National Physical Therapy Examination (NPTE) Practice Exam

Which laboratory value would be the most significantly affected in a patient with burns covering over 25 percent of their body surface area and exhibiting hypovolemia?

1. Hematocrit

2. Erythrocyte sedimentation rate

3. Oxygen saturation rate

4. Prothrombin time

The correct answer is: Hematocrit

In a patient with burns covering over 25 percent of their body surface area who is also exhibiting hypovolemia, the hematocrit value would be the most significantly affected. This is primarily due to the loss of fluid from the vascular system into the burned areas and the development of edema, leading to a state of hypovolemia. As the plasma volume decreases relative to the number of red blood cells, the concentration of red blood cells in the remaining plasma increases, causing a rise in hematocrit levels. This scenario describes a classic response to significant fluid loss, where the body's compensatory mechanisms result in an elevated hematocrit as it tries to maintain oxygen delivery despite a reduced blood volume. The other laboratory values mentioned would not show a direct or significant change under these circumstances. For instance, the erythrocyte sedimentation rate could be elevated due to inflammation but wouldn't provide immediate insight into the hypovolemic status or fluid loss from burns. Oxygen saturation rate, while an important measure of respiratory function, may remain stable unless respiratory distress occurs. Prothrombin time indicates coagulation status, which may not be as immediate or relevant in the context of acute hypovolemia due to burns. Thus, in the