The investigators assume that transcutaneous electric acupoint stimulation (TEAS) pretreatment may activate the endogenous protective mechanism, as a result protect the patients against subsequent surgical stress pregnancy. And TEAS may induce the production of endogenous analgesic transmitters, so develop an anesthetic-sparing effect. The investigators believe this intervention will reduce the subsequent incidence, duration and severity of organ dysfunction, possibly reducing the morbidity, even mortality. So in this study, the investigators hypothesize that TEAS before anesthesia and during surgery would decrease the morbidity and mortality of postoperative complications in 30 days after digestive surgery in elderly patients .

Patients older than 65 years old are at higher risk of postoperative morbidity and mortality. With the increasing number of old patients scheduled for digestive surgery, exploring methods to decrease postoperative morbidity is very important. Noninvasive methods may be easier to clinically use. Transcutaneous electric acupoint stimulation (TEAS)has been proved to decrease need for general anesthetics during anesthesia, and to alleviate systemic inflammatory response. Considering the morbidity and mortality after surgery is closely related to use of anesthetics and inflammatory response,TEAS may be a good selection for improving postoperative outcomes.Among the postoperative complications, pulmonary complication and systemic inflammatory response syndrome is with higher incidence, so we will focus on these two complications in our study.

Inclusion Criteria:

• Provide written informed consent
• Age ≥65 years of age
• Elective digestive surgery under general anesthesia

Exclusion Criteria:

• ASA(American Society of Anesthesiologists) status> Ⅲ
• Patients undergoing surgery within 12 h of admission to hospital
• Patients undergoing surgery of the chest
• Patients suffered from neurologic disorder or impaired mental state
• Patients with contraindications to the use of electro-acupuncture, such as skin damage or infection at the acupoints
• Patients with experience of transcutaneous electrical stimulation treatment