Comparison of Central Venous to Mixed Venous Oxygen Saturation in Patients With Low Cardiac Index and Filling Pressures After Coronary Artery Surgery

Abstract

To evaluate the correlation and agreement between mixed venous oxygen saturation (SvO(2)) and central venous oxygen saturation (ScvO(2)) in patients with low cardiac index and filling pressures after coronary artery surgery. Prospective observational study. Tertiary care academic hospital. Sixty consecutive patients with a cardiac index <2 L/min/m(2) and a pulmonary artery occlusion pressure <12 mmHg after coronary artery surgery were included. Patients were monitored by a pulmonary artery catheter and a central venous catheter positioned in the superior vena cava. SvO(2) and ScvO(2) were simultaneously measured before (T0) and after (T1) normalization of the cardiac index (>2.5 L/min/m(2)) by fluid therapy. Sixty pairs of measures were obtained at T0 and at T1. Bias between SvO(2) and ScvO(2) was -0.6% (T0) and -0.8% (T1). Limits of agreement were from -19.2% to 18% (T0) and from -15.6% to 14% (T1), and the correlation coefficient was 0.463 (T0) and 0.72 (T1). SvO(2) and ScvO(2) changes from T0 to T1 (DeltaSvO(2) and DeltaScvO(2)) were calculated. The bias between DeltaSvO(2) and DeltaScvO(2) was -0.25. Limits of agreement were from -20% to 19.5%, and the correlation coefficient was 0.6. In patients with low cardiac index and filling pressures after coronary artery surgery, ScvO(2) could not be used as a direct alternative for SvO(2). After fluid therapy and normalization of the cardiac index, differences between individual values remained large, and the disagreement between ScvO(2) and SvO(2) changes was significant.