What is a cause of refractory shock in the canine patient?

• A. Tension pneumothorax
• B. Dehydration due to mild diarrhea
• C. Myocardial infarction
• D. Hypoglycemia

Answer: (A)

When shock cannot be corrected by fluids and standard resuscitation, think about obstructive causes that prevent the heart from filling and pumping effectively. Tension pneumothorax does this by trapping air under pressure in the chest, which collapses the lung on one side and pushes the mediastinum forward. This dramatically reduces venous return to the heart, causing rapid, severe hypotension that often does not respond to fluids alone until the pressure is relieved. In a canine patient, the emergency action is rapid decompression (needle thoracostomy or chest tube placement) to restore venous return and cardiac output.

The other options don’t fit as well because dehydration from mild diarrhea is a hypovolemic cause that typically improves with volume replacement; myocardial infarction, while possible, is uncommon in dogs and would present with cardiogenic shock that has a different management approach; and hypoglycemia causes shock that responds quickly to glucose administration.