• Yuhong Li, Shengmei Zhu, Fangping Bao, Jianhong Xu, Xiang Yan, and Xudong Jin.
• Department of Anesthesiology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People's Republic of China. yuh_li2002@hotmail.com
• Anesth. Analg. 2006 Jun 1; 102 (6): 1847-50.

AbstractMinimal 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.

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