The Effect Of Dexmedetomidine On The EC50 Of Ropivacaine For Ultrasound-guided Transvrersus Abdominis Plane Block

Objective:To observe the effect of dexmedetomidine on the median effective concentration(EC50)of ropivacaine for ultrasound-guided transversus abdominis plane block.Methods:60 patients undergoing elective laparoscopic cholecystectomy were randomly divided into RD group and R group.In RD group,40 ml of ropivacaine with lug/kg dexmedetomidine was injected into the transverse abdominis plane,while subjects in R group received 40 ml of ropivacaine with normal saline.The method of Dixon-Massey was used to calculate the EC50 and 95%confidence interval(95%CI)of ropivacaine for ultrasound-guided transversus abdominis plane block.Following indexes were recorded:Quality of Recovery-40 Score(QoR-40)on 24h after the operation;patient’s heart rate(HR)and mean arterial pressure(MAP)on arriving at the anesthesia preparation room(t0),10min after finishing transversus abdominis plane block(t1),20min after finishing transversus abdominis plane block(t2),1 min before intubation(t3),being intubated(t4),establishing pneumoperitoneum(t5)and 5 min after establishing pneumoperitoneum(t6);the amount of propofol and remifentanil during the operation;first exhaust time through anus;the use of analgesic after the surgery;Visual Analogue Scale(VAS)and Ramsay sedation score on entering the anesthesia preparation room(T0),1h(T1),3h(T2),6h(T3),12h(T4),24h(T5),48h(T6)after surgery and the incidence of adverse reactions.Results:The EC50 of ropivacaine in the R group was 0.209%,95%CI was 0.197%to 0.220%and the EC50 of the RD group was 0.168%,95%CI was 0.158%to 0.178%.The EC50 of ropivacaine in the RD group was lower than R group(P<0.05).Compared with the R group,MAP of the RD group decreased at t2 and increased at t3(P<0.05).The score of physical comfort,emotional state,pain and total score of QoR-40on 24h after the operation in the RD group was higher than R group(P<0.05).There were no significant differences in the amount of propofol and remifentanil during the operation,first exhaust time through anus,the use of analgesic,VAS score,Ramsay sedation score and the incidence of adverse reactions(P>0.05).Conclusion:Dexmedetomidine as a local anesthetic adjuvant for transversus abdominis plane block can reduce the EC50 of ropivacaine,maintain hemodynamic stability and improve the quality of postoperative recovery of patients.