Clinical Research Directory

Inclusion Criteria: 1. Age ≥ 65 years. 2. Scheduled for non-cardiac major surgery with general anesthesia that is expected to last more than 2h. 3. ASA Physical Status I-III. 4. Weight \>50 kg. 5. Written informed consent. Exclusion Criteria: 1. Pre-existing neuropsychiatric diseases (Alzheimer's disease, Schizophrenia, Parkinson's Disease, Seizures, etc.). 2. Pre-existing cognitive impairment (MMSE\<18). 3. Preoperative delirium. 4. Severe circulatory instability (preoperative left ventricular ejection fraction less than 30%, unstable angina, severe coronary artery disease, sick sinus syndrome, etc.). 5. Contraindication to the acetaminophen use, including serum creatinine \> 177µmol/L or aminotransferses \> 3 times the upper limit of normal. 6. Alcohol or drug abuse within a year before surgery. 7. Inability to communicate because of severe visual/auditory dysfunction or language barrier.