The goal of this clinical trial is to learn the effect of intravenous esketamine in postoperative negative behavior changes in children compared to placebo (a look-alike substance that contains no drug). It will also learn about the effect of esketamine in emergence delirium. The main questions are:

Dose esketamine lower the incidence of postoperative negative behavior changes compared to placebo? Dose esketamine lower the incidence of emergence delirium compared to placebo? Researchers will compare esketamine to placebo to see if esketamine works to treat postoperative negative behavior change and emergence delirium.

Participants will:

Receive intravenous esketamine or placebo (a look-alike substance that contains no drug) during anesthesia induction; Fill in the Post hospitalization behavior questionnaire for ambulatory surgery postoperative 1, 7, and 30

Approximately half of children who undergo general anesthesia experience emergence delirium (ED) and postoperative negative behavioral changes (PNBC). There was a positive correlation between delirium during recovery and the change in negative behaviour after the operation.

Esketamine has sedative, analgesic and anti-traumatic stress effects. Based on literature analysis and preliminary trials, this study suggests that intraoperative use of low-dose esketamine may reduce the incidence of emergence delirium and postoperative negative behavior changes in children.

This prospective randomized controlled trial was conducted to compare the effect of intravenous esketamine in the incidence of emergence delirium and postoperative negative behavior changes in children compared to placebo (a look-alike substance that contains no drug) to provide a reference for optimizing clinical anesthesia medication regimens.

Inclusion Criteria:

• American society of Aneshesiologists physical status I or II;
• Aged 3-7 years;
• Scheduled for elective tonsillectomy and (or) adenoidectomy.

Exclusion Criteria:

• Parents refusing to allow their children to participate;
• Intake of sedative or analgesic medication within 48 hours before surgery;
• Developmental delay;
• Psychosis;
• Body mass index > 30 kg/m2;
• Allergy to study drugs;
• Major life changes 1 month before the operation, such as the divorce of parents, death of parents, moving to a new home, changing to a new kindergarten, etc.;
• Any other conditions that precluded study inclusion.

After publication, the individual deidentified participant data underlying published results, the study protocol, and the statistical analysis plan can be accessed upon reasonable request from the corresponding author.

The researcher would like to share the individual deidentified participant data beginning three months following the publication of the main results.

All the individual participant data collected during the trial, the study protocol, the statistical analysis plan, and the clinical study report can be accessed with approval from the corresponding author.