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 μg, 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 μg (group R, n=26) or plain bupivacaine 13 mg with fentanyl 20 μg (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) 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 μg 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 μg for spinal anaesthesia in lower abdominal surgery.