Transcranial Doppler in carotid endarterectomy

Purpose: To evaluate the role of transcranial Doppler monitoring in reducing the complications of carotid endarterectomy, by analysing: (1) perioperative intracerebral blood flow velocity; (2) embolic load; and (3) effect of Dextran-40 therapy on patient outcome. Design: Retrospective case series. Methods: The study cohort consisted of 30 consecutive patients undergoing 32 carotid endarterectomy procedures. Continuous transcranial Doppler (TCD) monitoring of the ipsilateral middle cerebral artery (MCA) was performed to obtain flow velocities and embolic count. Flow velocity changes were analysed in relation to electroencephalographic (EEG) changes. A Dextran-40 infusion was instituted for patients who experienced a post-arteriotomy embolic load of [50 counts/hour. Results: The average middle cerebral artery velocity (MCAvel) drop on cross clamping was 46 ± 12.1%, expressed as a percentage of the individual's 24-hour pre-operative value. Clamping ischaemia developed in six cases (18.8%) of which three (9.4%) demonstrated TCD changes only, and three demonstrated both TCD and EEG changes (9.4%). The average i ncrease in MCAvelat 60–120 minutes postarteriotomy, was 18 ± 17.5%; six cases developed hyperaemia. Postoperative emboli were seen in 88% of cases with 31% of patients demonstrating embolic loads of >50/hour. Conclusions: Perioperative transcranial Doppler monitoring (1) is a useful adjunct to EEG assessment of cross clamping ischaemia, providing information in real time, on MCA blood velocity deterioration that may antecede irreversible change (2) detects postoperative hyperaemic response, and (3) allows quantification of microembolic loads that, when high, have been shown to be a precursor to localised cerebral ischaemia and can be effectively treated with Dextran-40 infusion.