What does mixed venous oxygen saturation (SVO2) reflect?

What does mixed venous oxygen saturation (SVO2) reflect?

• A. It directly measures tissue oxygen consumption.
• B. It reflects the balance between oxygen delivery and consumption.
• C. Normal range is 60%-80%, indicating the balance between oxygen delivery and consumption.
• D. It measures systemic arterial oxygen saturation.

Answer: (C)

SVO2 shows the balance between oxygen delivery to the tissues and oxygen they are consuming. It’s measured from mixed venous blood in the pulmonary artery, so it reflects global tissue oxygen extraction rather than a single organ. Normally it sits roughly in the 60–80% range, which indicates that delivery is adequate for the body's metabolic needs. If the value falls below this range, tissues are pulling more oxygen than is being delivered, signaling inadequate DO2 or increased VO2. If it rises above the range, it can mean reduced oxygen extraction or an excess of delivery, such as in sepsis with impaired cellular utilization or very high flow states. It is not a direct measure of tissue oxygen consumption, nor does it indicate arterial oxygen saturation.

SVO2 shows the balance between oxygen delivery to the tissues and oxygen they are consuming. It’s measured from mixed venous blood in the pulmonary artery, so it reflects global tissue oxygen extraction rather than a single organ. Normally it sits roughly in the 60–80% range, which indicates that delivery is adequate for the body's metabolic needs. If the value falls below this range, tissues are pulling more oxygen than is being delivered, signaling inadequate DO2 or increased VO2. If it rises above the range, it can mean reduced oxygen extraction or an excess of delivery, such as in sepsis with impaired cellular utilization or very high flow states. It is not a direct measure of tissue oxygen consumption, nor does it indicate arterial oxygen saturation.