Background: Sufentanil is often added to ropivacaine and levobupivacaine to provide epidural analgesia in labour. The aim of this study was to compare the analgesic potencies of epidural ropivacaine and levobupivacaine in combination with sufentanil 0.5 microg/mL, using the minimum local analgesic concentration (MLAC) model with up-down sequential allocation.
Methods: In this prospective study parturients with cervical dilation >or= 3cm who requested epidural analgesia between 0800 and 1500 were enrolled. They were randomly allocated to receive 20 mL of either ropivacaine (group R) or levobupivacaine (group L) both with sufentanil 0.5 microg/mL. Thirty minutes after initial injection a continuous infusion was started and maintained until delivery. The numbers of additional doses of 0.2% ropivacaine and 0.25% levobupivacaine needed to maintain the visual analogue pain score <10/100 mm were recorded. The median effective concentrations were estimated from up-down sequential allocations and overall dose requirements of ropivacaine and levobupivacaine were compared.
Results: 53 women were recruited to the study. The MLAC of ropivacaine was 0.023% w/vol (95% CI, 0.005-0.041) compared with levobupivacaine which was 0.020% w/vol (95% CI, 0.008-0.032). The hourly dose of ropivacaine was 13.3 (SD 5.8) mg/h which was similar to levobupivacaine 14.4 (SD 9.7) mg/h. The total doses used for labour analgesia were 56.1 (SD 32.3) mg of ropivacaine (n=26) and 58.6 (SD 27.5) mg of levobupivacaine (n=26).
Conclusion: When sufentanil 0.5 microg/mL was added to either ropivacaine or levobupivacaine for labour analgesia, no significant difference in analgesic potency was observed.