International journal of obstetric anesthesia
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Int J Obstet Anesth · Jul 1997
Randomized Controlled Trial Clinical TrialFeto-maternal distribution of ropivacaine and bupivacaine after epidural administration for cesarean section.
Ropivacaine is a new amino amide local anesthetic less lipophilic and with a lower affinity for plasma proteins than bupivacaine. The purpose of this study was to examine the feto-maternal distribution of ropivacaine and bupivacaine after epidural administration for cesarean section. Healthy parturients were randomly allocated in a double-blinded manner to receive either 0.5% ropivacaine or 0.5% bupivacaine through a lumbar epidural catheter. ⋯ At delivery, the maternal free plasma concentration of ropivacaine was more than twice that of the free concentration of bupivacaine (0.072 vs 0.032 microg/ml, P = 0.002). The free concentration of ropivacaine was about twice that of bupivacaine in the umbilical venous (0.06 vs 0.03 microg/ml, P = 0.001) and umbilical arterial (0.05 vs 0.02 microg/ml, P = 0.007) plasma. The more rapid plasma clearance of bupivacaine compared to ropivacaine, leading to lower maternal plasma concentrations and hence to lower umbilical concentrations at delivery, could be explained by the higher lipid solubility, hence greater distribution volume, of bupivacaine.