Intravenous anesthesia has been widely used in endoscopic retrograde cholangiopancreatography (ERCP). In the past decade, many practices have been carried out under the propofol-based monitored anesthesia care without endotracheal intubation in patients undergoing ERCP.

Ciprofol is a newly developed intravenous anesthetic with a potency 4-5 times than that of propofol. Ciprofol seems a promising anesthetic agent for intravenous anesthesia but the evidence supported its application in ERCP is still limited.

This is a prospective, randomized, double-blind trial comparing the incidence of hypoxia in the propofol versus ciprofol intravenous Anesthesia. A total 136 patients will be recruited and randomly assigned to either the propofol or the ciprofol group. The primary outcome is the proportion of patients experiencing hypoxia. The secondary outcomes include: the incidence of hypotension in perioperative period; the incidence of conversion from intravenous anesthesia to general anesthesia; sedation-related procedure interruption; carbon dioxide( CO2) accumulation during operation; Patients' satisfaction with anesthesia and postoperative recovery / VAS score / incidence of nausea and vomiting; the incidence of intraoperative and postoperative adverse events, such as adverse excretion, severe hypoxemia, severe circulatory dysfunction; length of stay and mortality within 30 days after operation.

Inclusion Criteria:

• patients undergoing ERCP, ASA I-III
• normal renal function
• BMI ≥ 18kg/m 2 and ≤ 30kg/m 2

Exclusion Criteria:

• Previous serious cerebrovascular accidents and other neurological diseases
• mental diseases, long-term use of drugs that affect the function of the central nervous system, benzodiazepines or opioids
• history of anesthetic allergy
• preoperative hypotension or preoperative SpO2 < 90%, or chronic respiratory failure
• patients suspected of having difficult airways
• screening for drug addiction and alcohol abuse within the first 3 months (> = 6standarddrinks/day)
• patients diagnosed with severe cardiopulmonary disease, or respiratory or respiratory diseases such as sleep apnea syndrome;
• bradycardia or atrioventricular block.
• participate in other clinical trials within 4 weeks;
• cognitive or communication abnormalities determined by the researchers;
• emergent and critical conditions during the operation;
• other conditions that the researchers believe are not suitable to participate in the study.