title: The effects of age on the median effective concentration of ropivacaine for motor blockade after epidural anesthesia with ropivacaine.
abstract: Minimal local analgesic concentrations have been defined as the median effective concentration (EC50). In this study, we sought to examine the effect of age on motor blockade and determine the motor block EC50 of elderly patients after epidural administration of ropivacaine in patients undergoing urological or minor lower limb surgery. ASA physical status I-II patients were enrolled in 1 of 2 age groups (Group 1: > or =70 yr; Group 2: <70 yr). Each received a 15-mL bolus of epidural ropivacaine without epinephrine. The first patient in each group received 0.425%. Up-down sequential allocation was used to determine subsequent concentrations at a testing interval of 0.025%. Effective motor blockade was defined as a modified Bromage score >0 within 30 min. The motor blockade EC50 of ropivacaine was 0.383% (95% confidence interval, 0.358%-0. 409%) in group 1 and 0.536% (95% confidence interval, 0.512%-0.556%) in group 2 (P < 0.01). We conclude that age is a determinant of motor blockade EC50 of ropivacaine with epidural administration.
authors.affiliation: Department of Anesthesiology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China. yuh_li2002@hotmail.com
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Li
authors.forename: Shengmei
authors.initials: S
authors.lastname: Zhu
authors.forename: Fangping
authors.initials: F
authors.lastname: Bao
authors.forename: Jianhong
authors.initials: J
authors.lastname: Xu
authors.forename: Xiang
authors.initials: X
authors.lastname: Yan
authors.forename: Xudong
authors.initials: X
authors.lastname: Jin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D000577:Amides / Q000008:administration & dosage*; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007866:Leg / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019148:Neuromuscular Blockade; D000077212:Ropivacaine; D013520:Urologic Surgical Procedures
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine