Etomidate Emulsion for Sedation in Patients Scheduled for Upper Gastrointestinal (GI) Endoscopy

Inclusion Criteria: * Patients scheduled for painless gastroscopy * 18-80 year old * 18 H2 ≤ weight ≤ 35 H2 (H indicates height) * American Society of Anesthesiologists (ASA) physical status class 1-3 * The duration of surgery is ≤ 60 min ( duration of surgery was defined as the interval time from insert to withdraw of catheter) * Without liver, kidney and heart disease history * No previous history of abnormal recovery of anesthesia in surgery Exclusion Criteria: * Patients whom do not wish to perform painless gastroscopy or participate in the study * Patients with medical history of severe heart, lung, liver, kidney or metabolic disease * Patients with abnormal ECG presented as heart rate 50 \< beat/min * Patients who suffered from acute inflammation of respiratory tract within the past 2 weeks and did not be cured of it before participating in the study * Hypertension patient with preoperative blood pressure \> 180/90 mmHg; hypotension patients with preoperative blood pressure \< 90/60 mmHg; * Patients with neuromuscular disease, mental disorders * Hemoglobin is less than 90 g/L * Patients with suspected abuse of Anesthesia and Analgesia * Patients who were predicted to have or had previous difficult airway ( difficult airway is defined as the clinical situation in which a conventionally trained anesthesiologist experiences three failures of intubation) * Patients with known emulsion or opioid allergy * Patients who will be noncompliant or unable to communicate * Patients who received long-term treatment with hormone or had history of adrenocortical suppression * Patients received coadministration of other sedative, analgesic ( including injection, oral or usage of relevant Chinese patent medicine) before, during or 15 min after the procedure * Patients who appeared nausea and vomit, dizziness * Patients with sever diabetes mellitus, hyperkaliemia or significant electrolyte disturbances