Transcranial Doppler: preventing stroke during carotid endarterectomy.

Carotid endarterectomy (CEA) is more effective at preventing strokes than medical therapy alone in those patients with severe symptomatic stenosis of the internal carotid artery and this benefit persists despite a perioperative stroke/death rate of approximately 5%. Thromboembolism has been established as the underlying cause of the majority of perioperative strokes, but this could not be detected using the existing methods of monitoring or quality control. Early studies demonstrated that transcranial Doppler monitoring (TCD) could detect intraoperative embolism, but the clinical significance of this finding was questioned as the incidence of these emboli far exceeded the incidence of perioperative strokes. This study aimed to establish the clinical relevance of TCD-detected emboli during CEA by differentiating emboli into two broad categories; air and particulate, and comparing the quantity of each with a variety of clinical outcomes including neurological and cognitive function, retinal fundoscopy, automated visual fields and CT/MRI brain scans. This prospective study was performed on 100 consecutive patients undergoing CEA with all assessments performed pre- and postoperatively by independent specialists in the relevant fields. Embolisation was detected in 92% of successfully monitored operations. Most emboli were characteristic of air microbubbles and not associated with the development of adverse clinical events. However, emboli characteristic of particulate material were detected during the initial dissection phase and in the recovery phase after final restoration of flow. These particulate emboli were associated with the development of both neurological and cognitive deficits. In particular, persistent embolisation after final restoration of flow heralded incipient carotid artery thrombosis and the development of stroke. Early intervention based on the TCD evidence of continuing embolisation can prevent the stroke from occurring.