American Association of Critical-Care Nurses (AACN) Certification Practice Test

Which type of shock is characterized by initially high cardiac output followed by decreased cardiac output?

1. Hypovolemic shock

2. Cardiogenic shock

3. Septic shock

4. Anaphylactic shock

The correct answer is: Septic shock

Septic shock is characterized by an initial phase where the cardiac output is high, often due to systemic vasodilation and increased heart rate as the body attempts to compensate for infection and maintain tissue perfusion. During this initial response, the body releases various substances, including cytokines, which lead to vasodilation. However, as the condition progresses, factors such as myocardial depression, increased vascular permeability, and depletion of intravascular volume can result in decreased cardiac output. This progression from high to low cardiac output, coupled with other signs of organ dysfunction, is a hallmark feature of septic shock. In contrast, the other types of shock have different physiological responses. Hypovolemic shock is primarily characterized by a decrease in blood volume, leading to decreased cardiac output from the outset. Cardiogenic shock involves the heart's inability to pump effectively from the beginning, resulting in low cardiac output. Anaphylactic shock, while it also involves significant vasodilation, usually does not exhibit initial high cardiac output but rather a rapid decrease as the shock state develops. Understanding the pathophysiology of septic shock is essential for recognizing and treating it effectively.