Placental transfer and neonatal effects of epidural sufentanil and fentanyl administered with bupivacaine during labor

Labor Analgesia Initiation With Dural Puncture Epidural Versus Conventional Epidural Techniques: A Randomized Biased-Coin Sequential Allocation Trial to Determine the Effective Dose for 90% of Patients of Bupivacaine

BACKGROUND

The dural puncture epidural (DPE) technique has a faster onset, better sacral spread, and improved bilateral coverage when compared to the conventional epidural (EPL) technique. Whether these qualities translate into a lower bupivacaine dose to provide initial analgesia is unknown. We sought to determine the effective dose of bupivacaine to achieve initial (first 30 minutes) labor analgesia in 90% of patients (ED90) with the DPE and EPL techniques, using a biased-coin, sequential allocation method.

METHODS

A total of 100 women of mixed parity with term, singleton gestation at ≤5 cm dilation with no major comorbidities were randomized to receive a DPE or an EPL technique. An experienced anesthesiologist performed these techniques and administered an allocated dose of plain bupivacaine diluted with isotonic sterile 0.9% saline to a total volume of 20 mL via the EPL catheter. Bupivacaine doses for each subject were determined by the response of the previous subject, using a biased-coin sequential allocation method, with success defined by a numeric rating scale (NRS) < 3 at 30 minutes. Outcome assessments were performed by an investigator blinded to the technique and bupivacaine dose. Sensory and motor blockade and maternal or fetal side effects were recorded every 5 minutes for the first 30 minutes. The ED90 of bupivacaine with each technique was estimated using centered isotonic regression.

RESULTS

A total of 95 women were included in the final analysis. The ED90 of bupivacaine was estimated at 29.30 mg (90% confidence interval [CI], 28.55-31.56) with a DPE technique and 45.25 mg (90% CI, 42.80-52.03) with an EPL technique.

CONCLUSIONS

Using a biased-coin, sequential allocation method, the DPE technique requires less bupivacaine to achieve effective initial analgesia (ED90) when compared to the EPL technique.

Association between labor epidural analgesia and gut microbiota: A prospective cohort study

Background

Labor epidural analgesia (LEA) may influence gut microbiota. We explored the association between LEA and gut microbiota for both mothers and their newborns.

Methods

In this prospective cohort study, parturients aged 25-35 years with a gestational age of 37-42 weeks and planned vaginal delivery were recruited. Twenty-one parturients received LEA (the LEA group), and 24 did not (the control group). Maternal and neonatal fecal samples were collected, and the gut microbiota profiles were analyzed using the 16S rRNA gene sequencing. The impact of LEA on gut microbiota was assessed using the general liner models.

Results

We showcased the gut microbiota profile from the phyla to species levels based on data on 45 mother-newborn dyads. The results of α- and β-diversity suggested significant changes in gut microbiota between the LEA and control groups. After adjusting for baseline confounders, the administration of LEA had positive correlations with R. ilealis (β = 91.87, adjusted P = 0.007) in mothers; LEA also had negative correlations with A. pittii (β = -449.36, adjusted P = 0.015), P. aeruginosa (β = -192.55, adjusted P = 0.008), or S. maltophilia (β = -142.62, adjusted P = 0.001) in mothers, and with Muribaculaceae (β = -2702.77, adjusted P = 0.003) in neonates.

Conclusion

LEA was associated with changes in maternal and neonatal gut microbiota, and future studies are still required to assess their impact on clinical outcomes and explore the mechanisms.

Maternal and neonatal effects of epidural levobupivacaine combined with fentanyl or sufentanil for elective cesarean-section in brachycephalic breeds

The aim of this study was to compare the safety and clinical efficacy of epidural levobupivacaine combined with fentanyl or sufentanil for bitches undergoing elective cesarean-section and the impact of these anesthetic protocols on neonatal viability. The anesthetic protocol consisted of intramuscular morphine (0.2 mg/kg), followed by an intravenous bolus of propofol, in a dose sufficient to allowed the puncture of the lumbosacral space. The dogs were randomly allocated to receive 0.5 % levobupivacaine plus fentanyl (2.5 µg/kg; LF: n = 9) or sufentanil (1 µg/kg; LS; n = 11). Maternal cardiorespiratory parameters were monitored at specific time points during surgery. Intraoperative propofol supplementation was based on the presence of head and/or thoracic limb movements. Neonatal reflex responses and the Apgar score (range 0-10 points) were assessed at 5 and 60 minutes after birth. Puppy mortality rate was recorded until 24 hours after birth. Data were analyzed using two-way ANOVA, Tukey's test, Wilcoxon signed rank test, and Fisher's exact test (P < 0.05). Intraoperatively, maternal cardiorespiratory variables and propofol requirements were similar between groups, with no detection of anesthetic complications. The puppy reflex responses did not differ between groups at any time point. The medians (range) of Apgar scores were lower (P = 0.016) in the LF [5 (1-9)] at 5 minutes in comparison with LS [6 (2-9)], while no intergroup differences were recorded at 60 minutes [LF = 8 (2-10); LS = 9 (6-10]. The total mortality rate was 4.1 %. In the LS group, no puppies died, while in the LF 8 % of the puppies died in the first 24 hours after birth (P = 0.11). Epidural levobupivacaine combined with fentanyl or sufentanil provided minimal maternal and neonatal adverse effects, but neither protocol enabled the performance of a C-section in 100 % of the French and English bulldogs, without propofol supplementation.

Evaluating the Pharmacokinetics of Fentanyl in the Brain Extracellular Fluid, Saliva, Urine, and Plasma of Newborns from Transplacental Exposure from Parturient Mothers Dosed with Epidural Fentanyl Utilizing PBPK Modeling

BACKGROUND AND OBJECTIVE

Fentanyl can mitigate the mother and newborn complications resulting from labor pain. However, fentanyl shows a narrow therapeutic index between its respiratory depressive and analgesic effects. Thus, prenatally acquired high fentanyl levels in the newborn brain extracellular fluid (bECF) may induce respiratory depression which requires therapeutic drug monitoring (TDM). TDM using saliva and urine in newborns can reduce the possibility of infections and distress associated with TDM using blood. The objective of this study was to develop  a physiologically based pharmacokinetic (PBPK) model to predict fentanyl concentrations in different newborn tissues due to intrauterine exposure.

METHODS

A fentanyl PBPK model in adults after intravenous and epidural administration was built, validated, and scaled to pregnancy and newborn populations. The dose that the newborn received transplacentally at birth was calculated using the pregnancy model. Then, the newborn bECF, saliva, plasma, and urine concentrations after such a dose were predicted using the newborn PBPK model.

RESULTS

After a maternal epidural dose of fentanyl 245 µg, the predicted newborn plasma and bECF levels were below the toxicity thresholds. Furthermore, the salivary threshold levels in newborns for fentanyl analgesic and respiratory depression effects were estimated to be 0.39 and 14.7-18.2 ng/ml, respectively.

CONCLUSION

The salivary TDM of fentanyl in newborns can be useful in newborns exposed to intrauterine exposure from parturient females dosed with epidural fentanyl. However, newborn-specific values of µ-opioid receptors IC50 for respiratory depression are needed.

Fentanyl in the labor epidural impacts the results of intrapartum and postpartum maternal and neonatal toxicology tests

BACKGROUND

A positive urine fentanyl toxicology test may have considerable consequences for peripartum individuals, yet the extent to which fentanyl administration in a labor epidural may lead to such a positive test is poorly characterized.

OBJECTIVE

This study aimed to quantify the extent to which neuraxial fentanyl in labor neuraxial analgesia can lead to a positive peripartum maternal or neonatal urine toxicology test.

STUDY DESIGN

We performed a prospective cohort study of pregnant participants planning a vaginal delivery with neuraxial analgesia. Participants with a history of substance use disorder, hypertension, or renal or liver disease were excluded. A urine sample was collected before initiation of neuraxial analgesia, each time the bladder was emptied during labor, and up to 4 times postpartum. Neonatal urine was collected once. Urine fentanyl testing was performed using 2 common toxicology testing methods, namely immunoassay and liquid chromatography with tandem mass spectrometric detection.

RESULTS

A total of 33 maternal-infant dyads yielded a total of 178 urine specimens. All maternal specimens were negative for fentanyl using liquid chromatography with tandem mass spectrometric analysis and immunoassay before initiation of neuraxial analgesia. Intrapartum, 26 of 30 (76.7%) participants had positive liquid chromatography with tandem mass spectrometry results for fentanyl or its metabolites, and 12 of 30 (40%) participants had positive immunoassay results. Postpartum, 19 of 21 (90.5%) participants had positive liquid chromatograph with tandem mass spectrometric results, and 13 of 21 (61.9%) had a positive immunoassay result. Of the 13 neonatal specimens collected, 10 (76.9%) were positive on liquid chromatography with tandem mass spectrometry analysis, the last of which remained positive 29 hours and 50 minutes after delivery.

CONCLUSION

Neuraxial fentanyl for labor analgesia may lead to positive maternal and neonatal toxicology tests at various times after epidural initiation and cessation and at different rates depending on the testing method used. Caution should be used in interpreting toxicology test results of individuals who received neuraxial analgesia to avoid false assumptions about nonprescribed use.

Association of epidural analgesia during labor with neurodevelopment of children during the first three years: the Japan Environment and Children's Study

BACKGROUND

Epidural analgesia relives pain during labor. However, the long-term effects on neurodevelopment in children remain unclear. We explored associations between exposure to epidural analgesia during labor and childhood neurodevelopment during the first 3 years of life, in the Japan Environment and Children's Study (JECS), a large-scale birth cohort study.

METHODS

Pregnant women were recruited between January 2011 and March 2014, and 100,304 live births of singleton children born at full-term by vaginal delivery, and without congenital diseases were analyzed. Data on mothers and children were collected using a self-administered questionnaires and medical record transcripts. The children's neurodevelopment was repeatedly assessed for five domains (communication, gross motor, fine motor, problem solving, and personal-social), using the Ages and Stages Questionnaires, Third Edition, at six time points from age 6 to 36 months. After adjusting for potential confounders, the associations between exposure to epidural analgesia during labor and children's neurodevelopment at each time point were assessed.

RESULTS

Of the 42,172 children with valid data at all six time points, 938 (2.4%) were born to mothers who received epidural analgesia during labor. Maternal exposure to epidural analgesia was associated with neurodevelopmental delays during the first 3 years after birth. Delay risks in gross and fine motor domains were the greatest at 18 months (adjusted odds ratio (aOR) [95% confidence interval (CI)]: 1.40 [1.06, 1.84] and 1.54 [1.17, 2.03], respectively), subsequently decreasing. Delay risks in communication and problem-solving domains were significantly high at 6 and 24 months, and remained significant at 36 months (aOR [95% CI]: 1.40 [1.04, 1.90] and 1.28 [1.01, 1.61], respectively). Exposure to epidural analgesia was also associated with the incidence of problem solving and personal-social delays from 18 to 24 months old. Neurodevelopmental delay risks, except for communication, were dominant in children born to mothers aged ≥30 years at delivery.

CONCLUSIONS

This study showed that maternal exposure to epidural analgesia during labor was associated with neurodevelopmental delays in children during the first 3 years after birth.

Epidural analgesia in labor: A narrative review

Lumbar epidural is the most effective form of pain relief in labor with around 30% of laboring women in the UK and 60% in the USA receiving epidural analgesia. Associations of epidural on maternal, obstetric, and neonatal outcomes have been the subject of intense study, though a number of uncertainties persist. The present narrative review explores important areas of research surrounding epidural analgesia in obstetric patients including methods of initiation and administration, choice of local anesthetic solution, and the addition of adjuvants. Key meta-analyses exploring associations of epidural analgesia on maternal and neonatal outcomes are identified and summarized.

Predicting Maternal-Fetal Disposition of Fentanyl Following Intravenous and Epidural Administration Using Physiologically Based Pharmacokinetic Modeling

Fentanyl is an opioid analgesic used to treat obstetrical pain in parturient women through epidural or intravenous route, and unfortunately can also be abused by pregnant women. Fentanyl is known to cross the placental barrier, but how the route of administration and time after dosing affects maternal-fetal disposition kinetics at different stages of pregnancy is not well characterized. To address this knowledge gap, we developed a maternal-fetal physiologically based pharmacokinetic (mf-PBPK) model for fentanyl to evaluate the feasibility to predict the maternal and fetal plasma concentration-time profiles of fentanyl after various dosing regimens. As fentanyl is typically given via the epidural route to control labor pain, an epidural dosing site was developed using alfentanil as a reference drug and extrapolated to fentanyl. Fetal hepatic clearance of fentanyl was predicted from CYP3A7-mediated norfentanyl formation in fetal liver microsomes (intrinsic clearance = 0.20 ± 0.05 µl/min/mg protein). The developed mf-PBPK model successfully captured fentanyl maternal and umbilical cord concentrations after epidural dosing and was used to simulate the concentrations after intravenous dosing (in a drug abuse situation). The distribution kinetics of fentanyl were found to have a considerable impact on the time course of maternal:umbilical cord concentration ratio and on interpretation of observed data. The data show that mf-PBPK modeling can be used successfully to predict maternal disposition, transplacental distribution, and fetal exposure to fentanyl. SIGNIFICANCE STATEMENT: This study establishes the modeling framework for predicting the time course of maternal and fetal exposures of fentanyl opioids from mf-PBPK modeling. The model was validated based on fentanyl exposure data collected during labor and delivery after intravenous or epidural dosing. The results show that mf-PBPK modeling is a useful predictive tool for assessing fetal exposures to fentanyl opioid therapeutic regimens and potentially can be extended to other drugs of abuse.

A Randomized Controlled Comparison of Epidural Analgesia Onset Time and Adverse Reactions During Labor With Different Dose Combinations of Bupivacaine and Sufentanil

OBJECTIVES

The purpose was to compare the effects of 3 different dose combinations of bupivacaine and sufentanil on the onset of analgesia and the occurrence of side effects.

MATERIALS AND METHODS

One hundred sixty-nine pregnant women were randomly assigned to 3 groups: the B1S5 group received 0.1% bupivacaine+5 μg sufentanil in 15 mL; the B125S5 group received 0.125% bupivacaine+5 μg sufentanil in 15 mL; and the B1S10 group received 0.1% bupivacaine+10 μg sufentanil in 15 mL. The primary outcome was the analgesic onset time, and the secondary outcomes were mode of delivery, patient satisfaction, maternal and neonatal side effects (pruritus, hypotension, sedation, motor block, decreased fetal heart rate, fever, and interference with breastfeeding).

RESULTS

The median (inter-quartile range) time to achieve effective analgesia was significantly faster in the B125S5 group than in the B1S5 group (10 [11-14 {4-30}] min vs. 15 [17-20 {5-30}] min, P<0.001). There was no significant difference in the analgesia onset time between the B1S10 and B125S5 groups (10 [11-14 {4-30}] min vs. 12 [13-15 {3-30}] min, P=0.202). Pruritus, hypotension, motor block, maternal satisfaction, delivery mode, decreased fetal heart rate, total bupivacaine dose and breastfeeding scores were not significantly different among the 3 groups except the sufentanil dosage and incidence of mild drowsiness and fever (the B1S10 group had significantly higher fever than the other groups).

DISCUSSION

The B125S5 combination may be superior to the B1S5 and B1S10 combinations as an initial dose for epidural analgesia to achieve rapid effective analgesia with minimal side effects.

The Effect of Epidural Nalbuphine Combined With Ropivacaine on Epidural Analgesia During Labor: A Multicenter, Randomized, Double-blind, Controlled Study

OBJECTIVES

The addition of a small dose of opioids during epidural labor analgesia can enhance the local analgesic effect, reduce the dose of local anaesthetic required, and minimize motor blockade. For the treatment of visceral pain, studies have shown that κ-opioid receptor agonist are more effective than μ-receptor agonists. This study compared the effectiveness of epidural nalbuphine and sufentanil in combination with ropivacaine for labor analgesia, respectively.

MATERIALS AND METHODS

We conducted a prospective, randomized, double-blind, multicentre clinical trial. Parturients who requested labor pain relief were randomly assigned to either the nalbuphine group or sufentanil group. After 5 minutes of initial dose, parturients in nalbuphine group received 10 mL 0.1% ropivacaine plus 0.3 mg/mL nalbuphine solution. The sufentanil group received the same ropivacaine dose plus 0.3 μg/mL sufentanil. The primary outcome was the duration of analgesia (the time to the first requirement for additional medication). Secondary outcomes included the ropivacaine dose per hour, and adverse reactions.

RESULTS

Between November 2018 and February 2019, 180 parturients were recruited for the study. The study showed that the duration of analgesia was shorter in the nalbuphine group as compared with the sufentanil group (P=0.040). The ropivacaine dose per hour in nalbuphine group 9.3 (2.4) mg was significantly greater versus sufentanil group 8.4 (2.5) mg (P=0.024). No serious adverse events directly associated with the analgesics were observed.

DISCUSSION

The analgesia effects of 0.3 mg/mL nalbuphine with ropivacaine are inferior to 0.3 μg/mL sufentanil with ropivacaine in labor analgesia. No serious side effects, either in the mother or in the fetus, were observed.

Rates of Fentanyl Positivity in Neonatal Urine Following Maternal Analgesia During Labor and Delivery

BACKGROUND

Fentanyl is commonly given as an analgesic during labor and delivery. The extent of transplacental drug transfer and fetal exposure is not well studied. We analyzed the relationship between neonatal urine fentanyl results and various peripartum factors.

METHODS

A total of 96 neonates with urine toxicology screening between January 2017 and September 2018 were included in the study. Medical record review was used to obtain maternal, neonatal, and anesthesia parameters. A subset of 9 specimens were further tested for levels of fentanyl and norfentanyl by liquid chromatography-tandem mass spectrometry.

RESULTS

In 29% (n = 24) of cases associated with fentanyl-containing labor analgesia, neonatal toxicology screens were positive for the presence of fentanyl. Positive test results strongly correlated with the cumulative dose and duration of labor analgesia (P < 0.001). The odds of positive neonatal fentanyl screen results increased 4-fold for every 5 hours of maternal exposure to labor analgesia. Importantly, however, neonatal outcomes for infants with positive and negative urine fentanyl screens were the same.

CONCLUSIONS

Our study establishes that maternal fentanyl analgesia is strongly associated with positive neonatal urine fentanyl screens and suggests that more judicious use of these laboratory tests may be warranted.

Potential impact of epidural labor analgesia on the outcomes of neonates and children

This review summarizes recent evidences regarding the potential influences of epidural labor analgesia (ELA) on the outcomes of neonates and children. Terms and relevant words including “ELA,” “ELA and neonatal outcomes,” “ELA and children's development,” and “ELA and children's neurocognitive development” were used to search articles published in PubMed database up to October 2019. Original articles and reviews regarding potential influences of ELA on neonates and children were identified. Relevant references of the selected articles were also screened. The anesthetics used during ELA can be absorbed, enter the fetus, and produce neonatal depression; however, these effects are less severe than those during systematic opioid analgesia. The impact of anesthetic exposure during ELA on children's neurodevelopment has not been fully studied, but would be mild if any. ELA increases the risk of intrapartum maternal fever; the latter may be harmful to neonatal outcomes. The use of ELA may increase birth injury by increasing instrumental delivery, although long-term adverse events are rare. On the other hand, ELA may reduce maternal depression and, thus, produce favorable effects on neurocognitive development in childhood; but evidences are still lacking in this aspect. ELA may produce both favorable and unfavorable effects on neonates and children. These effects should be discussed with parturient women before making decisions. The potential harmful effects should be carefully managed. The overall impacts of ELA on neonatal and children's outcomes need to be studied further.

A priori choice of neuraxial labour analgesia and breastfeeding initiation success: a community-based cohort study in an Italian baby-friendly hospital

OBJECTIVE

To investigate whether the nature of the decision about receiving neuraxial labour analgesia is associated with breastfeeding initiation success (BIS), defined as exclusive breastfeeding until discharge associated with postnatal weight loss <7% at 60 hours from birth.

DESIGN

Single-centre community-based cohort study.

SETTING

An Italian baby-friendly hospital, from 1 July 2011 to 22 September 2015.

PARTICIPANTS

Inclusion criteria: women vaginally delivering singleton cephalic newborns and willing to breastfeed.

EXCLUSION CRITERIA

women who delivered in uterus-dead fetuses, were single or requested but did not receive neuraxial analgesia. Overall, 775 out of the 3628 enrolled women received neuraxial analgesia.

RESULTS

Compared with women who tried to cope with labour pain, those who decided a priori to receive neuraxial analgesia had less BIS (planned vaginal birth: 2121/3421 (62.0%), vs 102/207 (49.3%; p<0.001; risk difference (RD), 12.7%); actual vaginal birth: 1924/2994 (64.3%), vs 93/189 (49.2%; p<0.001; RD, 15.1%)). Multivariable analyses with antelabour-only confounders confirmed both associations (planned vaginal birth: relative risk (RR), 0.65; 95% CI, 0.48 to 0.87; actual vaginal birth: RR, 0.59; 95% CI, 0.43 to 0.80). Although women who requested analgesia as a last resort had less BIS than did those successfully coping with labour pain in the bivariable analyses (planned vaginal birth: 1804/2853 (63.2%), vs 317/568 (55.8%; p=0.001; RD, 7.4%); actual vaginal birth: 1665/2546 (65.4%), vs 259/448 (57.8%; p=0.002; RD, 7.6%)), multivariable analyses with either antelabour-only or peripartum confounders did not confirm these associations (planned vaginal birth: RR, 0.99; 95% CI, 0.80 to 1.23; actual vaginal birth: RR, 0.90; 95% CI, 0.69 to 1.16).

CONCLUSIONS

Compared with trying to cope with labour pain, a priori choice of neuraxial analgesia is negatively associated with BIS. Conversely, compared with having successfully coped with pain, requesting neuraxial analgesia as a last resort is not negatively associated with BIS.

Effects of Adrenaline on maternal and fetal fentanyl absorption in epidural analgesia: A randomized trial

BACKGROUND

The combination of low-dose local anesthesia and lipophilic opioids such as fentanyl is established as a standard solution for labor epidural analgesia. Fentanyl increases efficacy, but may have negative effects on the neonate in terms of reduced neonatal neurologic and adaptive capacity scores and breast feeding. We hypothesized that addition of adrenaline 2 μg/mL to a solution of bupivacaine 1 mg/mL and fentanyl 2 μg/mL would reduce the systemic uptake of fentanyl, resulting in reduced serum fentanyl in the fetus at birth.

METHODS

Forty-one nulliparous women requesting epidural analgesia were randomized to epidural analgesia with or without adrenaline. Blood samples were drawn from the mother with regular intervals, and at delivery. An umbilical vein blood sample (used as a proxy for fetal exposure) was drawn after clamping.

RESULTS

There were no significant differences between the groups in fentanyl concentrations in the umbilical vein and maternal serum at birth. There was a significantly lower mean area under the maternal serum-concentration curve for the first 2 hours of treatment in the adrenaline group (mean difference 0.161 nmol h/L [0.034; 0.289], P = .015), implying slower systemic uptake in the adrenaline group initially. There were no significant differences in treatment duration, motor block, Apgar scores, umbilical pH and base excess, or mode of delivery.

CONCLUSIONS

The addition of adrenaline to an epidural solution containing fentanyl lowered maternal systemic serum fentanyl concentration during the first 2 hours, but did not lower serum fentanyl concentration in the umbilical vein and mother at delivery.

Practice Bulletin No. 177: Obstetric Analgesia and Anesthesia

Labor causes severe pain for many women. There is no other circumstance in which it is considered acceptable for an individual to experience untreated severe pain that is amenable to safe intervention while the individual is under a physician's care. Many women desire pain management during labor and delivery, and there are many medical indications for analgesia and anesthesia during labor and delivery. In the absence of a medical contraindication, maternal request is a sufficient medical indication for pain relief during labor. A woman who requests epidural analgesia during labor should not be deprived of this service based on the status of her health insurance. Third-party payers that provide reimbursement for obstetric services should not deny reimbursement for labor analgesia because of an absence of "other medical indications." Anesthesia services should be available to provide labor analgesia and surgical anesthesia in all hospitals that offer maternal care (levels I-IV) (). Although the availability of different methods of labor analgesia will vary from hospital to hospital, the methods available within an institution should not be based on a patient's ability to pay.The American College of Obstetricians and Gynecologists believes that in order to allow the maximum number of patients to benefit from neuraxial analgesia, labor nurses should not be restricted from participating in the management of pain relief during labor. Under appropriate physician supervision, labor and delivery nursing personnel who have been educated properly and have demonstrated current competence should be able to participate in the management of epidural infusions.The purpose of this document is to review medical options for analgesia during labor and anesthesia for surgical procedures that are common at the time of delivery. Nonpharmacologic options such as massage, immersion in water during the first stage of labor, acupuncture, relaxation, and hypnotherapy are not covered in this document, though they may be useful as adjuncts or alternatives in many cases.

Physiological mechanisms, behavioral and psychological factors influencing the transfer of milk from mothers to their young

This article is part of a Special Issue "Parental Care".Producing milk to support the growth of their young is a central element of maternal care in mammals. In spite of the facts that ecological constraints influence nursing frequency, length of time until weaning and the composition of milk, there is considerable similarity in the anatomy and physiology of milk production and delivery across mammalian species. Here we provide an overview of cross species variation in nursing patterns and milk composition as well as the mechanisms underlying mammary gland development, milk production and letdown. Not all women breastfeed their infants, thus in later sections we review studies of factors that facilitate or impede the initiation and duration of breastfeeding. The results of these investigations suggest that the decisions to initiate and maintain breastfeeding are influenced by an array of personal, social and biological factors. Finally, studies comparing the development of breastfed and formula fed infants as well as those investigating associations between breastfeeding, maternal health and mother/infant interaction are reviewed. Leading health agencies including the World Health Organization and CDC advocate breastfeeding for at least the first 6months postpartum. To achieve these rates will require not only institutional support but also a focus on individual mother/infant dyads and their experience.

The Association Between Common Labor Drugs and Suckling When Skin-to-Skin During the First Hour After Birth

BACKGROUND

Intrapartum drugs, including fentanyl administered via epidural and synthetic oxytocin, have been previously studied in relation to neonatal outcomes, especially breastfeeding, with conflicting results. We examined the normal neonatal behavior of suckling within the first hour after a vaginal birth while in skin-to-skin contact with mother in relation to these commonly used drugs. Suckling in the first hour after birth has been shown in other studies to increase desirable breastfeeding outcomes.

METHOD

Prospective comparative design. Sixty-three low-risk mothers self-selected to labor with intrapartum analgesia/anesthesia or not. Video recordings of infants during the first hour after birth while being held skin-to-skin with their mother were coded and analyzed to ascertain whether or not they achieved Stage 8 (suckling) of Widström's 9 Stages of newborn behavior during the first hour after birth.

RESULTS

A strong inverse correlation was found between the amount and duration of exposure to epidural fentanyl and the amount of synthetic oxytocin against the likelihood of achieving suckling during the first hour after a vaginal birth.

CONCLUSIONS

Results suggest that intrapartum exposure to the drugs fentanyl and synthetic oxytocin significantly decreased the likelihood of the baby suckling while skin-to-skin with its mother during the first hour after birth.

Evidence and consensus based guideline for the management of delirium, analgesia, and sedation in intensive care medicine. Revision 2015 (DAS-Guideline 2015) - short version

In 2010, under the guidance of the DGAI (German Society of Anaesthesiology and Intensive Care Medicine) and DIVI (German Interdisciplinary Association for Intensive Care and Emergency Medicine), twelve German medical societies published the “Evidence- and Consensus-based Guidelines on the Management of Analgesia, Sedation and Delirium in Intensive Care”. Since then, several new studies and publications have considerably increased the body of evidence, including the new recommendations from the American College of Critical Care Medicine (ACCM) in conjunction with Society of Critical Care Medicine (SCCM) and American Society of Health-System Pharmacists (ASHP) from 2013. For this update, a major restructuring and extension of the guidelines were needed in order to cover new aspects of treatment, such as sleep and anxiety management. The literature was systematically searched and evaluated using the criteria of the Oxford Center of Evidence Based Medicine. The body of evidence used to formulate these recommendations was reviewed and approved by representatives of 17 national societies. Three grades of recommendation were used as follows: Grade “A” (strong recommendation), Grade “B” (recommendation) and Grade “0” (open recommendation). The result is a comprehensive, interdisciplinary, evidence and consensus-based set of level 3 guidelines. This publication was designed for all ICU professionals, and takes into account all critically ill patient populations. It represents a guide to symptom-oriented prevention, diagnosis, and treatment of delirium, anxiety, stress, and protocol-based analgesia, sedation, and sleep-management in intensive care medicine.

A double-blind study on analgesic effects of fentanyl combined with bupivacaine for extradural labor analgesia

Background:

The intermittent technique of labor extradural analgesia has been showing promising results over other techniques. This study was done to assess and compare the efficacy of two different doses of fentanyl mixed with low doses of bupivacaine in intermittent labor extradural analgesia.

Materials and Methods:

90 ASA grade I-II parturients in active labor with a cervical dilatation of 3–7 cm were randomly allocated to three different groups:

Group A: 10 ml bupivacaine 0.125% + fentanyl 10 μg (1 μg/ml)

Group B: 10 ml bupivacaine 0.125% + fentanyl 20 μg (2 μg/ml)

Group C: 10 ml bupivacaine 0.125% (the control group)

All patients were preloaded with 10-15 ml/kg Lactated Ringer's solution. Labor analgesia was maintained by intermittent boluses of the drug combination.

Results:

The mean time of the onset of analgesia was significantly lower (P<0.05) and the duration of analgesia was significantly higher (P<0.01) in Group B when compared with Groups A and C (P<0.001). Patient satisfaction was considerably better in Group B (P<0.01). However, in both groups, the progression of labor was found to be slightly more prolonged than Group C. The level of the sensory and motor block was comparable in both the groups and was at the T8–T10 level; it was comparable and the level of motor blockade (Bromage score = 0, 1) in each group was also not significant (P>0.05).

Conclusion:

The addition of fentanyl (2 μg/ml) to bupivacaine 0.125% decreases the time of the onset of analgesia and increases the duration of analgesia and level of maternal satisfaction during labor as compared to fentanyl (1 μg/ml).

Bupivacaine in combination with fentanyl or sufentanil in epidural/intrathecal analgesia for labor: a meta-analysis

This study is to compare the effectiveness of combinational use of bupivacaine with fentanyl (BUPI-FEN) and sufentanil (BUPI-SUF) in epidural/intrathecal analgesia for labor. Electronic databases were searched for relevant research papers published between 1985 and 2014. Meta-analyses of mean differences or odds ratios were performed and statistical heterogeneity between the studies tested by I(2) index. Ten studies recruiting a total of 728 women in labor were selected. Concentrations of the anesthetics used as mean ± sd were bupivacaine 0.115 ± 0.056%, fentanyl 0.0007 ± 0.001%, and sufentanil 0.00017 ± 0.00022%. Duration of analgesia was not significantly different between BUPI-SUF and BUPI-FEN administered mothers (mean difference [95%CI] of -33.55 [-74.94, 7.83] minutes; P = .11) under random effects. The onset of analgesia was also not significantly different between both groups (mean difference [95%CI] of -0.61 [-1.38, 0.16] minutes; P = .12). The number of neonates with Apgar score < 7 was significantly lower in BUPI-FEN group (odd ratio [95%CI] of 0.31 [0.10, 0.95]; P < .05). Pruritus incidence was similar. In conclusion, BUPI-FEN combination exhibits significantly better tolerability at an approximate ratio of 6 FEN:1 SUF, albeit, both fentanyl and sufentanil in combination with bupivacaine provide similar analgesic properties via the epidural or intrathecal routes for labor pain relief.

The effects of epidural/spinal opioids in labour analgesia on neonatal outcomes: a meta-analysis of randomized controlled trials

PURPOSE

Epidural/spinal opioids are increasingly used to relieve parturients' pain in labour. Some studies indicate that opioids can induce side effects in neonates, such as respiratory depression and neurobehavioural changes. This meta-analysis aimed to clarify the effects of opioids in labour analgesia on neonates.

SOURCE

PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE™ were searched for relevant randomized controlled trials (RCTs). The neonatal data of Apgar scores, Neurological and Adaptive Capacity Scores (NACS), and umbilical cord pH values were extracted. Statistical analyses were carried out using Review Manager 5.2 and Stata(®) 10.

PRINCIPAL FINDINGS

Twenty-one trials with 2,859 participants were included in our meta-analysis. No difference in the incidence of Apgar scores < 7 was shown between the opioid and control groups at one minute (risk difference [RD] 0.0%, 95% confidence interval [CI]: -3.0 to 2.0, P = 0.78; I (2) = 0%, 95% CI: 0 to 50) and at five minutes (RD -1.0%, 95% CI: -2.0 to 1.0, P = 0.31; I(2) = 0%, 95% CI: 0 to 50). No significant differences were found in the NACS at two hours (mean difference [MD] -0.35, 95% CI: -1.70 to 1.01, P = 0.62; I(2) = 0%, 95% CI: 0 to 79) and at 24 hr (MD -0.45, 95% CI: -1.36 to 0.46, P = 0.33; I(2) = 3%, 95% CI: 0 to 26). Also, no significant differences were found in umbilical cord artery pH (MD -0.02, 95% CI: -0.06 to 0.03, P = 0.48; I(2) = 80%, 95% CI: 46 to 92) and vein pH (MD -0.03, 95% CI: -0.07 to 0.00, P = 0.08; I(2) = 77%, 95% CI: 36 to 91). No significant publication bias was found.

CONCLUSION

The common doses of fentanyl and sufentanil used with an epidural/spinal technique in labour analgesia are safe for neonates up to 24 hr after delivery. In future studies, more attention should be paid to the long-term side effects in neonates.

Relationship between use of labor pain medications and delayed onset of lactation

BACKGROUND

Despite estimates that 83% of mothers in the United States receive labor pain medications, little research has been done on how use of these medications affect onset of lactation.

OBJECTIVE

To investigate whether use of labor pain medications is associated with delayed onset of lactation (DOL).

METHODS

We analyzed data from the 2005-2007 Infant Feeding Practices Study II, a longitudinal study of women from late pregnancy through the entire first year after birth (n = 2366). In multivariable logistic regression analyses, we assessed the relationship between mothers' use of labor pain medication/method and DOL (milk coming in > 3 days after delivery).

RESULTS

Overall, 23.4% of women in our sample experienced DOL. Compared with women who delivered vaginally and received no labor pain medication, women who received labor pain medications had a higher odds of experiencing DOL: vaginal with spinal/epidural only (aOR 2.05; 95% CI, 1.43-2.95), vaginal with spinal/epidural plus another medication (aOR 1.79; 95% CI, 1.16-2.76), vaginal with other labor pain medications only ([not spinal/epidural]; aOR 1.84; 95% CI, 1.14-2.98), planned cesarean section with spinal/epidural only (aOR 2.13; 95% CI, 1.39-3.27), planned cesarean with spinal/epidural plus another medication (aOR 2.67; 95% CI, 1.35-5.29), emergency cesarean with spinal/epidural only (aOR 2.17; 95% CI, 1.34-3.51), and emergency cesarean with spinal/epidural plus another medication (aOR 3.03; 95% CI, 1.77-5.18).

CONCLUSION

Mothers who received labor pain medications were more likely to report DOL, regardless of delivery method. This information could help inform clinical decisions regarding labor/delivery.

Epidural analgesia in labour and neonatal respiratory distress: a case-control study

BACKGROUND

Epidural analgesia is the commonest mode for providing pain relief in labour, with a combination of bupivacaine and fentanyl most often used in practice.

OBJECTIVE

To test whether late-preterm and term neonates exposed to opioids in epidural analgesia in labour are more likely to develop respiratory distress in the immediate neonatal period.

METHODS

A case-control study was conducted of singleton infants born during January 2006 to December 2010. Cases were neonates ≥34 weeks gestation, who developed respiratory distress within 24 h of life requiring supplemental oxygen ≥2 h and/or positive pressure ventilation in the neonatal intensive care unit. Controls were gestation and site-matched neonates who did not develop any respiratory distress within the same period. The information on exposure to epidural analgesia and on potential confounding variables was obtained from the standardised delivery record, routinely filled out on all women admitted to the labour wards.

RESULTS

In our study, 206 cases and 206 matched controls were enrolled. Exposure to epidural analgesia was present in 146 (70.9%) cases as compared with 131 (63.6%) of the controls. The association between exposure to epidural analgesia and respiratory distress in neonates was statistically significant upon adjustment for all potential confounders (adjusted OR: 1.75, 95% CI 1.03 to 2.99; p = 0.04). When data was separately analysed for term and late-preterm infants, the results were consistent across these subpopulations, showing no interaction effect.

CONCLUSIONS

Late-preterm and term infants exposed to maternal epidural analgesia in labour are more likely to develop respiratory distress in the immediate neonatal period.

Neonatal neurobehavioral organization after exposure to maternal epidural analgesia in labor

OBJECTIVE

To explore relationships between maternal epidural analgesia and two measures of neurobehavioral organization in infants at the initial feeding 1 hour after birth.

DESIGN

Prospective comparative design.

SETTING

Inner-city community hospital, Chicago, Illinois.

PARTICIPANTS

Convenience sample of 52 low-risk, mainly Black and Latino, mother/infant dyads.

METHODS

Mothers self-selected to labor with epidural or no labor pain medication. Neonatal neurobehavioral organization was measured in term infants at the initial feeding 1 hour after birth. A nutritive sucking apparatus generated data on total number of sucks and sucking pressure. Video recordings of infants (before and after the initial feeding) were coded for behavioral states, with analysis on frequency of alertness.

RESULTS

Total number of sucks and sucking pressure were not related to epidural exposure, although an epidural drug dosage effect on total number of sucks was evident when gender was a factor. Unmedicated girls demonstrated more sucks than girls in the high-dosage epidural group (p=.027). Overall, girls exhibited stronger sucking pressure than boys (p=.042). Frequency of alertness was not related to epidural exposure, although longer labor was related to greater alertness (p=.003), and Latino infants were more alert than Black infants (p=.002).

CONCLUSIONS

Results suggest attenuated neonatal nutritive sucking organization in girls after exposure to high maternal epidural dosages. In comparison to boys, girls may have enhanced neurobehavioral organization at birth. Race/ethnicity and alertness may have spurious associations in which hidden factors drive the relationship.

[Fetomaternal pharmacology : anesthesiological approach in surgical interventions during pregnancy]

The choice of anesthesia procedure for surgical interventions in pregnancy is particularly important considering the responsibility for the unborn child and the patient. Uncertainties with the treatment of this patient group and lacking routine are common. Nevertheless, 0.5-2% of pregnant women require non-gynecological surgery. In this respect knowledge about the interrelationship between physiological changes and pharmacological effects with potentially negative impact for the embryo, fetus or neonate is of particular importance. In this article the physiology relevant for anesthesia during pregnancy is discussed and commonly used drugs are reviewed to enable anesthesiologists to formulate concepts to preclude adverse effects for the mother and child and to provide an adequate therapy.

Evidence and consensus-based German guidelines for the management of analgesia, sedation and delirium in intensive care--short version

Targeted monitoring of analgesia, sedation and delirium, as well as their appropriate management in critically ill patients is a standard of care in intensive care medicine. With the undisputed advantages of goal-oriented therapy established, there was a need to develop our own guidelines on analgesia and sedation in intensive care in Germany and these were published as 2(nd) Generation Guidelines in 2005. Through the dissemination of these guidelines in 2006, use of monitoring was shown to have improved from 8 to 51% and the use of protocol-based approaches increased to 46% (from 21%). Between 2006-2009, the existing guidelines from the DGAI (Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin) and DIVI (Deutsche Interdisziplinäre Vereinigung für Intensiv- und Notfallmedizin) were developed into 3(rd) Generation Guidelines for the securing and optimization of quality of analgesia, sedation and delirium management in the intensive care unit (ICU). In collaboration with another 10 professional societies, the literature has been reviewed using the criteria of the Oxford Center of Evidence Based Medicine. Using data from 671 reference works, text, diagrams and recommendations were drawn up. In the recommendations, Grade "A" (very strong recommendation), Grade "B" (strong recommendation) and Grade "0" (open recommendation) were agreed. As a result of this process we now have an interdisciplinary and consensus-based set of 3(rd) Generation Guidelines that take into account all critically illness patient populations. The use of protocols for analgesia, sedation and treatment of delirium are repeatedly demonstrated. These guidelines offer treatment recommendations for the ICU team. The implementation of scores and protocols into routine ICU practice is necessary for their success.

The effect of continuous morphine administration on maternal plasma oxytocin concentration and uterine contractions after open fetal surgery

OBJECTIVE

A major complication of open fetal surgery is prematurity. We propose that fetal and maternal stress/pain after surgery may affect the concentration of circulating oxytocin and the frequency of uterine contractions, thus increasing the risk of preterm delivery. The objective of this study was to test whether continuous morphine sulfate administration after open fetal surgery has an effect on maternal plasma oxytocin concentration and the frequency of uterine contractions.

METHODS

An established time-pregnant primate model for open fetal surgery was used. From the time of surgery until the end of the three-day study period, three animals received prophylactic antibiotics, a bolus of indomethacin, and a bolus of morphine sulfate (group I). Three other animals received the same prophylactic antibiotics and an i.v. bolus of indomethacin, as well as a continuous i.v. infusion of morphine sulfate throughout the entire study period (group II). Maternal blood samples were collected to determine oxytocin plasma concentrations. Oxytocin was measured by radioimmunoassay. Uterine activity was continuously recorded through an amniotic fluid catheter and quantified as number of contractions (10 mmHg increase from base line in intrauterine pressure) per hour (UCs/h).

RESULTS

The mean maternal plasma oxytocin concentration was higher (p < 0.01) and the number of uterine contractions more frequent (p < 0.05) in the group of animals with intermittent doses of morphine than in the group that received morphine continuously.

CONCLUSIONS

These data suggest that maternal plasma oxytocin concentration and uterine activity after open fetal surgery may be related to inadequate maternal/fetal analgesia/sedation.

Pain management for the pregnant, lactating, and neonatal to pediatric cat and dog

Little information on the approach to analgesia in pregnant, nursing, or extremely young animals is available in the veterinary literature. Various analgesics and analgesic modalities are discussed, with emphasis placed on preference and caution for each group. Management of pain is extremely important in all animals but especially in the extremely young, in which a permanent hyperalgesic response to pain may exist with inadequate therapy. Inappropriate analgesic selection in pregnant and nursing mothers may result in congenital abnormalities of the fetus or neonate. Inadequate analgesia in nursing mothers may cause aggressive behavior toward the young. Review of the human and veterinary literature on the various analgesics available for use in this group of patients is discussed.

FETAL PAIN

The concept of fetal pain is becoming more and more relevant since the possibilities for invasive intrauterine treatment are increasing. However, there is much debate as to whether the fetus is mature enough to be able to perceive pain. But what is ‘pain’? One cannot determine whether a fetus feels pain unless one has a conception of what pain is. There is a difference in opinion about what pain really is and that is also the difficulty in studies on fetal pain: we cannot simply ask the fetus whether or not it feels pain. We can only give indirect evidence of possible harmful effects of stressful stimuli on the developing fetus. In this review we will first explore the meaning of ‘pain’. We will then discuss fetal anatomic, neurophysiologic and behavioural development and the responses which are thought to be required to experience pain. Finally, we discuss some ethical considerations and suggestions on fetal anaesthesia.

Clinical anesthesia causes permanent damage to the fetal guinea pig brain

Exposure of the immature brain to general anesthesia is common. The safety of this practice has recently been challenged in view of evidence that general anesthetics can damage developing mammalian neurons. Initial reports on immature rats raised criticism regarding the possibly unique vulnerability of this species, short duration of their brain development and a lack of close monitoring of nutritional and cardiopulmonary homeostasis during anesthesia. Therefore, we studied the neurotoxic effects of anesthesia in guinea pigs, whose brain development is longer and is mostly a prenatal phenomenon, so that anesthesia-induced neurotoxicity studies of the fetal brain can be performed by anesthetizing pregnant female pigs. Because of their large size, these animals made invasive monitoring of maternal and, indirectly, fetal well-being technically feasible. Despite adequate maintenance of maternal homeostasis, a single short maternal exposure to isoflurane, whether alone or with nitrous oxide and/or midazolam at the peak of fetal synaptogenesis, induced severe neuroapoptosis in the fetal guinea pig brain. As detected early in post-natal life, this resulted in the loss of many neurons from vulnerable brain regions, demonstrating that anesthesia-induced neuroapoptosis can cause permanent brain damage.

Newborn skin temperature two days postpartum during breastfeeding related to different labour ward practices

AIM

To investigate (1) the skin temperature pattern in newborns two days after birth in connection to breastfeeding and to examine (2) if the administration of epidural analgesia (EDA) and oxytocin (OT) infusion during labour influences this parameter at this point of time.

METHOD

Forty-seven mother-infant pairs were included in the study: nine mothers had received OT stimulation during labour (OT group), 20 mothers had received an EDA and OT during labour (EDA group), while 18 mothers had received neither EDA nor OT stimulation during labour (control group). A skin temperature electrode was attached between the newborn's shoulder blades. The newborn was placed skin-to-skin on the mother's chest and covered with a blanket. The temperature was recorded immediately after the newborn was put on the mother's chest and at 5, 10, 20 and 30 min.

RESULTS

The temperature measured when the newborns were put skin-to-skin on their mothers' chest was significantly higher in the infants of the EDA group (35.07 degrees C) when compared to the control group (34.19 degrees C, p=0.025). Skin temperature increased significantly (p=0.001) during the entire experimental period in the infants belonging to the control group. The same response was observed in infants whose mothers received OT intravenously during labour (p=0.008). No such rise was observed in infants whose mothers were given an EDA during labour.

CONCLUSION

The results show that the skin temperature in newborns rises when newborns are put skin-to-skin to breastfeed two days postpartum. This effect on temperature may be hampered by medical interventions during labour such as EDA.

Intrapartum epidural analgesia and breastfeeding: a prospective cohort study

Background

Anecdotal reports suggest that the addition of fentanyl (an opioid) to epidural analgesia for women during childbirth results in difficulty establishing breastfeeding. The aim of this paper is to determine any association between epidural analgesia and 1) breastfeeding in the first week postpartum and 2) breastfeeding cessation during the first 24 weeks postpartum.

Methods

A prospective cohort study of 1280 women aged ≥ 16 years, who gave birth to a single live infant in the Australian Capital Territory in 1997 was conducted. Women completed questionnaires at weeks 1, 8, 16 and 24 postpartum. Breastfeeding information was collected in each of the four surveys and women were categorised as either fully breastfeeding, partially breastfeeding or not breastfeeding at all. Women who had stopped breastfeeding since the previous survey were asked when they stopped.

Results

In the first week postpartum, 93% of women were either fully or partially breastfeeding their baby and 60% were continuing to breastfeed at 24 weeks. Intrapartum analgesia and type of birth were associated with partial breastfeeding and breastfeeding difficulties in the first postpartum week (p < 0.0001). Analgesia, maternal age and education were associated with breastfeeding cessation in the first 24 weeks (p < 0.0001), with women who had epidurals being more likely to stop breastfeeding than women who used non-pharmacological methods of pain relief (adjusted hazard ratio 2.02, 95% CI 1.53, 2.67).

Conclusion

Women in this cohort who had epidurals were less likely to fully breastfeed their infant in the few days after birth and more likely to stop breastfeeding in the first 24 weeks. Although this relationship may not be causal, it is important that women at higher risk of breastfeeding cessation are provided with adequate breastfeeding assistance and support.

A Randomized Comparison of Programmed Intermittent Epidural Bolus with Continuous Epidural Infusion for Labor Analgesia

Bolus injection through an epidural catheter may result in better distribution of anesthetic solution in the epidural space compared with continuous infusion of the same anesthetic solution. In this randomized, double-blind study we compared total bupivacaine consumption, need for supplemental epidural analgesia, quality of analgesia, and patient satisfaction in women who received programmed intermittent epidural boluses (PIEB) compared with continuous epidural infusion (CEI) for maintenance of labor analgesia. The primary outcome variable was bupivacaine consumption per hour of analgesia. Combined spinal epidural analgesia was initiated in multiparas scheduled for induction of labor with cervical dilation between 2 and 5 cm. Subjects were randomized to PIEB (6-mL bolus every 30 min beginning 45 min after the intrathecal injection) or CEI (12-mL/h infusion beginning 15 min the after the intrathecal injection). The epidural analgesia solution was bupivacaine 0.625 mg/mL and fentanyl 2 microg/mL. Breakthrough pain in both groups was treated initially with patient-controlled epidural analgesia (PCEA) followed by manual bolus rescue analgesia using bupivacaine 0.125%. The median total bupivacaine dose per hour of analgesia was less in the PIEB (n = 63) (10.5 mg/h; 95% confidence interval, 9.5-11.8 mg/h) compared with the CEI group (n = 63) (12.3 mg/h; 95% confidence interval, 10.5-14.0 mg/h) (P < 0.01), fewer manual rescue boluses were required (rate difference 22%, 95% confidence interval of difference 5% to 38%), and satisfaction scores were higher. Labor pain, PCEA requests, and delivered PCEA doses did not differ. PIEB combined with PCEA provided similar analgesia, but with a smaller bupivacaine dose and better patient satisfaction compared with CEI with PCEA for maintenance of epidural labor analgesia.