Selection of the source of mixed venous blood samples in severely traumatized patients.

The technic of balloon flotation catheterization represents a significant advance in providing an additional aid to diagnosis, clinical assessment, and management of the critically ill. The fact that such patients are admitted to an intensive care unit (ICU) invariably presumes that their management will include close and accurate monitoring of the cardiovascular and respiratory systems. In a prospective study of 51 patients, not in clinical shock, in an ICU, the authors demonstrated that superior vena cava samples are not a reliable index of mixed venous blood saturation in the critically injured patient, and that a pulmonary arterial catheter is essential for obtaining true mixed venous samples for valid estimations of intrapulmonary shunts and arteriovenous O2 content differences.