Determination of Minimal Motor-blocking Local Analgesic Concentration of Epidural Bupivacaine in the Postoperative Analgesia

Objective The aim of this study was to determine the minimal motor-blocking concentration of epidural bupivacaine in the postoperative epidural analgesia.Methods 30 ASA Ⅰ women who went gynaecologic operation and requested epidural analgesia were enrolled in the study.Epidural catheter was placed at L2-3 and advanced for 3 cm in the epidural space in a cephalad direction.Each received a 10 ml bolus of epidural bupivacaine.The first woman received 0.400%.Up-down sequential allocation was used to determine subsequent concentration:to increase the concentration one level if the previous woman did not respond and to reduce the concentration one level if the previous woman did respond.The up-down sequences were analyzed by using the Brownlee method to quantify the minimal motor-blocking local analgesic concentration.TWO-sided P0.05 defined significance.Results The minimal motor-blocking concentration of epidural bupivacaine in the post-operative epidural analgesia was 0.443%,(95% confidence interval,0.4288%-0.4576%).Conclusion The minimal motor-blocking local analgesic concentration of bupivacaine quantified in this study was a theoretic guideline for the clinical use of bupivacaine in the post-operative epidural analgesia.