Repeated USMLE Questions Step 1- 186

A 58-year-old woman is brought to the emergency room complaining of lightheadedness for 4 hours. She has diarrhea with loose stool for 2 days. She explains her symptoms as flu and she drinks lots of water as her neighbor advised her to avoid dehydration. Her physician told her that she should take combined solution of sodium chloride (NaCl) and glucose to prevent dehydration.

What is the mechanism of action of this mixture to improve dehydration?

A- It reduces bowel contractions and consequently improves diarrhea

B- Glucose provides energy for NaCl to increase gastric emptiness

C- The mixture helps to increase secretion of water and Na through the large intestine

D- Cotransport of glucose and NaCl across the intestinal membrane facilitates absorption of water and Na.

Answer





Glucose and NaCl cotransport is the mechanism of the sodium pump. This action facilitates absorption of water and Na through the intestinal membrane and help to relieve dehydration. Ingestion of water only causes loss of Na due the difference of osmosis in the intestinal lumen and eventually enhance dehydration.

The correct answer is D