Randomized double-blind comparison of ropivacaine-fentanyl and bupivacaine-fentanyl for spinal anaesthesia for urological surgery.

BACKGROUND: Early studies have suggested that ropivacaine causes less motor block than bupivacaine, which might be advantageous in spinal anaesthesia for short procedures. The aim of this study was to compare plain ropivacaine 10 mg and plain bupivacaine 10 mg, both with fentanyl 15 microg, for spinal anaesthesia in urological surgery.

METHODS: This was a prospective randomized double-blind study. After written informed consent had been obtained, 34 ASA I-III patients scheduled for urological surgery were randomly assigned to receive intrathecal injection of either plain ropivacaine 10 mg with fentanyl 15 microg (ropivacaine group) or plain bupivacaine 10 mg with fentanyl 15 microg (bupivacaine group) using a combined spinal-epidural technique.

RESULTS: All patients achieved sensory block to the T10 dermatome or higher at 15 min after intrathecal injection. One patient in the ropivacaine group was excluded because of unexpectedly prolonged surgery. The primary outcome, the duration of motor block, was shorter in the ropivacaine group (median, 126 min; interquartile range, 93-162 min) compared with the bupivacaine group (median, 189 min; interquartile range, 157-234 min; difference between medians, 71 min; 95% confidence interval, 28-109 min; P = 0.003). The duration of complete motor block was also shorter in the ropivacaine group compared with the bupivacaine group. There was no difference in the onset time of motor block. The characteristics of sensory block and the haemodynamic changes were similar between the groups.

CONCLUSION: Plain ropivacaine 10 mg plus fentanyl 15 microg provided similar sensory anaesthesia, but with a shorter duration of motor block, compared with plain bupivacaine 10 mg plus fentanyl 15 microg when used for spinal anaesthesia in urological surgery.