Internal jugular bulb blood velocity as a continuous indicator of cerebral blood flow during open heart surgery

Most techniques for measuring cerebral blood flow (CBF) can not be performed rapidly enough to detect sudden changes in CBF. However, measurement of internal jugular bulb (IJB) blood velocity may offer real-time information on changes in CBF. In the current study, we measured IJB blood velocity and CBF in anesthetized humans.

In protocol 1, IJB blood velocity was continuously measured using an intravascular 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 3-French intravascular Doppler catheter was placed in the right IJB, and CBF measurements 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 rotating A scan ultrasonic catheter (5-French) in three patients.

IJB blood velocity responded quickly to changes in arterial pressure or body temperature during CPB. The percent change in IJB blood velocity 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 velocity was -5.6% and the standard deviation was 16%. Despite a large reduction in arterial pressure or IJB pressure, there were no significant changes in the IJB dimension.

The results suggest that IJB blood velocity may represent a clinically useful monitor of changes in CBF in anesthetized humans.