Critical Care Registered Nurse (CCRN) Practice Exam

Neurogenic shock primarily results from the loss of sympathetic tone due to disruption of the autonomic nervous system, typically following a spinal cord injury. In this state, there is unopposed parasympathetic activity, which leads to widespread vasodilation. As a result, the peripheral blood vessels dilate, causing a decrease in systemic vascular resistance and, consequently, hypotension. This vasodilation contributes to inadequate perfusion and oxygen delivery to vital organs, manifesting as signs and symptoms of shock.

The other options refer to conditions that can result in shock but do not specifically address the mechanisms involved in neurogenic shock. Increased blood volume generally does not cause shock; instead, it is associated with conditions like hypervolemia. Myocardial infarction leads to cardiogenic shock due to reduced cardiac output, and severe allergic reactions can cause anaphylactic shock through massive release of histamines and vasodilatory substances, but these mechanisms are distinct from those that define neurogenic shock. Thus, the correct answer focuses on the specific pathophysiological processes involved in neurogenic shock, emphasizing the role of sympathetic tone loss.