Mixed Venous Oxygen Tension and Hyperlactatemia

Mixed venous oxygen tension (PVo2), cardiac output (Q), and arterial oxygen tension (Pao2) were measured in 20 patients with severe cardiac or pulmonary disease or both to determine which of these variables would best predict hyperlactatemia and survival. There was no correlation between Pao2 and either hyperlactatemia or survival, possibly because all oxygen tensions were greater than 40 mm Hg. There was a good correlation between Q and both hyperlactatemia and survival, and a slightly better correlation between PVo2 and both hyperlactatemia and survival. Mixed venous oxygen tension, a reflection of both Pao2 and Q, was a better predictor of hyperlactatemia and death than either arterial Pao2 or Q alone. It is also more easily measured and, therefore, more clinically useful than either Q, as a predictor of anaerobiosis and survival, or blood lactate concentration, as a predictor of survival. A mixed venous oxygen tension below 28 mm Hg was usually associated with hyperlactatemia and was always associated with death.