A patient experiences severe vomiting and diarrhea. Which acid-base disturbance and electrolyte changes are expected?

• A. Metabolic alkalosis with hypokalemia
• B. Metabolic acidosis with possible hypokalemia and hyponatremia due to GI losses
• C. Respiratory acidosis with hyperkalemia
• D. Metabolic acidosis with hypernatremia

Answer: (B)

GI losses from diarrhea primarily remove bicarbonate from the body, which lowers blood pH and produces metabolic acidosis. They also drain potassium and sodium, so hypokalemia and hyponatremia are common as the body loses these electrolytes and as volume depletion affects electrolyte balance. Vomiting, on the other hand, tends to cause metabolic alkalosis because stomach acid (hydrogen ions) and chloride are lost, but when diarrhea is also present and often more substantial, the bicarbonate loss from stool tends to dominate the acid-base picture. The result is a metabolic acidosis with potential hypokalemia and hyponatremia due to GI losses. The other patterns—metabolic alkalosis, respiratory acidosis, or metabolic acidosis with hypernatremia—don’t align as well with the combination of GI losses described here.