Which factor could contribute to low values of ScvO2?

Low values of ScvO2, or central venous oxygen saturation, indicate that the tissues are extracting more oxygen than what is being delivered via the blood. A significant factor that could contribute to low ScvO2 values is a decrease in cardiac output. When cardiac output is reduced, the amount of oxygenated blood reaching the tissues decreases, leading to an increased extraction of oxygen by tissues to meet their metabolic needs. This results in lower levels of oxygen remaining in the venous blood returning to the heart, thus lowering ScvO2.

In contrast, increased hemoglobin concentration and increased arterial oxygen saturation would generally support higher ScvO2 values, as they can enhance the oxygen-carrying capacity and oxygen available in the bloodstream, respectively. Normal muscle metabolism would also not contribute to low ScvO2 values, as it would indicate typical oxygen usage rather than excessive extraction. Therefore, the factor that leads to low ScvO2 is the decrease in cardiac output.