New York State Basic Emergency Medical Technician (EMT-B) Practice Exam

If a patient is experiencing shock, what physiological response primarily contributes to the condition?

1. Increased blood volume

2. Decreased cardiac output

3. Increased heart rate

4. Vasoconstriction of peripheral vessels

The correct answer is: Decreased cardiac output

The condition of shock is characterized by inadequate perfusion of tissues and organs, which can lead to cellular dysfunction and, if unaddressed, result in organ failure. A key physiological response that contributes to shock is decreased cardiac output. This occurs because the heart is unable to effectively pump enough blood to meet the body's demands, which can happen for various reasons such as loss of blood volume, pump failure, or extreme vasodilation. When cardiac output decreases, there is less blood circulating through the body, which reduces the supply of oxygen and nutrients to tissues, exacerbating the shock state. The body attempts to compensate for this by activating different mechanisms, but if cardiac output remains inadequate, shock progresses, leading to more severe consequences. While increased heart rate and vasoconstriction of peripheral vessels can occur as compensatory responses in an attempt to maintain perfusion, they do not directly contribute to shock itself. In fact, these responses aim to counteract the decreased cardiac output. Similarly, increased blood volume is generally not associated with shock; rather, shock often involves fluids being lost or inadequately pumped, leading to a decrease in effective circulating volume.