A double-blind comparison of 0.5% bupivacaine and 0.75% ropivacaine administered epidurally in humans

In an attempt to compare equipotent doses of epidurally administered bupivacaine and ropivacaine, 44 healthy patients, aged 18-70 years, undergoing lower extremity orthopedic procedures were studied in a randomized, double-blind manner. Twenty-one patients received a single epidural injection of 20 ml 0.5% bupivacaine at the L23 or L34 interspace and 23 patients received 20 ml 0.75% ropivacaine in a similar manner. Onset of and recovery from sensory anesthesia and motor block were recorded. No significant differences were found between the two anesthetic groups except for time to two-segment regression. Maximum block height (median (range] was T4 (T2-T8) and T5 (T2-L1) for bupivacaine and ropivacaine, respectively, and maximum motor block scores were 4 (2-6) and 4 (0-6) using the modified Bromage scale. Times to maximum height of sensory block for bupivacaine and ropivacaine, respectively, were 28 +/- 12 and 28 +/- 13 minutes; times to onset of block to T12 were 6 +/- 4 and 9 +/- 10 minutes; times to onset of maximum motor block were 32 +/- 17 and 47 +/- 29 minutes; times to two-segment regression were 2.7 +/- 0.8 and 3.4 +/- 1.0 hours (p less than 0.05); times to regression to T12 level were 4.8 +/- 0.9 and 4.7 +/- 0.95 hours; times to total recovery of sensation were 6.5 +/- 0.9 and 6.6 +/- 1.0 hours, and times to recovery of motor function were 4.4 +/- 0.9 and 4.1 +/- 0.9 hours. In two instances (both with bupivacaine), anesthesia was judged clinically inadequate.