Remimazolam has shown promising results for sedation in colonoscopy . Alfentanil is widely used in the analgesia of ERCP . The purpose of the study was to determine the median effective dose of remimazolam for duodenoscopy insertion during ERCP with alfentanil 10µg/kg.

1. Title:The median effective dose of remimazolam for duodenoscopy insertion during ERCP with alfentanil 10µg/kg.
2. Research center: Single center.
3. The population of the study: Age is between 18 and 85 years; ASA I andIII levels; Patients undergone elective ERCP surgery, non-intubation patients;
4. Sample size:The sample size was decided based on that of prior literature, which had demonstrated that at least six independent pairs with success/failure duodenoscopy insertion during ERCP are required for reliable estimates of the ED50 of remimazolam with the Dixon's up-and-down method, and data from seven independent pairs of patients were collected for this study. The ED50 (95% confidence interval, CI) of remimazolam for successful duodenoscopy insertion during ERCP was calculated according to the formula of Dixon and Massey.

6. Interventions:The dose of remimazolam for each patient was determined by the response of the previously tested patients using the modified Dixon's up-and-down method.The first patient was tested at 0.2mg/kg remimazolam (0.025mg/kg as a step size). Duodenoscopy insertion was conducted when MOAA/S≤1.The response of the patients to the duodenoscopy insertion during ERCP was categorized as either 'success (no movement)' or 'failure (movement).' Movement was defined duodenoscopy insertion a failure was as gross purposeful muscular movement, coughing or vomiting occurring during or within 2 minutes of insertion of duodenoscopy. No movement was depicted when the reactions mentioned earlier were absent.If BIS>75 and MOAA/S > 1 when 3 min after the intravenous injection of remimazolam, it was considered a failure, and the patient received rescue sedation..

Inclusion Criteria:

• Age is between 18 and 85 years
• ASA I and III, levels;
• Patients undergone elective ERCP surgery, non-intubation patients;

Exclusion Criteria:

• Chronic pain with long-term use of analgesics, psychotropic substances (including opioids, NSAIDs, sedatives, antidepressants), alcohol abusers, with known drug allergy;
• BMI<18,BMI>30
• Abnormal renal function (BUN or Cr ) ;
• Previous abnormal surgical anesthesia recovery history;
• Hypertension or systolic blood pressure greater than 160 mmHg or diastolic blood pressure greater than 95 mmHg when the patient admission to the operating room
• Suffering from esophageal reflux; • Sedatives, analgesics and antipruritic drugs were used 24 hours before operation;
• Expected difficult intubation ;
• Liver surgery history;
• Opioids allergy history;
• Take monoamine oxidase inhibitor or antidepressant within 15 days;
• COPD;
• Pregnant or parturient women;
• Involved in other drug trials within three months;
• Patients who can not communicate well with the researcher