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REGIONAL ANESTHESIA

The Effects of Age on the Median Effective Concentration of Ropivacaine for Motor Blockade After Epidural Anesthesia with Ropivacaine

Department of Anesthesiology, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People’s Republic of China

Address correspondence and reprint requests to Yuhong Li, PhD, Department of Anesthesiology, First Affiliated Hospital, School of Medicine, Zhejiang University, 310003 Hangzhou, People’s Republic of China. Address e-mail to yuh_li2002{at}hotmail.com.

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: 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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