Is transcranial Doppler effective in avoiding the hazards of carotid surgery?

The middle cerebral artery flow velocities were measured to test the hypothesis that transcranial Doppler is a useful technique for intraoperative monitoring in 50 consecutive carotid endarterectomies which were performed under local anaesthesia. The patients' neurological status was continuously monitored. The peak middle cerebral artery velocities were measured before clamping, during clamping and after restoration of flow, and again 24 h and 4 weeks later. Clamping produced a decrease in the velocity of the middle cerebral artery, from 97 to 45 cm/s (P < 0.001). Neurological manifestations occurred in eight patients; one patient lost consciousness, and seven experienced transient focal deficits during the procedure. Another three (6%) developed minor strokes postoperatively. The velocity changes were similar in those who developed complications to those who did not. These results do not support the view that transcranial Doppler monitoring is helpful in deciding whether to use a shunt during carotid endarterectomy. Further data are needed to evaluate the importance of transcranial Doppler monitoring during carotid surgery.