Which of the following can cause obstructive shock?

• A. Tension pneumothorax
• B. Anaphylaxis
• C. Sepsis
• D. Hypoglycemia

Answer: (A)

Obstructive shock happens when something blocks blood flow through the heart or great vessels, so the heart can’t fill or pump effectively. A tension pneumothorax fits this mechanism because air trapped in the chest increases intrathoracic pressure, compressing the vena cava and the heart, shifting the mediastinum, and markedly reducing venous return and cardiac output. This drop in preload and output leads to the low perfusion and hypotension seen in obstructive shock.

The other examples fit different shock types: anaphylaxis and sepsis cause distributive shock via widespread vasodilation and fluid leakage rather than a physical obstruction to blood flow. Hypoglycemia is a metabolic problem that can impair perfusion indirectly but does not create an obstruction to cardiac filling or outflow.