The aim of this multicenter, prospective, randomized, double-blind and large sample study is to explore the preventive effect of low-dose droperidol on POD in elderly patients after non-cardiac surgery, providing new approach for reducing the incidence of POD and improving the prognosis and quality of life.

Inclusion Criteria:

• Age≥65 years
• American Society of Anesthesiologists (ASA): I-III
• Planning to undergo elective non-cardiac surgery under general anesthesia with endotracheal intubation, including digestive, orthopedic, urologic and gynecological surgery
• Estimated operation time more than 2 hours
• Not expected to be admitted to ICU postoperatively
• Proficient in Chinese
• Informed consent

Exclusion Criteria:

• Morbid obesity with BMI >35 kg/m2;
• History of psychological and neurological diseases, such as depression, schizophrenia, epilepsy, severe central nervous system depression, Parkinson's disease, Alzheimer's disease, myasthenia gravis, basal ganglia disease, etc;
• Corrected QT (QTc) of electrocardiogram> 500ms;
• Preoperative liver insufficiency (Child Pugh grade C);
• End-stage renal disease requiring dialysis;
• Severe heart failure [Metablic equivalent (METs)<4];
• Allergic to droperidol;
• Inability to communicate due to coma or dementia in preoperative period;
• Preoperative delirium, assessed by 3D-CAM;
• More than three standard alcoholic drinks per day (≈10 g alcohol , equivalent to 50 g of strong Chinese spirits);
• Participating in conflicting clinical trials;
• Expected to have an additional operation within 7 days after the index operation.