Fiber colonoscopy, as a terminal examination method for lower gastrointestinal diseases, often brings varying degrees of pain, discomfort, tension, and anxiety to patients. Therefore, currently in clinical practice, intravenous anesthesia is often chosen to reduce discomfort. At present, intravenous propofol and fentanyl are most widely used in clinical practice, but intravenous general anesthesia can lead to hemodynamic fluctuations and an increase in anesthesia related complications such as prolonged hospital stay after surgery. Propofol and remifentanil have the characteristics of fast onset, short duration of action, and rapid awakening. The purpose of this study is to observe the efficacy and adverse reactions of remifentanil combined with low-dose propofol in patient-controlled analgesia and sedation during colonoscopy, in order to explore the safety and effectiveness of this method.

Fibercolonoscopy, as a terminal examination method for lower digestive tract diseases, often brings different degrees of pain and discomfort, tension and anxiety to patients. Therefore, at present, intravenous anesthesia is often used in clinical practice to reduce discomfort, and intravenous propofol combined with fentanyl is the most widely used in clinical practice. But intravenous general anesthesia can lead to hemodynamic fluctuations and an increase in anesthesiation-related complications such as longer stays in the hospital after surgery. Complications related to sedation and analgesia have attracted increasing attention in recent years. Studies have shown that most of the adverse events in endoscopy are related to the sedation and analgesia drugs used. With the successful application of patient-controlled analgesia (PCA) in the field of postoperative analgesia, this technique has also been used in the sedation and analgesia of gastroenteroscopy in recent years. Propofol has the characteristics of quick action, short time of action and rapid recovery, so it is very suitable for the anesthesia and sedation of painless abortion and painless gastroenteroscopy. Remifentanil, as an opioid μ receptor agonist, is easily hydrolyzed rapidly by non-specific esterases in plasma and tissues due to the ester bond contained in its chemical structure. Therefore, it has unique pharmacokinetic characteristics such as rapid intravenous injection, small volume of distribution, rapid clearance after drug withdrawal, no accumulation, metabolism is not affected by liver and kidney function, and has been widely used in various surgeries in recent years, especially in the anesthesia of short surgeries.

Inclusion Criteria:

1. American Society of Anesthesiologists (ASA) Grade I - II;
2. Age 18-75 years old;
3. Body mass index (BMI) <25㎏/㎡;
4. no mental and nervous system diseases;

Exclusion Criteria:

1. Refusal to cooperate or difficulty communicating;
2. History of drug allergy;
3. Long-term alcoholism and dependence on stabilizing and opioid drugs;
4. Patients with past history of intestinal surgery or past difficulty in endoscopic surgery;
5. People with hearing impairment