Effects of ultrasound-guided caudal versus perianal blocks on intraoperative anal sphincter tone and postoperative analgesia during sphincter-sparing procedures: A randomized comparative trial

Abstract

Background

Data comparing the effects of caudal epidural anaesthesia and perianal block during anal sphincter sparing procedures under general anaesthesia are limited. We aimed to compare the efficacy and safety of ultrasound-guided caudal block versus perianal block on anal sphincter muscle tone and in reducing postoperative pain among patients undergoing anal sphincter-sparing procedures.

Methods

This randomized double-blinded study enrolled 46 adult patients, American Society of Anesthesiologists physical status I or II, who underwent anal sphincter sparing procedures under general anaesthesia. Patients were randomly assigned to one of two groups (23 patients each). Group A received an ultrasound-guided caudal block, while Group B received a perianal block. The primary outcome was duration of postoperative analgesia. Secondary outcomes included total postoperative morphine consumption, postoperative pain intensity, time to postoperative ambulation, intraoperative external anal sphincter muscle tone by Digital rectal scoring system (DRESS), patient satisfaction, and incidence of complications.

Results

Patients in group A had a statistically significant longer time to first request for analgesia and lower morphine consumption than those in group B (2.50 ± 0.27 vs. 1.57 ± 0.53 h, and 3.30 ± 2.18 mg vs. 5.87 ± 2.05 mg, P < .001). Although these differences are modest in magnitude, they may contribute to improved recovery when combined with multimodal analgesia strategies. Moreover, caudal block resulted in shorter time to ambulation (2.17 ± 0.38 vs 3.48 ± 0.53 h), and low numeric pain scores (1.96 ± 0.56 vs. 3.48 ± 0.66, P < .001). The DRESS and Likert scores were significantly higher in patients in group A than in group B (2.83 ± 0.38 vs. 2.22 ± 0.42, and 3.78 ± 0.42 vs. 2.48 ± 0.66, P < .001).

Conclusion

In anal sphincter-sparing operations, ultrasound-guided caudal epidural blocks combined with general anaesthesia may improve pain management, reduce opioid requirements, and thereby reduce the incidence of postoperative nausea and vomiting, while maintaining anal sphincter tone compared to local perianal block.