The DEX group will receives dexmedetomidine intraoperative.

The placebo group will receives 0.9% saline intraoperative.

Ten minutes after anesthesia induction and endotracheal intubation, patients assigned to dexmedetomidine group were given a loading dose of dexmedetomidine 0.6 μg/kg over 10 minutes, followed by continuous infusion at a rate of 0.4 μg/kg/h until the start of dural closure.

Postoperative delirium is assessed by the combination of the Richmond Anxiety Scale (RASS) and the Confusion assessment method for intensive care unit (CAM-ICU) or the 3-minute diagnostic interview for CAM (3D-CAM) as applicable.

Delirium consists of four main characteristics: acute onset of a change in mental status or a fluctuating level of consciousness, inattention, disorganized thinking and an altered level of consciousness. The patient was diagnosed as delirious if both the first and second features were present, and either the third or fourth was present.

In the ICU, the delirium assessment was performed in two steps. The arousal level was first assessed by RASS. If the patient was not responsive to verbal stimuli (i.e. RASS score ≤-4), the remaining delirium assessment was aborted, and the patient was recorded as comatose. When the RASS score was greater than or equal to 3, delirium was evaluated using the CAM-ICU. Patients in general ward were evaluated by 3D-CAM.

Numerical Rating Scales, ranging from 0 to 10 points, with 10 representing the worst imaginable pain.

Quality of sleep was assessed by the Richards Campbell sleep questionnaire (RCSQ) and with a 0-100-mm visual analog scale, with higher scores indicating better sleep quality.