Application Of Different Parameters Of Transcranial Doppler Ultrasound Monitoring In Carotid Endarterectomy

Objective: Carotid endarterectomy(CEA)is an operation featuring the resection of the thickened carotid endarterectomy,which was mainly applied to the treatment of carotid artery stenosis,so as to prevent the occurrence of ischemic stroke.As the critical step of surgery requires carotid artery occlusion,different degrees of hypoperfusion may occur after occlusion according to the different intracranial compensatory conditions of individuals.Therefore,intraoperative monitoring is needed to determine whether carotid artery shunt and other measures are necessary.However,the methods of intraoperative monitoring and the standard of intraoperative shunt are still controversial.Currently,Transcranial Doppler(TCD)is used as an intraoperative monitoring tool,and the percentage decrease of middle cerebral artery average blood flow velocity(TCD%)after carotid artery occlusion is used as the index to judge the transcranial flow.However,there are few studies on the residual value of mean flow velocity of middle cerebral artery after carotid artery occlusion(TCDmin).This study aims to use Sensory evoked potential(SEP)as the criterion to judge the brain tissue ischemia of patients,to compare the accuracy of two parameter indexes of TCD monitoring to judge the brain tissue hypoperfusion,and to explore which parameter is more suitable to be used as the index to judge the carotid artery shunt surgery.Methods: Intraoperative monitoring was conducted for patients with carotid artery stenosis who met surgical indications and finally underwent carotid endarterectomy at the Third Neurosurgery Department of Shengjing Hospital Affiliated to China Medical University from October 2020 to January 2022.According to the amplitude changes of somatosensory evoked potential after carotid artery occlusion,patients were divided into ischemia group and non-ischemia group.Transcranial Doppler ultrasound was used to record the average blood flow velocity of the middle cerebral artery on the operating side of the two groups during the operation.Mann-Whitney U test was used to compare the two indexes of median cerebral artery residual flow velocity(TCDmin)and percentage of decreased average flow velocity(TCD%)after carotid artery occlusion between the two groups,as well as the mean arterial blood pressure,heart rate,partial pressure of carbon dioxide,and arterial oxygen saturation at baseline and after carotid artery occlusion between the two groups.ROC curve analysis was used to evaluate the diagnostic efficacy of TCDmin and TCD% in determining cerebral hypoperfusion of patients,and to calculate their respective diagnostic thresholds,accuracy,sensitivity and specificity.Results: A total of 48 patients received CEA surgery,among which TCD monitoring was successfully carried out in 44 patients,SEP monitoring was successfully carried out in 44 patients,and finally 40 patients were successfully combined monitoring.After data collation,32 patients(age 64.84±5.32 years old,3 females)had high quality intraoperative monitoring data.Statistical analysis is available.Among them,5 patients whose somatosensory evoked potential N20/P25 amplitude decreased by more than 50% after carotid artery occlusion were included in the ischemia group,and the other 27 patients whose somatosensory evoked potential amplitude decreased by less than 50% after carotid artery occlusion were included in the non-ischemia group.There were significant differences in TCD%(P=0.016)and TCDmin(P=0.013)between the ischemia group and the non-ischemia group.There were no significant differences in mean arterial blood pressure,heart rate,partial pressure of carbon dioxide and arterial oxygen saturation between the two groups at baseline and after carotid artery occlusion(P > 0.05).ROC curve analysis of TCD% and TCDmin showed that the areas under the curve of TCD% and TCDmin were 0.837 and 0.841,respectively.The diagnostic thresholds were 66% and11cm/s,respectively.The diagnostic accuracy,sensitivity and specificity were TCD%90.63%,60.0% and 96.3%,respectively.TCDmin 93.75%,80.0%,96.3%.Conclusion: The decreased percentage of mean blood flow velocity(TCD%)and the residual value of mean blood flow velocity(TCDmin)of middle cerebral artery after carotid artery occlusion both had the ability to determine whether there was cerebral hypoperfusion after carotid artery occlusion.Mean residual flow velocity of middle cerebral artery(TCDmin)can be used as a reference index to judge cerebral hypoperfusion after carotid artery occlusion.Our study shows that when the median cerebral artery flow velocity is less than 11cm/s,brain tissue is hypoperfusion and carotid shunt should be performed.