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