Venous oxygen content measures how much oxygen remains in the blood after tissues have extracted what they need, and low values can signal poor oxygen delivery or high tissue demand.
Normal — mixed venous oxygen reserve intact.
Mildly low — watch delivery vs. demand.
Moderately low — increased extraction or falling delivery.
Severely low — supply/demand mismatch.
Given: Hgb 15 g/dL, SvO₂ 72%, PvO₂ 40 mmHg.
14.50.12Venous blood still carries oxygen — the amount reflects the balance of supply and demand.
Either the body isn't delivering enough oxygen, or the tissues are extracting unusually more than normal — as happens with fever, sepsis, shivering, or seizures. It's a red flag that oxygen supply and demand are out of balance.
Roughly 14–15 mL of oxygen per deciliter, corresponding to a mixed venous saturation (SvO₂) of about 70–75%.
CaO₂ is arterial content — oxygen before tissues use any. CvO₂ is what's left in venous blood after extraction. The gap between them reflects how much oxygen the tissues consumed.
True mixed venous saturation comes from a pulmonary artery catheter. A central venous sample (ScvO₂) is a commonly used approximation that runs a few percent higher.