Local anesthetic requirements are greater in dystocia than in normal labor

Determination of the Optimal Volume of Programmed Intermittent Epidural Bolus When Combined With the Dural Puncture Epidural Technique for Labor Analgesia: A Random-Allocation Graded Dose-Response Study

BACKGROUND

The dural puncture epidural (DPE) and the programmed intermittent epidural bolus (PIEB) techniques are recent innovations for labor analgesia. The optimal volume of PIEB during traditional epidural analgesia has been investigated previously but it is unknown whether these findings are applicable to DPE. This study aimed to determine the optimal volume of PIEB for effective labor analgesia after initiation of analgesia using DPE.

METHODS

Parturients requesting labor analgesia received dural puncture with a 25-gauge Whitacre spinal needle and then had analgesia initiated with 15 mL of ropivacaine 0.1% with sufentanil 0.5 μg/mL. Analgesia was maintained using the same solution delivered by PIEB with boluses given at a fixed interval of 40 minutes starting 1 hour after the completion of the initial epidural dose. Parturients were randomized to 1 of 4 PIEB volume groups: 6, 8, 10, or 12 mL. Effective analgesia was defined as no requirement for a patient-controlled or manual epidural bolus for 6 hours after the completion of the initial epidural dose or until full cervical dilation. The PIEB volumes for effective analgesia in 50% of parturients (EV50) and 90% of parturients (EV90) were determined using probit regression.

RESULTS

The proportions of parturients with effective labor analgesia were 32%, 64%, 76%, and 96% in the 6-, 8-, 10-, and 12-mL groups, respectively. The estimated values for EV50 and EV90 were 7.1 (95% confidence interval [CI], 5.9-7.9) mL and 11.3 (95% CI, 9.9-15.2) mL, respectively. There were no differences in side effects, including hypotension, nausea and vomiting, and fetal heart rate (FHR) abnormalities among groups.

CONCLUSION

Under the conditions of the study, after initiation of analgesia using DPE, the EV90 of PIEB for effective labor analgesia using ropivacaine 0.1% with sufentanil 0.5 μg/mL was approximately 11.3 mL.

Vaginal birth after cesarean in women with no prior vaginal delivery carrying a large for gestational age baby

BACKGROUND

To study the factors associated with successful labor after cesarean (LAC) among women with no prior vaginal delivery, delivering a large for gestational age (LGA) baby.

METHODS

A retrospective case-control study at two tertiary medical centers in Israel, including all women undergoing LAC with no prior vaginal delivery during 2010-2020, delivering a singleton LGA newborn. Factors associated with successful vaginal delivery were examined by a multivariable analysis.

RESULTS

Overall, 323/505 (64.0%) had a successful LAC. Arrest of labor as the indication for previous CD was less common in the LAC success group [39 (12.1%) vs. 58 (31.9%), P < .001]. The rate of epidural analgesia was higher in the LAC success group [249 (77.1%) vs. 122 (67.0%), P = .014]. The rate of weight centile ≥97th was lower in the LAC success group [64 (19.8%) vs. 51 (28.0%), P = .035], as well as the rate of higher LAC birthweight than previous cesarean birthweight [264 (81.7%) vs. 162 (89.0%), P = .030]. In a multivariable logistic regression analysis, maternal height (aOR [95% CI]:1.09 (1.01, 1.17), P = .014) and epidural anesthesia (aOR [95% CI]:3.68 (1.31, 10.32), P = .013) were the only independent factors associated with LAC success.

CONCLUSIONS

Among primiparous women undergoing LAC carrying LGA newborns, the vaginal delivery rate is acceptable; however, uterine rupture risk is increased. Epidural administration is a modifiable factor and should be taken into consideration during LAC management.

Sonographic fetal head circumference is associated with trial of labor after cesarean section success

PURPOSE

The purpose is to study the association of the fetal sonographic head circumference (SHC) with trial of labor after cesarean (TOLAC) success rate, among women with no prior vaginal deliveries.

METHODS

A retrospective case-control study including all women with no prior vaginal delivery undergoing TOLAC during 3/2011-6/2020 with a sonographic estimated fetal weight within one week from delivery. TOLAC success and failure groups were compared.

RESULTS

Of 1232 included women, 948 (76.9%) delivered vaginally. The mean fetal SHC was smaller in the TOLAC success group (330 ± 10 vs. 333 ± 11 mm, p < 0.001). In a multivariate regression analysis, predelivery BMI, hypertensive disorders, gestational age at prior CD, SHC and epidural analgesia administration were independently associated with TOLAC success. A ROC analysis of the multivariable model composed of the factors found independently associated with TOLAC success, excluding SHC, yielded an area under curve of 0.659 (95% CI 0.622-0.697) compared with 0.668 (95% CI 0.630-0.705) with SHC included.

CONCLUSION

Smaller SHC is independently associated with TOLAC success among women that did not deliver vaginally before, and has additive clinical value for the prediction of TOLAC success when combined with non-sonographic factors.

Trial of labor after cesarean in primiparous women with fetal macrosomia

KEY MESSAGE

Spontaneous labor onset, epidural anesthesia and prior cesarean for non-arrest disorders are strong predictors of successful vaginal birth after cesarean in women delivering a macrosomic fetus.

PURPOSE

Lower rates of successful vaginal birth after cesarean in association with increasing birthweight were previously reported. We aimed to determine the factors associated with successful trial of labor after cesarean (TOLAC) among primiparous women with fetal macrosomia.

METHODS

A retrospective cohort study conducted during 2005-2019 at two university hospitals, including all primiparous women delivering a singleton fetus weighing ≥ 4000 g, after cesarean delivery at their first delivery. A multivariate analysis was performed to evaluate the characteristics associated with TOLAC success (primary outcome).

RESULTS

Of 551 primiparous women who met the inclusion criteria, 50.1% (n = 276) attempted a TOLAC and 174 (63.0%) successfully delivered vaginally. In a multivariate analysis, spontaneous onset of labor (aOR [95% CI] 3.68 (2.05, 6.61), P < 0.001), epidural anesthesia (aOR [95% CI] 2.38 (1.35, 4.20), P = 0.003) and history of cesarean delivery due to non-arrest disorder (aOR [95% CI] 2.25 (1.32, 3.85), P = 0.003) were the only independent factors associated with TOLAC success. Successful TOLAC was achieved in 82.0% (82/100) in the presence of all three favorable factors, 61.3% (65/106) in the presence of two factors and 38.6% (27/70) in the presence of one or less of these three factors (P < 0.001).

CONCLUSION

Spontaneous onset of labor, epidural anesthesia and prior cesarean delivery due to non-arrest disorders were independently associated with higher vaginal birth after cesarean rate among women with fetal macrosomia, with an overall favorable success rate in the presence of these factors. These findings should be implemented in patient counseling in those contemplating a vaginal birth in this setting.

Trial of Labor After Cesarean of Small for Gestational Age Neonates Among Women with No Prior Vaginal Delivery - a Retrospective Study

To evaluate the characteristics and outcomes of women who had never delivered vaginally and underwent a trial of labor after cesarean (TOLAC) of small for gestational age (SGA) neonates, and to identify risk factors for unplanned repeat cesarean delivery. A retrospective cohort study from two tertiary medical centers. All women undergoing a TOLAC with no prior vaginal delivery, delivering a singleton SGA neonate at term between 2005 and 2020 were included. Factors associated with successful vaginal delivery were examined by a multivariable analysis. Of the 255 women who met the inclusion criteria and underwent TOLAC, 72.2% delivered vaginally. In a multivariable analysis, maternal height [adjusted odds ratio (aOR) (95% CI): 1.10 (1.02-1.19), p = 0.012] and epidural administration [aOR (95% CI): 2.78 (1.0-7.73), p = 0.050] were positively independently associated with TOLAC success, and hypertensive disorders were negatively independently associated with TOLAC success [aOR (95% CI): 0.52 (0.004-0.74), p = 0.029]. The success rate of TOLAC among women with no prior vaginal delivery, delivering a SGA neonate is relatively high. Maternal height, hypertensive disorders, and epidural administration are independent factors associated with TOLAC success. Epidural administration is a modifiable factor and should be taken in consideration during TOLAC management.

The relationship between resited epidural catheters after secondary epidural catheter failure and vaginal delivery: A retrospective case-control study

BACKGROUND

There are cases where epidural analgesia is initially effective but subsequently fails and needs to be resited. We evaluated the rate of normal vaginal delivery and operative delivery among parturients who had resited epidurals compared to parturients with epidurals that were not resited.

METHODS

A retrospective electronic medical review of parturients with a singleton gestation attempting normal vaginal delivery under epidural analgesia between the years 2012-2016 was conducted. Resited epidurals were defined as epidurals that were considered effective but subsequently removed and reinserted. For each resited epidural, two previous and two consecutive deliveries of parturients with normally functioning epidural catheter inserted by the same anesthesiologist were matched controls (non-resited epidurals).

RESULTS

There were 35,984 attempted vaginal deliveries with 118 resited epidurals and 472 non-resited epidurals. When adjusted for nulliparity, oxytocin administration, sex and weight of the baby, and maternal BMI, labor epidural catheter replacement was not associated with need for instrumental or caesarean delivery, (OR 1.5, 95% CI 0.91-2.49, P = .11).

CONCLUSIONS

Need for labor epidural catheter replacement does not appear to be associated with need for operative delivery based on this single-centre cohort analysis.

Prediction of breakthrough pain during labour neuraxial analgesia: comparison of machine learning and multivariable regression approaches

INTRODUCTION

Risk-prediction models for breakthrough pain facilitate interventions to forestall inadequate labour analgesia, but limited work has used machine learning to identify predictive factors. We compared the performance of machine learning and regression techniques in identifying parturients at increased risk of breakthrough pain during labour epidural analgesia.

METHODS

A single-centre retrospective study involved parturients receiving patient-controlled epidural analgesia. The primary outcome was breakthrough pain. We randomly selected 80% of the cohort (training cohort) to develop three prediction models using random forest, XGBoost, and logistic regression, followed by validation against the remaining 20% of the cohort (validation cohort). Area-under-the-receiver operating characteristic curve (AUC), sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were used to assess model performance.

RESULTS

Data from 20 716 parturients were analysed. The incidence of breakthrough pain was 14.2%. Of 31 candidate variables, random forest, XGBoost and logistic regression models included 30, 23, and 15 variables, respectively. Unintended venous puncture, post-neuraxial analgesia highest pain score, number of dinoprostone suppositories, neuraxial technique, number of neuraxial attempts, depth to epidural space, body mass index, pre-neuraxial analgesia oxytocin infusion rate, maternal age, pre-neuraxial analgesia cervical dilation, anaesthesiologist rank, and multiparity, were identified in all three models. All three models performed similarly, with AUC 0.763-0.772, sensitivity 67.0-69.4%, specificity 70.9-76.2%, PPV 28.3-31.8%, and NPV 93.3-93.5%.

CONCLUSIONS

Machine learning did not improve the prediction of breakthrough pain compared with multivariable regression. Larger population-wide studies are needed to improve predictive ability.

Outcomes of intrathecal analgesia in multiparous women undergoing normal vaginal delivery: A randomised controlled trial

Background and Aims

Although intrathecal analgesia is an effective option during labour, there is a need to establish sustainable and assured analgesia during the entire labour process. We aimed to assess the effect of adding dexmedetomidine, fentanyl or morphine to low-dose bupivacaine-dexamethasone for intrathecal labour analgesia in multiparous women.

Methods

This was a triple-blind, randomised controlled trial that included 140 multiparous women. Eligible women were randomly allocated to have intrathecal bupivacaine-dexamethasone with dexmedetomidine (group D), fentanyl (group F), morphine (group M) or saline (placebo) (group C). The duration of analgesia, intrathecal block characteristics and maternal and foetal outcomes were assessed and analysed.

Results

The longest analgesia duration and S1 regression time was recorded in group D followed by groups M, F and C, respectively, with statistical significance between all of them (P < 0.001). The shortest analgesia onset time and the highest sensory levels were recorded in group D followed by group F then group M with statistical significance between all of them (P < 0.001 and 0.003, respectively). Visual analogue scale values were comparable among groups M, F and D (P > 0.05) at most of the measurement time points and at the peak of the last uterine contraction before delivery while being significantly lower than those in group C (P < 0.001). However, there were similar motor block characteristics and normal neonatal outcomes in all groups.

Conclusion

In comparison to morphine and fentanyl, dexmedetomidine addition to intrathecal bupivacaine-dexamethasone significantly prolonged the duration and accelerated the onset of labour analgesia, with a good maternal and neonatal outcome.

Effect of epidural analgesia in trial of labor after cesarean on maternal and neonatal outcomes in China: a multicenter, prospective cohort study

BACKGROUND

The trial of labor after cesarean section (TOLAC) is a relatively new technique in mainland of China, and epidural analgesia is one of the risk factors for uterine rupture. This study aimed to evaluate the effect of epidural analgesia on primary labor outcome [success rate of vaginal birth after cesarean (VBAC)], parturient complications and neonatal outcomes after TOLAC in Chinese multiparas based on a strictly uniform TOLAC indication, management and epidural protocol.

METHODS

A total of 423 multiparas undergoing TOLAC were enrolled in this study from January 2017 to February 2018. Multiparas were divided into two groups according to whether they received epidural analgesia (study group, N = 263) or not (control group, N = 160) during labor. Maternal delivery outcomes and neonatal characteristics were recorded and evaluated using univariate analysis, multivariable logistic regression and propensity score matching (PSM).

RESULTS

The success rate of VBAC was remarkably higher (85.55% vs. 69.38%, p < 0.01) in study group. Epidural analgesia significantly shortened initiating lactation period and declined Visual Analogue Score (VAS). It also showed more superiority in neonatal umbilical arterial blood pH value. After matching by PSM, multivariable logistic regression revealed that the correction of confounding factors including epidural analgesia, cervical Bishop score at admission and spontaneous onset of labor were still shown as promotion probability in study group (OR = 4.480, 1.360, and 10.188, respectively; 95%CI = 2.025-10.660, 1.113-1.673, and 2.875-48.418, respectively; p < 0.001, p = 0.003, and p < 0.001, respectively).

CONCLUSIONS

Epidural analgesia could reduce labor pain, and no increased risk of postpartum bleeding or uterine rupture, as well as adverse effects in newborns were observed. The labor duration of multiparas was increased, but within acceptable range. In summary, epidural analgesia may be safe for both mother and neonate in the three studied hospitals.

TRIAL REGISTRATION

Chineses Clinical Trial Register, ChiCTR-ONC-17010654. Registered February 16th, 2017.

Labor Epidural Analgesia to Cesarean Section Anesthetic Conversion Failure: A National Survey

Background

If conversion of labor epidural analgesia to cesarean delivery anesthesia fails, the anesthesiologist can be confronted with a challenging clinical dilemma. Optimal management of a failed epidural top up continues to be debated in the absence of best practice guidelines.

Method

All members of the Obstetric Anaesthetists' Association in the United Kingdom were emailed an online survey in May 2017. It obtained information on factors influencing the decision to utilize an existing labor epidural for cesarean section and, if epidural top up resulted in no objective sensory block, bilateral T10 sensory block, or unilateral T6 sensory block, factors influencing the management and selection of anesthetic technique. Differences in management options between respondents were compared using the chi-squared test.

Results

We received 710 survey questionnaires with an overall response rate of 41%. Most respondents (89%) would consider topping up an existing labor epidural for a category-one cesarean section. In evaluating whether or not to top up an existing labor epidural, the factors influencing decision-making were how effective the epidural had been for labor pain (99%), category of cesarean section (73%), and dermatomal level of blockade (61%). In the setting of a failed epidural top up, the most influential factors determining further anesthetic management were the category of cesarean section (92%), dermatomal level of blockade (78%), and the assessment of maternal airway. Spinal anesthesia was commonly preferred if an epidural top up resulted in no objective sensory block (74%), bilateral T10 sensory block (57%), or unilateral T6 sensory block (45%). If the sensory block level was higher or unilateral, then a lower dose of intrathecal local anesthetic was selected and alternative options such as combined-spinal epidural and general anesthesia were increasingly favored.

Discussion

Our survey revealed variations in the clinical management of a failed epidural top up for cesarean delivery, suggesting guidelines to aid decision-making are needed.

A Review of the Impact of Obstetric Anesthesia on Maternal and Neonatal Outcomes

Obstetric anesthesia has evolved over the course of its history to encompass comprehensive aspects of maternal care, ranging from cesarean delivery anesthesia and labor analgesia to maternal resuscitation and patient safety. Anesthesiologists are concerned with maternal and neonatal outcomes, and with preventing and managing complications that may present during childbirth. The current review will focus on recent advances in obstetric anesthesia, including labor anesthesia and analgesia, cesarean delivery anesthesia and analgesia, the effects of maternal anesthesia on breastfeeding and fever, and maternal safety. The impact of these advances on maternal and neonatal outcomes is discussed. Past and future progress in this field will continue to have significant implications on the health of women and children.

Epidural analgesia at trial of labor after cesarean (TOLAC): a significant adjunct to successful vaginal birth after cesarean (VBAC)

INTRODUCTION

Epidural analgesia has been considered a risk factor for labor dystocia at trial of labor after cesarean (TOLAC) and uterine rupture. We evaluated the association between exposure to epidural during TOLAC and mode of delivery and maternal-neonatal outcomes.

MATERIALS AND METHODS

A single center retrospective study of women that consented to TOLAC within a strict protocol between 2006 and 2013. Epidural "users" were compared to "non-users". Primary outcome was the mode of delivery: repeat in-labor cesarean or vaginal birth after cesarean (VBAC). Secondary outcomes were maternal/neonatal morbidities. Univariate/multivariate analyses for associations between epidural and mode of delivery were adjusted for significant covariates/mediators.

RESULTS

Of a total of 105,471 births registered, 9464 (9.0%) were eligible for TOLAC; 7149 (75.5%) women consented to TOLAC, among which 4081 (57.1%) had epidural analgesia. The in labor cesarean rate was significantly lower for the epidural "users" 8.7% vs. "non-users" 11.8%, P<0.0001, with a parallel increased rate of instrumental delivery. Uterine rupture rates were comparable: 0.4% and 0.29%, respectively (P=0.31). The adjusted multivariate model showed that epidural "users" were more likely to experience a VBAC, odds ratio (OR) 4.58 [3.67; 5.70]; P<0.0001 with a similar rate of adverse maternal-neonatal outcomes.

CONCLUSION

Epidural analgesia at TOLAC may emerge as a safe and significant adjunct for VBAC.

The nature of labour pain: An updated review of the literature

BACKGROUND

The pain experience associated with labour is complex. Literature indicates psychosocial and environmental determinants of labour pain, and yet methods to support women usually target physiological attributes via pharmacological interventions.

AIM

To provide an update of our understanding of labour pain based on modern pain science. The review aims to help explain why women can experience labour pain so differently - why some cope well, whilst others experience great suffering. This understanding is pertinent to providing optimal support to women in labour.

METHOD

A literature search was conducted in databases Medline, Cumulative Index to Nursing and Allied Health Literature and PsycINFO, using search terms labor/labour, childbirth, pain, experience and perception. Thirty-one papers were selected for inclusion.

FINDINGS

Labour pain is a highly individual experience. It is a challenging, emotional and meaningful pain and is very different from other types of pain. Key determinants and influences of labour pain were identified and grouped into cognitive, social and environmental factors.

CONCLUSION

If a woman can sustain the belief that her pain is purposeful (i.e. her body working to birth her baby), if she interprets her pain as productive (i.e. taking her through a process to a desired goal) and the birthing environment is safe and supportive, it would be expected she would experience the pain as a non-threatening, transformative life event. Changing the conceptualisation of labour pain to a purposeful and productive pain may be one step to improving women's experiences of it, and reducing their need for pain interventions.

Analysis and evaluation of the effectiveness of epidural analgesia and its relationship with eutocic or dystocic delivery

OBJECTIVE

Numerous studies have demonstrated the difference in the verbal rating scale with regard to obstructed labour and induced labour, so that obstructed labour and foetal macrosomia have been related to a greater sensation of pain during labour, particularly in the first stage. Even the epidural analgesia is linked to the need for instrumented or caesarean section due to foetal obstruction. The goal of the study is to analyze and evaluate the effectiveness of epidural analgesia in normal versus obstructed labour.

PATIENTS AND METHODS

One hundred and eighty pregnant women were included in an observational, analytical, longitudinal and prospective study, that was performed in the Obstetrics Department of the Hospital Universitario Dexeus. All the nulliparous or multiparous over 36 weeks of pregnancy, after 3cm of cervical dilatation in spontaneous or induced labor were included. All the patients were given epidural analgesia according to protocol.

RESULTS

The basic descriptive methods were used for the univariate statistical analysis of the sample and the Mann-Whitney U test was used for the comparison of means between both groups. The correlations between variables were studied by means of the Spearman coefficient of correlation. The differences regarded as statistically significant are those whose P<.05.

CONCLUSION

In our population there were no statistically significant differences in the effectiveness of epidural analgesia in normal versus obstructed labour. Patients who got epidural analgesia and had obstructed labors have the same degree of verbal rating scale as patients that do not had obstructed labors (P>.05).

Outcomes of induced versus spontaneous labor

PURPOSE

Induced labor is associated with a higher request for analgesia than spontaneous labor. This study compared duration of labor, mode of delivery, quantity of blood loss, type of perineal outcome and neonatal outcomes between women in induced labor and women in spontaneous labor, both on epidural analgesia (administered at cervical dilation  ≤ 4 cm).

METHODS

In a two-year longitudinal cohort study, data were gathered from nulliparous women with a single cephalic pregnancy of at least 37 weeks attending the labor and delivery ward in Policlinico San Matteo Fundation-Pavia. Data were compared for women with early labor analgesia in (1) spontaneous labor (Robson group 1) and (2) induced labor (dinoprostone - vaginal insert or gel, Robson group 2a).

RESULTS

Of the 1104 women who underwent epidural analgesia in the study period, 531 were included: 326 in spontaneous labor and 205 in induced labor. The only significant difference found was duration of the first stage, which lasted 305 (200-390) min in spontaneous labor compared to 205 min (120-345) in induced labor (p  <0.001).

CONCLUSIONS

In women on early epidural analgesia, induction is associated with a shorter duration of the first stage of labor and does not affect other outcomes.

The degree of labor pain at the time of epidural analgesia in nulliparous women influences the obstetric outcome

Background

The increased pain at the latent phase can be associated with dysfunctional labor as well as increases in cesarean delivery frequency. We aimed to research the effect of the degree of pain at the time of epidural analgesia on the entire labor process including the mode of delivery.

Methods

We performed epidural analgesia to 102 nulliparous women on patients' request. We divided the group into three based on NRS (numeric rating scale) at the moment of epidural analgesia; mild pain, NRS 1-4; moderate pain, NRS 5-7; severe pain, NRS 8-10. The primary outcome was the mode of delivery (normal labor or cesarean delivery).

Results

There were significant differences in the mode of delivery among groups. Patients with severe labor pain had a significantly higher cesarean delivery compared to patients with moderate labor pain (P = 0.006). The duration of the first and second stage of labor, fetal heart rate, use of oxytocin and premature rupture of membranes had no differences in the three groups.

Conclusions

Our research showed that the degree of pain at the time of epidural analgesia request might influence the rate of cesarean delivery. Further research would be necessary for clarifying the mechanism that the augmentation of pain affects the mode of delivery.

Epidural analgesia in labour and risk of caesarean delivery

BACKGROUND

A Cochrane Systematic Review of randomised controlled trials of epidural analgesia compared with other or no analgesia in labour reported no overall increased risk of caesarean delivery. However, many trials were affected by substantial non-compliance, and there are concerns about the external validity of some trials for contemporary maternity populations. We aimed to explore the association between epidural analgesia in labour and caesarean delivery in clinical practice and compare with findings from randomised controlled trials.

METHODS

Population-based cohort of pregnant women (n = 210 708) without major obstetrical complications who delivered a singleton live infant in hospitals in New South Wales, Australia, 2007-10. Data were obtained from linked, validated population-based data collections. Propensity score matching was used to examine the association between epidural analgesia in labour and caesarean delivery.

RESULTS

Epidural analgesia in labour was used by a third (31.5%, n = 66 317) of the women, and 9.8% (n = 20 531) had a caesarean delivery. Epidural analgesia in labour was associated with increased risk of caesarean delivery {risk ratio [RR] 2.5, [95% confidence interval (CI) 2.5, 2.6]}. The association with epidural analgesia in labour was higher for caesarean delivery for failure to progress {RR 3.0, [95% CI 2.9, 3.0]} than for caesarean delivery for fetal distress {RR 1.9, [95% CI 1.8, 2.0]}.

CONCLUSIONS

Epidural analgesia in labour is associated with caesarean delivery in a large maternity population. Population-based studies contribute important data about obstetrical care, when research settings and participants may not represent the clinical settings or broader population in which obstetrical interventions in labour are applied.

A prospective observational study of ethnic and racial differences in neuraxial labor analgesia request and pain relief

BACKGROUND

As ethnic and racial diversity increases, it is important that anesthesia providers understand the expectations and concerns of this changing population regarding labor analgesia. Our objective was to evaluate ethnic/racial differences in labor analgesia characteristics with regard to the timing of request for neuraxial analgesia.

METHODS

Three hundred ninety-seven parturients were enrolled in this prospective observational cohort study. Term laboring parturients who planned vaginal delivery and requested neuraxial labor analgesia were eligible for inclusion. Data collected included cervical dilation at the time of neuraxial analgesia request, self-identified ethnicity/race, parity, education, insurance status, pain score before and after the initiation of neuraxial analgesia, and mode of delivery. The primary outcome was cervical dilation at the time of neuraxial analgesia request. Ethnicity/race classification was determined by asking the patient, "How would you define your ethnicity?" Patients were categorized into the ethnic/racial groups of non-Hispanic White, African American, Hispanic, or other. Univariate associations between cervical dilation and categorical variables were examined. Multivariate analysis was performed for the primary outcome of cervical dilation at the time of initiation of neuraxial analgesia.

RESULTS

At the time of neuraxial analgesia placement, the mean difference in cervical dilation of Hispanic parturients was 0.8 cm compared to non-Hispanic Whites (95% confidence interval [CI], 0.1-1.4; P = 0.047). After controlling for education, reason for placement, labor augmentation, and mode of delivery in a multivariate model, Hispanic parturients had 0.5 cm greater cervical dilation compared to non-Hispanic Whites, which was not significant (95% confidence interval, -0.1 to 1.1; P = 0.089).

CONCLUSIONS

Our data indicate that ethnicity/race plays a small role in acceptance and request for neuraxial labor analgesia.

Neuraxial analgesia effects on labour progression: facts, fallacies, uncertainties and the future

Approximately 60% of women who labour in the USA receive some form of neuraxial analgesia, but concerns have been raised regarding whether it negatively impacts the labour and delivery process. In this review, we attempt to clarify what has been established as truths, falsities and uncertainties regarding the effects of this form of pain relief on labour progression, negative and/or positive. Additionally, although the term 'epidural' has become synonymous with neuraxial analgesia, we discuss two other techniques, combined spinal-epidural and continuous spinal analgesia, that are gaining popularity, as well as their effects on labour progression.

The role of maternal attachment in the experience of labor pain: a prospective study

OBJECTIVE

To examine the influence of attachment dimensions and sociodemographic and physical predictors in the experience of labor pain.

METHODS

Eighty-one pregnant women were assessed during their third trimester of pregnancy and during labor. The perceived intensity of pain in the early stages of labor (3 cm of cervical dilatation) and before the administration of patient-controlled epidural analgesia was measured using a visual analog scale. Pain was also assessed indirectly based on anesthetic doses. Attachment was assessed using the Adult Attachment Scale-Revised.

RESULTS

Attachment anxiety and avoidance were positively and significantly correlated with labor pain and anesthetic consumption. In the multivariate models, attachment anxiety was a significant predictor of higher pain at 3 cm of cervical dilatation (β = 0.36, p = .042) and before the administration of patient-controlled epidural analgesia (β = 0.51, p = .002). Older age (β = 0.31, p = .005), a shorter duration of labor (β= -0.41, p = .001), and attachment avoidance (β = 0.41, p = .004) were significant predictors of higher anesthetic use.

CONCLUSIONS

The study findings suggest that perceived labor pain and anesthetic use are strongly associated with attachment, rather than demographic and physical factors. These data support the importance of understanding the experience of labor pain within an attachment theoretical framework.

Advances in labor analgesia

The pain of childbirth is arguably the most severe pain most women will endure in their lifetimes. The pain of the early first stage of labor arises from dilation of the lower uterine segment and cervix. Pain from the late first stage and second stage of labor arises from descent of the fetus in the birth canal, resulting in distension and tearing of tissues in the vagina and perineum. An array of regional nerve blocks, systemic analgesic, and nonpharmacologic techniques are currently used for labor analgesia. Nonpharmacologic methods are commonly used, but the effectiveness of these techniques generally lacks rigorous scientific study. Continuous labor support has been shown to decrease the use of pharmacologic analgesia and shorten labor. Intradermal water injections decrease back labor pain. Neuraxial labor analgesia (most commonly epidural or combined spinal-epidural) is the most effective method of pain relief during childbirth, and the only method that provides complete analgesia without maternal or fetal sedation. Current techniques commonly combine a low dose of local anesthetic (bupivacaine or ropivacaine) with a lipid soluble opioid (fentanyl or sufentanil). Neuraxial analgesia does not increase the rate of cesarean delivery compared to systemic opioid analgesia; however, dense neuraxial analgesia may increase the risk of instrumental vaginal delivery.

The effects of hydrotherapy on anxiety, pain, neuroendocrine responses, and contraction dynamics during labor

BACKGROUND

Hydrotherapy (immersion or bathing) is used worldwide to promote relaxation and decrease parturient anxiety and pain in labor, but the psychophysiological effects of this intervention remain obscure.

DESIGN

A pretest-posttest design with repeated measures was used to examine the effects of hydrotherapy on maternal anxiety and pain, neuroendocrine responses, plasma volume shift (PVS), and uterine contractions (CXs) during labor. Correlations among variables were examined at three time points (preimmersion and twice during hydrotherapy).

METHODS

Eleven term women (mean age 24.5 years) in spontaneous labor were immersed to the xiphoid in 37 degrees C water for 1 hr. Blood samples and measures of anxiety and pain were obtained under dry baseline conditions and repeated at 15 and 45 min of hydrotherapy. Uterine contractions were monitored telemetrically.

RESULTS

Hydrotherapy was associated with decreases in anxiety, vasopressin (V), and oxytocin (O) levels at 15 and 45 min (all ps < .05). There were no significant differences between preimmersion and immersion pain or cortisol (C) levels. Pain decreased more for women with high baseline pain than for women with low baseline levels at 15 and 45 min. Cortisol levels decreased twice as much at 15 min of hydrotherapy for women with high baseline pain as for those with low baseline pain. beta-endorphin (betaE) levels increased at 15 min but did not differ between baseline and 45 min. During immersion, CX frequency decreased. A positive PVS at 15 min was correlated with contraction duration.

CONCLUSIONS

Hydrotherapy during labor affects neuroendocrine responses that modify psychophysiological processes.

Labor pain at the time of epidural analgesia and mode of delivery in nulliparous women presenting for an induction of labor

OBJECTIVE

To assess whether the degree of labor pain at the initiation of neuraxial analgesia is associated with mode of delivery.

METHODS

Nulliparous women who presented to the labor department for an induction of labor, who were between 37 and 41 weeks of gestation, and who requested labor epidural analgesia with a pain score of 0-3 (low pain) and a cervical dilatation less than 4 cm were assessed retrospectively. Maternal and neonatal outcome including mode of delivery and duration of labor were compared with a similar group of women with pain scores of 4-6 (moderate pain), and 7-10 (severe pain). Assessing whether there was an association between pain level at the time of epidural and operative delivery rates was analyzed using a chi test for trend and by logistic regression to include potentially relevant covariates.

RESULTS

We found 185 nulliparous women with low pain and compared them with a randomly selected equal number of women in each of the other pain groups. There was no significant association between pain groups in terms of duration of the first or second stage of labor or mode of delivery. Women with low pain had an operative delivery rate (instrumental assisted vaginal delivery plus cesarean delivery) of 49%, compared with 45% and 45% in those with moderate and severe pain, respectively (P=.40).

CONCLUSION

We did not find an association between the degree of labor pain at initiation of epidural analgesia and mode of delivery or duration of labor.

LEVEL OF EVIDENCE

II.

Genetic variability of the mu-opioid receptor influences intrathecal fentanyl analgesia requirements in laboring women

Labor initiates one of the most intensely painful episodes in a woman's life. Opioids are used to provide analgesia with substantial interindividual variability in efficacy. mu-Opioid receptor (muOR, OPRM1) genetic variants may explain differences in response to opioid analgesia. We hypothesized that OPRM1 304A/G polymorphism influences the median effective dose (ED(50)) of intrathecal fentanyl via combined spinal-epidural for labor analgesia. Nulliparous women were prospectively recruited around 35 weeks gestation (n=224), and genotyped for 304A/G polymorphism. Those requesting neuraxial labor analgesia were enrolled in one of the two double-blinded trials: up-down sequential allocation (SA, n=50) and a separate confirmatory random-dose allocation trial (RA, n=97). Effective analgesia from intrathecal fentanyl was defined by >or=60 min analgesia with verbal rating score <or=1 (scale 0-10) and was compared between mu OR 304A homozygotes (Group A) and women carrying at least one 304G allele (Group G). OPRM1 304G allele frequency f(-) was 0.18. Using SA, intrathecal fentanyl ED(50) was 26.8 microg (95% CI 22.7-30.9) in Group A and 17.7 microg (95% CI 13.4-21.9) in Group G (p<0.001; 304A homozygosity increased the ED(50) 1.5-fold). RA confirmed that 304A homozygosity significantly increases intrathecal fentanyl ED(50) (27.4 microg in Group A and 12.8 microg in Group G [p<0.002; 2.1-fold]). We demonstrate for the first time that the muOR 304G variant significantly reduces intrathecal fentanyl ED(50) for labor analgesia, suggesting women with the G variant may be more responsive to opioids and require less analgesic drugs. These findings for intrathecal fentanyl pharmacogenetics may have implications for patients receiving opioids in other settings.

Advances in and limitations of up-and-down methodology: a précis of clinical use, study design, and dose estimation in anesthesia research

Sequential design methods for binary response variables exist for determination of the concentration or dose associated with the 50% point along the dose-response curve; the up-and-down method of Dixon and Mood is now commonly used in anesthesia research. There have been important developments in statistical methods that (1) allow the design of experiments for the measurement of the response at any point (quantile) along the dose-response curve, (2) demonstrate the risk of certain statistical methods commonly used in literature reports, (3) allow the estimation of the concentration or dose-the target dose-associated with the chosen quantile without the assumption of the symmetry of the tolerance distribution, and (4) set bounds on the probability of response at this target dose. This article details these developments, briefly surveys current use of the up-and-down method in anesthesia research, reanalyzes published reports using the up-and-down method for the study of the epidural relief of pain during labor, and discusses appropriate inferences from up-and-down method studies.

Comparison of computer integrated patient controlled epidural analgesia vs. conventional patient controlled epidural analgesia for pain relief in labour

Computer integrated-patient controlled epidural analgesia (CI-PCEA) is a novel drug delivery system. It automatically titrates the background infusion rate based on the individual parturient's need. In this randomised trial, we compared the local anaesthetic consumption by parturients using CI-PCEA with demand only patient controlled epidural analgesia (PCEA) for labour analgesia. We recruited 40 parturients after approval by the ethics committee. Group PCEA (n = 20) received demand only PCEA. Group CI-PCEA (n = 20) received a similar PCEA regimen but the computer integration titrated the background infusion to 5, 10 or 15 ml x h(-1) if the patient required one, two or three demand boluses, respectively, in the previous hour. The background infusion decreased by 5 ml x h(-1) if there was no demand bolus in the previous hour. The sample size was calculated to show equivalence in local anaesthetic used. The time weighted consumption of local anaesthetic was similar in both groups (mean difference 0.7 mg x h(-1), 95% confidence interval [CI: -2.5, 1.1]; p = 0.425). The CI-PCEA group had higher maternal satisfaction scores: mean (SD) 93 (7) vs. 86 (11), p = 0.042. CI-PCEA does not increase the use of local anaesthetic when compared with demand only PCEA but does increase patient satisfaction.

Obese parturients have lower epidural local anaesthetic requirements for analgesia in labour †

BACKGROUND

There are no studies comparing local anaesthetic requirements for obese and normal parturients. Obesity has been associated with a higher incidence of Caesarean section and higher levels of epidural block have also been found in obese obstetric patients, suggesting they may require less local anaesthetic. The aim of our study was to estimate the minimum local analgesic concentration (MLAC) of bupivacaine for obese and non-obese parturients.

METHODS

Otherwise healthy parturients (n=32) requesting epidural analgesia were enrolled in this up-down sequential allocation study. Women were in active labour (3-6 cm cervical dilatation) with visual analogue pain scores (VAPS) >40/100 mm. Subjects with BMI >30 kg m(-2) were allocated to the obese group and BMI < or = 30 kg m(-2) were allocated to the normal group. The initial epidural dose for both groups was 20 ml 0.1% w/v bupivacaine (20 mg), with a dosing increment of 0.01% w/v VAPS < or = 10/100 mm defined effective analgesia. The MLAC was estimated using up-down reversals and probit regression with P<0.05 as significant.

RESULTS

Groups were similar except for BMI and weight (P<0.001). Local anaesthetic requirements were significantly (P<0.001) reduced by a factor of 1.68 (95% CI 1.32-2.29) in the obese group, with significantly higher initial level of block (P<0.001).

CONCLUSION

We found obese parturients to have significantly decreased epidural bupivacaine analgesic requirements. A contributing factor to obese patients having more difficult labours may be that relatively larger doses of local anaesthetic are administered than actually required. It may be worth considering lowering the concentrations and doses with which we initiate analgesia in obese parturients.

Current status and clinical relevance of studies of minimum local-anaesthetic concentration (MLAC)

PURPOSE OF REVIEW

Studies comparing the effects of epidural local anaesthetics have been limited by the lack of knowledge of their relative potencies. In 1995 the concept of the minimum local-anaesthetic concentration (MLAC) was introduced, this has been defined primarily as the median effective analgesic concentration in the first stage of labour. Pharmacologically, this model aims to determine equipotent analgesic concentrations of local anaesthetics, to compare motor effects and to evaluate the relative toxicity during labour. However, results of recent MLAC studies are not uniform and rather confusing, and thus, the basic validity of the MLAC concept for determining local-anaesthetic potency is increasingly discussed.

RECENT FINDINGS

MLAC studies have postulated that ropivacaine is up to 40% less potent than bupivacaine, but as potent as levo-bupivacaine. Intriguingly, bupivacaine has been shown to be as effective as levo-bupivacaine in identical experimental protocols. Modified MLAC studies resulted additionally in local anaesthetic-sparing effects of epidural/intrathecal opioids, clonidine and epinephrine. MLAC studies have also been applied to compare the relative analgesic as well as relative motor-blocking potency of local anaesthetics.

SUMMARY

Relative differences in local anaesthetics' potencies derived from MLAC examinations are meaningful and correct from the pharmacological point of view, but they cannot simply be transferred to daily clinical practice. Thus, MLAC values should not be misinterpreted as these data are not suggested to be suitable to define and quantify the pharmacodynamics of local anaesthetics, nor to unequivocally predict their toxicological profile in clinically relevant concentrations.

The risk of cesarean delivery with neuraxial analgesia given early versus late in labor

BACKGROUND

Epidural analgesia initiated early in labor (when the cervix is less than 4.0 cm dilated) has been associated with an increased risk of cesarean delivery. It is unclear, however, whether this increase in risk is due to the analgesia or is attributable to other factors.

METHODS

We conducted a randomized trial of 750 nulliparous women at term who were in spontaneous labor or had spontaneous rupture of the membranes and who had a cervical dilatation of less than 4.0 cm. Women were randomly assigned to receive intrathecal fentanyl or systemic hydromorphone at the first request for analgesia. Epidural analgesia was initiated in the intrathecal group at the second request for analgesia and in the systemic group at a cervical dilatation of 4.0 cm or greater or at the third request for analgesia. The primary outcome was the rate of cesarean delivery.

RESULTS

The rate of cesarean delivery was not significantly different between the groups (17.8 percent after intrathecal analgesia vs. 20.7 percent after systemic analgesia; 95 percent confidence interval for the difference, -9.0 to 3.0 percentage points; P=0.31). The median time from the initiation of analgesia to complete dilatation was significantly shorter after intrathecal analgesia than after systemic analgesia (295 minutes vs. 385 minutes, P<0.001), as was the time to vaginal delivery (398 minutes vs. 479 minutes, P<0.001). Pain scores after the first intervention were significantly lower after intrathecal analgesia than after systemic analgesia (2 vs. 6 on a 0-to-10 scale, P<0.001). The incidence of one-minute Apgar scores below 7 was significantly higher after systemic analgesia (24.0 percent vs. 16.7 percent, P=0.01).

CONCLUSIONS

Neuraxial analgesia in early labor did not increase the rate of cesarean delivery, and it provided better analgesia and resulted in a shorter duration of labor than systemic analgesia.