Effects of Esketamine on the Incidence of Postoperative Delirium and Postoperative Sleep Disturbance in Elderly Patients After Major Non-cardiac Surgery

Inclusion Criteria: 1. Age ≧ 65 years; 2. ASA Ⅰ-Ⅲ; 3. Elective major non-cardiac surgery; 4. Voluntary signed informed consent. Exclusion Criteria: 1. People with mental illness; 2. Suffering from serious central nervous system disorders such as arkinson's disease, Alzheimer's disease, etc; 3. Elevated intracranial pressure; 4. Emergency or trauma surgery; 5. Prior history of postoperative delirium or postoperative cognitive decline; 6. The patient has impaired hearing or impaired vision; 7. Suffering from severe systemic underlying diseases (e.g. cardiac insufficiency, malignant arrhythmia, malignant hypertension, hepatic failure, renal failure, etc.); 8. The patient is in chronic pain; 9. The patient is severely malnourished; 10. Patients with stage 3 or 4 malignant tumors, pancreatic cancer, allbladder cancer, cholangiocarcinoma and other tumors with high malignancy and poor prognosis. 11. history of allergy to or contraindication to esketamine; 12. inability or unwillingness to complete questionnaires or clinical testing; 13. Unable or unwilling to use a postoperative intravenous analgesic pump.