Comparison of extradural ropivacaine and bupivacaine

Ropivacaine, a new long acting amide type local anaesthetic, was compared with bupivacaine in a randomized double-blind study. One hundred and ten patients undergoing extradural anaesthesia received a test dose of 3 ml of 1% lignocaine with adrenaline which was followed by 15 ml of one of five solutions: 0.5, 0.75 or 1.0% ropivacaine or 0.5 or 0.75% bupivacaine. There was little difference between the groups with respect to speed of onset or sensory block. The duration of analgesia was increased by increasing the concentration of both drugs, but this had minimal effect on onset time or extent of block. When the same concentration of each drug was administered, there were inconsistent differences in duration of sensory block, none of which was statistically significant. Increasing concentration of both drugs resulted in greater degree and longer duration of motor block. Ropivacaine produced a slower onset, shorter duration and less intense motor block than the same concentration of bupivacaine. The cardiovascular changes were similar in all groups.