American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What is the typical mVO2 status in hypovolemic shock?

1. High

2. Low

3. Normal

4. Variable

The correct answer is: Low

In hypovolemic shock, there is a significant reduction in circulating blood volume, often due to factors such as hemorrhage or fluid loss. This decreased volume leads to decreased venous return, which in turn affects cardiac output. As a result, there is insufficient oxygen delivery to tissues. The term mVO2 refers to mixed venous oxygen saturation, which reflects the balance between the delivery of oxygen and the consumption of oxygen by tissues. In the state of hypovolemic shock, the body prioritizes blood flow to vital organs, but with reduced perfusion pressure and cardiac output, tissues may not receive enough oxygen to meet their metabolic requirements, resulting in an overall decrease in oxygen consumption at the tissue level. Consequently, mixed venous oxygen saturation tends to be low in this condition, as there is a larger difference between the oxygen being delivered and the amount being consumed. Thus, a low mVO2 status accurately reflects the physiological derangement associated with hypovolemic shock, indicating inadequate tissue perfusion and oxygenation.