Postoperative delirium is with increased incidence in elderly patients. Previous studies have shown that acupuncture related techniques could induce protection against brain ischemia and improve outcome after cerebral diseases. In this study the effect of transcutaneous electrical acupoint stimulation combined with auricular acupressure on postoperative delirium will be evaluated.

Postoperative delirium (POD) is an acute neurological disorder that commonly happens between postoperative days 1 and 3 and more common reported in elderly patients. The rate of delirium differs depending on the patients' characteristics, surgery types and setting of health care. The prevalence of delirium range from 18% to 35 % in a general medical service, and up to half of older patients postoperatively. It has been documented that POD is associated with an increase in mortality and morbidity, increased use of hospital resources, and higher cost of health care. The conventional preventive methods for delirium have focused on minimization or elimination of the predisposing and precipitating factors. Yet, few effective therapies are available for treating POD. New treatments are needed to reduce the prevalence and severity of delirium.

Complementary therapies, particularly acupuncture, have gained increasing attention for their possible value in the prevention and treatment of neurological disorders. Both basic and clinical studies have suggested that acupuncture may be beneficial to postoperative delirium. In functional MRI studies of healthy subjects and nervous system dysfunction patients, acupuncture has been shown to stimulate hippocampus, amygdala and insula, areas of the brain associated with memory, cognition and emotion.

In the clinical, TEAS has been reported to be effective in alleviating delirium in elderly patients with silent lacunar infarction. Evidence also showed that auricular acupunctures are efficacious for preventing postoperative agitation in geriatric patients

Given evidences of the possible efficacy of TEAS and auricular acupressure, we aim to do a 2-arm, randomized, controlled, single-blinded, pragmatic trial to investigate whether transcutaneous electrical acupoint stimulation combined with auricular acupressure is more effective in reducing postoperative delirium in elderly patients than usual care.

Inclusion Criteria:

• Patients scheduled for elective abdominal surgery under general anesthesia
• American Society of Anesthesiologists (ASA) physical status class≤Ⅲ;
• Mini mental state examination (MMSE) score>20;

Exclusion Criteria:

• Implantation of a cardiac pacemaker, cardioverter, defibrillator or internal hearing aids;
• Documented alcohol or substance abuse within 3 months before surgery;
• Dermatological conditions or frail skin;
• Dysesthesia or infection over the acupoint stimulation skin area;
• Limb abnormalities;
• Allergy to ECG pads;
• Use of psychoactive medications;
• Severe visual or auditory impairment;
• Preoperative history of schizophrenia, epilepsy, parkinsonism, depression, or myasthenia gravis;
• Brain injury or neurosurgery.

The data of the study will be available for sharing after publishing, including data of the outcomes

The data of the study will be available for sharing after publishing on peer-reviewed journals, and will be available for 5 years

transcutaneous electrical acupoint stimulation and auricular acupressure is given by an investigator who is not involved in anesthesia and outcome assessment