Nitrous oxide for pain in labor--why not in the United States?

Obstetric analgesia and anaesthesia in SARS-CoV-2-positive parturients across 10 maternity units in the north-west of England: a retrospective cohort study

Since the start of the COVID-19 pandemic, few studies have reported anaesthetic outcomes in parturients with SARS-CoV-2 infection. We reviewed the labour analgesic and anaesthetic interventions utilised in symptomatic and asymptomatic parturients who had a confirmed positive test for SARS-CoV-2 across 10 hospitals in the north-west of England between 1 April 2020 and 31 May 2021. Primary outcomes analysed included the analgesic/anaesthetic technique utilised for labour and caesarean birth. Secondary outcomes included a comparison of maternal characteristics, caesarean birth rate, maternal critical care admission rate along with adverse composite neonatal outcomes. A positive SARS-CoV-2 test was recorded in 836 parturients with 263 (31.4%) reported to have symptoms of COVID-19. Neuraxial labour analgesia was utilised in 104 (20.4%) of the 509 parturients who went on to have a vaginal birth. No differences in epidural analgesia rates were observed between symptomatic and asymptomatic parturients (OR 1.03, 95%CI 0.64-1.67; p = 0.90). The neuraxial anaesthesia rate in 310 parturients who underwent caesarean delivery was 94.2% (95%CI 90.6-96.0%). The rates of general anaesthesia were similar in symptomatic and asymptomatic parturients (6% vs. 5.7%; p = 0.52). Symptomatic parturients were more likely to be multiparous (OR 1.64, 95%CI 1.19-2.22; p = 0.002); of Asian ethnicity (OR 1.54, 1.04-2.28; p = 0.03); to deliver prematurely (OR 2.16, 95%CI 1.47-3.19; p = 0.001); have a higher caesarean birth rate (44.5% vs. 33.7%; OR 1.57, 95%CI 1.16-2.12; p = 0.008); and a higher critical care utilisation rate both pre- (8% vs. 0%, p = 0.001) and post-delivery (11% vs. 3.5%; OR 3.43, 95%CI 1.83-6.52; p = 0.001). Eight neonates tested positive for SARS-CoV-2 while no differences in adverse composite neonatal outcomes were observed between those born to symptomatic and asymptomatic mothers (25.8% vs. 23.8%; OR 1.11, 95%CI 0.78-1.57; p = 0.55). In women with COVID-19, non-neuraxial analgesic regimens were commonly utilised for labour while neuraxial anaesthesia was employed for the majority of caesarean births. Symptomatic women with COVID-19 are at increased risk of significant maternal morbidity including preterm birth, caesarean birth and peripartum critical care admission.

Multicenter Study Evaluating Nitrous Oxide Use for Labor Analgesia at High- and Low-Altitude Institutions

BACKGROUND

Nitrous oxide (N2O) has been used nationally as an analgesic in many clinical settings. While neuraxial analgesia is still the most commonly used labor analgesic in the United States, there is increasing use of N2O in labor. Given the reduction in the partial pressure of gases at a higher altitude, N2O has been reported to have reduced analgesic properties. However, there is no study to date evaluating the impact of altitude on labor analgesia and N2O.

METHODS

We conducted a multicenter retrospective data analysis of a N2O registry collected from 4 institutions over a 3-year period. We compared the impact of altitude on 50% N2O administration for labor analgesia, conversion rates to another analgesic modality, as well as collected side effect frequencies and conversion predictors. Multivariable regression models were used to compare clinical characteristics and outcomes between parturients at high and low altitudes, while adjusting for race, ethnicity, education, and age (logistic and linear regressions for categorical and quantitative outcomes, respectively).

RESULTS

A total of 1856 laboring parturients (age 18-50) were included in the analysis. The odds of converting from 50% N2O to another analgesic modality had no statistically significant difference between high- versus low-altitude institutions (adjusted odds ratio [aOR], 1.13; 95% confidence interval [CI], 0.90-1.42; P = .3). Yet, when parturients at low altitude converted from N2O, they were more likely (aOR, 3.03; 95% CI, 1.59-5.88) to choose neuraxial analgesia instead of another analgesic modality when compared to high-altitude parturients. This is possibly due to higher epidural rates at the low-altitude institutions. When parturients at high altitude did convert into another modality, they were more likely (aOR, 2.19; 95% CI, 1.14-4.21) to convert due to inadequate pain relief compared to low-altitude parturients; however, missing data may have affected this finding. Laboring individuals at low altitude were significantly more likely to experience side effects (aOR, 2.13; 95% CI, 1.45-3.12). Those requiring labor augmentation, assisted vaginal, or cesarean delivery converted to neuraxial analgesia significantly more often than those that delivered via spontaneous vaginal delivery (P < .05) in both high- and low-altitude groups.

CONCLUSIONS

This is the first study evaluating 50% N2O as a labor analgesic at high altitude. As expected, we found lower side effects at high altitude, likely due to the lower partial pressure of N2O. However, there was not a statistically significant increase in conversion from N2O to another analgesic modality at high altitude and no clinically significant differences in neonatal outcomes.

Pro-Con Debate: Nitrous Oxide for Labor Analgesia

This Pro-Con debate will provide the practitioner with an evidence-based knowledge approach to assist the clinician in determining whether to employ (Pro) or not to employ (Con) this technique in the obstetrical suite for labor analgesia. Nitrous oxide has been used safely in dentistry and medicine for many centuries. However, accumulating preclinical and clinical evidence increasingly suggests previously unrecognized adverse maternal and fetal effects of nitrous oxide, which warrants reconsideration of its use in pregnant women and a more detailed informed consent. Nitrous oxide is associated with metabolic, oxidative, genotoxic, and transgenerational epigenetic effects in animals and humans that may warrant limiting its usefulness in labor. This debate will discuss and review the clinical uses, advantages, and disadvantages of nitrous oxide on occupational effects of nitrous oxide exposure, neuroapoptosis, FDA warning on inhalational anesthetics and the developing brain, research limitations, occupational exposure safety limits, effects on global warming, and potential for diversion.

Population-Based Risk Factors for Shoulder Dystocia

OBJECTIVE

To re-examine the risk factors for shoulder dystocia given the increasing rates of obesity and diabetes in pregnant women.

DESIGN

Retrospective observational study.

SETTING

Five hospitals located in Wisconsin, Florida, Maryland, Michigan, and Alabama.

PARTICIPANTS

We evaluated 19,236 births that occurred between April 1, 2011, and July 25, 2013.

METHODS

Data were collected from electronic medical records and used to evaluate the risk of shoulder dystocia. Data were analyzed using a generalized linear mixed model, which controlled for clustering due to site.

RESULTS

When insulin was prescribed, gestational diabetes was associated with an increased risk of shoulder dystocia (odds ratio = 2.10, 95% confidence interval [1.01, 4.37]); however, no similar association was found with regard to gestational diabetes treated with glycemic agents or through diet. Use of epidural anesthesia was associated with an increased risk for shoulder dystocia (odds ratio = 3.47, 95% confidence interval [2.72, 4.42]). Being Black or Hispanic, being covered by Medicaid or having no insurance, infant gestational age of 41 weeks or greater, and chronic diabetes were other significant risk factors.

CONCLUSION

With the changing characteristics of pregnant women, labor and birth clinicians care for more pregnant women who have an increased risk for shoulder dystocia. Our findings may help prospectively identify women with the greatest risk.

Should Nitrous Oxide Be Used for Laboring Patients?

Nitrous oxide, long used during labor in Europe, is gaining popularity in the United States. It offers many beneficial attributes, with few drawbacks. Cost, safety, and side effect profiles are favorable. Analgesic effectiveness is highly variable, yet maternal satisfaction is often high among the women who choose to use it. Despite being less effective in treating labor pain than neuraxial analgesic modalities, nitrous oxide serves the needs and preferences of a subset of laboring parturients. Nitrous oxide should, therefore, be considered for inclusion in the repertoire of modalities used to alleviate pain and facilitate effective coping during labor.

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

Background

The use of pain-relieving drugs during labor is now part of standard care in many countries throughout the world. Each method of pain relief has its own risks and benefits, variations in effectiveness, and availability and acceptability.

Objectives

This study aimed to assess the efficacy and safety of intramuscular pethidine as an analgesic during labor by comparing it to inhaled 50% nitrous oxide (Entonox).

Methods

In this clinical trial study, 100 women who expected to have a natural childbirth were observed. The inclusion criteria for this study were the commencement of spontaneous labor pain along with appropriate maternal and fetal indications for vaginal delivery. By using random numbers, each subject was randomly allocated to one of two groups, with one group using Entonox and the other receiving an intramuscular injection of 0.5 mg/kg of pethidine for pain relief. The intensity of labor pain experienced by the subjects and the outcomes of the deliveries were collected with questionnaires.

Results

The average pain scores in the Entonox and pethidine groups were 3.94 ± 1.4 and 5.6 ± 1.1, respectively, 30 minutes after intervention (P = 0.001), but there was not a significant difference in the severity of the pain (5.06 ± 1.4 and 4.7 ± 1.1 for the Entonox and pethidine groups, respectively) between the subjects in each group 60 minutes after the intervention (P = 0.592). No significant differences were seen in the duration and interval of uterine contractions, maternal complications, Apgar scores, and the duration of the first and second stage of labor between the two studied groups (P > 0.05). An analysis of the pooled risk differences showed that none of the side effects investigated were significantly different between the two groups except for mouth dryness, which was significantly higher in nitrous oxide users (P = 0.044).

Conclusions

Inhaled nitrous oxide seems to give better pain relief in the short term compared to a single dose of pethidine. Entonox, which is more convenient to administer than an intramuscular injection of pethidine, is also regarded as safe both for mothers and neonates.

Trends in Perinatal Care and Implications for Frontline Nurse Leaders

The perinatal trends presented in this article are based on recent topics from conferences, journals, the media, as well as from input from perinatal nurses. Trends in patient care are influenced by evidence known for decades, new research, emerging and innovative concepts in healthcare, patient and family preferences, and the media. Trends discussed in this article are rethinking the due date, birth outside the hospital setting, obstetric hospitalists as birth attendants, nitrous oxide for pain in childbirth, hydrotherapy and waterbirth in the hospital setting, delayed cord clamping, disrupters of an optimal infant microbiome, skin-to-skin care during cesarean surgery, and breast-sleeping and the breast-feeding dyad. In addition, the authors developed implications for perinatal nurses related to each trend. The goal is to stimulate reflection on evidence that supports or does not support current practice and to stimulate future research by discussing some of the current trends that may influence the care that perinatal nurses provide during the birthing year.

Introduction of Inhaled Nitrous Oxide and Oxygen for Pain Management during Labour - Evaluation of Patients' and Midwives' Satisfaction

Aim: Effective pain management during labour is important because pain affects the birth experience. Epidural analgesia is effective but often it may not be possible; however, inhaled analgesia offers another option. Use of inhaled nitrous oxide and oxygen for pain management in labour is well established in obstetrics but is still not used much in Germany. This study aimed to investigate the acceptance of the inhaled analgesia of inhaled nitrous oxide and oxygen by midwives and pregnant women during labour. Material and Methods: In this observational study carried out between April and September 2013, a total of 66 pregnant women received inhaled nitrous oxide and oxygen during labour on request and after prior assessment of suitability. After the birth, all of the women and the responsible midwives were interviewed about their experience and satisfaction with the inhaled analgesia. Results: A statistically significant reduction of pain was achieved with nitrous oxide and oxygen. The inhaled analgesia was mostly used by women who refused epidural analgesia. The likelihood of using inhaled nitrous oxide and oxygen again was reported as higher for patients who tolerated it well (p = 0.0129) and used it in the second stage of labour (p = 0.0003) and when bearing down (p = 0.0008). Conclusion: Inhaled nitrous oxide and oxygen is an effective method for pain management during labour and is accepted well by women in labour and by midwives.

Eliciting preferences for key attributes of intrapartum care in the Netherlands

BACKGROUND

As part of the move toward "patient-centered care," women's preferences with regard to maternity services have become increasingly important to policy makers. To realize optimal patient-centered care, knowledge of patients' preferences is essential. The aim of our study was to assess the strength and relative importance of women's preferences for different aspects of intrapartum care in The Netherlands, where women have easy access to both home and hospital birth.

METHODS

A discrete choice experiment was conducted at 16 weeks of gestation as part of a Dutch multicenter, prospective cohort study from 2007 to 2011 of low-risk, nulliparous women. Responses were analyzed per intended place of birth group: midwifery-led home (n = 191) and hospital birth (n = 152) and obstetric-led hospital birth (n = 188).

RESULTS

We analyzed 562 questionnaires. Women in all groups preferred the possibility of influencing decision making and pain-relief treatment during birth and no co-payment for childbirth. Women with an intended home birth preferred a home-like birth setting with the assistance of a midwife and transport during birth in case of complications. Type of birth setting and transport during birth were not considered important to women with an intended midwifery- or obstetric-led hospital birth.

CONCLUSION

Policies aimed at the improvement of maternity care must take into account women's preferences for the possibility of pain-relief treatment and the fact that all women desire a high level of involvement in decision making. Furthermore, efforts to change maternity care systems must consider how to counter the culturally embedded nature of women's preferences.

Maternal expectations and experiences of labor analgesia with nitrous oxide

BACKGROUND

Although there are various methods for painless delivery such as using entonox gas, most of the people are unfamiliar or concerned about it yet.

OBJECTIVES

The purpose of this study was to assess maternal expectations and experience of labor analgesia with nitrous oxide.

PATIENTS AND METHODS

In a clinical trial study, 98 pregnant women in active phase of delivery were studied randomly in two groups (intervention group = 49, control group = 49) after obtaining written consent. Efficacy, experience satisfaction, and also expectation of pregnant women about entonox gas in two groups were compared, likewise in intervention group before and after using entonox gas.

RESULTS

Most of the pregnant women receiving entonox gas had less labor pain (91.8%), and were satisfied with it (98%). The severity of pain in the most of entonox user was moderate level (46.94%), while for the control group it was severe (55.10%) which was significant, 40.82% of the mother in entonox group had a severe pain and 10.20% had a very severe pain, whereas in the control group (55.10%) of the mother had a severe pain and 26.53% of the had very severe pain (P = 0.004). efficacy of labor pain was in moderate level in most cases. 49% of pregnant women receiving gas described their experience as a good and excellent. 80.9% indicated that they will request the mentioned painless method in the future. The amount of suffering from gas side effects was mild in most patients of intervention group (63%). Expectations of the majority of pregnant women in intervention group (before receiving gas) and control group for painless delivery were weak (65.3%, 40.9%). The percentage of positive expectations had increased after receiving entonox gas (P = 0.01). There was a difference between the expectations of intervention group receiving entonox gas and control group (P = 0.001). Positive expectations were more in intervention group than the control group. Most differences of expectations in intervention group before and after receiving the gas were about higher efficacy (P = 0.001), more satisfaction (P = 0.001), fewer complications (P = 0.001), information about gas as painless delivery method (P = 0.02), and also previous experience of intolerable labor pain (P = 0.04).

CONCLUSIONS

This study has shown that using entonox gas caused less labor pain, favorable expectations and experiences and also more maternal satisfaction.

Nitrous oxide as labor analgesia: clinical implications for nurses

A new interest in self-administered nitrous oxide for labor analgesia has emerged in recent years in the United States. It has been used widely in Europe for decades, with favorable results. The American College of Nurse-Midwives published a position statement in 2010 supporting the practice of self-administered nitrous oxide as an additional analgesia choice for laboring women. Recent literature on this subject has been directed toward midwives, obstetricians and/or anesthesiologists, with little emphasis for labor and delivery nurses. This article presents highlights of nursing care for women using self-administered nitrous oxide during labor and birth.

Inhaled analgesia for pain management in labour

BACKGROUND

Many women would like to have a choice in pain relief during labour and also would like to avoid invasive methods of pain management in labour. Inhaled analgesia during labour involves the self-administered inhalation of sub-anaesthetic concentrations of agents while the mother remains awake and her protective laryngeal reflexes remain intact. Most of the agents are easy to administer, can be started in less than a minute and become effective within a minute.

OBJECTIVES

To examine the effects of all modalities of inhaled analgesia on the mother and the newborn for mothers who planned to have a vaginal delivery.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2012), ClinicalTrials.gov, and Current Controlled Trials (2 June 2012), handsearched conference proceedings from the American Society of Clinical Anesthesia (from 1990 to 2011), contacted content experts and trialists and searched reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials comparing inhaled analgesia with other inhaled analgesia or placebo or no treatment or other methods of non-pharmacological pain management in labour.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed trials for eligibility, methodological quality and extracted all data. Data were double checked for accuracy.

MAIN RESULTS

Twenty-six studies, randomising 2959 women, were included in this review.Inhaled analgesia versus a different type of inhaled analgesia Pain relief was measured using a Visual Analogue Scale (VAS) from 0 to 100 mm where 100 corresponds to the most relief. Pain intensity was measured using a VAS from 0 to 100 mm, where 0 corresponds to no pain at all and 100 corresponds to the worst pain. The highest score for pain relief is the most positive in contrast to 'pain intensity' in which the higher score is more negative. Flurane derivatives were found to offer better pain relief than nitrous oxide in first stage of labour as measured by a lower pain intensity score (average mean difference (MD) 14.39, 95% confidence interval (CI) 4.41 to 24.37, three studies, 70 women), also a higher pain relief score for flurane derivatives compared with nitrous oxide (average MD -16.32, 95% CI -26.85 to -5.79, two studies, 70 women). Substantial heterogeneity was found in the analyses of pain intensity (P = 0.003) and in the analysis of pain relief (P = 0.002).These findings should be considered with caution because of the questionable design of the included cross-over trials. More nausea was found in the nitrous oxide group compared with the flurane derivatives group (risk ratio (RR) 6.60 95% CI 1.85 to 23.52, two studies, 98 women).Inhaled analgesia versus placebo or no treatment Placebo or no treatment was found to offer less pain relief compared to nitrous oxide (average RR 0.06, 95% CI 0.01 to 0.34, two studies, 310 women; MD -3.50, 95% CI -3.75 to -3.25, one study, 509 women). However, nitrous oxide resulted in more side effects for women such as nausea (RR 43.10, 95% CI 2.63 to 706.74, one study, 509 women), vomiting (RR 9.05, 95% CI 1.18 to 69.32, two studies, 619 women), dizziness (RR 113.98, 95% CI 7.09 to 1833.69, one study, 509 women) and drowsiness (RR 77.59, 95% CI 4.80 to 1254.96, one study, 509 women) when compared with placebo or no treatment.There were no significant differences found for any of the outcomes in the studies comparing one strength versus a different strength of inhaled analgesia, in studies comparing different delivery systems or in the study comparing inhaled analgesia with TENS.Due to lack of data, the following outcomes were not analysed within the review: sense of control; satisfaction with childbirth experience; effect on mother/baby interaction; breastfeeding; admission to special care baby unit; poor infant outcomes at long-term follow-up; or costs.

AUTHORS' CONCLUSIONS

Inhaled analgesia appears to be effective in reducing pain intensity and in giving pain relief in labour. However, substantial heterogeneity was detected for pain intensity. Furthermore, nitrous oxide appears to result in more side effects compared with flurane derivatives. Flurane derivatives result in more drowsiness when compared with nitrous oxide. When inhaled analgesia is compared with no treatment or placebo, nitrous oxide appears to result in even more side effects such as nausea, vomiting, dizziness and drowsiness. There is no evidence for differences for any of the outcomes comparing one strength verus a different strength of inhaled analgesia, comparing different delivery systems or comparing inhaled analgesia with TENS.

Aromatherapy and massage intrapartum service impact on use of analgesia and anesthesia in women in labor: a retrospective case note analysis

BACKGROUND

Over the past decade, interest in complementary therapies and alternative medicine has escalated among midwives and the general public in response to increased demand from expectant mothers for more choice, control, and continuity in labor.

OBJECTIVE

The aim of this study was to explore if an aromatherapy and massage intrapartum service (AMIS) reduced the need for analgesia during labor. This article reports results related to the effects of an AMIS on type of analgesia chosen by women in labor, and on rates of anesthesia--one aspect of the full study.

SETTING/LOCATION

The study was conducted in a general maternity unit in southwest England, UK.

DESIGN

A quantitative research approach was taken, whereby contemporaneously completed service evaluation forms of 1079 women (601 nulliparous women and 478 multiparous women; AMIS group) were retrospectively analyzed in comparison with the birth records of an equal number of similar women (comparison group). Data analysis was achieved by entering data from the forms and comparison sample into an SPSS package and running statistical tests.

RESULTS

In the AMIS group, overall analgesia usage was higher for transcutaneous electrical stimulation at 34%, compared with 15.9% (p<0.001 allowing for parity), and for nitrous oxide and oxygen at 87.6%, compared with 80.8% (p<0.001). Pethidine use did not differ after adjustment for parity at 30.1%, compared with 24.2% (p=0.27) in the AMIS and comparison groups, respectively. Rates were lower in the AMIS group for epidural anesthesia at 29.7%, compared with 33.8% (p=0.004 allowing for parity) in the comparison group; spinal anesthesia at 6%; compared with 12.1% (p<0.001) in the comparison group; and general anesthesia at 0.8%, compared with 2.3% (p=0.033) in the comparison group.

CONCLUSIONS

Having an AMIS appears to have a positive impact on reducing rates of all types of intrapartum anesthesia. The Service is a beneficial addition to conventional midwifery practice that may influence mode of delivery and reduce general anesthesia rates.

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.

Oxytocin as a "high alert medication": a multilayered challenge to the status quo

Oxytocin is the drug most commonly associated with preventable adverse perinatal outcomes. In 2007 it was added to the Institute for Safe Medication Practices short list of medications "bearing a heightened risk of harm," which may "require special safeguards to reduce the risk of error." In January 2009 the American Journal of Obstetrics and Gynecology published a Clinical Opinion paper about oxytocin's inclusion on the list and how the obstetrics profession in the United States should respond. The authors call for the development of specific evidence-based guidelines to reduce the likelihood of patient harm by limiting elective use of oxytocin, decreasing the need for indicated use, reducing dosages during necessary use, giving more responsibility and authority for the patient's safety to the professional who is "at the bedside administering and monitoring the oxytocin infusion" (i.e., the nurse), and accepting that "more time rather than more oxytocin is generally preferable" once adequate uterine activity has been achieved. It is unfortunate that this important paper discounted the risk of harm from cesarean sections and did not mention the strong linkage between epidural analgesia and use of oxytocin. Physicians, midwives, nurses, and others should examine and discuss these issues further in view of increased alertness to the risk of harm from unsafe use of oxytocin.