Clinical Research Directory

Inclusion Criteria: 1. Age ≥60 years but \<90 years; 2. Scheduled to undergo cardiac surgery with cardiopulmonary bypass under general anesthesia; 3. Expected to stay in the intensive care unit (ICU) for at least 1 night after surgery. Exclusion Criteria: Patients who meet any of the following criteria will be excluded. 1. Refuse to participate in the study; 2. Preoperative history of schizophrenia, epilepsy, Parkinsonism, or myasthenia gravis; 3. Preoperative obstructive sleep apnea (previously diagnosed as obstructive sleep apnea, or the snoring, tiredness, observed apnea, high blood pressure-body mass index, age, neck circumference and gender \[STOP-Bang\] questionnaires ≥3); 4. Inability to communicate during the preoperative period because of coma, profound dementia or language barrier; 5. Preoperative sick sinus syndrome, severe sinus bradycardia (\< 50 beats per minute), or second-degree atrioventricular block or above without pacemaker; 6. Severe hepatic dysfunction (Child-Pugh class C); 7. Severe renal dysfunction (requirement of renal replacement therapy) before surgery; 8. Presence of delirium (diagnosed by the Confusion Assessment Method \[CAM\]/CAM for the Intensive Care Unit \[CAM-ICU\]); 9. Current treatment with dexmedetomidine or clonidine.