ABSTRACT
Objective To compare clinical effects of ropivacaine and hupivacaine administered in epidural space and study their pharmacokinetics and transfer across placenta. Methods Eighteen full-term nulliparous women aged 22-35yr, weighing 50-70 kg scheduled for cesarean section were randomized to one of two groups; group R received 0.75% ropivacame and group B received 0.5% hupivacaine for epidural block. Sensory and motor block, incidence of hypotension, blood gases of umbilical venous blood, Apgar score and NACS score of the neonates were investigated. Blood samples were taken from external jugular vein at 10, 15,30,60 and 120 min after epidural administration of local anesthetic and from umbilical vein for determination of plasma concentration of ropivacaine or bupivacaine by chromatography. Results The onset time and termination of sensory and motor block, the maximal height of block, incidence of hypotension, blood gases of umbilical venous blood, Apgar score and NACS score of the neonates were similar between the two groups. The plasma concentration of ropivacaine and bupivacaine peaked (613?90) ng.ml-1 and (51.3163.2) ng.ml-1 respectively, at 15-30 min after epidural administration. UV/ MV ratio was similar between the two groups (0.42 ? 0. 12 vs 0.48?0.15). Conclusion 0.75% ropivacaine and 0.5% bupivacaine administered in epidural space for cesarean section can produce adequate analgesia and equivalent clinical effects. Placental transfer of ropivacaine and bupivacaine are similar. The plasma concentration of ropivacaine and bupivacaine of maternal blood and umbilical venous blood are markedly lower than the concentration causing toxrcity, but safety margin of ropivacaine is wider than that of bupivacaine.