Adequate Agreement Between Venous Oxygen Saturation in Right Atrium and Pulmonary Artery in Critically Ill Children

Objective: To determine the agreement between venous oxygen saturation in right atrium (Srao2) and pulmonary artery (Svo2) in critically ill pediatric patients.

Design: Retrospective, observational study.

Setting: Multidisciplinary pediatric intensive care unit from a general university hospital.

Patients: Thirty critically ill children in whom a pulmonary artery catheter (PAC) was inserted for catecholamine refractory shock (septic and cardiogenic, n = 18) and postoperative management (liver and cardiac transplant, n = 12).

Measurements And Main Results: Ninety measurements of Srao2 and Svo2 were obtained after placement of PAC and every 6 hrs for the first 12 hrs of pediatric intensive care unit admission. The agreement between Srao2 and Svo2 was determined through Bland and Altman methodology, concordance correlation coefficient, and the frequency of differences between Srao2 and Svo2. The frequency of differences between both saturations was evaluated in three categories: +/-1%-5%, +/-6%-9%, and higher than +/-10%. The first category was the threshold to consider both variables interchangeable. Changes of Srao2 related to clinically significant (>5%) increases and drops of Svo2 were analyzed. Srao2 and Svo2 were not significantly different: median (interquartile range) 83% (75%-86%) and 81% (75%-85%), respectively (p = 0.23). The frequency of differences between Srao2 and Svo2 was +/-1%-5%, 71 (79%); +/-6%-9%, 14 (15.5%); and higher than +/-10%, 5 (5.5%). Bland and Altman analysis showed a 2% bias with a 95% limits of agreement of -6.9% to 10.9%. The concordance correlation coefficient was 0.90. Svo2 increased in 11/90 measurements and Srao2 followed it 82% of the times. Svo2 decreased in 7/90 measurements and Srao2 followed it 100% of the times.

Conclusion: The concordance analysis performed allows to conclude that there is an appropriate agreement between Svo2 and Srao2. This finding may become clinically relevant considering the difficulties associated to the use of PAC in children.