Comparison of Equipotent Doses of Ropivacaine-fentanyl and Bupivacaine-fentanyl in Spinal Anaesthesia for Lower Abdominal Surgery

The aim of this randomised, double-blind study was to compare equipotent doses of plain ropivacaine and bupivacaine (19.5 mg and 13 mg respectively), both with fentanyl 20 microg, for spinal anaesthesia in lower abdominal surgery. After written informed consent had been obtained, 52 ASA I to II male patients scheduled for lower abdominal surgery were randomly assigned to receive intrathecal plain ropivacaine 19.5 mg with fentanyl 20 microg (group R, n =26) or plain bupivacaine 13 mg with fentanyl 20 microg (group B, n =26) in 3 ml. The level and duration of sensory block, intensity and duration of motor block, time to mobilise and patient satisfaction were recorded. All patients achieved sensory block to T10 or higher The level of sensory block was significantly higher in group B (T4 [T3 to T7] vs T7 [T4 to T9], P <0.05). There was no difference in the onset time of motor block. The duration of motor block (Bromage score >0) was shorter in group R (139+/-39 minutes vs group B 182+/-46 minutes, P <0.05). The duration and intensity of complete motor block (Bromage score=3) were also shorter in group R (90+/-25 minutes vs 130+/-40 minutes, P <0.05). We conclude that plain ropivacaine 19.5 mg plus fentanyl 20 microg is associated with a lower level of sensory block and a shorter duration of motor block when compared to bupivacaine 13 mg plus fentanyl 20 microg for spinal anaesthesia in lower abdominal surgery.