[The oxygen saturation of blood in the venae cavae, right-heart chambers, and pulmonary artery, comparison of formulae to estimate mixed venous blood in healthy infants and children (author's transl)].

For the localization and quantification of arterio-venous shunts of the heart and great vessels, accurate definition of the degree of oxygen saturation of venous blood in the venae cavae, right heart and pulmonary artery is essential. Hitherto only a few investigations in a small number of healthy subjects were published. Extensive investigations to define normal mixed venous blood in infants and children are unknown. This presentation is an analysis of the data on oxygen saturation of venous blood in 305 healthy children or patients with insignificant cardiac defects. Shunt lesions were excluded. A comparison of several formulae used to estimate the oxygen saturation of mixed venous blood from caval samples has been made. The sources of error in the estimation of mixed venous blood and the implications for the calculation of the shunt-volume are investigated in 122 patients without cardiac defects. The mean oxygen saturation from the right ventricle most nearly approached the mean oxygen saturation of the pulmonary artery whereas high inferior vena cava saturations correlated poorly with mixed venous blood. Superior vena cava, the mean oxygen saturation of the right atrium and the formula 3 x SVC + HIVC divided by 4 = MVB (where SVC is superior vena cava, HIVC is high inferior vena cava MVB is and mixed venous blood) gave a satisfactory regression and have nearly the same value for prediction of mixed venous blood.