What is a primary cause of neurogenic shock?

A primary cause of neurogenic shock is CNS injury or spinal anesthesia. Neurogenic shock occurs when there is a disruption in the autonomic pathways, often due to injury to the central nervous system (CNS), particularly the spinal cord. This disruption leads to an inability to maintain vascular tone, resulting in vasodilation and a significant drop in blood pressure.

In cases of spinal cord injury, especially at or above the T6 level, the sympathetic nervous system cannot exert its usual effects, leading to peripheral vasodilation. This can cause bradycardia (a slower heart rate) as the lack of sympathetic input leads to unopposed vagal activity. Similarly, spinal anesthesia can block the sympathetic outflow to the blood vessels, also resulting in hypotension and the characteristic signs of neurogenic shock.

Understanding the mechanism behind neurogenic shock highlights how it is fundamentally different from other forms of shock, such as those caused by blood loss (hypovolemic shock), pulmonary embolisms (obstructive shock), or sepsis (distributive shock due to infection). These other conditions involve different pathophysiological processes and effects on the cardiovascular system.