Fragile brain is the most common phenomenon seen in the patients undergoing CEA. The patients with fragile brain have a high incidence of postoperative brain dysfunction. This study intends to apply EEG monitoring (Sedline) to CEA to investigate whether EEG monitoring can reduce the incidence of postoperative neurological complications in CEA patients and improve their prognosis.

220 patients with CEA were randomly divided into 2 groups. Group S [Sedline monitoring + Transcranial Doppler (TCD) + regional cerebral oxygen saturation (rS02)，n=110] and group C [Bispectral index (BIS)/Sedline monitoring + TCD +rSO2,n=110], recording intraoperative and postoperative conditions, neuropsychology scale assessment, blood examination and imaging examination. The incidence of postoperative neurological complications was compared between the two groups.

Inclusion Criteria:

1. Patients undergoing elective carotid endarterectomy;
2. All those who agree to join the trial and sign the informed consent form;
3. ASAI to III.

Exclusion Criteria:

1. Those who refuse to sign the informed consent form;
2. ASA Level IV and above;
3. Unstable angina or acute myocardial infarction within 4 to 6 weeks before surgery, and heart function NYHA III to IV;
4. Those with severe liver and kidney function diseases;
5. Preoperative combined cognitive impairment; [MMSE reference demarcation value: illiterate (uneducated) group ≤ 19 points, primary school (education years ≤ 6 years) group ≤ 22 points, secondary school or above (education years) 6 years) group ≤26 points; MoCA reference demarcation value: illiterate ≤13, primary school ≤19, middle school and above ≤24. ]
6. Preoperative combined anxiety and depression; (SDS or SAS>41 points)
7. Patients with an endotracheal intubation returning to the ICU;
8. severe allergic reactions, major bleeding, etc. during surgery, causing severe fluctuations in hemodynamics;
9. The subject actively requested to withdraw from the study or to be lost to follow-up.