Transcranial Doppler microembolus detection in the identification of patients at high risk of perioperative stroke

Objectives: Perioperative ischaemic stroke is the leading cause of morbidity and mortality associated with carotid endarterectomy (CEA). The aim was to test the hypotheses that the detection of microembolic ultrasonic signals (MES) with transcranial Doppler ultrasound (TCD) during and after the operation may be of value in identifying patients at increased perioperative stroke risk. Design: Open prospective case series. Patients and Methods: Eighty-one consecutive patients undergoing CEA with TCD monitoring. Preoperative, intraoperative and interval postoperative TCD monitoring of the middle cerebral artery (MCA) ipsilateral to the operated carotid artery. On-line pre-and intraoperative MES counting and blinded off-line analysis of postoperative MES counts. End-points were any focal neurological deficit and death at 30 days postoperatively. Results: MES were detected in 94% of patients intraoperatively and 71% of cases during the first postoperative hour. MES counts ranged from 0 to 25 per operative phase (range of median counts 0-8) and from 0 to 212 per hour postoperatively (range of median counts 0-4). Eight cases (10%) developed postoperative MES counts greater than 50/h. Five of these eight cases evolved ischaemic neurological deficits in the territory of the insonated MCA, indicating a strong association between frequent postoperative microembolism and the development of early cerebral ischaemia (chi(2)=34.2, p<0.0001). Intraoperative MES were not associated with clinical outcome measures. Conclusions: MES counts of greater than 50/h in the early postoperative phase of carotid endarterectomy are predictive of the development of ipsilateral focal cerebral ischaemia.