To investigate the clinical efficacy of different doses of esketamine combined with caudal block (CB) in pediatric hypospadias surgery (PHS), and the optimal dose of esketamine.

A total of 120 pediatric patients aged 2 to 6 years with congenital hypospadias (CH) who underwent tubuloplasty with longitudinal incision of the urethral plate at Xuzhou Medical University Affiliated Xuzhou Children′s Hospital from April 2023 to September 2024 were selected. All children were classified as American Society of Anesthesiologists (ASA) physical status Ⅰ or Ⅱ. They were randomly assigned to group S1, S2 and S3 by a random number table, with 40 children in each group. Esketamine was administered via intravenous injection at doses of 0.81, 0.97, and 1.13 mg/kg, respectively. The CH children in 3 groups received continuous oxygen via face mask at a flow rate of 5 L/min after entering the operating room. Each group received the corresponding dose of esketamine via intravenous injection. Once the children′s Modified Observer′s Assessment of Alertness and Sedation score ≤1 point, they were positioned in the left lateral decubitus position. A senior deputy chief anesthesiologist then performed an ultrasound-guided CB. The operation time, time to recover after anesthesia, and movement inhibition rate of esketamine combined with CB were recorded in the three groups. The heart rate, mean arterial pressure (MAP), and pulse oxygen saturation (SpO₂) were recorded at the time of entering the operating room, 1 minute after intravenous injection of esketamine, immediately after CB, immediately after the end of the operation, immediately after entering the recovery room, and immediately after leaving the recovery room (T′0-T′5). The incidence of adverse reactions (blurred vision, drooling, respiratory depression, etc.) during and after the operation was also recorded. The Pediatric Anesthesia Emergence Delirium Scale (PAED) scores were recorded immediately after entering the recovery room, and 10, 20, 30 minutes after entering the recovery room, and immediately after leaving the recovery room (T1-T5). The chi-square test, one-way analysis of variance and analysis of variance for repeated measures were used to compare the above indicators among three groups of CH children. The procedures followed in this study were approved by the Medical Ethics Committee of Xuzhou Medical University Affiliated Xuzhou Children′s Hospital (Approval No. 2023-05-71-H71). All guardians of the pediatric patients signed informed consent forms for clinical study. There were no statistically significant differences in age and weight among the pediatric patients in three groups (P>0.05).

①There were no statistically significant differences in the rates of movement inhibition during caudal puncture and the operation time among three groups (P>0.05). The time to recover after anesthesia of children in groups S1, S2, and S3 was (40.9±0.6), (41.3±0.7), and (41.7±0.5) min, respectively. The overall comparison among the three groups showed statistically significant difference (P<0.05). Further pairwise comparisons showed that compared with groups S1 and S2, the time to recover after anesthesia of children in group S3 was significantly prolonged (F=33.23, 21.98; P<0.001). There was no statistically significant difference in time to recover after anesthesia between groups S1 and S2 (P>0.05). ②The results of analysis of variance of repeated measurement data of PAED scores at T1-T5, and mean arterial pressure, heart rate, and SpO₂ at T′0-T′5 in the three groups of children showed that the interaction effects of different treatment measures and time factors were not statistically significant (P_{treatment×time}>0.05). Further analysis of the main effect of treatment measures (different esketamine doses) showed that the main effect of different esketamine doses on the PAED scores of children at T1-T5 was statistically significant (P_treatment=0.036). After Bonferroni correction for pairwise comparisons (adjusted α=0.017), pairwise comparisons of PAED scores of three groups at T1-T5 showed that there were no statistically significant differences in PAED scores of S3 group compared with those of S1 and S2 groups at T1-T5 (P=0.033, 0.316). However, the average PAED scores of S3 group at each time were higher than those of the other two groups. There was no statistically significant main effect of different esketamine doses on the MAP, heart rate, and SpO₂ of the children at T′0-T′5 (P_treatment=0.941, 0.844, 0.275). ③There were no statistically significant differences in the incidence rates of adverse reactions such as blurred vision, delirium, and drooling among the three groups (P>0.05).

The effects of 0.81, 0.97, and 1.13 mg/kg esketamine combined with CB on suppressing motor responses during caudal puncture in children undergoing PHS, as well as on the children′s PAED score, MAP, heart rate, SpO₂, and adverse reactions, are comparable. However, the time to recover after anesthesia of 0.81 mg/kg esketamine combined with CB was the shortest, which was the appropriate dose of esketamine.