Carotid endarterectomy monitored with transcranial Doppler.

Intraoperative transcranial Doppler monitoring of cerebral ischemia during carotid clamping under general anesthesia was done in 238 carotid artery operations, mostly endarterectomy. Depending on the severity of reduction of middle cerebral artery mean velocity, patients were classified as no, mild, or severe ischemia at clamping. With a carotid shunt, velocity was always in the "no ischemia" category during shunting. For patients with no ischemia, stroke was significantly lower without a shunt (2/175 no shunt versus 2/12 shunt). For mild ischemia, shunting did not affect the stroke rate (1/20 no shunt versus 0/9 shunt). For severe ischemia, strokes were less frequent with a shunt (4/9 no shunt versus 0/13 shunt). Intraoperative electroencephalogram predicted most, but not all severely ischemic cases. Carotid back pressure correlated with Doppler velocity, but transcranial Doppler was more helpful. Transcranial Doppler is a new and valuable technique in carotid surgery.