[Computation of mixed venous oxygen saturation in intracardial shunts and its dependence on age, anesthesia and premedication].

In patients with an intracardiac shunt, the oxygen saturation of the mixed venous blood cannot be measured, but it must be estimated from the oxygen saturation in the superior and in the inferior vena cava. We have evaluated the results of patients who had definitively no shunt and who had been catheterized for other reasons. Based on statistical principles we developed formulas to calculate the oxygen saturation of the mixed venous blood. We examined three group of patients: a) Children up to 11 years catheterized during general anaesthesia (58 patients) b) Children up to 11 years catheterized after premedication but without general anaesthesia (53 patients) c) Adults catheterized without general anaesthsia (59 patients) We found that the formulas from the patients who had been catheterized during general anaesthesia were quite different from those without anaesthesia. In the patients without an anaesthesia the superior vena cava was coupled with a much higher factor than the inferior vena cava; in patients with anaesthesia, the contribution of the inferior vena cava was stronger. The age of the patients had no significant influence on our formulas.