The role of intraoperative transcranial Doppler monitoring in carotid artery surgery.

Of 135 carotid artery reconstructions performed under general anesthesia in 127 patients (mean age 68 years), 119 were performed with continuous intraoperative Doppler recording of the middle cerebral artery. This investigation was impossible in nine (6.7%) cases because of the absence of a visible temporal window, and results were deemed uninterpretable in six (4.5%) additional cases. The goals of this study were to test the feasibility and reliability of transcranial Doppler monitoring in the evaluation of intracranial perfusion and to determine the risk of cerebral ischemia during carotid artery clamping. The two outcome parameters measured were mean velocity and percentage of decreased flow in the middle cerebral artery during clamping. Patients were divided into four groups based on variations in these parameters. Groups I and IIA (low risk) represented 69.7% of cases, group IIB (significant risk) represented 21.9%, and group III (major risk) represented 8.4%. Transcranial Doppler monitoring appears to be a reliable means of observing middle cerebral artery flow during carotid surgery and in our opinion provides objective criteria for determining the need for an indwelling shunt. Accordingly, in this study no neurologic complications imputable to clamping were observed. Transcranial Doppler monitoring can also be used to ensure correct functioning of the shunt and to detect intraoperative embolic complications.