Pharmacodynamics Of Local Anesthetics For Postoperative Epidural Analgesia In Gynecological Surgery

Pharmacodynamics of Local Anesthetics for PostoperativeEpidural Analgesia in Gynecological Surgery Objective:Pharmacological effects and administration methods of local anesthetics for postoperative epidural analgesia had been studied largely, but still have not a specific standard method. This study was designed to research the pharmacodynamics of local anesthetics for postoperative epidural analgesia in gynecological surgery, include:l.The minimum local analgesic concentration (ECSII)2.The minimum local analgesic concentration of combined fentanyl3.Eds of ropivacaine and its effective clinical concentration Methods:1. 120 patients (ASAl-li), scheduled se lective gynecological surgery under epidural+lumbar anesthes ia, were randomly assigned into 4 groups: R(ropivacaine) group, B (bupivacaine) group, RF(ropi vacaine-t-fentany 1) group, BF (hup i vaca i rie + fenlany 1) group. All patients received postoperative epidural analgesia with 10ml local anesthetics of different concent rat ion with or without fentanyl (2M-g/ml). The concentration was determined by the response of a previous pat lent to a higher or lower conrentrati on using double-blinded, up-down sequential allocation.The analgesic efficacy was assessed with visual analog pain scores (VAS), and effectiveness was defined as having a VAS<3. EC50 was determined respectively by dixon's method. 2. 90 patients (ASAI-II), scheduled selective gynecologicaloperation under epidural+lumbar anesthesia, were randomly assigned into 9 groups (n=10) according to the concentration of ropivacaine for postoperative epidural analgesia.The patients in group 1 to 7 received postoperative epidural analgesia with 10ml ropivacaine which was scheduled concentration respectively. The analgesic efficacy was assessed with visual analog pain scores (VAS), and effectiveness was defined as having a VAS^S. The analgesic efficacy and drug concentration were analyzed with regression. EC,=, of ropivacaine was determined by the regression equation.The patients of group 8 and 9 respectively received postoperative epidural analgesia with 10ml ropivacaine, of which concentrations were 1.5 times and 2 times of EC玈. The analgesic efficacy was determined by VAS and motor block was assessed with modified Bromage scores. Results:1. EC,,, of R group was 0.098% and EC.,, of B group was 0.052%, difference between groups was statistically significant (P<0.05).And the titer ratio is 1.88:1. EC,, of ropivacaine-t-fentanyl (2l-ig/rnl) was 0. 069% Which was significantly lower than that of ropivacaine only. EC*, in BF group was 0.041%, Which was significantly lower than that in B group.2. Regresion of ropivacaine for postoperative epidural analgesia was Y(analgesic efficacy)=a X X (drug concentration) +b. If analgesic effectiveness was defined as having a VAS^3, EC9S of ropivacaine was 0. 156%. All patients ingroup 8 had a VAS<3 except one who's VAS was between 3 and 5, and all patients' Bromage scores were 0. In group 9, all patients had a VAS<3; Two modified Bromage scores were 1, the rest were 0. Difference of VAS and Bromage between groups was insignificant (P>0. 05). All patients in the two groups had not symptoms like hypotension, bradycardia, respiratory depression, nausea and vomitus, etc. Conclusion:The analgesic efficacy of bupivacaine may be better than that of ropivacaine for postoperative epidural analgesia, and its titer ratio is 1.88: 1.Teamed with fentanyl (2ug/ml) , the EC.% of local anesthetic can be significantly decreased.The analgesic efficacy of ropivacainel of 1. 5-2. 0 times EC玸 for postoperative epidural analgesia can assured, and no motor block may not happen.