EFFICACY AND KINETICS OF EXTRADURAL ROPIVACAINE - COMPARISON WITH BUPIVACAINE

Ninety-one patients were allocated randomly to three groups to receive 1 % ropivacaine 10 ml, 0.5 % ropivacaine 20ml or 0.5 % bupivacaine 20 ml extradurally. Intermittent sensory (pinprick) and motor (Bromage sc ale) assessments of the block produced were recorded, with an assessme nt of the qualify of the block and the requirement for supplementary a nalgesia. There was little difference between the groups in frequency, onset, duration or spread of sensory block. However, the motor block produced by 0.5 % ropivacaine was less intense and of shorter duration than that with bupivacaine. The block produced by the smaller volume of ropivacaine was less reliable clinically than the larger, more dilu te, solution and more anaesthetic supplements were required in that gr oup. Cardiovascular changes were similar in all three groups. The peak plasma concentration of ropivacaine was significantly greater and T-1 /2 significantly shorter than those of bupivacaine, although no patien t showed any features of systemic toxicity. The systemic kinetics of r opivacaine were not influenced significantly by varying the concentrat ion or volume administered.