[Determination of EC50 of ropivacaine and bupivacaine for postoperative epidural analgesia by up-down sequential allocation].
OBJECTIVE
To determine the median effective concentration (EC50) of ropivacaine and bupivacaine for postoperative epidural analgesia, and compare the efficacy of the 2 analgesics.


METHODS
Sixty-five patients (ASA I to II) scheduled for elective gynaecological surgeries were randomly assigned into ropivacaine and bupivacaine groups to receive postoperative epidural analgesia with the indicated analgesics (20 ml). The concentration was determined by the response of a previous patient to a higher or lower concentration using double-blinded, up-down sequential allocation. The analgesic efficacy was assessed with 100 mm visual analog pain scores (VAS), and effectiveness was defined as having a VAS <or=10 mm.


RESULTS
EC50 was determined by the formula of Dixon and Massey, which was 0.098% and 0.058% for ropivacaine and bupivacaine respectively.


CONCLUSIONS
Up-down sequential allocation is a simple, efficient and reliable method for EC50 determination of ropivacaine and bupivacaine, and the former has a lower efficacy during postoperative epidural analgesia.
Yang
Ji-wu
JW
Department of Anesthesiology, Nanfang Hospital, First Military Medical University, Guangzhou 510515, China.
Gu
Miao-ning
MN
Xu
Jian-she
JS
Chen
Ye-ming
YM
D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D015360:Analgesia, Epidural; D002045:Bupivacaine / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D010149:Postoperative Pain / Q000188:drug therapy*; D000077212:Ropivacaine
D000577:Amides; D000077212:Ropivacaine; D002045:Bupivacaine