The significance of microemboli detection by means of transcranial Doppler ultrasonography monitoring in carotid endarterectomy.

PURPOSE Carotid endarterectomy (CEA) performed with continuous transcranial Doppler monitoring provides a unique opportunity to determine the number of cerebral microemboli and to relate their occurrence to the surgical technique. The purpose of this study was to assess in CEA the impact of cerebral microembolism on clinical outcome and brain architecture. We also evaluated the influence of the audible transcranial Doppler signal on the surgeon and his or her technique. METHODS In a prospective series of 301 patients, CEA was monitored with electroencephalography and transcranial Doppler ultrasonography of the ipsilateral middle cerebral artery. Preoperative and intraoperative risk factors were entered in a logistic regression analysis program to assess their correlation with cerebral outcome. To evaluate the impact of cerebral microembolism on brain architecture, we compared preoperative and postoperative computed tomography scans or magnetic resonance images of the brain in two subgroups of 58 and 40 patients, respectively. RESULTS Seven (2.3%) patients had intraoperative transient ischemic symptoms, three (1%) had intraoperative strokes, 1 (0.3%) had transient ischemic symptoms after operation, and 10 (3.3%) had postoperative strokes. Four (1.3%) patients died. Microemboli (> 10) noticed during dissection were related to both intraoperative (p < 0.002) and postoperative (p < 0.02) cerebral complications. Microemboli that occurred during shunting were also related to intraoperative complications (p < 0.007). Microembolism never resulted in new morphologic changes on postoperative computed tomography scans. On the contrary, the phenomenon of more than 10 microemboli during dissection was significantly (p < 0.005) related to new hyperintense lesions on postoperative T2-weighted magnetic resonance images. CONCLUSIONS During CEA the presence of microembolism (> 10 microemboli) during dissection shows a statistically significant relationship with perioperative cerebral complications and with new ischemic lesions on magnetic resonance images of the brain. Moreover, microembolism during shunting is also related to intraoperative complications. Surgeons can be guided by the audio Doppler and emboli signals by changing their technique. This change may result in a decrease of microembolism and consequently in a decline of the intraoperative stroke rate.