Measurement of mixed venous oxygen saturation (SvO2) from the pulmonary artery is used for the calculations of the VO2 and has been advocated as an indirect index of tissue of tissue oxygenation and prognostic predictor in critically ill patients. Catheterization of pulmonary artery is costly, has inherent risks and its usefulness remains under debate. Not surprisingly the monitoring of central venous oxygen saturation (ScvO2) was suggested as a simpler and chipper assessment of global DO2 to VO2 ratio.