Might right atrium oxygen saturation replace mixed venous blood saturation for hemodynamic monitoring?

Purpose: Mixed venous blood oxygen saturation should be measured in the pulmonary artery. It is an indirect index of tisular perfusion. The aim of this study is to determine whether the right atrium (RA) oxygen saturation might replace that of the pulmonary artery (PA). Methods: All patients who were admitted to the intensive care unit of the Instituto de Investigaciones Médicas "A. Lanari" and the Sanatorio Jockey Club between August and December 1996 and those who required a Swan-Ganz catheter, were included. The samples were taken in immediate succession (first PA and then RA) and the measurements were performed immediately after extraction. Results: 29 patients were included, their ages were 64.65±18.43 (range: 23 to 92) and 17 (58.62%) were male. The RA oxygen saturation was 67.46±11.38% and the PA 67.10±11.43% (t=1.54, p=0.13). Correlation of simultaneous measurements of RA and PA oxygen saturation was r=0.99 and r₂=0.98 (p<0.0001). Conclusions: we did not find any significant difference between RA and PA oxygen saturation and we found a high degree of correlation between them. Clinical Implications: Our findings suggest that the insertion of a catheter in the RA allows the monitoring of mixed venous blood saturation. The cost is lower, it does not require specialized technical support or costly equipment and complications associated with its use should be fewer.