Distributive shock occurs when which mechanism predominates?

• A. An injury causes restriction of the heart muscle and impairs its pumping function.
• B. Widespread dilation of the blood vessels causes blood to pool in the vascular beds.
• C. Severe bleeding causes tachycardia in order to distribute blood to the organs faster.
• D. Temporary but severe vasodilation causes a decrease in blood supply to the brain.

Answer: (B)

Distributive shock is driven by widespread vasodilation that reduces systemic vascular resistance and causes blood to pool in the venous system. When vessels dilate throughout the circulation, much of the blood becomes sequestered in the vascular beds, so there’s less blood returning to the heart and less blood reaching tissues, even if the heart pump is working. This pooling and loss of effective circulating volume is the hallmark of distributive shock, seen in conditions like sepsis, anaphylaxis, and neurogenic shock.

The described mechanism matches this pattern: widespread dilation of the blood vessels leads to blood pooling in the vascular beds, creating the perfusion problems characteristic of distributive shock. The other options point to different shock types or consequences—cardiogenic shock from impaired heart pumping, hypovolemic shock from severe blood loss, or vasodilation effects that don’t capture the systemic pooling aspect.