive lung disease

2. Hyperventilation due to anxiety

3. Persistent diarrhea

4. Vomiting

The correct answer is: Persistent diarrhea

Metabolic acidosis is characterized by a decrease in bicarbonate (HCO3-) levels in the blood, resulting in a lower blood pH. The scenario involving persistent diarrhea is most likely to result in metabolic acidosis. In cases of persistent diarrhea, there is a significant loss of bicarbonate, which is primarily found in the intestinal secretions. The kidneys can compensate for some loss of bicarbonate, but prolonged diarrhea overwhelms this capacity. This loss reduces the buffering capacity of the blood, leading to an accumulation of acids, thus causing a state of metabolic acidosis. While bacterial pneumonia may lead to respiratory acidosis or mixed acid-base disorders due to hypoventilation and CO2 retention, it is not primarily associated with metabolic acidosis. Hyperventilation causes respiratory alkalosis due to increased CO2 elimination. Vomiting typically results in the loss of gastric acid and can lead to metabolic alkalosis rather than acidosis. In summary, persistent diarrhea leads to significant bicarbonate loss, making it the scenario most likely to result in metabolic acidosis. This understanding is crucial for diagnosing and managing acid-base disorders in clinical practice.