A Randomized Controlled Trial Comparing Use of Enthonox With Pethidine for Pain Relief in Primigravid Women During the Active Phase of Labor

Effectiveness of Nitrous Oxide versus Pethidine/Midazolam for Pain Relief in Minor Gynecological Operative Procedures: A Randomized Controlled Trial

Aim and Objective: To compare the analgesic effectiveness of the patient-controlled inhaled nitrous oxide (Entonox^®) with intravenous opioids (pethidine/midazolam) in reducing pain during minor gynecological operative procedures, including manual vacuum aspiration (MVA), fractional curettage and dilatation and curettage. Materials and Methods: Patients undergoing minor gynecological procedures from August 2021 to December 2022 were randomized to receive nitrous oxide or intravenous pethidine (50-75 micrograms) plus midazolam (2 mg). Pain scores during and post-procedure, satisfaction level, and side effects were assessed and compared. Results: A total of 106 patients met the inclusion criteria, including 53 in the pethidine/midazolam group and 53 in the nitrous oxide group. Baseline characteristics were comparable (p-value > 0.05). Pain scores during, immediately and 30 min after procedures were not significantly different in two groups (4.94 ± 3.15, 2.74 ± 2.57, 1.58 ± 2.13 vs. 5.47 ± 2.80, 2.98 ± 2.70, 1.64 ± 2.70; p-value: 0.174, 0.634, 0.889, for pethidine/midazolam vs. nitrous oxide group, respectively. Satisfaction scores were comparable in both groups (p-value > 0.05). However, the rate of side effects was significantly lower in the nitrous oxide group (3.8% vs. 28.3%; p-value 0.001). Additionally, the discharge scores showed a significantly faster recovery time in the nitrous oxide group at 60 and 90 min after the procedure; median (IQR): 10 (9-10) vs. 9 (8-10) and 10 (10-10) vs. 10 (8.5-10); p-value 0.002 and 0.029, respectively). Conclusions: Nitrous oxide is as effective as pethidine/midazolam for pain relief in minor gynecological operative procedures but associated with significantly lower side effects and significantly faster recovery time.

Parturients' Stated Preferences for Labor Analgesia: A Discrete Choice Experiment

OBJECTIVE

The objective was to investigate the extent to which treatment benefits, risks and costs affected parturients' preferences for labor analgesia.

METHODS

We recruited 248 healthy parturients prior to labor at an antenatal ward and administered a discrete choice experiment survey. Parturients were asked to choose among four hypothetical forms of labor analgesia: epidural analgesia, pethidine, Entonox and no analgesia, which were defined by: pain score, duration of second stage of labor, risks of instrumental delivery, back pain and permanent nerve injury, and out-of-pocket cost. We used mixed logit model to calculate the relative importance of each attribute (out of 100).

RESULTS

Parturients preferred receiving labor analgesia over not receiving analgesia and those who had positive past experience with epidural preferred epidural over other modalities. Out-of-pocket cost (28%), duration of second stage of labor (26%) and pain score following treatment (18%) were the most important attributes.

CONCLUSION

Out-of-pocket cost was a major concern. Parturients prioritized having lower pain and shorter labor experience over risks associated with epidural analgesia. Parturients should be presented with realistic range of risks of side-effects so that they can decide how to balance risks against benefits and costs associated with child labor.

Entonox® versus Pethidine in Labor Pain Relief: A Randomized Controlled Trial

BACKGROUND

Pain relief during labor is a part of standard care in modern obstetrics. Several modalities used for pain relief have their own disadvantages and benefits in terms of side effects, effectiveness, availability, and satisfaction. The objectives of this study are primarily to compare the effectiveness and patients' satisfaction for pain relief during labor between pethidine and inhaled 50% nitrous oxide (Entonox^®).

METHODS

Laboring women at 37-41 + 6 weeks of gestation were randomly allocated to receive pethidine (50 mg intravenously) or Entonox^® for reducing labor pain. Pain scores were evaluated at 0, (baseline), 30, 60, 90, and 120 min after initiation, using the visual analog scale (VAS) and also satisfaction score after delivery using the verbal rating scale (VRS). The secondary outcomes were also assessed, including APGAR scores, labor course, side effects, and cesarean section rate.

RESULTS

A total of 136 laboring women underwent randomization into two groups, but only 58 and 65 in the pethidine group and the Entonox^® group were available for analysis. The median pain scores at baseline, 30, 60, and 90 min were comparable between both groups (p-value > 0.05); however, pain score at 120 min in the pethidine group was significantly higher (p-value: 0.038). The median of satisfaction score was significantly higher in the Entonox^® group (4 vs. 3; p-value 0.043). All of the secondary outcomes were comparable between the two groups.

CONCLUSIONS

Both have comparable effectiveness, but Entonox^® has a higher satisfaction score. Entonox^® could be an alternative to pethidine for reducing labor pain, because of its efficacy, ease for self-adjustment for satisfaction, and no serious effects on the labor course and newborns.

Association of Self-Administered Nitrous Oxide for Labor Analgesia With Maternal and Neonatal Process and Outcome Measures

OBJECTIVE

To describe patterns of use of self-administered nitrous oxide (N₂O) during labor and to determine if maternal and neonatal process and outcome measures differ for women who use N₂O compared to women who do not use N₂O.

DESIGN

Retrospective, full-census, observational cohort.

SETTING

An upper midwestern U.S., urban, 75-bed quaternary perinatal center with more than 5,000 annual births.

PARTICIPANTS

The participants included two groups of women: 400 who used N₂O during labor and a comparison group of 6,733 who met N₂O eligibility but did not use N₂O.

METHODS

We used descriptive statistics to examine patterns of use of N₂O during labor between January 2015 and March 2017. We examined associations of N₂O with process (length of first and second stages of labor, time from hospital admission to birth, time from birth to hospital discharge, and total length of stay) and outcome measures (shoulder dystocia, instrumentation, vaginal lacerations, Apgar scores at 5 minutes, nursery disposition) using multivariate linear, logistic, and ordinal regression models.

RESULTS

Three percent (12/400) of women who used N₂O discontinued because of side effects. Among participants with vaginal births who used N₂O, 17.6% (62/352) used N₂O as the only form of pain medication during labor. We found no significant differences in maternal and neonatal outcome measures between the two groups. Among the process measures examined, we found a mean 2-hour-longer time from admission to birth and total length of stay in the N₂O group (p < .05) compared to the non-N₂O group.

CONCLUSION

Most participants who used N₂O (290/352, 82.3%) transitioned to other pain modalities during labor. Maternal and neonatal process and outcome measures were comparable relative to other pain management modalities, with the exception of longer time durations for two measures.

Parenteral opioids for maternal pain management in labour

BACKGROUND

Parenteral opioids (intramuscular and intravenous drugs including patient-controlled analgesia) are used for pain relief in labour in many countries throughout the world. This review is an update of a review first published in 2010.

OBJECTIVES

To assess the effectiveness, safety and acceptability to women of different types, doses and modes of administration of parenteral opioid analgesia in labour. A second objective is to assess the effects of opioids in labour on the baby in terms of safety, condition at birth and early feeding.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (11 May 2017) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials examining the use of intramuscular or intravenous opioids (including patient-controlled analgesia) for women in labour. Cluster-randomised trials were also eligible for inclusion, although none were identified. We did not include quasi-randomised trials. We looked at studies comparing an opioid with another opioid, placebo, no treatment, other non-pharmacological interventions (transcutaneous electrical nerve stimulation (TENS)) or inhaled analgesia.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of each evidence synthesis using the GRADE approach.

MAIN RESULTS

We included 70 studies that compared an opioid with placebo or no treatment, another opioid administered intramuscularly or intravenously or compared with TENS applied to the back. Sixty-one studies involving more than 8000 women contributed data to the review and these studies reported on 34 different comparisons; for many comparisons and outcomes only one study contributed data. All of the studies were conducted in hospital settings, on healthy women with uncomplicated pregnancies at 37 to 42 weeks' gestation. We excluded studies focusing on women with pre-eclampsia or pre-existing conditions or with a compromised fetus. Overall, the evidence was graded as low- or very low-quality regarding the analgesic effect of opioids and satisfaction with analgesia; evidence was downgraded because of study design limitations, and many of the studies were underpowered to detect differences between groups and so effect estimates were imprecise. Due to the large number of different comparisons, it was not possible to present GRADE findings for every comparison.For the comparison of intramuscular pethidine (50 mg/100 mg) versus placebo, no clear differences were found in maternal satisfaction with analgesia measured during labour (number of women satisfied or very satisfied after 30 minutes: 50 women; 1 trial; risk ratio (RR) 7.00, 95% confidence interval (CI) 0.38 to 128.87, very low-quality evidence), or number of women requesting an epidural (50 women; 1 trial; RR 0.50, 95% CI 0.14 to 1.78; very low-quality evidence). Pain scores (reduction in visual analogue scale (VAS) score of at least 40 mm: 50 women; 1 trial; RR 25, 95% CI 1.56 to 400, low-quality evidence) and pain measured in labour (women reporting pain relief to be "good" or "fair" within one hour of administration: 116 women; 1 trial; RR 1.75, 95% CI 1.24 to 2.47, low-quality evidence) were both reduced in the pethidine group, and fewer women requested any additional analgesia (50 women; 1 trial; RR 0.71, 95% CI 0.54 to 0.94, low-quality evidence).There was limited information on adverse effects and harm to women and babies. There were few results that clearly showed that one opioid was more effective than another. Overall, findings indicated that parenteral opioids provided some pain relief and moderate satisfaction with analgesia in labour. Opioid drugs were associated with maternal nausea, vomiting and drowsiness, although different opioid drugs were associated with different adverse effects. There was no clear evidence of adverse effects of opioids on the newborn. We did not have sufficient evidence to assess which opioid drug provided the best pain relief with the least adverse effects.

AUTHORS' CONCLUSIONS

Though most evidence is of low- or very-low quality, for healthy women with an uncomplicated pregnancy who are giving birth at 37 to 42 weeks, parenteral opioids appear to provide some relief from pain in labour but are associated with drowsiness, nausea, and vomiting in the woman. Effects on the newborn are unclear. Maternal satisfaction with opioid analgesia was largely unreported. The review needs to be examined alongside related Cochrane reviews. More research is needed to determine which analgesic intervention is most effective, and provides greatest satisfaction to women with acceptable adverse effects for mothers and their newborn.

Effect of Entonox for pain management in labor: A systematic review and meta-analysis of randomized controlled trials

Background and aim

Entonox was one of the important methods for pain management in the delivery process. In previous years some studies have assessed the effect of this method in Iran. In this regard, the aim of this study was to systematically review studies addressing the effect of Entonox for pain management in labor.

Methods

This systematic review and meta-analysis study was conducted in 2016. The required data was collected using keywords such as ”Entonox”, “nitrous oxide”, ”vaginal delivery”, ”pain relief”, “obstetric”, “labor pain”, and “labor analgesia”, from databases including Google scholar, PubMed, Science Direct, Magiran, SID, and Scopus, and hand-searching of related and valid journals and references of articles. Articles published from 2000 to 2016 were searched. To conduct meta-analysis, CMA:2 (Comprehensive Meta-analysis) was used.

Results

Finally, 14 articles were included in the study. Pain relief standard difference in mean between-groups was −1.01 (95% CI: −1.59 to −0.43, Q=148.5, df=8, p=0.02, I²=76) this difference was significant (p<0.05). The overall Apgar score standard difference in mean between-groups (Entonox vs. comparison) was 0.12 (95% CI: 0.01 to 0.23, Q=109.4, df=16, p=0.00, I²=85.3) this difference was significant (p<0.05). The results of mothers’ satisfaction rate show that mothers in Entonox group has a high level of satisfaction rate.

Conclusion

According to results of studies published in Iran, it seems that Entonox is an effective method for pain relief in vaginal delivery, as well as for improving infant Apgar score and mothers’ satisfaction rate. Pain relief through Entonox can be used as a strategy for cesarean section reduction plan in Iran.