Continues monitoring of SvO2 was carried aut using an Oxi metrix pulmonary arthery catheter in 12 patients undergoing aortic surgery. Hemodynamic measurements were made before skin incision (baseline values), before aortic cross clamping, after aortic declamping and postoperatively during shivering. Hemodynamic measurements were also taken whenever SvO2 changed more than 10% from baseline value. Results showed that in clinical setting, if SvO2 do not change more than 10% from baseline values, an equilibrium exists between oxygen delivery (DO2) and oxygen consumption (VO2). As DO2 and VO2 were correlate after measuring cardiac output from the same technique, a mathematical correction of a common error for linear calculations was applied. It was also concluded that changes of SvO2 greater than 10% of baseline values should prompt the assessment of hemoglobin, cardiac output, SaO2 and oxygen demand, but changes of SvO2 less than 10% of baseline value should not prompt measurements.