• Medge D Owen, John A Thomas, Trevor Smith, Lynn C Harris, and Robert D'Angelo.
• Department of Anesthesiology, Section of Obstetric Anesthesia, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1009, USA. mowen@wfubmc.edu
• Anesth. Analg. 2002 Jan 1;94(1):179-83, table of contents.

UnlabelledFifty percent effective dose estimates for ropivacaine and bupivacaine suggest that ropivacaine is 40% less potent than bupivacaine to initiate labor analgesia. At clinically used concentrations, however, the drugs seem indistinguishable for initiating and maintaining labor analgesia. We designed this study to evaluate a concentration near the reported 50% effective dose values for ropivacaine and bupivacaine in an attempt to detect differences between the drugs during routine clinical use. Fifty-nine nulliparous women in labor were randomized to receive 0.075% ropivacaine or bupivacaine, each with fentanyl 2 microg/mL. After epidural placement and the administration of a lidocaine/epinephrine test dose, 20 mL of study solution was administered and a patient-controlled epidural infusion was initiated with the following settings: 6 mL/h basal rate, 5 mL bolus, 10 min lockout, and 30 mL/h limit. Breakthrough pain was treated with 10-mL boluses of study solution. By using a study design to detect a 40% difference in hourly drug use between groups, we found no statistically significant differences in the amount of local anesthetic used, verbal pain scores, sensory levels, motor blockade, labor duration, mode of delivery, side effects, or patient satisfaction. We conclude that 0.075% ropivacaine and bupivacaine, with fentanyl, are equally effective for labor analgesia using the patient-controlled epidural analgesia technique.ImplicationsAt small concentrations, ropivacaine and bupivacaine when combined with fentanyl are equally effective for labor analgesia. Patients self-administered similar volumes of 0.075% ropivacaine or bupivacaine solutions containing fentanyl (2 microg/mL) suggesting that at this concentration, and with the addition of fentanyl, ropivacaine and bupivacaine can be used interchangeably.

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