Continuous measurement of changes in internal carotid and vertebral arterial blood flow with chronically implanted ultrasonic Doppler probes in anesthetized and conscious rabbits

Chronically implanted ultrasonic Doppler flowmeters were used to obtain simultaneously recorded flow velocity signals from internal carotid and vertebral arteries, and the sagittal sinus, in rabbits. All three signals increased to 144 +/- 7-215 +/- 35% of baseline during hypercapnia (arterial Pco2 55 mmHg) in both anesthetized and conscious animals. During the period of change in inspired CO2, the relationship between simultaneously recorded mean internal carotid and mean sagittal sinus signals was linear, with the correlation ranging from 0.83 to 0.96. Since forebrain arterial inflow must approximate forebrain venous outflow, the high correlation between internal carotid and sagittal sinus signals indicates that these measures provide reliable and valid indices of cerebral blood flow (CBF). Vertebral and internal carotid angiography confirmed the location of Doppler probe. Chronically implanted ultrasonic Doppler flowmeters can, thus, provide continuous noninvasive measurements of cerebral arterial flow in both anesthetized and conscious rabbits.