Nitrous oxide for analgesia in external cephalic version at term: prospective comparative study

External cephalic version: Success rates with and without nitrous oxide

BACKGROUND

External cephalic version (ECV) is a technique used to reduce the incidence of cesarean deliveries due to malpresentation. Nitrous oxide is an inhaled analgesic that may be used for pain relief for women undergoing external cephalic version.

OBJECTIVE

To compare the conversion rate of non-cephalic to cephalic presentation in ECV with and without nitrous oxide.

STUDY DESIGN

A retrospective cohort analysis was performed including all singleton, term gestation ECVs between January 2016 and June 2017 at a single institution. Multivariable logistic regression was used to compare women who had ECV with nitrous oxide versus ECV without nitrous oxide. The primary outcome was successful rate of conversion to cephalic presentation and the secondary outcome was the rate of vaginal delivery.

RESULTS

During the study period, 167 women underwent ECV: 77 with nitrous oxide and 90 without nitrous oxide. Of the 77 women who used nitrous oxide, 25 (32.5%) were successful and 17 of these women delivered vaginally (68%). Of the women who underwent ECV without nitrous oxide, 29 (32.2%) successfully converted and 21 of these delivered vaginally (72%). After controlling for confounders, the use of nitrous oxide had no clinically or statistically significant difference on ECV success rates (OR 1.08, 95% CI 0.52-2.23).

CONCLUSION

Nitrous oxide does not seem to affect conversion rate to cephalic presentation in ECV. Further studies are needed to determine the impact of nitrous oxide on women's decision to undergo ECV and on patient satisfaction and tolerability.

Effect of nitrous oxide use on external cephalic version success rate; a systematic review and meta-analysis

INTRODUCTION

Several adjuvant interventions have been evaluated for improving the success rate of the external cephalic version (ECV) and reducing the rate of cesarean delivery (CD). Evidence regarding the effect of Nitrous oxide is limited to a small number of participants with inconsistent results on pain score and success rate. This study aims to examine the effect of inhaled nitrous oxide on the success rate and pain score for women undergoing ECV.

MATERIAL AND METHODS

Survey on ECV reports from inception till June 2020 were made from MEDLINE, EMBASE, PubMed, Ovid Medline, ClinicalTrials.gov, the Cochrane Library and Google Scholars. Peer-review studies that examined the success rate of ECV from the application of nitrous oxide during ECV attempts compared with or without the use of other analgesic agents were obtained. The study population comprising women with singleton pregnancies having a non-vertex presentation at least 36 weeks, were categorized into one of two treatment groups: ECV attempt with nitrous oxide (nitrous oxide group) and ECV attempt with or without another analgesia (control group). The primary outcome was the ECV success rate, defined by conversion to vertex-presentation following the procedure. The secondary outcomes were pain scores during ECV attempt and CD rate. The study quality scores were evaluated as a source of heterogeneity by fitting meta-regression models to the individual study effect sizes.

RESULTS

Of the 26 records identified, two randomized trials and one prospective cohort study (720 women; 434 in the nitrous oxide group and 286 controls) were deemed adequate for meta-analysis. ECV success rate did not differ significantly between the nitrous oxide group and the control group (p = .825; OR 1.036; 95% CI, 0.756, 1.419). In addition, the use of nitrous oxide did not affect pain scores during ECV attempt (p = .457; OR 0.759; 95% CI, -1.240, 2.759) and there was no difference in the incidence of CD as well (p = .943; OR 1.013; 95% CI, 0.703, 1.46).

CONCLUSION

The use of nitrous oxide during ECV attempts was not associated with an increase in ECV success rate and does not affect pain scores. PROSPERO Registration No. CRD42020197933.

A Systematic Review and Meta-analysis of Clinical Trials of Neuraxial, Intravenous, and Inhalational Anesthesia for External Cephalic Version

BACKGROUND

External cephalic version (ECV) is a frequently performed obstetric procedure for fetal breech presentation to avoid cesarean delivery. Neuraxial, intravenous, and inhalational anesthetic techniques have been studied to reduce maternal discomfort caused by the forceful manipulation. This study compares the effects of these anesthetic techniques on ECV and incidence of cesarean delivery.

METHODS

We conducted a comprehensive literature search for published randomized controlled trials (RCTs) or well-conducted quasi-randomized trials of ECV performed either without anesthesia or under neuraxial, intravenous, or inhalational anesthesia. Pairwise random-effects meta-analyses and network meta-analyses were performed to compare and rank the perinatal outcomes of the 3 anesthetic interventions and no anesthesia control, including the rate of successful version, cesarean delivery, maternal hypotension, nonreassuring fetal response, and adequacy of maternal pain control/satisfaction.

RESULTS

Eighteen RCTs and 1 quasi-randomized trial involving a total of 2296 term parturients with a noncephalic presenting singleton fetus were included. ECV under neuraxial anesthesia had significantly higher odds of successful fetal version compared to control (odds ratio [OR] = 2.59; 95% confidence interval [CI], 1.88-3.57), compared to intravenous anesthesia (OR = 2.08; 95% CI, 1.36-3.16), and compared to inhalational anesthesia (OR = 2.30; 95% CI, 1.33-4.00). No association was found between anesthesia interventions and rate of cesarean delivery. Neuraxial anesthesia was associated with higher odds of maternal hypotension (OR = 9.33; 95% CI, 3.14-27.68). Intravenous anesthesia was associated with significantly lower odds of nonreassuring fetal response compared to control (OR = 0.36; 95% CI, 0.16-0.82). Patients received neuraxial anesthesia reported significantly lower visual analog scale (VAS) of procedure-related pain (standardized mean difference [SMD] = -1.61; 95% CI, -1.92 to -1.31). The VAS scores of pain were also significantly lower with intravenous (SMD = -1.61; 95% CI, -1.92 to -1.31) and inhalational (SMD = -1.19; 95% CI, -1.58 to -0.8) anesthesia. The VAS of patient satisfaction was significantly higher with intravenous anesthesia (SMD = 1.53; 95% CI, 0.64-2.43).

CONCLUSIONS

Compared to control, ECV with neuraxial anesthesia had a significantly higher successful rate; however, the odds of maternal hypotension increased significantly. All anesthesia interventions provided significant reduction of procedure-related pain. Intravenous anesthesia had significantly higher score in patient satisfaction and lower odds of nonreassuring fetal response. No evidence indicated that anesthesia interventions were associated with significant decrease in the incidence of cesarean delivery compared to control.

Nitrous oxide analgesia for external cephalic version: A randomized controlled trial

STUDY OBJECTIVE

Our study sought to determine whether or not nitrous oxide analgesia decreases pain compared to oxygen placebo during external cephalic version for breech presentation. Procedural success may be limited by pain and anxiety. Although neuraxial anesthesia has been studied extensively for these procedures, many centers lack resources for routine use. Nitrous oxide is noninvasive, has minimal side effects and requires limited facilities. We hypothesized that its analgesic properties would decrease pain compared to oxygen placebo during external cephalic version.

DESIGN

Double-blinded randomized placebo-controlled trial.

SETTING

Labor and delivery triage room.

PATIENTS

Forty-eight patients, ≥18 years of age, 37-weeks' gestation or beyond, singleton pregnancy, breech presentation, and American Society of Anesthesiology physical status I-III, having an external cephalic version.

INTERVENTIONS

Patients undergoing external cephalic version were randomized to receive self-administered 50% nitrous oxide/50% oxygen versus 100% oxygen placebo.

MEASUREMENTS

The primary outcome measured was intra-procedural pain. Secondary outcomes were intra-procedural anxiety, patient satisfaction, and procedure difficulty.

MAIN RESULTS

Forty-eight patients were enrolled; 23 received nitrous oxide and 25 received oxygen. No difference was noted in mean pain scores (nitrous oxide 5.5 ± 2.3, placebo 5.4 ± 2.7, [CI_95% = -1.40, 1.51]; P = 0.943) or anxiety scores (nitrous oxide 1.6 ± 2.0, placebo 1.2 ± 1.8, [CI_95% = -0.74, 1.45]; P = 0.515). Procedural difficulty (1-10 scale, 1 = very easy, 10 = extremely difficult) was not different between groups (nitrous oxide 6.1 ± 2.2, placebo 6.1 ± 3.2, [CI_95% = -1.54, 1.66]; P = 0.944). There was a significant increase in the number of version attempts in the nitrous oxide group (nitrous oxide 3.9 ± 1.9, placebo 2.8 ± 1.4, [CI_95% = 0.05, 2]; P = 0.046). Patient satisfaction was significantly lower in the nitrous oxide group (nitrous oxide 4.3 ± 4.0, placebo 6.9 ± 3.6, [CI_95% = -4.93, -0.34]; P = 0.025).

CONCLUSION

Despite the desirable properties of nitrous oxide, there was no analgesic benefit over oxygen for external cephalic version. Its routine use for these procedures was not supported.

Effectiveness of nitrous oxide in external cephalic version on success rate: A randomized controlled trial

INTRODUCTION

Approximately 4% of singleton pregnancies at term are in breech presentation. External cephalic version (ECV) can reduce the risks of noncephalic birth and cesarean delivery, but this maneuver can be painful. Our aim was to analyze the effect of administering inhaled nitrous oxide for analgesia on the ECV success rate.

MATERIAL AND METHODS

This prospective, randomized, single-blind, controlled trial included women with singleton pregnancies in breech presentation at term who were referred for ECV in a tertiary care center. Women were assigned according to a balanced (1:1) restricted randomization design to inhale either nitrous oxide (N₂ O) in a 50:50 mix with oxygen or medical air during the procedure. The main outcomes reported are the ECV success rate, degree of pain, adverse event rate, and women's satisfaction.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01948115.

RESULTS

The study included 150 women (nitrous oxide group: n = 74; medical air: n = 76). Inhaled nitrous oxide was not associated with a higher ECV success rate than medical air (24.3 vs 19.7%, P = 0.51). Among parous women (n = 34 in each group), the ECV success rate appeared higher in the nitrous oxide group, respectively 47.1% (n = 16) vs 23.5% (n = 8) (P = 0.042). Neither the median pain level nor adverse event rates differed significantly in women with inhaled nitrous oxide compared with medical air.

CONCLUSIONS

Use of an equimolar mixture of oxygen and nitrous oxide during ECV appears safe. Although it does not seem to change the overall success rate, it may increase success in parous women.

[Breech Presentation: CNGOF Guidelines for Clinical Practice - External Cephalic Version and other Interventions to turn Breech Babies to Cephalic Presentation]

OBJECTIVES

To provide guidelines regarding efficiency and safety of external cephalic version (ECV) attempt and alternatives methods to turn breech babies to cephalic presentation.

METHODS

MedLine and Cochrane Library databases search in French and English and review of the main foreign guidelines between 1980 and 2019.

RESULTS

ECV is associated with a decreasing rate of breech presentation at birth (LE2), and potentially with a lower rate of cesarean section (LE3) without an increase of severe maternal (LE3) and perinatal morbidity (LE3). It is therefore recommended to inform women with a breech presentation at term that ECV should be attempt (Professional consensus). ECV attempt should be performed with immediate access to an operating room for emergency cesarean (Professional consensus). The ECV attempt before 37 weeks, compared to ECV attempt after 37 weeks, increases the rate of cephalic presentation at birth (LE2) but with a small increase risk of moderate prematurity (LE2). ECV attempt should be performed from 36SA (Professional consensus). The main factors associated with successful ECV attempt are multiparity (LE3) and no maternal obesity (LE3). Parenteral tocolysis (β mimetic or atosiban), for ECV attempt at term is associated with a higher success rate (LE2), higher rate of achieved cephalic presentation in labor (LE2) and a lower cesarean section rate (LE2). It is recommended to use parenteral tocolysis for ECV attempt at term in order to increase its success rate (grade B). The ECV attempt is associated with an increase in transient FHR abnormalities (LE3), it is therefore recommended that cardiotocography should be performed prior and during 30minutes after the procedure (Professional consensus). There is no argument for recommending the practice of delayed cardiotocography after ECV attempt (Professional consensus). The risk of significant positivity (>30mL) of the Kleihauer test after ECV attempt is low (<0.1%) (LE3), it is not recommended to systematically perform a Kleihauer test after ECV attempt (professional consensus). In case of RH-1 negative women, it is recommended to ensure systematic RH-1 prophylaxis (Professional consensus). In case of breech presentation at term, acupuncture, moxibustion and postural methods are not effective in reducing breech presentation at birth (LE2), and are therefore not recommended (Grade B).

CONCLUSION

According to the clear benefits and the low risks of ECV attempt, all women with a breech presentation at term should be informed that ECV should be attempted to decrease breech presentation at birth and cesarean section.

Maternal and perinatal outcomes in external cephalic version: prognostic factors for the success of the technique

Background We aimed to analyze the success rate of external cephalic version (ECV) for breech presentations performed in our center between March 2011 and March 2016. We evaluated factors related to a successful ECV, delivery mode, complications and newborn status after ECV. Methods Analysis of assembled data of 327 consecutive ECVs in the third trimester was done. Results The total success rate was 56.6%. After a successful ECV, 85.9% of the fetuses were delivered vaginally. Logistic regression analysis of background factors leading to a successful ECV showed that tocolysis with ritodrine and anterior placenta were each significantly correlated with the rate of successful version. No severe complications were registered during the ECVs, and all babies had normal Apgar scores at delivery. Conclusion These findings suggest that attempting an ECV in breech presentations, once or even twice, seems to be an appropriate management given that a successful ECV decreases the rate of cesarean section in this group of patients and by doing so, it might also decrease the risk of cesarean sections in future pregnancies.

European Society of Anaesthesiology Task Force on Nitrous Oxide: a narrative review of its role in clinical practice

Nitrous oxide (N₂O) is one of the oldest drugs still in use in medicine. Despite its superior pharmacokinetic properties, controversy remains over its continued use in clinical practice, reflecting in part significant improvements in the pharmacology of other anaesthetic agents and developing awareness of its shortcomings. This narrative review describes current knowledge regarding the clinical use of N₂O based on a systematic and critical analysis of the available scientific literature. The pharmacological properties of N₂O are reviewed in detail along with current evidence for the indications and contraindications of this drug in specific settings, both in perioperative care and in procedural sedation. Novel potential applications for N₂O for the prevention or treatment of chronic pain and depression are also discussed. In view of the available evidence, we recommend that the supply of N₂O in hospitals be maintained while encouraging its economic delivery using modern low flow delivery systems. Future research into its potential novel applications in prevention or treatment of chronic conditions should be pursued to better identify its role place in the developing era of precision medicine.

Non-Neuraxial Labor Analgesia: Options

Although it is the most effective method to treat labor pain, neuraxial analgesia may be undesired, contraindicated, unsuccessful, or unavailable. Providing safe choices for labor pain relief is a central goal of health care providers alike. Consequently, knowledge of the efficacy, clinical implementation, and side effects of various non-neuraxial strategies is needed to provide appropriate options for laboring patients. In addition to nonpharmacologic alternatives, inhaled nitrous oxide and systemic opioids represent two broad classes of non-neuraxial pharmacologic labor analgesia most commonly available. This review summarizes the current published literature for these non-neuraxial labor analgesic options.

This baby is not for turning: Women's experiences of attempted external cephalic version

BACKGROUND

Existing studies regarding women's experiences surrounding an External Cephalic Version (ECV) report on women who have a persistent breech post ECV and give birth by caesarean section, or on women who had successful ECVs and plan for a vaginal birth. There is a paucity of understanding about the experience of women who attempt an ECV then plan a vaginal breech birth when their baby remains breech. The aim of this study was to examine women's experience of an ECV which resulted in a persistent breech presentation.

METHODS

A qualitative descriptive exploratory design was undertaken. In-depth semi-structured interviews were conducted and analysed thematically.

RESULTS

Twenty two (n = 22) women who attempted an ECV and subsequently planned a vaginal breech birth participated. Twelve women had a vaginal breech birth (55 %) and 10 (45 %) gave birth by caesarean section. In relation to the ECV, there were five main themes identified: 'seeking an alternative', 'needing information', 'recounting the ECV experience', 'reacting to the unsuccessful ECV' and, 'reflecting on the value of an ECV'.

CONCLUSIONS

ECV should form part of a range of options provided to women, rather than a default procedure for management of the term breech. For motivated women who fit the safe criteria for vaginal breech birth, not being subjected to a painful experience (ECV) may be optimal. Women should be supported to access services that support vaginal breech birth if this is their choice, and continuity of care should be standard practice.