Endoscopic ultrasound (EUS) has evolved to become an important diagnostic tool and its interventional role is rapidly expanding. In order to improve patient's comfort and satisfaction during and after procedure, the use of sedation is usually recommended. However, sedation may be associated with serious adverse events of including hypotension, aspiration and respiratory depression. Moreover, the cost of performing the procedure would be increased due to the costs of the medications and the need of additional personnel in monitoring of the patient. As a result, the drive to seek alternative and safer approaches of pain-relief during EUS is ever present. Electroacupuncture (EA) has been used in Traditional Chinese Medicine (TCM) for more than 2000 years. The benefits and success of EA in treatment of acute and chronic pain of various origins have been well-recognised. Many researches have been performed to address the role of EA in treating pain and anxiety during OGD and colonoscopy. However, only limited data is availabe in the Chinese and the Western literature concerning the use of EA in EUS. Therefore it is worthwhile to conduct a well-designed study to evaluate the role of EA in treating pain during EUS.

Inclusion Criteria:

• Consecutive patients (aged between 18 and 80 years) undergoing first-time elective day-case EUS, patients with American Society of Anesthesiologists (ASA) grading I-II, and informed consent available.

Exclusion Criteria:

• Patients with previous experience of acupuncture, patients with coagulopathy, patients with previous history of upper gastrointestinal surgery, patients who are diagnosed with irritable bowel syndrome according to Rome III criteria, 12 patients with chronic pain syndrome, patients with psychiatric disorder, patients with poor cognitive function, patients with renal impairment, patients with obstructive sleep apnea syndrome, patients with cardiac arrhythmias, patients with cardiac pacemaker, patients who are pregnant, and patients who are allergic to the acupuncture needles or Propofol/Alfentanil.