How do hypovolemic and septic shocks differ in etiology and hemodynamics?

• A. Hypovolemic: due to volume loss; septic: due to infection causing vasodilation and poor perfusion
• B. Both due to infection causing vasodilation
• C. Hypovolemic due to infection; septic due to dehydration
• D. Septic shock is a type of obstruction to blood flow

Answer: (A)

Understanding how the cause of shock shapes the circulation is what this item tests. Hypovolemic shock occurs when there is a significant loss of circulating volume, such as from bleeding or severe dehydration. With less blood returning to the heart (reduced preload), the heart pumps less blood each beat, so stroke volume and overall cardiac output fall. In response, the body increases sympathetic tone, raising systemic vascular resistance to help maintain blood pressure. The result is low preload and low output, with the circulatory system trying to compensate by constricting vessels.

Septic shock, brought on by infection, involves a different problem: widespread inflammation that causes vasodilation and leaking of fluid from the vessels. This vasodilation lowers systemic vascular resistance and can cause perfusion to be inadequate even if total blood volume is normal or high. Early in septic shock, cardiac output may be normal or even elevated because the heart is working against a low resistance (afterload), but as the condition progresses, myocardial function can deteriorate and perfusion worsens. The key contrast is volume loss driving low preload in hypovolemia, versus infection-driven vasodilation and distributive failure in sepsis.

So the best description is that one is due to volume loss causing reduced preload and output with compensatory vasoconstriction, while the other is due to infection causing vasodilation and poor perfusion with variable effects on cardiac output.