CEREBRAL VENOUS OXYGEN-SATURATION IS NO I NDICATOR OF CEREBRAL BLOOD-FLOW

The arteriovenous oxygen content difference (avDO(2)) of the brain is dependent on O-2 consumption (CM-RO(2)) and cerebral blood flow (CBF), With unchanging arterial O-2 content, avDO, is inversely related to c erebral venous O-2 saturation (SO2), Measurement of SO2 in the jugular bulb not only provides information about the O-2 balance of the brain , but may give an important estimation of CBF if a clinically useful c orrelation is proven. The aim of the present study was to verify this aspect. Methods, Sixty-two male patients undergoing coronary revascula risation were investigated. The study was approved by the local Ethica l Committee and each patient gave written informed consent on the preo perative day, At four points during the perioperative course arterial and cerebral venous SO2 and CBF were measured. Cerebral venous blood w as sampled from a catheter in the superior bulb of the right internal jugular vein, CBF was measured using the argon wash-in technique. All sampled data were pooled and evaluated, Results. As expected from theo ry, cerebral venous SO2 and avDO(2) showed a close linear relationship (r=-0.892). However, only a weak hyperbolic relationship was found be tween cerebral venous SO2 and CBF, In addition, no direct correlation between CMRO(2) and SO2 in the jugular bulb could be demonstrated, Con clusions, In this clinical study, a close relationship between cerebra l venous SO2 and CBF was not found, This was primarily due to the high variability of cerebral O-2 uptake, Changes in cerebral venous SO2 ma y therefore not be used as an estimate of perioperative changes in CBF .