Data are presented as mean (standard deviation), median (interquartile range) or n (%). P values are from independent samples ttests, Mann–Whitney comparison, chi-squared or Fisher’s exact tests, as appropriate. *P <0.05 indicates statistically significant differences between groups.P a values are from Wilcoxon matched-pairs signed-rank test for intragroup comparisons.P <0.05 indicates statistically significant differences compared with preoperative values. CON, control; KET, esketamine; NRS, numeric rating scale; PACU, post-anesthesia care unit; RASS, Richmond Agitation Sedation Scale; PONV, postoperative nausea and vomiting.