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OBSTETRIC ANESTHESIA

Epidural Infusions of Ropivacaine and Bupivacaine for Labor Analgesia: A Randomized, Double-Blind Study of Obstetric Outcome

Bee B. Lee, MBBS, FANZCA^*, Warwick D. Ngan Kee, MBChB, MD, FANZCA^*, Floria F. Ng, RN, BASc^*, Tze K. Lau, MBBS, MD, MRCOG, and Eliza L. Y. Wong, RN, MPH^*

*Department of Anaesthesia & Intensive Care and Department of Obstetric and Gynaecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, China

Address correspondence to Bee Beng Lee, Department of Anaesthesia & Intensive Care, Prince of Wales Hospital, Shatin, New Territories, Hong Kong, China. Address e-mail to bblee{at}cuhk.edu.hk

	Abstract

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

 
Studies have shown better obstetric outcome when ropivacaine 0.25% was used for labor epidural analgesia compared with bupivacaine 0.25%, but it is controversial whether there is any difference at smaller concentrations. In a prospective, double-blind trial, we randomized 350 ASA physical status I and II parturients with term cephalic singleton pregnancies to receive epidural labor analgesia using ropivacaine or bupivacaine. Analgesia was initiated with a 0.25% solution and maintained with a continuous infusion of a 0.1% solution with fentanyl 0.0002%. Supplementary boluses of 0.25% solution were given when requested. Labor was managed according to institutional standard labor ward protocols. Among patients who delivered vaginally, the duration of the first stage of labor was shorter in the ropivacaine group (median, 520 min; interquartile range, 377–745 min) compared with the bupivacaine group (645 min; interquartile range, 460–820 min; P = 0.009), but there was no difference in any other obstetric or neonatal outcomes. The mode of delivery was similar between groups, with operative (instrumental vaginal and cesarean) delivery rates of 61.8% (95% confidence interval, 54.4%–68.8%) in the ropivacaine group and 58.4% (95% confidence interval, 50.9%–65.5%) in the bupivacaine group (P = 0.72).

IMPLICATIONS: In a randomized-controlled study, we found no major outcome advantage of continuous epidural infusion of ropivacaine 0.1% with fentanyl 0.0002% over bupivacaine 0.1% with fentanyl 0.0002% for labor analgesia. Although ropivacaine was associated with a shorter first stage of labor, the relative difference is probably of limited clinical importance, and there was no difference in the mode of delivery.

	Introduction

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

 
There is controversy about whether epidural analgesia may affect the progress and outcome of labor. Ropivacaine has been introduced into obstetric anesthetic practice with the proposed advantage of causing less motor block compared with bupivacaine (1,2), but it is unclear whether ropivacaine is associated with any clinical benefit, particularly with regard to obstetric outcome. In 1998, Writer et al. (3) published a prospective meta-analysis that showed a greater frequency of spontaneous vaginal delivery and a smaller incidence of instrumental delivery with ropivacaine 0.25% compared to bupivacaine 0.25%. Although the authors concluded that ropivacaine therefore seemed to be more suitable than bupivacaine for labor analgesia, they suggested the need for further outcome studies using smaller concentration solutions. Small concentration solutions of local anesthetics, usually with the addition of a lipophilic opioid, are now used routinely in many units, including our own.

Several studies have compared small concentrations of ropivacaine with bupivacaine for labor analgesia (4–13). These studies found small differences in motor block but no difference in instrumental or cesarean delivery rates. However, most of these were small studies and not specifically designed or adequately powered to determine differences in obstetric outcome. In our unit, audit data revealed a strong association between the use of epidural analgesia in labor and operative delivery (forceps delivery, vacuum extraction, and cesarean delivery). Thus, we considered our local population to be suitable for a study of obstetric outcome. Accordingly, we performed a randomized, double-blind trial to compare obstetric outcome after epidural analgesia in labor using small concentrations of ropivacaine or bupivacaine, both with fentanyl. The primary outcome of the study was the rate of operative (instrumental vaginal or cesarean) delivery. Secondary outcomes were the quality of analgesia, maternal side effects, and neonatal outcome.

	Methods

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

 
With approval from the Clinical Research Ethics Committee of the Chinese University of Hong Kong and written informed consent from patients, we recruited 350 ASA physical status I and II laboring women with term cephalic singleton pregnancies who requested epidural analgesia, into this prospective, randomized, double-blind trial. Patients were excluded if they had received parenteral meperidine in the preceding 2 h, had preeclampsia, insulin-dependent gestational diabetes mellitus, previous cesarean delivery, or any medical contraindication to epidural analgesia.

A research nurse initially approached all parturients who matched the inclusion criteria when they were first admitted into the labor ward and before they requested epidural analgesia. After explaining the study, advance consent was obtained from those who agreed. At the same time, we explained and demonstrated the use of a 100-mm visual analog scale ruler to these parturients for quantification of their pain at the peak of uterine contractions (0 mm = no pain and 100 mm = worst pain). Subsequently, if patients requested epidural analgesia, one of the investigators rechecked eligibility for recruitment and confirmed and finalized written consent for the study before the procedure.

Parturients were randomly allocated to either the ropivacaine group (n = 175) or bupivacaine group (n = 175) by the drawing of sequentially numbered, opaque sealed envelopes, each containing a code based on a computer-generated random number list. To maintain blinding, local anesthetic solutions were prepared by an anesthesiologist or one of the investigators who was not involved in subsequent patient assessment or management.

After IV prehydration with 500 mL of lactated Ringer’s solution, an epidural catheter was inserted using aseptic precautions under local anesthesia at the L2-3 or L3-4 intervertebral space using a loss-of-resistance technique. An epidural test dose of 3 mL of lidocaine 2% with epinephrine 1:200,000 was given. Five minutes later, after confirming a negative response to this test dose, analgesia was initiated using 5-mL increments of ropivacaine 0.25% (ropivacaine group) or bupivacaine 0.25% (bupivacaine group), repeated at 10 and 20 min as requested by patients. If there was no analgesic response or sensory block level apparent after a total of 15 mL, the epidural catheter was considered nonfunctional and was re-sited after 30 min.

After the initial dose, analgesia was maintained using a continuous infusion of ropivacaine 0.1% with fentanyl 0.0002% (2 µg/mL) (ropivacaine group) or bupivacaine 0.1% with fentanyl 0.0002% (bupivacaine group), which were the concentrations used in our usual clinical practice. Infusions were started at 8 mL/h and adjusted as required within a range of 4 to 12 mL/h. Further boluses of 5–10 mL of ropivacaine 0.25% or bupivacaine 0.25% were given from the allocated randomized syringes for breakthrough pain. These requests were relayed to the anesthesiologist by the midwives caring for the parturient.

Parturients were nursed in a semilateral position, with continuous cardiotocograph monitoring. Episodes of hypotension, defined as systolic blood pressure <80% of baseline and <100 mm Hg, were managed by rapid infusion of lactated Ringer’s solution 5 mL/kg and IV boluses of ephedrine 3–6 mg, as required.

Epidural infusions were maintained throughout labor and were continued through the second stage. However, if maternal effort was judged to be inadequate by the attending obstetrician or midwife, the anesthesiologist was called to assess the parturient and could reduce or stop the epidural infusion, as considered appropriate.

Parturients were managed according to our unit’s standard labor protocol (Appendix 1). In particular, the attending obstetricians and midwives, who were blinded to each patient’s group, managed the second stage of labor according to the standard labor ward practice, which remained unchanged for the study. All obstetrical decisions were made independent of the fact that the patient was participating in the study.

Patient demographics, obstetric history, and intrapartum details were recorded. Assessments were made before inserting the epidural catheter, at 5-min intervals while initial analgesia was established, and then at 2-h intervals throughout the first stage of labor, starting 1 h after insertion of the epidural catheter. At each assessment, visual analog pain scores (VAPS) were recorded as pain at the peak of a uterine contraction. The highest dermatomal level of sensory block was determined using loss of temperature discrimination to ice. Motor block was assessed using a modified Bromage score (0 = no motor block, 1 = not able to flex hip, 2 = not able to bend knee, and 3 = not able to move ankle or foot). Maternal blood pressure and heart rate were recorded, and any incidences of hypotension requiring treatment were noted.

We recorded the following data for each patient: mode of delivery, indication for instrumental or cesarean delivery, duration of each stage of labor, duration and rates of epidural infusion, number and dose of supplementary epidural top-ups, total dose of ropivacaine or bupivacaine used, neonatal birthweight, Apgar scores, and umbilical cord blood gases (measured using a Ciba-Corning 278 Blood Gas System analyzer, Ciba-Corning Diagnostics, Medfield, MA).

All patients were followed up on the day after delivery by a research nurse. A patient satisfaction score for the labor epidural analgesia based on a four-point scale (1 = excellent, 2 = good, 3 = fair, and 4 = poor) was obtained. Any complications such as back pain or headache were also recorded.

Sample size was calculated based on analysis of audit data over 3 yr (1995–1997) from our unit that, after application of exclusion criteria, showed a rate of operative delivery of 72% (cesarean delivery 44% and instrumental vaginal delivery 28%) in patients who received epidural analgesia using infusions of bupivacaine-fentanyl during labor. Power analysis was based on an effect size of 13 percentage points between groups (i.e., reduction of the operative delivery rate to 59%), which is equivalent to the magnitude of the difference reported by Writer et al (3).

We calculated that a sample size of 164 patients per group was required to have 80% power at an level of 0.05 (PASS 6.0, NSCC, Kaysville, UT). To allow for a maximum potential dropout rate of 5%, we increased the sample size to 175 patients per group. Power analysis was based on one-tailed calculations, but all subsequent analyses were two-tailed.

The null hypothesis was that there was no difference in the rate of operative delivery between the two groups. Continuous parametric data were compared using Student’s t-test, ordinal data were compared using the Mann-Whitney U-test, and nominal data using the ² test. Multinomial logistic regression was used to identify factors associated with operative delivery. We assigned 3 levels to the dependent variable "mode of delivery" in the multinomial logistic regression: normal vaginal delivery, instrumental vaginal delivery, and cesarean delivery, with normal vaginal delivery assigned as the reference group. Factors that were significant at P < 0.10 on univariate analysis were entered into the model. The model’s calibration was assessed by the Hosmer-Lemeshow goodness-of-fit ² test, and its predictive accuracy was assessed by the area under the receiver operating characteristic curve (c-index in logistic regression). An area of 0.5 indicates no predictive discrimination, and an area of 1.0 indicates perfect separation of patients with different outcomes.

Relative risks were calculated for patients who delivered by instrumental vaginal and cesarean delivery, respectively, with reference to patients with normal vaginal delivery. Relative risks are reported instead of odds ratio because the outcome measure was common (>10%) (14). Bootstrapping was performed with 1000 replications to validate the final logistic model. Statistical analysis was performed using STATA version 7.0 (College Station, TX). Values of P < 0.05 were considered statistically significant.

	Results

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

 
Patient recruitment and data collection occurred over 24 consecutive months (August 1999 to August 2001). A total of 346 patients completed the study. Two patients in each group were excluded because of violations of study protocol: epidural catheter not re-sited despite unilateral block (one case), inadequately functioning or nonfunctioning epidural catheters replaced with combined spinal epidural (two cases), and dislodged epidural catheter (one case). There were no differences in demographic data, and parity was evenly distributed between groups (Table 1). Few multiparas used epidural for labor analgesia; most patients in both groups were nulliparas, with only 26 multiparas in the ropivacaine group and 18 multiparas in the bupivacaine group, respectively (²; P = 0.26).

Characteristics of epidural analgesia, VAPS, sensory and motor block, incidence of hypotension and vasopressor requirement, supplementary epidural top-ups, duration of epidural infusions, total dose of local anesthetic used, birthweight, umbilical cord blood gases, Apgar scores, and patient satisfaction were similar between groups (Tables 3 and 4; Fig. 1).

View larger version (17K): [in this window] [in a new window]   Figure 1. Visual analog pain scores (VAPS) during the first stage of labor. VAPS were similar between the ropivacaine group and bupivacaine group (repeated-measures analysis of variance). Values are median and 25th centile (for bupivacaine) and 75th centile (for ropivacaine) error bars. Only one set of either the 25th or 75th centiles is shown each, for clarity of presentation.

	Discussion

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

Whether epidural analgesia has adverse effects on the progress and outcome of labor has been the topic of much debate (15). One of the factors implicated in the association between epidural analgesia and increased rates of operative delivery is motor block from the epidural local anesthetic. This may decrease maternal mobility, reduce maternal effort in the second stage, and may also predispose to inadequate rotation of the fetal presenting part secondary to relaxation of pelvic floor muscles (16,17). All of these factors may potentially contribute to an increased requirement for operative vaginal or cesarean delivery.

Motor block from local anesthetic can be minimized either by reducing the concentration of local anesthetic or by choosing a local anesthetic with a high differential sensory:motor block ratio such as ropivacaine. The advantage of using a small concentration of local anesthetic was well demonstrated in the COMET trial (18). This showed that the instrumental vaginal delivery rate was less frequent when a small-dose epidural regimen (bupivacaine 0.1% with fentanyl 0.0002%) was compared with a traditional epidural regimen (bupivacaine 0.25%).

The advantage of using ropivacaine is more controversial. Some clinical studies have shown that ropivacaine provided analgesia with less motor block compared with similar concentrations of bupivacaine (3,19). This supports in vitro data that showed that ropivacaine produced less block of motor A-fibers for a similar degree of block of nociceptive C-fibers (20), although other studies found motor block to be similar (21–25). Writer et al. (3) reported a prospective meta-analysis of 6 randomized, double-blind studies (some of which were published separately (21,23–25)) with a total of 403 patients in which ropivacaine 0.25% was compared with bupivacaine 0.25%. They found that instrumental vaginal delivery was less frequent in women who received ropivacaine compared with those who received bupivacaine (27% versus 40%; P < 0.01). In contrast, in our study of a smaller concentration, although the median duration of the first stage of labor was shorter by two hours in the ropivacaine group, there was no difference in the mode of delivery. The difference in duration of labor (median duration, 8 hours 40 minutes for ropivacaine and 10 hours 45 minutes for bupivacaine), although interesting, is probably of limited clinical importance because there was no difference between groups in the duration of the second stage or the mode of delivery. Thus, our study does not support any major outcome advantage of ropivacaine at the concentration studied. We believe this is relevant to current clinical practice in which there has been a trend towards use of small concentrations of local anesthetics combined with a lipophilic opioid. Such combinations have replaced the larger concentration studied by Writer et al. (3) in a large proportion of units including our own. Other studies, except for one by Campbell et al. (8) comparing dilute solutions of both ropivacaine and bupivacaine combined with lipophilic opioids, concur with ours in showing no difference in obstetric outcome or motor block (4–7,9–13,26). We are unable to explain the differences between our findings and those of Campbell et al. (8) who studied a similarly small concentration of ropivacaine and bupivacaine (both 0.08%) combined with fentanyl but found a comparatively less frequent incidence of forceps delivery and motor block in their ropivacaine group.

Writer et al. (3) reported a smaller incidence of motor block in patients who received ropivacaine 0.25% compared to bupivacaine 0.25%. In contrast, in our study, there was only a small difference between groups that was not statistically significant. This is most likely related to the difference in concentrations of local anesthetic studied. In the study by Writer et al. (3), approximately one fourth of patients who received bupivacaine 0.25% and one fifth of patients who received ropivacaine 0.25% had Bromage scores of 2 or 3. In comparison, we found that when using a local anesthetic concentration that was 40% of that used by Writer et al. (3), the incidence of Bromage scores of 2 or 3 was only 12.1% in the bupivacaine group and 5.8% in the ropivacaine group. This suggests that at small concentrations, the difference in motor block between ropivacaine and bupivacaine is small; the concentration or dose of local anesthetic may be more important than the choice of drug. This finding is also apparent in the other studies quoted comparing dilute solutions of ropivacaine with bupivacaine (4–7,9–13,26).

In our study, we compared the same concentration (0.1%) of ropivacaine and bupivacaine because this is the concentration we have used clinically in daily practice. However, there is some evidence that ropivacaine may, in fact, be less potent than bupivacaine. This evidence comes mainly from studies that were designed to determine the minimum local analgesic concentration, defined as the median effective local analgesic concentration in a 20-mL volume in the first stage of labor (27,28). These studies used up-down sequential allocation methodology, (27,28) which is open and nonblinded, and the applicability of the results from these studies to small concentrations of local anesthetics has not been substantiated. Nonetheless, even if ropivacaine were less potent than bupivacaine at small concentrations, our results would still be valid because any bias resulting from use of a lower potency ropivacaine solution would most likely have been in favor of the alternate hypothesis and, therefore, would have been unlikely to have increased the risk of a type II error in our study. Moreover, because there was no difference in pain scores or drug consumption between groups in our study, this indirectly suggests that there was no important difference in the potency of the solutions used.

We designed our study specifically to compare obstetric outcome. The sample size was based on audit data from our unit, which showed a strong association between epidural analgesia and operative delivery. It was because of this association that we considered our population to be suitable for investigation. The rate of operative deliveries in patients who had epidural analgesia in labor in our previous audit period (72%) and in our study (60%) is probably more frequent than in many units in the United States. This may be related to a number of factors. Compared with some western countries, the rate of epidural analgesia in our unit is relatively small, ranging between 10%–15% in the past several years, with an overall cesarean delivery rate of 15%–20%. This may be a reflection of both cultural preference and the widespread reliance on systemic medications such as parenteral opioids and inhaled nitrous oxide-oxygen, despite the 24-hour availability of an epidural service. Given the relatively small usage of epidural analgesia in our unit, it is likely that those patients who do request epidural analgesia may be a subset with severe pain or prolonged labor. These patients are at greater risk for complicated labors, which may explain their relatively frequent rate of operative delivery. The reason for the slightly smaller rate of operative delivery in the present study compared with that in our audit data is uncertain. A reduction in the overall operative delivery rate was also reflected in more recent audit data that showed that the operative delivery rate was 64% (37% cesarean delivery and 27% instrumental vaginal delivery) among all parturients who had epidural analgesia in labor in the year 2000. It is possible this may reflect some changes in obstetric management. In our study, in which the operative delivery rate was smaller still, it is also possible that participation in the study itself may have had an influence on outcome by a Hawthorne-type effect.

In our study design, we used continuous epidural infusions because that was the standard technique in our unit at the time of study design. We found that VAPS were quite high in many patients towards the latter part of their labor. This may reflect some reluctance by our midwives to encourage epidural top-ups late in labor. It is possible that use of patient-controlled epidural analgesia (PCEA) administration may have allowed for better titration and resulted in lower pain scores. Compared with our continuous infusion technique, PCEA may also have resulted in greater power to detect a difference in drug consumption between groups.

In summary, we found no difference in the mode of delivery between ropivacaine 0.1% with fentanyl 0.0002% and bupivacaine 0.1% with fentanyl 0.0002% when given by continuous epidural infusion for labor analgesia. Although the use of ropivacaine resulted in a decrease in the duration of the first stage by approximately two hours in parturients who delivered vaginally, there were no differences in other outcomes including analgesia, sensory or motor block, drug consumption, and maternal satisfaction.

	Appendix 1: Labor Protocol

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

 

1. Electronic continuous fetal heart rate monitoring (CFHM) is used in all patients.
   
2. The progress of labor is assessed every 2 h or earlier if clinically indicated. The cervical dilation, station, and position of fetal head, and the degree of caput and molding are documented.
   
3. Progress of labor is considered abnormal if it is two or more hours behind the normal rate of progress (defined as 1 cm or more dilation per hour during the active phase of labor).
   
4. Management of abnormal progress of labor:

      i) Artificial rupture of membranes if membranes are still intact,
   

      ii) Oxytocin infusion according to standard departmental protocol if membranes have ruptured, or
   

      iii) Cesarean delivery if progress of labor is still abnormal despite adequate uterine contractions (at least three contractions per 10 min) after augmentation of labor.
   

   
   
5. Fetal distress:
      The diagnosis of fetal distress during the first stage of labor requires the presence of abnormal fetal heart rate pattern on CFHM and a fetal pH <7.20 from fetal scalp blood sampling (FBS). FBS may be omitted only if CFHM reveals an ominous pattern, which requires immediate abdominal delivery. During the second stage of labor, a diagnosis of fetal distress may be made based on CFHM alone.
   
6. Management of second stage of labor:
      Patients are allowed to push when full cervical dilation is confirmed and when they have the desire to bear down. If patients have no sensation of urge to push, the start of active pushing may be deferred up to 1 h in anticipation of further descent of the presenting part, at the discretion of the attending obstetrician. The epidural may be adjusted; if maternal effort is judged to be inadequate by the attending obstetrician, infusion rates are halved or stopped. Prolonged second stage is defined as failure to deliver the fetus after the start of pushing for 1 h (for nulliparae) or 30 min (for multiparae). Delivery will then be assisted by either Ventouse extraction or obstetric forceps or by cesarean delivery if instrumental delivery is contraindicated. The decision for this will be made entirely on the usual clinical criteria.
   
7. Neonatal Apgar scores, birthweight, and umbilical cord arterial and venous blood gases are recorded after delivery.
   

	Acknowledgments

 
Supported, in part, by a grant (no. 921015) from the Health Services Research Committee (HSRC), Hong Kong.

The authors wish to thank Dr. Anna Lee for help with data analysis and the midwives of the Labor Ward, Prince of Wales Hospital, Shatin, Hong Kong, China, for their assistance and cooperation with data collection.

	Footnotes

 
Presented, in part, at the 34th Annual Meeting of the Society for Obstetric Anesthesia and Perinatology (SOAP), Hilton Head Island, South Carolina, May 2002.

	References

Top Abstract Introduction Methods Results Discussion Appendix 1: Labor Protocol References

 

1. Kerkkamp HEM, Gielen MJM, Edström HH. Comparison of 0.75% ropivacaine with epinephrine and 0.75% bupivacaine with epinephrine in lumbar epidural anesthesia. Reg Anesth 1990; 15: 204–7.[Web of Science][Medline]
2. Brockway MS, Bannister J, McClure JH, et al. Comparison of extradural ropivacaine and bupivacaine. Br J Anaesth 1991; 66: 31–7.[Abstract/Free Full Text]
3. Writer WDR, Stienstra R, Eddleston JM, et al. Neonatal outcome and mode of delivery after epidural analgesia for labour with ropivacaine and bupivacaine: a prospective meta-analysis. Br J Anaesth 1998; 81: 713–7.[Abstract/Free Full Text]
4. Gautier P, De Kock M, Van Steenberge A, et al. A double-blind comparison of 0.125% ropivacaine with sufentanil and 0.125% bupivacaine with sufentanil for epidural labor analgesia. Anesthesiology 1999; 90: 772–8.[Web of Science][Medline]
5. Fischer C, Blanié P, Jaouën E, et al. Ropivacaine, 0.1%, plus sufentanil, 0.5 µg/ml, versus bupivacaine, 0.1%, plus sufentanil, 0.5 µg/ml, using patient-controlled epidural analgesia for labor: a double-blind comparison. Anesthesiology 2000; 92: 1588–93.[Web of Science][Medline]
6. Meister GC, D’Angelo R, Owen M, et al. A comparison of epidural analgesia with 0.125% ropivacaine with fentanyl versus 0.125% bupivacaine with fentanyl during labor. Anesth Analg 2000; 90: 632–7.[Abstract/Free Full Text]
7. Finegold H, Mandell G, Ramanathan S. Comparison of ropivacaine 0.1%-fentanyl and bupivacaine 0.125%- fentanyl infusions for epidural labour analgesia. Can J Anaesth 2000; 47: 740–5.[Web of Science][Medline]
8. Campbell DC, Zwack RM, Crone LL, Yip RW. Ambulatory labor epidural analgesia: bupivacaine versus ropivacaine. Anesth Analg 2000; 90: 1384–9.[Abstract/Free Full Text]
9. Owen MD, D’Angelo R, Gerancher JC, et al. 0.125% ropivacaine is similar to 0.125% bupivacaine for labor analgesia using patient-controlled epidural infusion. Anesth Analg 1998; 86: 527–31.[Abstract]
10. Dresner M, Freeman J, Calow C, et al. Ropivacaine 0.2% versus bupivacaine 0.1% with fentanyl: a double blind comparison for analgesia during labour. Br J Anaesth 2000; 85: 826–9.[Abstract/Free Full Text]
11. Sanchez-Conde P, Nicolas J, Rodriguez J, et al. Comparison of ropivacaine and bupivacaine for epidural analgesia during labor. Rev Esp Anestesiol Reanim 2001; 48: 199–203.[Medline]
12. Fernández-Guisasola J, Serrano ML, Cobo B, et al. A comparison of 0.0625% bupivacaine with fentanyl and 0.1% ropivacaine with fentanyl for continuous epidural labor analgesia. Anesth Analg 2001; 92: 1261–5.[Abstract/Free Full Text]
13. Owen MD, Thomas JA, Smith T, et al. Ropivacaine 0.075% and bupivacaine 0.075% with fentanyl 2 µg/mL are equivalent for labor epidural analgesia. Anesth Analg 2002; 94: 179–83.[Abstract/Free Full Text]
14. Zhang J, Yu KF. What’s the relative risk: a method of correcting the odds ratio in cohort studies of common outcomes. JAMA 1998; 280: 1690–1.[Abstract/Free Full Text]
15. Segal BS, Birnbach DJ. Epidurals and cesarean deliveries: a new look at an old problem. Anesth Analg 2000; 90: 775–7.[Free Full Text]
16. Stoddart AP, Nicholson KE, Popham PA. Low dose bupivacaine/fentanyl epidural infusions in labour and mode of delivery. Anaesthesia 1994; 49: 1087–90.[Web of Science][Medline]
17. Goodfellow CF, Hull MG, Swaab DF, et al. Oxytocin deficiency at delivery with epidural analgesia. Br J Obstet Gynaecol 1983; 90: 214–9.[Web of Science][Medline]
18. Comparative Obstetric Mobile Epidural Trial (COMET) Study Group UK. Effect of low-dose mobile versus traditional epidural techniques on mode of delivery: a randomised controlled trial. Lancet 2001; 358: 19–23.[Web of Science][Medline]
19. Muldoon T, Milligan K, Quinn P, et al. Comparison between extradural infusion of ropivacaine or bupivacaine for the prevention of postoperative pain after total knee arthroplasty. Br J Anaesth 1998; 80: 680–1.[Abstract/Free Full Text]
20. Bader AM, Datta S, Flanagan H, Covino BG. Comparison of bupivacaine- and ropivacaine-induced conduction blockade in the isolated rabbit vagus nerve. Anesth Analg 1989; 68: 724–7.[Abstract/Free Full Text]
21. Stienstra R, Jonker TA, Bourdrez P, et al. Ropivacaine 0.25% versus bupivacaine 0.25% for continuous epidural analgesia in labor: a double-blind comparison. Anesth Analg 1995; 80: 285–9.[Abstract]
22. McCrae AF, Jozwiak H, McClure JH. Comparison of ropivacaine and bupivacaine in extradural analgesia for the relief of pain in labour. Br J Anaesth 1995; 74: 261–5.[Abstract/Free Full Text]
23. Eddleston JM, Holland JJ, Griffin RP, et al. A double-blind comparison of 0.25% ropivacaine and 0.25% bupivacaine for extradural analgesia in labour. Br J Anaesth 1996; 76: 66–71.[Abstract/Free Full Text]
24. Muir HA, Writer D, Douglas J, et al. Double-blind comparison of epidural ropivacaine 0.25% and bupivacaine 0.25%, for the relief of childbirth pain. Can J Anaesth 1997; 44: 599–604.[Web of Science][Medline]
25. Gaiser RR, Venkateswaren P, Cheek TG, et al. Comparison of 0.25% ropivacaine and bupivacaine for epidural analgesia for labor and vaginal delivery. J Clin Anesth 1997; 9: 564–8.[Web of Science][Medline]
26. Clément HJ, Caruso L, Lopez F, et al. Epidural analgesia with 0.15% ropivacaine plus sufentanil 0.5 µg mL-1 versus 0.10% bupivacaine plus sufentanil 0.5 µg mL-1: a double-blind comparison during labour. Br J Anaesth 2002; 88: 809–13.[Abstract/Free Full Text]
27. Capogna G, Celleno D, Fusco P, et al. Relative potencies of bupivacaine and ropivacaine for analgesia in labour. Br J Anaesth 1999; 82: 371–3.[Abstract/Free Full Text]
28. Polley LS, Columb MO, Naughton NN, et al. Relative analgesic potencies of ropivacaine and bupivacaine for epidural analgesia in labor: implications for therapeutic indexes. Anesthesiology 1999; 90: 944–50.[Web of Science][Medline]

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