Efficacy of 1% ropivacaine at sacral segments in lumbar epidural anesthesia

BACKGROUND AND OBJECTIVES: It is suggested that the potency of 1% ropivacaine is comparable to that of 0.75% bupivacaine and higher than that of 2% lidocaine. Alkalinized lidocaine reportedly enhances the block of sacral segments during lumbar epidural anesthesia. We hypothesized that 1% ropivacaine might also block at the lumbosacral segments adequately during lumbar epidural anesthesia. METHODS: Forty-two patients undergoing lumbar epidural anesthesia at L4-5 or L5-S1 were randomly divided into 3 groups and received either 14 mL 2% lidocaine (lidocaine group), 2% lidocaine with epinephrine 1:200,000 and bicarbonate (lidocaine-epinephrine-bicarbonate group), or 1% ropivacaine (ropivacaine group). Pain threshold after repeated electrical stimulation was used to assess sensory block at the L2, S1, and S3 segments while motor block was evaluated using the modified Bromage Scale. RESULTS: Demographic data were comparable between the groups. Significant differences in the pH of each local anesthetic solution were found between the 3 groups. Pain thresholds at the S1 and S3 segments in the lidocaine-epinephrine-bicarbonate group were significantly higher and sensory block onset faster than in the other groups. However, no significant differences were found in either the pain threshold or the onset of sensory block of the L2 segment between the groups. No significant differences in the pain threshold, onset of sensory block, or Bromage Scale were found between the lidocaine and ropivacaine groups. CONCLUSIONS: We conclude that 1% ropivacaine does not improve block of sacral segments within 20 minutes following epidural ropivacaine administration.