The application of somatosensory evoked potential combined with transcranial Doppler ultrasound monitoring in carotid endarterectomy

Objective To explore the application value of combined monitoring of somatosensory evoked potential (SEP) and transcranial Doppler ultrasound (TCD) in carotid endarterectomy (CEA). Methods We retrospectively enrolled 50 patients with carotid stenosis who underwent CEA at Department of Neurosurgery, Chengde Central Hospital from January 2015 to January 2018. SEP and TCD were used in combination to record changes in N20 amplitude of SEP and blood flow velocity in the middle cerebral artery (MCA) by TCD monitoring. Whether or not to perform a bypass procedure was decided based on the monitoring results which was also used to judge whether the open carotid artery developed restenosis and assess the high brain perfusion. The data of the two monitoring methods were recorded during the operation and comparative analysis was performed. Results Intraoperative SEP monitoring results showed that 2 cases met the standard of bypass and then underwent intraoperative transferring. TCD monitoring showed that 8 cases reached the standard of bypass and included the above-mentioned 2 cases. The difference in the rate of conversion to standard was statistically significant using SEP (4.0%, 2/50) and TCD (16.0%, 8/50) (χ2=4.000, P=0.046). In those 2 patients whose monitoring results showed that they did not meet the standard of bypass, after opening blocked carotid artery in the operation, TCD monitoring showed severe restenosis or reocclusion, and the thrombus was opened again during the operation. However, there was no positive findings in SEP monitoring during this process. In 2 case with open-blocking carotid artery, whose data in both monitoring showed that they did not meet the standard of bypass, high perfusion was revealed by TCD, and no positive findings were found in SEP monitoring. There was no cerebral infarction, cerebral hemorrhage, hyperperfusion or death in 50 patients within 30 days after CEA. CT angiography results showed no carotid stenosis in this series. Conclusions The combined monitoring of SEP and TCD seems to have a high clinical value in CEA. The former may be more advantageous in making choice of intraoperative bypass. The latter may be more valuable in detection of severe restenosis or recurrent hyperperfusion after opening the carotid artery. Key words: Endarterectomy, carotid; Monitoring, intraoperative; Ultrasonography, Doppler; Evoked potential