Relation Between Mixed Venous Oxygen Saturation and Cerebral Oxygen Saturation Measured by Absolute and Relative Near-infrared Spectroscopy During Off-pump Coronary Artery Bypass Grafting.

In this clinical study the investigators compared mixed venous oxygen saturation (SmvO2) with relative and absolute cerebral oxygen saturation (rScO2) measurements. They hypothesized that previously reported contradictory results regarding the equivalence of SmvO2 and rScO2 might be related to time delay issues and to the measurement technology. 42 consenting patients undergoing elective off-pump coronary artery bypass grafting were included. 4 disposable oxygenation sensors were applied bilaterally on the patient's forehead for continuous, non-invasive registration of rScO2. The sensors of one monitor were placed just above the eyebrows, and the sensors of the other monitor were placed just above the former sensors. The sensors placement was determined at random by a computerized randomization list. SmvO2 was measured continuously via a pulmonary artery catheter. All variables were recorded continuously. The study ended at the end of the operation.