Gastroscopy, as a conventional examination for gastrointestinal tract disease, plays a very important role especially in early diagnosis and differential diagnosis of esophageal and gastric carcinoma. However, conventional gastroscopy is associated with several adverse effects (including throat discomfort, breath-holding, nausea, vomiting, laryngeal spasm and increased heart rate) due to which some patients are intolerant to this examination or even refuse the procedure due to fear of these effects. Recently, painless gastroscopy has been applied increasingly widely in outpatients to meet the increasing needs for comfortable medical care.

Painless gastroscopy is commonly performed under general anesthesia without establishing an artificial airway. This is associated with an even higher anesthetic risk than general anesthesia in the operating room due to more basic patient monitoring and life-supporting equipment, only one anesthetist to perform anesthesia, fatigue in anesthesia, the requirement for a high turnover rate, as well as limited understanding of a patient's condition. Therefore, the availability of sedatives and analgesics which can provide rapid onset, sufficient sedation and analgesia, a short recovery time and less adverse effects are the premise of performing painless gastroscopy. Currently, combined intravenous anesthesia with fentanyl and propofol, commonly used in the clinic, is still associated with a long duration of action, hypotension in some patients and prolonged recovery. Etomidate has been increasingly utilized for in-clinic diagnosis and treatment for procedures such as painless coloscopy and early induced abortion due to its rapid onset, rapid metabolism and minimal impact on the circulatory and respiratory systems. However, no study on combined intravenous anesthesia with fentanyl and etomidate for painless gastroscopy had previously been reported. The main purpose of this study is to explore the efficacy and safety of combined intravenous anesthesia with fentanyl and etomidate for painless gastroscopy compared with the combination of fentanyl and propofol in middle aged and elderly patients, and to provide reliable evidence for the implementation and promotion of comfortable medical care.

There are 6 centers for this trial: General Hospital of Chinese People's Liberation Army, Chaoyang Hospital Attached to the Capital Medical University, The Second Affiliated Hospital of Harbin Medical University, Renmin Hospital of Wuhan University Hubei General Hospital, The Affiliated Hospital of Xuzhou Medical College, Hospital of Chinese Air Force.

Inclusion Criteria:

• Preparing to take gastroscopy;
• Age:between 45 to 75 years old (middle-aged group: 45~59 years old; elderly group: 60~75 years old; the percentage of middle-aged group and elderly group are 60% and 40%, respectively);
• BMI: between 18 to 25 kg/m2;
• ASA classification: grade Ⅰ~Ⅱ.

Exclusion Criteria:

• Blood pressure before operation: >180 mm Hg or <90 mm Hg;
• ECG before operation: <50 beats per min;
• HGB before operation: <90 g/L;
• Infected with respiratory inflammation and not cured within 2 weeks;
• Sever heart, brain, pulmonary, heptic, renal diseases or diabetes;
• History of difficult airway or abnormal recovery from anesthesia before or difficult airway is predicted to occur ;
• Obvious electrolyte disturbance such as hyperkalemia;
• Treated with immunosuppressants such as hormones for a long time or prior inhibition of the adrenal cortex;
• Allergic to emulsion or opioids;
• Concomitant other sedatives or analgesics (including injectable or oral administration of treatment related to Chinese Traditional Patent Medicines);
• Suspected abuse of narcotic analgesics or sedatives;
• Patients for whom it is difficult to cooperate or communicate because of abnormalities of neuromuscular system or mental disorder.