What is a primary cause of shock in casualties?

Severe blood loss is a primary cause of shock in casualties because it significantly reduces the volume of circulating blood, which is critical for delivering oxygen and nutrients to vital organs. When a person experiences significant hemorrhage, the body cannot maintain an adequate blood pressure, leading to inadequate perfusion of tissues. This state, known as hypovolemic shock, can quickly become life-threatening if not addressed promptly.

The body attempts to compensate for this loss by increasing heart rate and constricting blood vessels to maintain perfusion to essential organs. However, if the blood loss is not stopped, and fluids are not replaced, this compensatory mechanism will eventually fail, leading to multi-organ failure and potentially death. In the context of Tactical Combat Casualty Care, rapid control of bleeding is essential to prevent shock and improve survival outcomes.

While the other options can also lead to shock, severe blood loss represents a more immediate and frequent cause in casualty situations, particularly in combat settings.