Serum lactate poorly predicts central venous oxygen saturation in critically ill patients: a retrospective cohort study.

Lactate can predict ScvO2 when patients are at or below the critical oxygen delivery threshold, but relatively few shock patients meet this criterion. In the overall population of critically ill patients, serum lactate predicts ScvO2 poorly, even after controlling for factors that may affect lactate production. Lactate and ScvO2 should not be assumed to be interchangeable markers of tissue oxygenation/perfusion.