Severe diarrhea is most likely to cause which acid-base disturbance?

Severe diarrhea is most likely to cause which acid-base disturbance?

• A. Metabolic acidosis
• B. Metabolic alkalosis
• C. Respiratory acidosis
• D. Respiratory alkalosis

Answer: (A)

When the gut loses a lot of bicarbonate in severe diarrhea, the blood’s buffering base is diminished. Bicarbonate is a key base in the body’s acid-base balance, so its loss lowers the serum bicarbonate level and the pH, producing metabolic acidosis. This often shows up as a hyperchloremic, non-anion gap metabolic acidosis because chloride rises to maintain electroneutrality after bicarbonate loss. The respiratory system will try to compensate by increasing ventilation to blow off CO2, but the primary disturbance is metabolic. Choices involving loss of CO2 or excess base loss from vomiting or diuretics don’t fit this mechanism, which is why metabolic acidosis is the correct answer.

When the gut loses a lot of bicarbonate in severe diarrhea, the blood’s buffering base is diminished. Bicarbonate is a key base in the body’s acid-base balance, so its loss lowers the serum bicarbonate level and the pH, producing metabolic acidosis. This often shows up as a hyperchloremic, non-anion gap metabolic acidosis because chloride rises to maintain electroneutrality after bicarbonate loss. The respiratory system will try to compensate by increasing ventilation to blow off CO2, but the primary disturbance is metabolic. Choices involving loss of CO2 or excess base loss from vomiting or diuretics don’t fit this mechanism, which is why metabolic acidosis is the correct answer.