Study on MEV90 of 0.5% ropivacaine for US-guided caudal epidural block in anorectal surgery

Pei Zhang; Hong Chang; Taoran Yang; Yalong Fu; Xuemei He; Jun Li; Mingan Yang; Rurong Wang; Xuehan Li

doi:10.3389/fmed.2022.1077478

Study on MEV90 of 0.5% ropivacaine for US-guided caudal epidural block in anorectal surgery

Front Med (Lausanne). 2023 Jan 19:9:1077478. doi: 10.3389/fmed.2022.1077478. eCollection 2022.

Authors

Pei Zhang¹, Hong Chang^{2

3

4}, Taoran Yang¹, Yalong Fu⁵, Xuemei He¹, Jun Li¹, Mingan Yang⁶, Rurong Wang^{1

4}, Xuehan Li¹

Affiliations

¹ Department of Anesthesiology, Laboratory of Anesthesia and Intensive Care Medicine, West China Hospital of Sichuan University, Chengdu, Sichuan, China.
² Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu, China.
³ West China School of Nursing, Sichuan University, Chengdu, China.
⁴ Chengdu Shang Jin Nan Fu Hospital, Chengdu, China.
⁵ Department of Anus Intestine, Karamay People's Hospital, Xinjiang, China.
⁶ Division of Biostatistics and Epidemiology, School of Public Health, San Diego State University, San Diego, CA, United States.

Abstract

Background: Choosing the appropriate concentration and volume of anesthetics is critical for a successful nerve block. The current study aimed to determine the minimum effective volume (MEV) of 0.5% ropivacaine for US-guided CEB in 90% of patients (MEV90) undergoing anorectal surgery. The aims were to reduce the occurrence of complications associated with a sacral blockade in anorectal surgery, broaden the indications for surgical procedures and treatment, and improve patient satisfaction. This study presents the groundwork for the development of individualized anesthetic programs. We believe that the study would serve as a reference for the use of caudal epidural block (CEB) in lower abdominal surgery for intraoperative and postoperative analgesia.

Methods: This study used a biased coin design (BCD) up-and-down method (UDM). We divided the participants into two groups based on gender, and each group independently performed the biased coin design up-and-down method. We used 0.5% ropivacaine for the first patient in each group; however, the volume was 10 ml for men and 8 ml for women. Therefore, the dose of anesthetics given to each patient was determined by the response of the previous patient. If the block of the previous patient failed, the volume was increased by 2 ml in the following patient. Otherwise, the next subject had an 11% chance of receiving a volume of 2 ml less or an 89% chance of receiving no volume change. We defined a successful block as painless surgery with anal sphincter relaxation 15 min after the drug injection. Enrollment was completed after 45 successful caudal blocks for each group.

Results: Caudal epidural block was successfully performed on 50 men and 49 women. The MEV90 of ropivacaine for CEB was calculated to be 12.88 ml (95% CI: 10.8-14 ml) for men and 10.73 ml (95% CI: 9.67-12 ml) for women. Men had a MEV99 of 13.88 ml (95% CI: 12.97-14 ml), and women had a MEV99 of 11.87 ml (95% CI: 11.72-12 ml).

Conclusion: With operability and general applicability, it is possible to increase the success rate of CEB for anorectal surgery to 99% as well as decrease the incidence of anesthesia-related complications. CEB can meet the needs of patients for rapid postoperative rehabilitation, improve patient satisfaction, and lay a solid foundation for postoperative analgesia.

Keywords: anorectal surgery; caudal block; minimum effective volume; ropivacaine; ultrasound.

Grants and funding

This study was supported by the National Key Research and Development Program of China (No. 2021YFC2009100) and the National Natural Science Foundation of China (Grant Nos. 81900064 and 82170079).