Transcranial Doppler intraoperative monitoring during carotid endarterectomy: experience with regional or general anesthesia, with and without shunting.

To determine whether continuous transcranial Doppler (TCD) can significantly alter therapeutic conduct during carotid endarterectomy, a retrospective study of 117 carotid endarterectomies was done. There was no perioperative mortality; one perioperative stroke was recorded in a patient who was symptomatic preoperatively. Continuous TCD of the ipsilateral middle cerebral artery (MCA) was attempted in 99 cases, and successful in 90; nine patients (9.1%) had inadequate temporal windows for MCA access. MCA velocities and emboli were recorded before and during carotid cross-clamping, and on clamp release. There were no significant velocity differences between the patients with regional and general anesthesia, and patients with and without carotid shunts, but there was a statistically significant difference in the total number of emboli (air and particulate transients) noted for the shunted and nonshunted patients after clamp release: 12.7 versus 23.6, respectively (p = 0.05). There was no significant difference when particulate and air microemboli were compared. During surgery TCD identified residual flow of less than 40% in the MCA in 17 patients (18.8%). TCD also identified hyperperfusion in two patients, shunt abnormalities in three patients, and influenced postop treatment in four patients, one of whom was returned to surgery. TCD is an important tool for identifying patients who would benefit from a shunt, preventing hyperperfusion, identifying postop emboli, and detecting technical errors.