Anesth Analg 2003;96:1173-1177
© 2003 International Anesthesia Research Society
OBSTETRIC ANESTHESIA
Ropivacaine 0.15% Plus Sufentanil 0.5 µg/mL and Ropivacaine 0.10% Plus Sufentanil 0.5 µg/mL Are Equivalent for Patient-Controlled Epidural Analgesia During Labor
Emmanuel Boselli, MD,
Richard Debon, MD,
Frédéric Duflo, MD,
Boris Bryssine, MD,
Bernard Allaouchiche, MD PhD, and
Dominique Chassard, MD PhD
Service d’Anesthésie-Réanimation, Hôtel-Dieu, Lyon, France
Address correspondence and reprint requests to Dominique Chassard, MD, PhD, Service d’Anesthésie-Réanimation, Hôtel-Dieu, 1 Place de l’Hôpital, 69288 Lyon Cedex 02, France. Address e-mail to dominique.chassard{at}chu-lyon.fr
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Abstract
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We compared the administration of 0.15% ropivacaine plus 0.5 µg/mL of sufentanil with that of 0.10% ropivacaine plus 0.5 µg/mL of sufentanil for labor analgesia with patient-controlled epidural analgesia (PCEA) to determine whether a decreased concentration of ropivacaine could produce equally effective analgesia. One-hundred-thirty healthy pregnant women at term were randomized in a double-blinded fashion. The PCEA settings were as follows: 12-mL initial bolus, 5-mL bolus dose, 5-min lockout interval, and 10 mL/h basal infusion. Patient demographics and labor characteristics were comparable in both groups. No differences were observed for pain scores, maternal satisfaction, volume of anesthetic solution administered, number of boluses requested and delivered, need for supplemental boluses, mode of delivery, motor block, side effects, or Apgar scores. Patients in the 0.10% ropivacaine group used significantly less drug than those in the 0.15% group (mean, 57 mg; 95% confidence interval, 50.5–63.5 mg; versus mean, 88.0 mg; 95% confidence interval, 74.4–93.3 mg, respectively; P < 0.0001). Ropivacaine 0.10% plus 0.5 µg/mL of sufentanil administered via PCEA for labor analgesia is equally effective as ropivacaine 0.15% plus 0.5 µg/mL of sufentanil, with a 30% local anesthetic-sparing effect and a 40% reduction in cost. However, this reduction in local anesthetic is not associated with a decrease in the incidence of motor block, side effects, or instrumental deliveries.
IMPLICATIONS: Ropivacaine 0.10% plus 0.5 µg/mL of sufentanil given via patient-controlled epidural anesthesia for labor analgesia is equally as effective as ropivacaine 0.15% plus 0.5 µg/mL of sufentanil, with a 30% local anesthetic-sparing effect and a 40% reduction in cost. This reduction in ropivacaine concentration is not associated with a decrease in the incidence of motor block, side effects, or instrumental deliveries.
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Introduction
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The use of ropivacaine for labor analgesia is increasing, in part because this local anesthetic is considered to be less cardiotoxic than bupivacaine and because it may be associated with a decreased incidence of motor blockade (1–3) . The addition of opioids in the anesthetic solution allows the use of a smaller concentration of local anesthetic (4). Hence, a trend toward the use of decreased concentrations of ropivacaine has been described in recent studies (5–7) . Most studies of patient-controlled epidural analgesia (PCEA) for labor and delivery have used bupivacaine or a mixture of bupivacaine and fentanyl, and only a few studies have evaluated mixtures of newer drugs, such as ropivacaine and sufentanil (3,5,8) . Moreover, there is little information regarding the administration of various concentrations of ropivacaine via PCEA during labor. This study compared the administration of 0.15% ropivacaine plus 0.5 µg/mL of sufentanil with that of 0.10% ropivacaine plus 0.5 µg/mL of sufentanil for labor analgesia with PCEA to determine whether a decreased concentration of ropivacaine could produce equally effective labor analgesia with a smaller total dose.
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Methods
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After approval by the local ethics committee and written consent were obtained, nulliparous or primiparous parturients who were ASA physical status I or II and in the first stage of labor were enrolled in the study. Women with severe medical or obstetrical complications, multiple gestation, or a contraindication to epidural analgesia and those who were unable to use a PCEA pump were excluded. Instruction on the use of the PCEA pump took place before the insertion of the epidural catheter. Parturients were told to press the demand button whenever they felt pain and to expect some relief within a few minutes.
An 18-gauge epidural catheter was inserted 3 cm into the epidural space at the L3-4 or L4-5 interspace in the sitting position. Catheters were aspirated gently for return of blood or cerebrospinal fluid and then tested by the injection of 3 mL of 2% lidocaine with 15 µg of epinephrine.
Parturients were then allocated randomly by a computer-generated list to one of two groups: Group 0.15% received 0.15% ropivacaine plus 0.5 µg/mL of sufentanil, and Group 0.10% received 0.10% ropivacaine plus 0.5 µg/mL of sufentanil. Trial medications were prepared by an anesthesiologist not directly involved in the patient’s care or data collection, and investigators were blinded to patient group. The catheter was connected to an IVAC PCAM® pump (Alaris Medical Systems Inc., San Diego, CA). Both groups received an initial bolus of 12 mL of the solution, followed after 30 min by a continuous infusion of 10 mL/h, which is the standard protocol of administration in our institution. Additional boluses of 5 mL with a lockout period of 5 min were allowed in both groups. The dose limits were 22 mL/h in both groups: with these limits, only one bolus was allowed during the first hour of infusion, and two boluses per hour were allowed thereafter. Parturients who experienced inadequate analgesia during labor, irrespective of PCEA use, could receive additional 5-mL boluses of the study solution administered by the nurse.
The pain scores before the start of the infusion and during labor were evaluated with a 10-cm visual analog scale (VAS: 0, no pain; 10, worst pain imaginable). In addition, motor block (modified Bromage scale: 0, bilateral sustained straightening of leg; 1, unable to straighten leg; 2, just able to flex knees; 3, foot movement only) and common side effects, such as nausea, somnolence, and pruritus, were recorded. The volume of the solution required and the number of boluses demanded and delivered were recorded at delivery (or at the time of decision for cesarean delivery).
Maternal and fetal heart rate were monitored continuously, and maternal noninvasive blood pressure was measured at regular intervals. Maternal hypotension, defined as a systolic blood pressure <100 mm Hg or a decrease of >25% from baseline, was treated by IV doses of ephedrine as needed and by assumption of the left lateral decubitus position and the administration of oxygen via a face mask. All fetal and maternal events, as well as therapeutic interventions, outcome of labor, and Apgar score at 1 and 5 min, were also recorded. Maternal satisfaction with labor analgesia was evaluated 2 h after the delivery by using a 10-cm VAS (0, not satisfied at all; 10, fully satisfied).
Statistical analyses were performed with the StatViewTM 5.0 software (SAS Institute, Cary, NC). Data are presented as mean (95% confidence interval [CI]) for continuous variables and percentages (95% CI) for discrete variables. Statistical analyses of demographic data, amount of anesthetic solution administered, duration of labor, and maternal satisfaction were performed with Student’s t-test. The incidence of oxytocin use, side effects or motor blockade, the mode of delivery, the need for supplemental boluses, and Apgar scores were analyzed with Fisher’s exact test. Pain scores during labor (VAS) were analyzed by using analysis of variance for repeated measures. P < 0.05 was considered to be significant. Group size (at least 50 patients per group) was calculated by using sample-size estimates (power = 80%; 
= 0.05) to detect a 25% difference in the total dose of ropivacaine between groups (SamplePowerTM 1.02; SPSS Inc., Chicago, IL).
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Results
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Of the 135 parturients enrolled in this study, 5 were excluded (2 in Group 0.15% and 3 in Group 0.10%) because of deviations in the protocol standard or incomplete data collection. One-hundred-thirty parturients completed the study: 67 in Group 0.15% and 63 in Group 0.10%. Demographic data and labor characteristics are presented in Table 1 and did not differ between the two groups.
The duration of analgesia was similar in the two groups (Table 2). The duration of the first stage of labor (defined as the time between epidural blockade and full cervical dilation) and of the second stage (defined as the time between full cervical dilation and the completion of vaginal delivery or the decision to proceed with cesarean delivery) was similar in both groups (Table 1). There was no difference in the mean (95% CI) total volume of anesthetic solution administered during the overall study period (57.0 mL [50.5–63.5 mL] for Group 0.10% versus 55.9 mL [49.6–62.2 mL] for Group 0.15%), but the mean (95% CI) total dose of ropivacaine in Group 0.10% was less than in Group 0.15% (57.0 mg [50.5–63.5 mg] versus 88.0 mg [74.4–93.3 mg], respectively; P < 0.0001) (Table 2). The mean (95% CI) total dose of sufentanil was similar in both groups: 28 µg (25–31 µg) for Group 0.10% versus 29 µg (25–32 µg) for Group 0.15% (Table 2).
Mean VAS pain scores at baseline and throughout labor showed no difference between groups (Fig. 1). The incidence of side effects, including motor block, nausea, pruritus, and somnolence, as well as patient satisfaction, PCEA characteristics, need for supplemental boluses, and Apgar scores, was also similar between groups (Tables 1–3). There was no difference between the two groups in the incidence of instrumental or cesarean delivery (Table 1). No case of prolonged hypotension, respiratory depression, or postpartum hemorrhage more than 500 mL occurred in either study group.
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Figure 1. Mean visual analog pain scores (VAS) during labor. There was no difference between groups (analysis of variance for repeated measures). Error bars indicate SD. Group 0.15% = 0.15% ropivacaine plus sufentanil 0.5 µg/mL; Group 0.10% = 0.10% ropivacaine plus sufentanil 0.5 µg/mL.
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Discussion
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Our results suggest that 0.15% ropivacaine plus 0.5 µg/mL of sufentanil is equivalent to 0.10% ropivacaine plus 0.5 µg/mL of sufentanil administered via PCEA for labor analgesia. Patient demographics, labor characteristics, maternal satisfaction, side effects, and Apgar scores were similar in both groups. Local anesthetic requirements were similar in both groups, except for the total dose of ropivacaine, which was 30% less in the 0.10% group.
Although there are conflicting data in the literature, epidural analgesia is most likely both volume and dose dependent (9). The response to a given dose is not necessarily the same if volume and concentration are varied (10). The rather large basal infusion of 10 mL/h chosen in our study may have affected our findings in a way that no difference in the total volume was observed between groups simply because the volumes administered were more than a particular threshold. If a smaller basal infusion volume had been selected, it is possible that a difference might have been detected.
There is a trend in recent clinical studies toward the use of decreased concentrations of ropivacaine during labor. Sia et al. (11) showed that both ropivacaine 0.20% and 0.125% provided comparably effective analgesia. Fischer et al. (5) compared ropivacaine 0.10% plus sufentanil 0.5 µg/mL administered via PCEA during labor with bupivacaine 0.10% plus sufentanil 0.5 µg/mL, and they concluded that 0.10% ropivacaine and 0.5 µg/mL of sufentanil produce effective pain relief in labor. More recently, Owen et al. (7) reported that ropivacaine 0.075% and bupivacaine 0.075% with fentanyl 2 µg/mL administered via PCEA were equally effective for labor analgesia.
One theoretical benefit of reducing the concentrations of local anesthetics is to reduce the incidence of side effects. Sia et al. (11) compared the incidence of motor block by reducing the concentration of ropivacaine from 0.20% to 0.125% in PCEA for labor. They concluded that both ropivacaine 0.20% and 0.125% provided comparably effective analgesia but that motor block was reduced with 0.125% ropivacaine. In our study, we observed a trend toward a less frequent, although not statistically significant, incidence of motor block in Group 0.10% (22.2% had a Bromage score of 1, versus 37.3% in the 0.15% group). No profound motor block, however, was observed in either group. Of greater clinical significance, no difference in the mode of delivery was observed between groups. Possible explanations for why a significant reduction in local anesthetic use in our study did not reduce side effects could be insufficient power of the study to detect very small differences in side effects between groups (the primary outcome was the total dose of ropivacaine) or that side effects may be less dose dependent below a particular threshold.
It has been suggested that analgesic requirements increase as labor progresses and that reducing the concentration of ropivacaine might lead to inadequate analgesia, particularly during the second stage of labor (12). However, in our study, we found no differences in the verbal pain score at any of the time points at which it was assessed. The number of boluses needed to relieve the pain was similar in the two groups throughout both the first and the second stage of labor. The need for supplemental boluses was small in each group: during the first stage of labor, only 1.6% of parturients in Group 0.15% and 0% in Group 0.10% requested more than two supplemental boluses, as did 3.1% and 0%, respectively, during the second stage of labor. These differences are in contrast to those reported in a study by Fischer et al. (5), in which 24% of parturients receiving 0.10% ropivacaine plus 0.5 µg/mL of sufentanil requested more than 2 supplemental boluses during the first stage and 27% during the second stage of labor. These differences in the need for supplemental boluses might be explained by the basal infusion of 10 mL/h administered in our study, whereas no basal infusion was administered in Fischer et al.’s study. However, the proper mode of anesthetic solution delivery (i.e., continuous versus nonbasal infusion, bolus size, and lockout interval) remains to be determined (13,14) .
Decreased concentrations of <0.10% ropivacaine have been studied by Owen et al. (7). The authors compared the administration of 0.075% ropivacaine and 0.075% bupivacaine with 2 µg/mL of fentanyl at a basal rate of 6 mL/h for labor analgesia via PCEA. In their study, 28% of parturients needed two or more supplemental boluses during the overall study period, whereas in our study, only 4.7% in the 0.15% group and 0% in the 0.10% group needed two or more supplemental boluses during labor. Moreover, whereas Owen et al. reported that 52% of parturients had incomplete perineal analgesia requiring supplementation, in our study only 10% of patients needed supplemental boluses of the study solution during the second stage of labor. Although the satisfaction scores were excellent in both studies, these differences suggest that a decrease in the concentration of ropivacaine provides an increased need for supplemental boluses and that a ropivacaine concentration <0.1% seems to be insufficient to provide adequate analgesia during the second stage of labor. However, Owen et al. used a 10-minute lockout interval, which could have contributed to the need for additional supplemental boluses. Moreover, differences in perineal analgesia might relate to differences between sufentanil and fentanyl doses or between patient expectations and the availability of anesthesia care providers.
The addition of opioids significantly reduces the concentration of local anesthetic needed to achieve satisfactory pain relief (4). The mean (95% CI) total dose of sufentanil in our study was similar in both groups (28 µg [25–31 µg] in the 0.15% group and 29 µg [25–32 µg] in the 0.10% group). With sufentanil 0.5 µg/mL in the anesthetic solution, our results show satisfactory pain relief and maternal satisfaction, with a small incidence of nausea (approximately 10%) and pruritus (approximately 10%). The incidence of side effects in our study was similar to that in other studies (15,16) .
Concentrations of less than the 0.5 µg/mL of sufentanil used in this study might have provided similar results. Bernard et al. (16) have compared the dose-range effects of sufentanil added to 0.125% bupivacaine on the quality of PCEA during labor. They concluded that comparable levels of analgesia may be achieved by concentrations ranging from 0.125 to 0.468 µg/mL and that pruritus incidence increases with the sufentanil dose, whereas no significant differences were observed in the incidence of nausea, vomiting, or feelings of sleepiness. Moreover, they showed no significant reduction in the PCEA total bupivacaine dose requirement with different incremental doses of sufentanil, which was in contrast with many previous studies.
Finally, another benefit of reducing the concentrations of ropivacaine is a potential reduction in the cost of analgesia. As prepared at our institution, 5 bottles of 10 mL of ropivacaine 0.20% are needed to prepare a 60-mL solution of 0.15% ropivacaine, whereas only 3 bottles are needed to prepare a 60-mL solution of 0.10% ropivacaine. This represents a 40% reduction in cost.
In conclusion, ropivacaine 0.10% plus 0.5 µg/mL of sufentanil given via PCEA for labor analgesia was found to be equally effective when compared with ropivacaine 0.15% plus 0.5 µg/mL of sufentanil, with a 30% local anesthetic sparing-effect. This benefit was not, however, associated with a decrease in the incidence of motor block, side effects, or instrumental deliveries. Moreover, ropivacaine 0.10% plus 0.5 µg/mL of sufentanil given via PCEA for labor analgesia seems effective during both the first and second part of labor. On the basis of these findings, we recommend the use of 0.10% ropivacaine plus 0.5 µg/mL of sufentanil for labor analgesia with PCEA. Further studies comparing smaller concentrations of ropivacaine and smaller concentrations of sufentanil, with or without background infusions, are needed to determine the minimal concentrations required to achieve the best analgesia associated with the least frequent incidence of side effects.
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References
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Accepted for publication December 10, 2002.
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Abstract
Introduction
