As an invasive operation, gastroscopy will cause children's nervousness, anxiety and uncooperative behavior, and even lead to the risk of bleeding and perforation, which will also affect the accuracy of the examination results.The purpose of this study is to explore the influence of different doses of esketamine on the induced dose ED95 of remazolam during gastroscopic placement in children, and to provide theoretical basis for the combined use of remimazolam besylate and esketamine in gastroscopic anesthesia in children.

Children aged 3-12 who underwent gastroscopy were randomly divided into two groups: L group with Esketamine 0.25mg/kg and the initial dose of Remimazolam was 0.3mg/kg ,M group with Esketamine 0.5mg/kg and the initial dose of Remimazolam was 0.2mg/kg.Judging whether the sedation level of the children can meet the requirements of gastroscopy placement after injecting Remimazolam.The next dose was adjusted to 0.05mg/kg according to biased coin design,to further explore the induced dose of ED95 of Remimazolam under the background of different doses of Esketamine.

Inclusion Criteria:

1. with American Society of Anesthesiologists (ASA) physical status I or II#;
2. aged 3#12 years#;
3. children with weight for age within the normal range#;
4. were scheduled to have a gastroscopy;

Exclusion Criteria:

1. Children who had gastrointestinal,Cardiovascular or endocrine dysfunction;
2. contraindication to preoperative sedation or had a known allergy or hypersensitive reaction to remimazolam and esketamine;
3. recently respiratory infection, mental disorder;
4. other reasons that researchers hold it is not appropriate to participate in this trial.