| Summary: | A major cause of perioperative strokes during carotid endarterectomy is intraoperative embolisation. Previous studies have identified that intraoperative embolisation can be detected by monitoring with transcranial Doppler sonography (TCD). However, these studies were unable to demonstrate a convincing link between embolisation and the development of neurological deficits and therefore, the clinical relevance of these TCD detected emboli remained uncertain. This study aimed to accurately determine the incidence and clinical relevance of TCD detected intraoperative embolisation during carotid endarterectomy. To do this 100 consecutive patients undergoing carotid endarterectomy were monitored with TCD. To assess the clinical impact of intraoperative embolisation all patients underwent the following pre- and postoperative assessments; neurological and cognitive function; retinal fundoscopy and automated visual fields; CT and MRI brain scans. During analysis of the intraoperative TCD recordings the operation was divided into its constituent stages and for each stage the number and character of emboli were determined. It was found that the majority of intraoperative emboli were characteristic of air and not associated with an adverse clinical outcome. However, emboli occurring during the dissection and recovery stages of the operation were characteristic of particulate emboli and associated with the development of neurological and cognitive deficits. In particular, gross, persistent particulate embolisation during the recovery phase of the operation heralded early carotid artery thrombosis and was associated with the development of major neurological deficits. The TCD detection of particulate emboli occurred before the development of neurological signs and with early operative intervention to correct the defect, neurological deficit could be avoided. This finding represents an important new clinical application of TCD monitoring and provides direct clinical evidence for the role of platelet emboli in the aetiology of stroke. The second part of the study was concerned with comparing methods of quality control to detect technical defects which may lead to embolisation. The techniques compared were Angioscopy, B-mode ultrasound, continuous wave Doppler and TCD. Angioscopy detected major technical errors in 12 patients (4 intimal flaps, thrombus in 8). TCD detected shunt malfunction in 13 patients (2 potentially serious) in addition to particulate embolisation detected during dissection and recovery. Continuous wave Doppler and B-mode ultrasound images were technically inadequate in 9 and 24 patients respectively and neither technique altered clinical management. Therefore it was concluded, that a combination of TCD monitoring and completion angioscopy provided the maximum yield in terms of diagnosing technical error and establishing the cause of perioperative morbidity and mortality.
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