Dose–Response Study of Epidural Ropivacaine for Labor Analgesia

Bee Beng Lee, Warwick D. Ngan Kee, Eliza L. Y. Wong, Justina Y. W. Liu
2001 Anesthesiology  
Ropivacaine has been introduced for use in epidural analgesia in labor. However, there have been few formal dose-response studies of ropivacaine in this setting. Methods: The authors performed a prospective, randomized, double-blind study examining the effectiveness of five different doses of ropivacaine (10, 20, 30, 40, and 50 mg) administered epidurally in a volume of 10 ml to establish analgesia in 66 parturients who were in active labor with cervical dilatation less than 4 cm. A dose was
more » ... sidered effective when the visual analog scale pain score decreased by 50% or more from baseline. Results: A sigmoid dose-response curve and a probit log dose-response plot (linear regression coefficient, r ‫؍‬ 0.84; coefficient of determination, r 2 ‫؍‬ 0.71) were obtained. The ED 50 (median effective dose) obtained based on the maximum likelihood estimation was 18.4 mg (95% confidence interval, 13.4 -25.4 mg). Time to onset of analgesia, duration of analgesia, time to two-segment regression of sensory block level, and incidence of motor block were not affected by the dosage of ropivacaine administered (P ‫؍‬ 0.93, 0.12, 0.55, and 0.39, respectively). However, the upper level of sensory block was doserelated (P < 0.01). Conclusion: In a traditional dose-response study, the ED 50 of ropivacaine required to initiate epidural analgesia in early labor was found to be 18.4 mg (95% confidence interval, 13.4 -25.4 mg).
doi:10.1097/00000542-200105000-00013 pmid:11388526 fatcat:nbo3y3sdeffbrc2ge22d4enbm4