Effect of dexmedetomidine on the median effective concentration of ropivacaine for postoperative analgesia in transversus abdominis plane block: an up-down sequential allocation study

Qin Ye ¹ Hongchun Xu ² Xiao Liu ¹ Xujiao Wang ¹ Fangjun Wang ^2*

• ¹ Zigong Fourth People's Hospital, Zigong, China
• ² Affiliated Hospital of North Sichuan Medical College, Nanchong, Sichuan Province, China

To observe the effect of dexmedetomidine on the median effective concentration (EC50, effective concentration in 50% of patients) of ropivacaine for postoperative analgesia in ultrasound-guided transversus abdominis plane block.Methods: patients undergoing elective laparoscopic cholecystectomy were randomly divided into RD group and R group. In RD group, 40 ml of ropivacaine with 1ug/kg dexmedetomidine was injected into the transverse abdominis plane, while subjects in R group received equal volume ropivacaine with normal saline. When the VAS ≤3 within 6 hours after surgery, the postoperative analgesia was assessed as effective.The Probit regression was used to calculate the EC50 and EC95 of ropivacaine for ultrasound-guided transversus abdominis plane block. The Quality of Recovery-40 (QoR-40) Score on 24h after surgery and the incidence of adverse reactions were recorded.The EC50 of ropivacaine calculated by the Probit regression was 0.207% (95% CI, 0.188%~0.228%) in the R group and 0.165% (95% CI, 0.146%~0.182%) in the RD group. The EC95 of ropivacaine was 0.255% (95% CI, 0.230%~0.499%) in the R group and 0.209% (95% CI, 0.187%~0.430%) in the RD group. The score of physical comfort, emotional state, pain and global score of QoR-40on 24 h after the operation in the RD group was higher than R group (P<0.05). There were no significant differences in the incidence of adverse reactions between the two groups (P＞0.05).Dexmedetomidine as a local anesthetic adjuvant can reduce the EC50 and EC95 of ropivacaine and improve the quality of postoperative recovery of patients for transversus abdominis plane block.