INTERNAL JUGULAR BULB BLOOD VELOCITY AS A CONTINUOUS INDICATOR OF CEREBRAL BLOOD-FLOW DURING OPEN-HEART-SURGERY

Background: Most techniques for measuring cerebral blood flow (CBF) ca n not be performed rapidly enough to detect sudden changes in CBF. How ever, measurement of internal jugular bulb (IJB) blood velocity may of fer real-time information on changes in CBF. In the current study, we measured IJB blood velocity and CBF in anesthetized humans. Methods: I n protocol 1, IJB blood velocity was continuously measured using an in travascular Doppler catheter during cardiac surgery under hypothermic cardiopulmonary bypass (CPB). CBF values obtained with a Kety-Schmidt method using inhalation of 30% argon in oxygen gas were compared with concurrent IJB blood velocity values in ten patients. A S-French intra vascular Doppler catheter was placed in the right IJB, and CBF measure ments were made before CPB, in a stable hypothermic period during CPB, at rewarming during CPB, and after CPB. In protocol 2, dimensions of right IJB were observed before and during CPB using an intravascular r otating A scan ultrasonic catheter (5-French) in three patients. Resul ts: IJB blood velocity responded quickly to changes in arterial pressu re or body temperature during CPB. The percent change in IJB blood vel ocity relative to pre-CPB value showed a good linear correlation with the percent change in CBF (%CBF = 0.87 X %IJB velocity + 17, r = 0.87) . The mean difference between percent changes in CBF and IJB blood vel ocity was -5.6% and the standard deviation was 16%. Despite a large re duction in arterial pressure or IJB pressure, there were no significan t changes in the IJB dimension. Conclusions: The results suggest that IJB blood velocity may represent a clinically useful monitor of change s in CBF in anesthetized humans.