|Year : 2018 | Volume
| Issue : 1 | Page : 35-42
A comparative study of low concentration of levobupivacaine versus ropivacaine with fentanyl for patient-controlled epidural labour analgesia
Priyanka Chuttani1, Udeyana Singh2, Anju Grewal2, Sunil Katyal2, Ashima Kaura3
1 Department of Anaesthesiology, PGIMER, Chandigarh, India
2 Department of Anaesthesiology, Dayanand Medical College and Hospital, Ludhiana, Punjab, India
3 Department of Obstetrics and Gynaecology, Dayanand Medical College and Hospital, Ludhiana, Punjab, India
|Date of Web Publication||13-Apr-2018|
Dr. Udeyana Singh
Department of Anaesthesiology, Dayanand Medical College and Hospital, Ludhiana, Punjab
Source of Support: None, Conflict of Interest: None
Background and Aims: Lumbar epidural analgesia is considered the modality of choice for labour analgesia. Despite its super analgesia and improved safety profile, it has been associated with maternal adverse effects like higher incidence of instrumental assisted vaginal delivery (AVD) and motor block leading to decreased ambulation. This study was designed to evaluate the efficacy of low concentrations of local anaesthetics (0.1% ropivacaine and 0.1% levobupivacaine) with 2 μg/ml fentanyl as a patient controlled epidural analgesia (PCEA) technique on the incidence of instrumental AVD along with evaluation of obstetric, maternal, and foetal outcomes. Materials and Methods: In this prospective study, 60 labouring parturients were randomly allocated into two equal groups to receive either 0.1% ropivacaine with 2 μg/ml fentanyl or 0.1% levobupivacaine with 2 μg/ml fentanyl as epidural solutions via PCEA pump infusions (4 ml/h) after 15 ml loading dose of the respective solutions. The incidence of instrumental AVD was noted as the primary outcome along with demographic data, maternal and foetal vital parameters, maternal VAS scores, degree of motor blockade and total epidural drug consumption. Results: The incidence of instrumental AVD was found to be 43.3% in the levobupivacaine group and 30% in the ropivacaine group. This difference was not statistically significant. Both the groups were comparable in terms of demographic data, maternal VAS scores, total epidural drug consumption and foetal APGAR scores. Conclusion: The use of newer local anaesthetics (levobupivacaine and ropivacaine) in low concentrations with opioids (fentanyl) as a PCEA technique may offer high maternal satisfaction in terms of quality of pain relief with fewer adverse events like instrumental AVD and adverse foetal outcomes.
Keywords: Labour analgesia, low-dose local anaesthetics, patient-controlled epidural analgesia
|How to cite this article:|
Chuttani P, Singh U, Grewal A, Katyal S, Kaura A. A comparative study of low concentration of levobupivacaine versus ropivacaine with fentanyl for patient-controlled epidural labour analgesia. J Obstet Anaesth Crit Care 2018;8:35-42
|How to cite this URL:|
Chuttani P, Singh U, Grewal A, Katyal S, Kaura A. A comparative study of low concentration of levobupivacaine versus ropivacaine with fentanyl for patient-controlled epidural labour analgesia. J Obstet Anaesth Crit Care [serial online] 2018 [cited 2020 Jun 1];8:35-42. Available from: http://www.joacc.com/text.asp?2018/8/1/35/230063
| Introduction|| |
Neuraxial techniques have been considered as the gold standard modality for labour analgesia. Inspite of the superior analgesia and improved safety of epidural labour analgesia, it has been associated with maternal and foetal adverse effects, including prolongation of labour, higher incidence of instrumental assisted vaginal delivery (AVD),, decreased ambulation mainly due to varying degrees of motor block especially with the use of higher concentrations of local anaesthetics.,,, Motor block has been implicated as one of the contributory factors for operative delivery. Long acting local anaesthetics like levobupivacaine and ropivacaine have been increasingly used along with adjuvants such as opioids to provide safe, effective and adequate pain relief during labour.,,, Lee et al. found no significant differences in the mode of delivery, duration of labour and foetal outcomes in the study comparing low concentration of ropivacaine (0.08%) and levobupivacaine (0.06%) with fentanyl (2 mcg/ml) for labour epidural analgesia. However, the study was besieged with the disadvantages of more frequent top ups in the levobupivacaine group and significantly increased total amount of local anaesthetic consumption in the ropivacaine group. Further improvement in safety of epidural labour analgesia was achieved following the introduction of the concept of patient controlled epidural analgesia (PCEA) by Gambling et al. in 1988.
Studies by various researchers comparing low dose levobupivacaine versus ropivacaine with and without fentanyl have observed varying results regarding the analgesic efficacy, drug consumption, motor and sensory blockade, and mode of delivery.,,
In this study, it was hypothesized that by combining an established PCEA technique with low concentration of relatively newer local anaesthetics along with an opioid, it will be possible to reduce the incidence of instrumental AVD. Hence, it was proposed to comparatively study the effect of low concentrations of epidural levobupivacaine versus ropivacaine with fentanyl for labour analgesia using PCEA technique primarily on the incidence of instrumental AVD along with evaluation of obstetric, maternal and foetal outcomes.
| Materials and Methods|| |
This study was conducted after approval by Hospital Ethics Committee on a total of 60 parturients (ASA-PS I, II) requesting labour analgesia. A written informed consent was obtained from every parturient. Parturients with history of anaphylaxis to local anaesthetics and allergy to the drugs used as well as those with any contraindication to epidural catheter placement were excluded.
Subjects were allocated in two groups:
- Group A: comprising 30 parturients who received 0.1% levobupivacaine with 2 μ/ml fentanyl
- Group B: comprising 30 parturients who received 0.1% ropivacaine with 2 μ/ml fentanyl.
Preparation of the drug
Among the sixty coded envelopes containing details of the drug combinations to be used, any one envelope was randomly opened for each parturient by an anaesthetist who was not a part of study any further. The respective drug combinations were prepared and marked with a coded label by the anaesthesiologist who was not a part of study and it was handed over to the anaesthesiologist performing the epidural block in a blinded manner. Neither the principal investigator/observer nor the parturient were aware of the nature of study solution. In group A and group B, respectively, 10 ml of 0.5% levobupivacaine and 25 ml of 0.2% ropivacaine was added to 2 ml of 0.005% fentanyl. Subsequently both mixtures were reconstituted to a volume of 50 ml with 0.9% sodium chloride solution, thereby achieving the concentration of 0.1% of levobupivacaine and ropivacaine, respectively.
Baseline monitoring of vitals including maternal heart rate, non-invasive arterial pressure and foetal heart rate were instituted and recorded. After establishing IV access, lumbar epidural insertion was done in L3-L4 interspace under all aseptic precautions using loss of resistance technique.
Participants were randomized using sealed envelope allocation to receive a loading dose of 15 ml of 0.1% levobupivacaine with 2mcg/ml fentanyl (group A) or 0.1% ropivacaine with 2 mcg/ml fentanyl (group B) delivered over 10 mins using a PCEA pump. This initial loading dose served as the test dose, which was given gradually under monitoring for any signs of inadvertent intrathecal or intravascular placement.
If the onset of analgesia did not occur within 30 minutes, a further 10 ml of study solution was delivered over 10 minutes via PCEA pump. Subsequently if the onset of analgesia did not occur within 60 minutes, 10 ml of bupivacaine 0.25% solution was administered (rescue analgesia) and the parturient was withdrawn from the study. Subsequent maintenance of labour analgesia was achieved using a PCEA pump programmed to deliver 5 ml of study solution as per parturient demand with a lock out interval of 15 minutes along with a background infusion (BI) of 4 ml/hour in both groups. Breakthrough pain [visual analog scale (VAS) >30 mm], defined as a parturient requesting additional analgesia irrespective of PCEA use was treated with additional 5 ml rescue boluses of study solution given manually by the anaesthesiologist and recorded. All parturients were nursed in either left lateral position or were given a 30° wedge under her right hip throughout labour.
Pain intensity was evaluated during contractions with a 100 mm VAS where 0 represents no pain and 100 represents worst pain imaginable. Assessment of pain was undertaken before epidural catheterization and at 30 minutes interval following loading dose completion. Reduction in pain score to less than equal to 30 mm was considered to represent the onset of analgesia.
Maternal pulse rate (PR), non-invasive arterial pressure (NIBP), oxygen saturation (SpO2) was measured at an interval of 5 minutes for 60 minutes and at 30 minutes interval thereafter. Hypotension was defined as decrease of 20% below baseline. When hypotension occurred, parturient was administered 100 ml boluses of intravenous fluids along with IV ephedrine in boluses of 6 mg and repeated if required. Foetal heart rate and uterine activity were monitored continuously throughout labour by cardiotocography and recorded at 10 minutes in the Performa.
Motor block and maternal adverse effects including pruritis, hypotension, nausea and vomiting were assessed at 30 minutes interval. Motor blockade was measured using 0 to 3 Modified Bromage scale.
The extent of sensory block was assessed by cold alcohol swab in the mid clavicular line from upper thoracic to lumbar dermatomes at 30 minutes interval.
The study was completed when spontaneous delivery occurred or when AVD or lower segment caesarean section (LSCS) was required. The duration of first, second and third stages of labour, total duration of labour, mode of delivery, 1 and 5 minutes APGAR score was recorded.
Total epidural drug consumption
The number of demand boluses and number of manual rescue boluses of study solution were documented. Hourly and total drug consumptions were measured at delivery. Total duration of epidural analgesia was observed. In addition, total dose of oxytocin used during labour was also documented.
Maternal satisfaction was assessed within one hour and twenty four hours after delivery using 100 mm VAS where 0 represents complete dissatisfaction and 100 represents complete satisfaction.
The blind was opened at the end of the study for the purpose of evaluating the effect of local anaesthetics. Our institutional data of instrumental AVD rates reported in a previous study evaluating PCEA regimen with parenteral analgesics for labour pain relief was found to be 36%. By assuming AVD rate (p) as 36% and calculating sample size by the following formula
n = (Z 2)p(100 − p)/d 2
Where n = sample size, Z = level of confidence taken as value of 1.96 with 95% confidence interval, p = expected prevalence in % and d = allowable error, sample size was calculated as 27.32 ≈ 27. Considering drop outs we have taken 30 as sample size for each group.
Quantitative parametric data such as age, weight, pulse rate (PR), foetal heart rate (FHR), systolic and diastolic blood pressure (SBP, DBP), number of demand boluses, time of first requirement of manual rescue bolus was compared between the two study groups using student's t-test. Quantitative non-parametric data such as height, cervical dilatation, period of gestation, oxygen saturation (SpO2), visual analogue scale (VAS), total duration of epidural analgesia, onset of analgesia, drug consumption, level of sensory block, duration of labour, total oxytocin consumption, number of uterine contractions, maternal satisfaction and APGAR score was compared between the study groups using Mann–Whitney U test. For comparing categorical data (parity, induced labour, number of manual rescue boluses, incidence of motor block, incidences of various modes of delivery, indications of instrumental AVD and caesarean delivery, maternal adverse effects), Chi square test and Fisher's exact test was performed. All tests were evaluated for 95% confidence interval. A probability value (P value) ≤0.05 was considered statistically significant. All statistical calculations were done using Statistical Package of Social Sciences (SPSS) 17 version statistical program for Microsoft Windows (SPSS Inc. Released 2008. SPSS statistic for windows, version 17.0, Chicago).
| Results|| |
Demographic parameters, i.e., age, weight, height, cervical dilatation, period of gestation and parity were statistically comparable among both the groups. Median cervical dilatation (centimeters) in group A was 4.00 (3–4 SD) and 4.00 (3–4 SD) in group B. Median period of gestation in weeks in was 38 (38–39) in group A and 39 (37.75–39) in group B. There was a preponderance of primipara (27 in each group) than multipara (3 in each group) parturients. However, parity was statistically comparable among both the groups.
Median pre-epidural VAS (out of 100 mm) was 80 (70–90) mm and 80 (80–90) mm in groups A and B, respectively, with no statistically significant difference.
No statistically differences were found in terms of pre-epidural parameters (PR, SBP, DBP, and SpO2) between both the groups.
Median onset of analgesia was 10 (10–15) minutes and 11 (10–15) minutes in groups A and B, respectively (P = 0.602).
Mean of total duration of epidural analgesia was 295.50 ± 198.11 minutes in group A and 343.67 ± 259.92 minutes in group B. This was not statistically significant.
Quality of pain relief was adequate with VAS of ≤30 mm at most of the time intervals in both the groups. Median VAS at all times was not significant among both the groups except at 8 hours 30 minutes. Statistically significant differences were noted in VAS between both groups at 8 hours 30 minutes (P value = 0.016) and the median was 30 (30–30) mm in group A and 50 (50–50) mm in group B.
Mean number of demand boluses per hour at all times were statistically insignificant among both groups except at ninth hour, which were 0.07 ± 0.25 in group A and 0.37 ± 0.76 in group B [Figure 1]. Therefore, the number of demand boluses per hour showed statistically significant difference at ninth hour between both groups (P = 0.046)
Mean total number of manual rescue boluses of study solution in group A and B were found to be 1.00 ± 2.75 and 0.50 ± 2.01, respectively. The difference was not statistically significant.
Mean time of first requirement of manual rescue bolus (hours) was 3.13 ± 0.75 and 2.63 ± 1.94 in groups A and B, respectively. Time of first requirement of manual rescue bolus did not vary statistically significantly among the two groups.
Mean hourly drug consumption (mg) was 12.90 ± 2.51 and 14.00 ± 6.31 in groups A and B, respectively. Only one parturient in Group A had duration of labour extending beyond 11 hours 30 minutes. Mean total drug consumption in milligrams (calculated by including loading dose, demand boluses, background infusion and manual rescue boluses) was found to be 58.71 ± 32.02 mg and 65.27 ± 41.34 mg in groups A and B, respectively. There were no observed statistically significant differences in hourly and total drug consumption among both the groups.
The median highest level of sensory block was T8, thus attaining adequate level of analgesia in both the groups.
Motor block did not occur in 93.33%parturients in each group. One parturient in group A developed Modified Bromage Grade I motor block, and two parturients in group B developed grade I motor block. Only one parturient in group A had grade II motor block. Grade III motor block was not observed in any parturient. Hence, there were no statistically significant differences in terms of intensity and incidence of motor block among both groups.
Obstetric and maternal outcomes
All the parturients in both the groups had induced labour. None of the parturients had spontaneous labour.
Mean consumption of units of oxytocin throughout labour was comparable in both groups (4.97 ± 3.65IU and 4.45 ± 2.90IU in groups A and B, respectively).
No statistically significant differences were found in duration of different stages of labour and total duration of labour [Table 1].
The incidence of instrumental AVD (F) was found to be 43.3% in group A and 30% in group B. The incidence of normal vaginal delivery (N) was 40% in group A and 46.7% in group B. The incidence of caesarean delivery (C) was 16.7% in group A and 23.3% in group B. No statistical significance was noted in regard to the mode of delivery between the two groups [Table 2]; [Figure 2].
|Table 2: Incidence of various modes of delivery, i.e., caesarean (C), instrument-assisted vaginal delivery (F) and normal vaginal delivery (N) (Percentage)|
Click here to view
The relative risk of instrumental AVD (F) was estimated to be 1.44 taking 95% confidence interval (range 0.730–2.859). The parturients in group A have 1.44 times chances of having instrumental AVD as compared to group B [Table 3].
Indications of caesarean delivery were found to be cephalopelvic disproportion (CD) [40% in group A and 42.9% in group B], foetal distress associated with loop of cord around neck (CAN) [0% in group A and 28.6% in group B], foetal distress associated with meconium-stained liquor (MSL) [20% in group A and 14.3% in group B], obstructed labour (OBL) [40% in group A and 0.0% in group B] deep transverse arrest (TA) [0.0% in group A and 14.3% in group B].
Indications of instrumental AVD included foetal distress associated with loop of CAN [53.8% in group A and 44.4% in group B], foetal distress associated with both loop of CAN and MSL [0% in group A and 11.1% in group B] and foetal distress associated with persistent occipito-posterior position (POP) [23.1% in group A and 11.1% in group B], deep TA [15.4% in group A and 33.3% in group B]. The indications of instrumental AVD and caesarean delivery were statistically comparable among both the groups.
Maternal parameters (pulse rate, systolic/diastolic BP, oxygen saturation) were comparable in both groups [Figure 3], [Figure 4], [Figure 5].
Mean maternal satisfaction on a visual analogue scale of (0–100) mm where 0 represents complete dissatisfaction and 100 represents complete satisfaction at 1 and 24 hours after delivery in group A was observed as 77.67 ± 19.95 mm. Mean maternal satisfaction at 1 and 24 hours after delivery in group B it was 80.00 ± 12.59 mm and 80.33 ± 12.99 mm. Maternal satisfaction at first and twenty fourth hour after delivery among both groups did not vary significantly in a statistical manner.
Only one parturient in each group developed hypotension and nausea. Pruritis was not observed in any parturient.
Foetal heart rate and median APGAR scores at 1 and 5 minutes among both groups did not show any statistically significant variation. No foetal adverse event was noted throughout the study in both the groups.
| Discussion|| |
Multiple factors like station and position of the foetal head, maternal pain and the urge to bear down, and epidural analgesia-induced motor block contribute to the outcome of second stage of labour. Among these factors leading to instrumental AVD, motor block of perineal or abdominal muscles resulting in impairment of Fergusson-Harris reflex (needed for bearing down efforts in the second stage) and abnormal internal rotation of foetal head have been proposed to be a major determinant in increasing instrumental AVD rates.,, Studies using ropivacaine in higher concentrations especially ≥0.2% have been found to be associated with greater motor blockade., This can be eliminated by using these local anaesthetic agents in a lower concentration (0.05–0.15%). However this curtails effective analgesia. Using an opioid along with local anaesthetics improves the analgesia while causing less motor blockade, thus reducing the incidence of AVD. The reason for choosing 0.1% concentration of local anaesthetic in this study was to achieve minimal motor blockade thereby targeting to decrease the incidence of instrumental AVD. Though ropivacaine is considered 40% less potent than levobupivacaine,,, we chose to evaluate equipotent lower concentrations based on the studies of Wang and Purdie et al., which demonstrate nearly similar clinical potencies of levobupivacaine and ropivacaine when used at concentrations ≤0.1%.,,
Newer drugs (levobupivacaine and ropivacaine) have high differential sensory-motor block ratio, less potential for cardio and neurotoxicity thereby offering better safety profile as compared to bupivacaine.,,,, PCEA, a well accepted technique of administering epidural labour analgesia, improves maternal analgesia and enhances parturient satisfaction with the use of lowest possible effective doses of local anaesthetics, thereby reducing the total drug consumption.,, This leads to minimal motor block and probable favourable effect on mode of delivery.,, This formed the basis of the use the PCEA technique along with background infusion of 4 ml/h in this study.
None of the parturients were excluded from the study as all the parturients achieved onset of analgesia within 30 minutes of administration of initial loading dose of study solutions. A uniform analgesia initiation and maintenance technique was used in all the subjects.
The confounding factors which can affect the progress and outcome of labour such as duration of all stages of labour, total duration of epidural analgesia, oxytocin consumption throughout labour, onset of analgesia, the highest level of sensory block (T8) and total local anaesthetic drug consumption among both groups varied insignificantly thus making the two groups comparably similar.
The incidence of instrumental AVD in this study was statistically comparable among both the groups A and B, i.e., the incidence was 43.3% in parturients receiving levobupivacaine and 30% in ropivacaine group. The relative risk ratio of instrumental AVD for group A parturients relative to group B was estimated to be 1.44 (95% confidence interval, 0.73–2.86), which was statistically insignificant.
Comparably similar incidence of AVD has been reported by various researchers.,,,- However, studies by Beilin et al. (9% and 6% in ropivacaine and levobupivacaine groups, respectively), Lee et al. (20% and 14% in ropivacaine and levobupivacaine groups, respectively), Lim et al. (15%), Finegold et al. (18%) report lower incidences of AVD. These reduced overall differences in instrumental AVD rates from those observed in this study could be attributed to use of lower concentrations of local anaesthetics (0.06–0.08%), or varying analgesic initiation techniques and in few circumstances, the retrospective nature of the study design. However, similar to the results of this study, Beilin et al. and Lee et al. did not observe any statistically significant differences in the mode of delivery among the studied local anaesthetic solutions (levobupivacaine and ropivacaine).,
Grade I and II motor block was observed only in 6.7% parturients in both the study groups. No statistical significant differences in motor block characteristics were elicited among both groups, which was comparably similar to the observed motor block incidence in studies by Purdie et al. and Beilin et al.,
A reduced total local anaesthetic consumption was seen in both groups, which was comparable to the observed results of studies investigating background infusion rates ≤5 ml/h., Reduced total local anaesthetic consumption in both the groups explains the negligible motor block observed here.
Apart from motor block, density of neuraxial analgesia also influences the outcome of second stage of labour. In an editorial, Chestnut stated that effective second stage analgesia increases the risk for instrumental AVD. The quality of analgesia in our study was adequate with VAS of ≤30 mm at most of the time intervals during first and second stage of labour in both the groups. Median VAS at various time intervals of first and second stage of labour was statistically comparable among both the groups except at 8.5 hours where VAS was statistically significantly higher in ropivacaine group. Consequently, we observed statistically significant increase in the number of demand boluses at ninth hour in ropivacaine group. Although the analgesic potency of levobupivacaine seems relatively higher as evidenced by lower VAS scores at 8.5 hrs along with a statistically insignificant trend to delayed time of first requirement of manual rescue bolus, it did not result into statistically significant differences in the total analgesic consumption among both the groups. Hourly and total local anaesthetic consumption was statistically comparable between both the groups, reflecting effective analgesia throughout all stages of labour. Hence, adequate dense analgesia leading to a decreased urge to push could be a contributory factor for the observed instrumental AVD rates.
Failure to wait by the obstetricians for a modest prolongation in duration of second stage of labour can be one of the contributing factors towards an overall higher instrumental AVD rates. This is evidenced by the relatively decreased observed duration of second stage of labour in this study as compared to the duration of second stage of labour observed by various researchers.,,, In addition to above, the predominant indications of instrumental AVD in this study were loop of cord around neck (53.8% in group A and 44.4% in group B), and malpositions such as deep transverse arrest (15.4% in group A and 33.3% in group B) and persistent occipito-posterior position (23.1% in group A and 11.1% in group B). These indications were statistically comparable between both the groups and led to early use of forceps for vaginal delivery.
The incidence of caesarean delivery was 16.7% in group A and 23.3% in group B, which was comparable to that reported in literature.,,,,, Indications for caesarean delivery were mainly obstetric causes and did not exhibit any causal relationship to epidural infusions in both the groups.
The observed 40% incidence of spontaneous normal vaginal delivery in group A (levobupivacaine) and 46.7% in group B (ropivacaine), which is similar to those observed in the studies by Lee et al (41.6%) and low dose infusion group of COMET trial (43%).
High maternal satisfaction evidenced by high VAS scores were similar to those reported by other studies.,
No adverse foetal outcomes occurred throughout the study in both the groups. These outcomes coincides with the favourable foetal outcomes observed in various other studies.,,,
Limitations of our study
Studies focussing to relate epidural analgesia with mode of delivery are fraught with limitations due to numerous like the timing of amniotomy, maternal fever, neonatal birth weight, which can influence the mode of delivery. The major limitation was the small sample size which was primarily chosen based on our institutional data of instrumental AVD rates reported in a previous study and secondary to a trend towards lower uptake of epidurals by parturients in our settings.
| Conclusion|| |
Hence, we conclude that epidural drug solutions of 0.1% levobupivacaine and 0.1% ropivacaine with fentanyl 2 mcg/ml using PCEA with background infusion of 4 ml/hr were equally efficacious in providing adequate analgesia for all stages of labour, exhibiting comparable reduced hourly and total local anaesthetic drug consumption with consequent negligible motor block, high maternal satisfaction and clinically insignificant adverse maternal or foetal effects. This regimen of epidural labour analgesia resulted in statistically insignificant differences in the mode of delivery, with comparable incidence of instrumental AVD among both the groups. These rates can be further reduced by employing a uniform obstetric protocol of delayed maternal pushing especially when the foetal heart rate is re-assuring and foetal head descent is progressing well.
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Conflicts of interest
There are no conflicts of interest.
| References|| |
Cambic CR, Wong CA. Labour analgesia and obstetric outcomes. Br J Anaesth. 2010;105:i50-60.
Sultan P, Murphy C, Halpern, Carvalho B. Effect of low concentrations versus high concentrations of local anaesthetics for labour analgesia on obstetric and anaesthetic outcomes: A meta-analysis. Can J Anesth 2013;60:840-54.
Anim-Somuah M, Smyth R, Howell C. Epidural versus non-epidural or no analgesia in labour. Cochrane Database Syst Rev 2005;4:CD000331.
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.
Wilson MJ, MacArthur C, Cooper GM, Shennan A, COMET Study Group UK. Ambulation in labour and delivery mode: A randomised controlled trial of high-dose vs mobile epidural analgesia. Anaesthesia 2009;64:266-72.
Boulier V, Gomis P, Lautner C, Visseaux H, Palot M, Malinovsky JM. Minimum local analgesic concentrations of ropivacaine and levobupivacaine with sufentanil for epidural analgesia in labour. Int J ObstetAnaesth 2009;18:226-30.
Purdie NL, Mc Grady EM. Comparison of patient controlled epidural bolus administration of 0.1% ropivacaine and 0.1% levobupivacaine, both with 0.0002% fentanyl, for analgesia during labour. Anaesthesia 2004;59:133-7.
Lee HL, Lo LM, Chou CC, Chuah EC. Comparison between 0.08% ropivacaine and 0.06% levobupivacaine for epidural analgesia during nulliparous labour. Chang Gung Med J 2011;34:286-91.
Atienzar MC, Palanca M, Torres F, Borras R, Gil S, Esteve I. A randomised comparison of levovupivacaine, bupivacaine and ropivacaine with fentanyl for labour analgesia. Int J Obstet Anesth 2008;17:106-11.
Gambling DR, Yu P, Cole C, McMorland GH, Palmer L. A comparative study of patient controlled epidural analgesia (PCEA) and continuous infusion epidural analgesia (CIEA) during labour. Can J Anesth 1988;35:249-54.
Beilin Y, Guinn NR, Bernstein HH. Local anaesthetics and mode of delivery: Bupivacaine versus ropivacaine versus levobupivacaine. Anesth Analg 2007;105:756-63.
Wong CA. Epidural and spinal analgesia/anesthesia for labor and vaginal delivery. In: Chestnut DH, Wong CA, Tsen LC, NgankeeWD, Beilin Y, MhyreJM, Nathan N, et al
., editors. Chestnut's Obstetric Anesthesia: Principles and Practice. 5th
ed. China: Saunders Elsevier; 2014. pp. 457-517.
Lieberman E, Davidson K, Lee-Parritz A, Shearer E. Changes in fetal position during labor and their association with epidural analgesia. Obstet Gynecol 2005;105:974-82.
Gogarten W, Van de Velde M, Soetens F, Van Aken H, Brodner G, Gramke HF, et al
. A multicentre trial comparing different concentrations of ropivacaine plus sufentanil with bupivacaine plus sufentanil for patient-controlled epidural analgesia in labour. Eur J Anaesthesiol 2004;21:38-45.
Sia AT, Ruban P, Chong JL, Wong K. Motor blockade is reduced with ropivacaine 0.125% for parturient-controlled epidural analgesia during labour. Can J Anaesth 1999;46:1019-23.
Wang LZ, Chang XY, Liu X, Hu XX, Tang BL. Comparison of bupivacaine, ropivacaine and levobupivacaine with sufentanil for patient-controlled epidural analgesia during labor: A randomized clinical trial. Chin Med J (Engl) 2010;123:178-83.
PolleyLS, Columb MO, Naughton NN, Wagner DS, van de Ven CJ. Relative analgesic potencies of ropivacaine and bupivacaine for epidural analgesia in labor: Implications for therapeutic indexes. Anesthesiology 1999;90:944-50.
Capogna G, Celleno D, Fusco P, Lyons G, Columb M. Relative potencies of bupivacaine and ropivacaine for analgesia in labour. Br J Anaesth 1999;82:371-3.
Lyons G, Columb M, Wilson RC, Johnson RV. Epidural pain relief in labour: Potencies of levobupivacaine and racemic bupivacaine. Br J Anaesth 1998;81:899-901.
Lee BB, NganKee WD, Ng FF, Lau TK, Wong EL. Epidural infusions of ropivacaine and bupivacaine for labor analgesia: A randomized, double-blind study of obstetric outcome. Anesth Analg 2004;98:1145-52.
Flood P, Rollins MD. Anesthesia for obstetrics. In: Millers R, Cohen NH, Eriksson LI, Fleisher LA, Wiener Kronish JP, Young WL, editors. Miller's Anesthesia. 8th
ed. Canada: Saunders Elsevier; 2015. pp. 2328-58.
Halpern SH, Carvalho B. Patient-controlled analgesia for labour. Anesth Analg 2009;108:921-7.
Carvalho B, Cohen SE, Giarrusso K, Durbin M, Riley ET, Lipman S. Ultra-light patient controlled epidural analgesia during labour: Effect of varying regimens on analgesia and physician workload. Int J Obstet Anesth 2005;14:223-9.
Halpern SH, Breen TW, Campbell DC, Muir HA, Kronberg J, Nunn R, et al
. A multicenter, randomized, controlled trial comparing bupivacaine with ropivacaine for labor analgesia. Anesthesiology 2003;98:1431-5.
Atienzar MC, PalancaJM, Borras R, Esteve I, Fernandez M, Miranda A. Ropivacaine 0.1% with fentanyl 2 microg mL(-1) by epidural infusion for labour analgesia. Eur J Anaesthesiol 2004;21:770-5.
Lee BB, NganKee WD, Lau WM, Wong AS. Epidural infusions for labor analgesia: A comparison of 0.2% ropivacaine, 0.1% ropivacaine, and 0.1% ropivacaine with fentanyl. Reg Anesth Pain Med 2002;27:31-6.
Lim Y, Ocampo CE, Supandji M, Teoh WH, Sia AT. A randomized controlled trial of three patient-controlled epidural analgesia regimens for labor. Anesth Analg 2008;107:1968-72.
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.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]