Inclusion Criteria:  American Society of Anesthesiologists（ASA）：II-III Aged between 40 and 80 years Patients scheduled for surgery of Carotid stenosis under general anaesthesia  Exclusion Criteria:  Has a history of mental illness can't cooperate, Serious heart block or cardiac decompensation or severe sinus slow (HR < 50 times/min), The abnormal nerve monitoring in operation, MMES preoperative score < 20 points, Any rescue unexpected occurred during the operation