|Year : 2013 | Volume
| Issue : 2 | Page : 70-73
Labor analgesia: An update on the effect of epidural analgesia on labor outcome
Department of Anaesthesia, Aga Khan University Hospital, Karachi, Pakistan
|Date of Web Publication||19-Dec-2013|
Department of Anaesthesia, Aga Khan University Hospital, Stadium Road, P.O. Box 3500, Karachi 74800
Source of Support: None, Conflict of Interest: None
Following the introduction of epidural for labor analgesia, debate has centered on the issue of its effect on outcome of labor; in terms of length of labor and increase in the rate of instrumental vaginal delivery and cesarean section (CS). There is no ideal study on the effect of epidural analgesia (EA) on the outcome of labor due to logistic problems in randomization, blinding and getting a control group; as a result these queries are partly answered. Despite these problems, it has been established that labor epidural has minimal effect on progress of established labor and maternal request should be a sufficient indication to start an epidural. Although instrumental vaginal delivery is probably increased with epidural but obstetrician practice, pain free patient and teaching opportunity are likely factors increasing the incidence. Maternal-fetal factors and obstetric management and not the use of EA are the most important determinants of the CS rate. The purpose of this review is to summarize data from controlled trials addressing the question of whether neuraxial labor analgesia causes an increased risk of CS or rate of instrumental delivery. In addition, the review discusses whether the timing of initiation of analgesia infl uences the mode of delivery.
Keywords: Cervical dilatation, cesarean section, epidural analgesia, instrumental vaginal delivery
|How to cite this article:|
Ismail S. Labor analgesia: An update on the effect of epidural analgesia on labor outcome. J Obstet Anaesth Crit Care 2013;3:70-3
|How to cite this URL:|
Ismail S. Labor analgesia: An update on the effect of epidural analgesia on labor outcome. J Obstet Anaesth Crit Care [serial online] 2013 [cited 2021 Apr 18];3:70-3. Available from: https://www.joacc.com/text.asp?2013/3/2/70/123297
| Introduction|| |
Labor analgesia affecting labor outcome is perhaps the longest lived controversy in the history of obstetric anesthesia. It started from 1847, when James Simpson administered ether to a woman in labor for child birth and has continued on this day in both academic and lay circles.
After the introduction of regional analgesia, debate has centered on three main issues:
Does regional analgesia increases the risk of cesarean section (CS) and instrumental vaginal delivery and does the timing of initiation of epidural analgesia (EA) play a role?
In addition, there have been challenges in designing and executing an ideal clinical trial to study the effect of EA on the labor outcome.
The purpose of this review is to highlight these challenges and summarize data from controlled trials addressing the question of whether neuraxial labor analgesia causes an increased risk of CS. In addition, the effect of EA on rate of instrumental delivery and the effect of timing of the institution of EA on the mode of delivery will be discussed.
| Challenges Faced in Conducting an Ideal Clinical Study On The Effect of Neuraxial Analgesia on Labor Outcome|| |
An ideal clinical study is prospective, randomized, double blinded and placebo controlled. No study of EA on the outcome of labor has fulfilled the criteria. The reason being that risk factor for dysfunctional labor, pre-disposes the women to select labor epidural. Therefore, most of the comparisons are between women who self-selected EA and those who did not, leading to selection bias.
Investigators have identified many characteristics of parturient requesting EA such as nulliparity, slower cervical dilation before analgesia, poor fetal status, maternal systemic disease, smaller pelvic outlets and pain in early labor.  Many of these factors mentioned are associated with slower labor leading to assisted or cesarean delivery.
Logistically, it is impossible to blind the patient, nurses, obstetrician and anesthetists to the presence and absence of functional EA. Decision to proceed with operative delivery is ultimately a subjective clinical one made by the obstetrician and the absence of blinding is very important. Another limitation in conducting randomized controlled trials (RCTs) is difficulty in controlling factors that are known to influence the outcome of labor for example, obstetric provider and labor management including active management of labor with oxytocin. Meta-analysis has found that parturients randomized to receive EA are more likely to receive oxytocin (risk ratio = 1.19, 95% confidence interval (CI) = 1.03-1.39). However, the 95% CI of the risk ratio is close to including one, with significant heterogeneity among the studies. 
Performing randomized prospective trials with placebo controls can have ethical concerns. Therefore, except for a few small studies, RCTs have compared two treatment groups, neuraxial analgesia and systemic opioid analgesia that is usually parenteral opioid, but parenteral opioids may themselves affect the course of labor.  High quality studies addressing the effect of systemic analgesia on the progress of labor are lacking. Since most of studies have been designed with systemic analgesia as control, it is difficult to assess how the control group affects the outcome of labor. In addition, it has been suggested that RCTs comparing neuraxial with systemic opioid analgesia lack external validity. 
Moreover, since EA provides better pain relief as compared to systemic analgesia, it is difficult to obtain consent and minimize crossover from the systemic analgesia group. Several of the randomized trials are found to be underpowered as detecting even a small difference in typical CS rates of 10-20% requires several 100 patients per group.
Protocol non-compliance is another problem as analysis of only protocol complaint patient introduces bias, because patients excluded from epidural group may belong to a low risk group, who progress easily through labor with minimal pain, whereas those excluded from an opioid group may be high-risk patients experiencing slow, painful labor. Analysis of intention to treat is complicated when large numbers are involved, further reducing the power of the study.
In addition, there has been concern that RCTs may not depict the true picture of the effect of neuraxial anesthesia on the rate of CS in actual clinical practice. The reason has being the strict inclusion and exclusion criteria of RCTs in an attempt to control other variables that might influence the outcome of labor. Thus, the results of the studies may not reflect the normal labor and obstetric or anesthetic management.
In addition to RCTs, impact studies are also performed to study the effect of EA on the rate of CS. An impact study is a study design in which one compares an outcome immediately before and after the introduction of an event, which in this case would be the introduction of labor EA service. The results of this type of study will be more applicable to the general population who as participants do not select their analgesia and also do not crossover due to lack of other options. However, there is an assumption in impact studies that there is no change in any other variables that can affect the rate of CS, which is one of the limitations of these impact studies.
| Risk of CS|| |
Results of the RCTs and systematic reviews published between 2001 and 2004 did not demonstrate any difference in the rate of CS between women receiving epidural and those who received only intravenous analgesia. ,,,,
A Cochrane review of 2005, included 21 studies involving 6664 women, all but one study compared EA with opiates.  There was no evidence of a significant difference in the risk of cesarean delivery (relative risk [RR] = 1.07, 95% CI = 0.93-1.23, 20 trials, 6534 women). 
The more recent Cochrane review of 2011, included 38 studies involving 9658 women; all but five studies compared EA with opiates.  The finding that was different from the Cochrane review of 2005  was an increased risk of CS for fetal distress (RR = 1.43, 95% CI = 1.03-1.97, 11 trials, 4816 women).  However, there was no evidence of a significant difference in the overall risk of CS (RR = 1.10, 95% CI = 0.97-1.25, 27 trials, 8417 women). 
Several studies have assessed the relationship between neuraxial analgesia and CS at the individual provider level. , In a study on 110 obstetricians, investigators did not find any relationship between the use of EA and rate of CS for dystocia among obstetricians.  In another study from a private hospital, obstetricians whose CS rates were >15% had lower epidural rate as compared to obstetricians with CS rates <15%. 
A meta-analysis using data from nine impact studies (n = 37,753) concluded that the rate of CS and operative vaginal deliveries did not change during a period of low to high EA rates, with a mean change in CS rate of −0.67% (CI = −2.0-0.74%). 
| Risk of Instrumental Vaginal Delivery|| |
Studies have shown that EA increases the rate of instrument-assisted vaginal deliveries although there is wide variability in practices between obstetricians and hospitals.  This increase has been attributed to the ease of instrumentation in a patient with relaxed pelvic muscles as also better resident teaching in such patients.
Sharma et al., in a RCT found the rate of instrumental delivery was 3% in patients receiving opioid as compared with 12% in the epidural group. 
Several large randomized control trials comparing high dose EA (0.25% bupivacaine) with low dose epidurals (0.0625-1% bupivacaine with fentanyl); have shown a high rate of instrumental delivery in the high dose group. , These studies found no difference in the rate of CS between the two groups supporting evidence that the dose of epidural solution has no effect on the rate of CS.
A Cochrane review, published in 2005, showed that EA was associated with an increased risk of instrumental vaginal birth (RR = 1.38, 95% CI = 1.24-1.53, 17 trials, 6162 women). 
Similar finding was observed in the more recent Cochrane review of 2011, indicating an increased risk of assisted vaginal birth (RR = 1.42, 95% CI = 1.28-1.57, 23 trials, 7935 women) and longer second stage of labor with EA (mean difference = 13.66 min, 95% CI = 6.67-20.66, 13 trials, 4233 women). 
| Rate of Cervical Dilatation and Timing of Initiation|| |
The optimal timing of EA during labor and delivery has been extensively studied. A landmark study by Wong et al. published in 2005,  showed no effect on the rate of CS and instrumental vaginal deliveries when early epidural is compared with late epidurals in nulliparous women with spontaneous labor. Following this there has been a number of studies along with a repeat study by Wong et al. in 2009 confirming the original results. 
Two systematic reviews performed on the timing effect of EA related to the mode of delivery , have found no correlation between the two demographic characteristics. The systematic review in 2007 by Marucci et al.  included five RCTs, one impact cohort study and three retrospective cohort studies, which found a similar rate for CS (odds ratio [OR] = 1.00, 95% CI = 0.82-1.23) and instrumental vaginal delivery in the early neuraxial analgesia and control group (OR = 1.00, 95% CI = 0.83-1.21). The second systematic review published in 2011,  studied the early EA, (strictly defined as 3 cm or less in the latent phase) on the mode of delivery. This meta-analysis of five randomized trials (n = 14,836) also concluded that early institution of EA has no effect on the rate of CS (risk ratio + 1.02, 95% CI = 0.96-1.08). Heterogeneity was absent among the studies. The result of all studies and meta-analysis suggests that the request for analgesia early in the labor, could be due to severe pain, could herald some other risk factors for CS like dysfunctional labor, large fetus or malposition of fetuses.
Moreover, group crossover has been observed between early and late epidural groups. RCT from Wong et al. in 2005,  indicated protocol violation in the late group, where these patients received EA at cervical dilation of <4 cm. Similarly a repeat RCT by Wong et al. in 2009,  indicated protocol violation in 35 women in late group receiving EA at the second request when cervical dilatation was <4 cm, as these women refused the study drug.  In the study by Wang et al.  comparison between early EA versus early opioid (25 mg meperidine intramuscularly) and late EA (when the cervix was at least 4 cm dilated), the late group showed a protocol violation in 41 of the 6399 women as they received EA when the cervix was <4 cm dilated; 102 women were randomly assigned to the early group whose cervix was >4 cm dilated.
In our observational study (in press) of 4697 patients who delivered from January 2011 to June 2012, there were 13.4% (n = 401) patients who received EA for labor. There was no significant difference in the rate of CS between patients who received epidural (CS rate = 28%) when compared with patients who did not receive epidural (CS rate = 31%). However, the rate of assisted delivery was almost double, with 8% in the epidural group as compared to 4.6% in patients not receiving epidural. We did not find any difference in the rate of CS among women who received epidural at less than 3 cm, between 3 and 5 cm and after 5 cm of cervical dilatation.
A review of the evidence by Cambic and Wong have also confirmed the findings of effective neuraxial labor analgesia not increasing cesarean delivery rate, even when administered early in the course of labor; however, there has been a prolonged second stage of labor and an increased rate of instrumental vaginal delivery. 
Therefore, the risk of CS is not increased by EA. Obstetrician practices and indirect factors play a role in the choice for operative delivery. Maternal-fetal factors and obstetric management and not the use of EA are the most important determinants of the CS rate.
An unacceptably high number of parturient experience severe pains during labor as it is the only condition, where it is considered acceptable to experience severe pain. Unfortunately, labor is one of the circumstances where it is perceived that analgesia might interfere with the progress of labor. Despite the perceived risk associated with labor analgesia, many women opt for this technique as no other method can provide almost complete analgesia.
American College of Obstetrician and Gynecologists and the American Society of Anesthesiologist have jointly endorsed the statement that "maternal request is sufficient medical indication for pain relief during labor" and EA is usually the preferred method. 
| Conclusion|| |
Due to the presence of logistic problems in designing studies on the effect of epidural on the progress of labor, definitive answers to the queries will not be possible. Instrumental vaginal delivery is probably increased with epidural but obstetrician practice, pain free patient and teaching opportunity are likely factors increasing the incidence. EA can be tailored to the individual patient's labor, medical condition and preferences to make childbirth a pleasant experience and not a horrifying nightmare that women will want to forget.
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