BACKGROUND: Mixed venous oxygen saturation (SO2) monitoring turned out to be invaluable in following up systemic cardiovascular status. But balloon-tipped flow-directed thermodilution catheter (Swan-Ganz catheter) insertion carries additional inherent risks other than those of central venous catheterization, and it costs much more expense than simple venous catheter. There has been a lot of papers which argue that central venous catheterization may substitute for the Swan-Ganz catheterization. In addition, it may be very difficult or impossible to insert the Swan-Ganz catheter in pediatric patients. This study was performed to determine whether Swan-Ganz catheterization might be replaced by the central venous catheterization in regards to SO2. METHODS: In 17 pediatric open heart surgery (OHS) patients, from the central venous catheter, the tip of which had been located in the center of right atrium (RA) and pulmonary artery, blood samples were drawn for gas analysis simultaneously, which was done immediately after emergence from cardiopulmonary bypass. RESULTS: There were no significant differences between RA blood and mixed venous blood gas analyses except oxygen saturation. The oxygen saturations of both were linearly correlated with each other. The relation was SO2=17 0.8 SRAO2 (R=0.77, p<0.05) CONCLUSIONS: It may be concluded that RA blood may be used for blood gas analysis in place of mixed venous blood immediately after pediatric open heart surgery.