Postoperative cognitive dysfunction (POCD) is a common complication of cardiac surgery, mainly manifested as mental confusion, anxiety, personality change and memory impairment, which seriously affects the quality of life of patients after surgery.Attention should be paid to the protection of neurological function in patients undergoing cardiac surgery during perioperative period.Nicardipine can selectively act on coronary arteries and cerebral vessels, increase coronary artery and cerebral blood flow, relieve coronary heart disease angina pectoris, protect brain tissue.The cerebral protective effect of nicardipine on cardiovascular surgery under CPB deserves further clinical study.About 15-20% of cardiac output (CO) in healthy adults is allocated to the brain , and cerebral blood flow is supplied by bilateral internal carotid artery (ICA) and vertebral artery (VA), among which ICA provides about 70%-80% of cerebral perfusion flow .However, the location of the internal carotid artery is superficial, the anatomical variation is less, and the ultrasonic Doppler technique is portable and simple to measure. It may be of certain clinical value to use the ultrasonic detection technology to quickly evaluate the cerebral perfusion during the perioperative period, and to early detect and avoid the intraoperative brain function injury.

Patients who were scheduled to undergo open-heart surgery under cardiopulmonary bypass were randomly divided into nicardipine group (group N) and normal saline control group (group C) by the digital table method. Group N was pumped with nicardipine 0.2-0.5μg/(kg·min) after CPB, while group C was given the same volume of normal saline. The basic hemodynamic parameters, rScO2, BIS, maximum systolic velocity of internal carotid artery (PSV-ICA), end-diastolic velocity of internal carotid artery (EDV-ICA), diameter of internal carotid artery (D-ICA), internal carotid artery blood flow (Q-ICA) and cerebral blood flow ratio (CBF/CO) were observed and recorded in the two groups at each time point ), cerebrovascular resistance (CVR) and the concentration of NSE, a biomarker of brain injury.The following hypothesis is proposed: during CPB, pump nicardipine can dilate the internal carotid artery and cerebral arterioles, increase cerebral blood flow, improve cerebral oxygen supply, and reduce the risk of postoperative cognitive dysfunction（POCD）.

Inclusion Criteria:

• 1: Age 60-80

  2: ASA Ⅱ-Ⅲ, NYHAⅠ-Ⅲ, EF ≥50%

  3: CABG under cardiopulmonary bypass

Exclusion Criteria:

• 1: Patients who had second heart surgery

  2: Patients with intellectual disabilities, deafness or other impairments in normal communication

  3: Previous neurosurgical procedures and history of cerebral infarction

  4: cancer

  5: Patients with moderate to severe carotid artery stenosis before operation

  6: Patients with obvious abnormal liver and kidney function affecting drug metabolism

  7: Patients taking psychotropic drugs

  8: Alcoholism, drug addiction, drug dependence

  9: The cardiopulmonary bypass time was greater than 120 minutes