What causes hypovolemic shock in burn patients?

Hypovolemic shock in burn patients primarily results from third spacing of fluids. When a patient suffers from burns, particularly severe ones, the body's normal regulatory mechanisms for fluid balance are disrupted. The damaged skin and underlying tissues lose their ability to contain fluids, leading to significant shifts of plasma and interstitial fluid from the intravascular space into the surrounding tissues — a process referred to as third spacing.

This fluid loss from the circulatory system reduces the overall blood volume available, which directly impacts circulation and can lead to inadequate perfusion of organs. As the intravascular volume decreases, the heart has less blood to pump, ultimately manifesting in symptoms of hypovolemic shock, such as low blood pressure, increased heart rate, and signs of tissue hypoperfusion.

In contrast, while excessive fluid loss through sweating, inadequate blood flow, and internal bleeding may also contribute to shock in different medical scenarios, they are not the primary factors concerning burns specifically. The dynamics of fluid loss in burns are markedly different due to the extensive damage to the skin and its ability to regulate fluid retention.