Endoscopic submucosal dissection is commonly performed under light to moderate sedation, and minimizing patient movement is of key importance for successful outcome. Propofol has widely replaced benzodiazepines as sedative drug of choice, and has been reported to enhance the quality of procedure in our past study. However, despite higher satisfaction scores of the endoscopists and faster post-procedural recovery, patient satisfaction scores were found to be higher in patients that received midazolam and meperidine instead of propofol and remifentanil. This seems to be due to the anterograde amnestic effects of midazolam rather than the quality of sedation itself. Investigator hypothesized that by premedicating the patient with low lose midazolam before receiving sedation for ESD with propofol and fentanyl, patient satisfaction would be enhanced without affecting endoscopic performance.

Inclusion Criteria:

1. Adult patients over the age of 19 diagnosed with early gastric cancer or gastric adenoma that are scheduled for endoscopic submucosal dissection
2. American society of anesthesiologist physical status 1~3

Exclusion Criteria:

1. Patient refusal
2. Patients that received sedatives within 24 hours prior to endoscopic submucosal dissection
3. History of gastrectomy or previous endoscopic submucosal dissection at same site
4. Allergies to propofol or its ingredients, soybeans or peanuts
5. Pregnant or breastfeeding patients
6. Patients with severe debilitating underlying medical conditions
7. Patients with altered mental status
8. Illiterate patients or foreigners