Surgical pleth index to predict the success of caudal block in pediatric patients under general anesthesia.

BACKGROUND: Caudal block is usually performed after general anesthesia in children, which makes it hard to assess the success of the block. The aim of this study was to determine whether the surgical pleth index can serve as an objective tool for assessing nociception and the success of caudal block in anesthetized children. METHODOLOGY: Sixty-two children aged 1-6 years, with American Society of Anesthesiologists Physical Status I and II, undergoing elective infraumbilical surgery, were included. All patients received general anesthesia with i-gel and caudal analgesia. The surgical pleth index, heart rate, and mean blood pressure were recorded throughout the procedure. Caudal block was assessed postoperatively with a gentle pinch. RESULTS: The patients were divided into Group S (caudal success) and Group F (caudal failure). In both groups, the SPI decreased after induction to nearly < 50. It continued to gradually decrease to ≈30 in Group S, whereas it increased sharply with incision in Group F to ≈76. After additional analgesia with fentanyl, the surgical pleth index decreased in Group F, but the mean surgical pleth index was significantly greater than in Group S (p < 0.01). The intergroup difference in surgical pleth index persisted throughout the procedure. A receiver operating curve showed that a surgical pleth index of 43.5 before incision has a sensitivity of 83.3% and a specificity of 67.9% for predicting successful caudal block. Heart rate and blood pressure increased significantly with incision in Group F, unlike in Group S. The intergroup difference in hemodynamics disappeared after additional analgesia. CONCLUSION: A surgical pleth index of ≤ 43.5 (which may be rounded to 40) can serve as a nociceptive index to predict the success of a caudal block in children. IEC REGISTRATION NUMBER: IEC2 549/2023 dated 19th March 2024. CLINICAL TRIALS REGISTRATION: (CTRI/2024/12/078281) dated 18th December 2024.