Relation between caval and pulmonary artery oxygen saturation in children.

The flow relation between that in the superior vena cava and inferior vena cava was studied in order to estimate the oxygen saturation of mixed venous blood in connection with heart catheterisation of children between the ages of 5 and 8 years without cardiac shunts. The investigation includes a group of 19 children examined during halothane anaesthesia and a group of 40 examined under local anaesthesia. The groups were comparable in respect of age and body surface. The results show that the oxygen saturation of mixed venous blood (MVB) is higher under general anaesthesia than during local anaesthesia, and that the oxygen saturation in the former group is highest in the superior vena cava (SVC) and lowest in the inferior vena cava (IVC), while the reverse is the case during examination under local anaesthesia. Based on multiple regression analysis, it is advisable, for children between the ages of 5 and 8 years, to use the formula MVBcalc = -0.85 + 0.81 SVC + 0.18 IVC for the estimation of the oxygen saturation in the mixed venous blood in children under general anaesthesia and the formula MVBcalc = 10.21 + 0.52 SVC + 0.34 IVC for children during local anaesthesia. When estimating mixed venous blood in younger children and during general anaesthesia or both, more emphasis should be laid on the flow through the superior vena cava.