1. Title: Effect of electroacupuncture on the incidence of postoperative delirium in elderly patients undergoing the major surgery.
2. Research center: Multicenter
3. The Design of the study: Randomized, double-blind, controlled study
4. The population of the study: Elderly patients（65≤age<90 years），it is planned to select a period/time limit for gastrointestinal tumor surgery, bile duct surgery, thoracic surgery or orthopedic surgery and so on under general anesthesia, and the estimated operation time≥ 2 hours.
5. Sample size: Enroll 1100 patients (550 patients in each group)
6. Interventions: Participants in the treatment group received acupuncture (0.30mm×70mm) at bilaterally Shenmen (HT7) acupoints (0.3-0.5 inch), Neiguan (PC6) acupoints (0.5-1 inch), Baihui (DU20) acupoint (0.5-0.8 inch) and Yintang (EX-HN3) acupoint (0.3-0.5 inch) 30 minutes before anesthesia induction. After "Deqi", electroacupuncture stimulation apparatus (HANS G6805-2, Huayi Co, Shanghai, China) is connected and maintained the end of operation. Participants in the control group received shallow needling (0.30mm×25mm) at bilateral sham HT7, PC6, DU20 and EX-HN3 (nonacupoints located 1 inch beside acupoints, about 20mm). Specifically, the depth of needle insertion into nonacupoints is 3-5mm and avoided manual stimulation and no "Deqi" without actual current output.
7. The aim of the research: To investigate the effect of electroacupuncture on the incidence of postoperative delirium within 5 days in elderly patients undergoing the major surgery.
8. Outcome： 1) Primary outcome：The incidence of delirium within 5 days after surgery； 2) Secondary outcome：The effects on postoperative NRS pain and sleep quality scores；Length of stay in hospital after surgery; Incidence of postoperative complications (including re-hospitalization); 30-day life quality and cognitive function after surgery; All-cause 30-day mortality after surgery.
9. The estimated duration of the study：5 years.

This study is a multicenter, randomized, double-blinded, placebo-controlled design. In this study, bilateral Shenmen, Neiguan, Baihui and Yintang acupoints were selected for perioperative electroacupuncture treatment, accompanied with evaluating the incidence of delirium within 5 days after surgery and the effects on postoperative NRS pain and sleep quality scores. To clarify the effect of electroacupuncture on the incidence of postoperative delirium in elderly patients undergoing the major surgery is of great significance to the clinical applications and popularization of traditional acupuncture treatment perioperatively across the world.

Inclusion Criteria:

1. Age≥65 and <90 years old；
2. Planning to undergo select timed/limited surgery such as gastrointestinal tumor surgery, bile duct surgery and thoracic surgery etc under general anesthesia, and the estimated operation time is more than 2 hours;；
3. Treatment without radiotherapy or chemotherapy prior to surgery；
4. Agree to participate in this study and sign informed consent；

Exclusion Criteria:

1. Refuse to participate in this study；
2. Preoperative history of schizophrenia, epilepsy, Parkinson's disease, or myasthenia gravis；
3. Inability to communicate in the preoperative period to complete preoperative evaluation because of severe dementia, coma, language barrier；
4. Brain injury or neurosurgery；
5. Critical condition (if the ASA grade is greater than or equal to grade IV before surgery); Severe renal impairment (dialysis treatment before surgery); Severe liver function impairment (Child-Pugh level C); Preoperative combined with severe heart disease, LVEF < 30%;
6. Previous experience of acupoint stimulation therapy or non-insensitive to acupoint stimulation；
7. The attending physician or researcher considers that there are other circumstances (reasons to be noted) that are not suitable for participation in this study.