Nitrous oxide for relief of labor pain: A systematic review

More than just joy: A qualitative analysis of participant experiences during nitrous oxide sedation

BACKGROUND

Nitrous oxide use is shifting from general anesthesia to sedation and pain control. Interest in novel uses of nitrous oxide in psychiatry is also growing. Thus, understanding the consequences of using nitrous oxide remains relevant. Previous quantitative research might not have fully captured the whole spectrum of nitrous oxide, whereas qualitative analysis can provide a more comprehensive description. This qualitative study aims to describe the subjective experiences of nitrous oxide use in healthy volunteers who have no prior history of recreational substance misuse.

METHODS

Twenty healthy male volunteers inhaled 50% nitrous oxide for 20 min. Females were excluded due to higher incidence of nausea with nitrous oxide. Afterwards, all participants answered an open-ended question about their experiences during sedation. The answers were then analyzed with inductive qualitative content analysis to identify emergent subcategories, categories, and overarching themes.

RESULTS

We identified two themes: nitrous oxide is mind-altering and produces sensory overload. The mind-altering properties were represented by dreamlike states and heightened emotions. Dreamlike states comprised changes in consciousness and scary, bizarre, or transcendental dreams. Pleasant dreams were not reported. Heightened emotions included euphoria, anxiety, and fear of losing control. Sensory overload consists of distorted perception, bodily sensations, and a heightened sense of surroundings.

CONCLUSIONS

Experiences under nitrous oxide sedation are extremely variable and not always pleasant. These findings can improve our understanding of the likes/dislikes of patients undergoing nitrous oxide sedation. Further qualitative studies should focus on the experiences of other groups, such as children or women in labor.

Perspectives on sustainable practices in the use of nitrous oxide for labour analgesia: A patient and staff survey

BACKGROUND

Climate change has emerged as the single biggest global health threat of the twenty-first century. Nitrous oxide accounts for the largest carbon footprint amongst our use of anaesthetic gas. It is a potent greenhouse gas possessing a global warming potential of approximately 265 times that of carbon dioxide. Despite recent curtailment of its use, it remains extensively employed as an analgesic for women in labour.

OBJECTIVES

Assessment of the opinions of post-natal women and staff on nitrous oxide use and to investigate whether knowledge of its environmental harm would influence their choice of labour analgesia.

DESIGN

Postnatal women and healthcare staff were invited to participate in a survey of nitrous oxide use as a labour analgesic and knowledge of its effect of the environment.

SETTING

A single-centre study in a major obstetric tertiary referral centre in Ireland in 2021.

MAIN OUTCOME MEASURES

To evaluate the awareness and perceptions of postnatal women and staff regarding the environmental impact of nitrous oxide and if it would affect their decision to use it in the future.

RESULTS

One hundred postnatal women and 50 healthcare staff completed the survey. One hundred and six post-natal women were invited to complete the survey, resulting in a response rate of 94%. Knowledge of nitrous oxide's environmental impact was low. After receiving information, 46% of patients were more inclined to seek epidural or request it earlier (54%) to limit their nitrous oxide use, while 51% would choose an alternative analgesia to avoid nitrous oxide altogether. Overwhelmingly, 99% believed they had the right to know about these harmful effects when choosing an analgesic option.

CONCLUSIONS

Patients should be informed of the environmental impact of nitrous oxide antenatally, empowering them to make informed decision on a climate friendly analgesic option if they wish.

Association Between Intrapartum Nitrous Oxide for Labor Analgesia and Short-Term Neonatal Outcomes

OBJECTIVE

To evaluate the association between intrapartum nitrous oxide use and adverse short-term neonatal outcomes.

METHODS

This was a retrospective cohort study of individuals with singleton gestations at 35 or more weeks who attempted labor and delivered at an academic hospital between June 1, 2015, and February 28, 2020. Data were extracted from the electronic medical record using billing and diagnostic codes. Patients were classified based on whether they received no intrapartum analgesia or received nitrous oxide only. Those who received other analgesia types were excluded. The primary outcome was neonatal intensive care unit (NICU) admission. Secondary outcomes included Apgar score less than 7 at 1 minute and 5 minutes, respiratory composite outcome (including meconium aspiration syndrome, neonatal bronchopulmonary disorders, neonatal transient tachypnea, and other neonatal respiratory distress that required NICU admission), hypoglycemia, and hyperbilirubinemia. Univariable and multivariable analyses were used to estimate the association between nitrous oxide exposure intrapartum and the selected outcomes.

RESULTS

Of 6,047 included, 4,153 (68.7%) received no analgesia, and 1,894 (31.3%) received nitrous oxide only. In comparison with individuals who received no analgesia, those who received nitrous oxide were more likely to be nulliparous, be of Black racial identity, have noncommercial insurance, and be less likely to deliver by intrapartum cesarean. The reception of nitrous oxide, compared with the reception of no analgesia, was associated with a lower likelihood of NICU admission (6.4% vs 8.1%; adjusted odds ratio [aOR] 0.77, 95% CI, 0.62-0.96) and an increased likelihood of neonatal hyperbilirubinemia (aOR 1.23, 95% CI, 1.08-1.41). Inhaled nitrous oxide exposure, in comparison with the reception of no analgesia, was not associated with the other secondary outcomes, including Apgar score less than 7 at 1 minute (odds ratio [OR] 0.74, 95% CI, 0.50-1.10) or 5 minutes (OR 0.91, 95% CI, 0.32-2.60), respiratory composite outcome (OR 0.91, 95% CI, 0.70-1.17), and hypoglycemia (OR 0.82, 95% CI, 0.64-1.05).

CONCLUSION

In this single-center retrospective cohort of low-risk patients, intrapartum inhaled nitrous oxide, compared with the reception of no analgesia, was associated with a decreased risk for NICU admission but with an increased risk for hyperbilirubinemia; other outcomes did not differ. These findings may be used to counsel patients when considering nitrous oxide for labor analgesia.

A Pharmacotherapeutic Approaches for Managing Labour Pain Using Synthetic Drugs and Natural Therapies

The birth of a child is a critical and potentially traumatic experience for women, entailing multiple physiological and psychosocial changes. The psychological effects of childbirth pain can have both immediate and long-term effects on the mother's health and her bond with her child. Many studies investigated the different ranges of synthetic drugs available for pain control in labour, inclusive of neuraxial analgesics, inhaled analgesics, and various opioids. The inadequate efficacy and unfavourable side effects of these synthetic drugs prevent appropriate pharmacotherapy, resulting in a quest for natural therapies for reducing labour pain. Herbal therapies (aromatherapy) using several essential oils obtained from various natural plants are another alternative that calms and manages the mind and body through aromatic compounds that have neurological and physiological effects. The review discussed the safety profile of various synthetic drugs with their dosage information and also deliberated on the mechanism and safety profile of various natural plants that are used in aromatherapy. The review also briefly highlighted the other non-pharmacological miscellaneous techniques such as TENS, hypnosis, immersion in water, acupuncture, massage, and different other tactics that aim to assist women in coping with pain in labour.

Nitrous Oxide Abuse: Clinical Outcomes, Pharmacology, Pharmacokinetics, Toxicity and Impact on Metabolism

The recreational use of nitrous oxide (N2O), also called laughing gas, has increased significantly in recent years. In 2022, the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) recognized it as one of the most prevalent psychoactive substances used in Europe. Chronic nitrous oxide (N2O) exposure can lead to various clinical manifestations. The most frequent symptoms are neurological (sensitive or motor disorders), but there are also other manifestations like psychiatric manifestations or cardiovascular disorders (thrombosis events). N2O also affects various neurotransmitter systems, leading to its anesthetic, analgesic, anxiolytic and antidepressant properties. N2O is very challenging to measure in biological matrices. Thus, in cases of N2O intoxication, indirect biomarkers such as vitamin B12, plasma homocysteine and plasma MMA should be explored for diagnosis and assessment. Others markers, like oxidative stress markers, could be promising but need to be further investigated.

Relationship between COMT Gene Polymorphism, Anxiety, and Pain Perception during Labour

BACKGROUND

The COMT gene polymorphism is associated with neurological and psychiatric disorders and pain perception. The present study investigates the existence of anxiety and pain perception in relation to the COMT (catechol-O-methyltransferase) gene polymorphism in labouring women (during "natural" childbirth) with or without inhaled analgesia.

METHODS

A total of 181 women who chose vaginal birth were enrolled in this study. To present the difference in pain perception, the parturients were divided into one group (n = 90) that chose labour analgesia with inhaled nitrous oxide (50% nitrous oxide and 50% oxygen) and one group (n = 91) without analgesia. The blood samples were taken during the pregnancy as a part of routine pregnancy controls in the hospital. The COMT gene polymorphism was detected with the PCR technique. The pain perception of parturients was self-evaluated two times according to the VAS (Visual Analogue Scale), and anxiety as a personality trait was determined with the STAI-T (State Trait Anxiety Inventory). Pain perception as well as anxiety were compared according to COMT genotypes.

RESULTS

In the 181 pregnant women, there were 40 women (22%) of wild homozygotes (GG) of COMT, 95 women (53%) of mutant heterozygotes (GA), and 46 women (25%) of mutant homozygotes (AA). A negative association of pain perception with the GA (mutant heterozygote) polymorphism of the COMT gene versus the wild-type (GG polymorphism) was observed. The GA polymorphism of the COMT gene was associated with 0.46 units lower pain perception compared to the wild type (GG). The anxiety trait score in group AA was lower than in groups GA and GG. The difference reached statistical significance only when comparing AA versus GA (p > 0.042). Analgesic efficacy of nitrous oxide was noticed in 22% of labouring women who reported moderate pain (VAS score 4-7).

CONCLUSIONS

The COMT gene polymorphism was associated with pain perception and anxiety among parturients. The COMT gene polymorphism GA was associated with negative pain perception among labouring women. Nitrous oxide showed statistical significance in anxiolytic efficacy during labour in women with mild anxiety as a personality trait. Anxiolytic efficacy of nitrous oxide has shown better efficacy in parturients with the COMT gene polymorphism AA.

Nitrous oxide: a unique official French addictovigilance national survey

Introduction

Nitrous oxide has become over the last few years a public health problem in many countries. France has a dedicated health monitoring system dedicated to the surveillance of the abuse, dependence and consequences associated with the use of psychoactive substances coordinated by the French National Agency for the Safety of Medicines and Health Products.We present the French national survey of nitrous oxide.

Materials and methods

We analyzed all the cases with nitrous oxide from 2012 to 2021: number of notifications, characteristics of the subjects and consumption, consequences reported and their evolutions over time. In addition, we have made a special focus on the four main complications reported.

Results

A total of 525 cases were received with an exponential increase since 2019. We observed changes in the characteristics of the notifications with an increase in the proportion of women [42.7% in 2021 vs. 30.8% in 2020 (p = 0.02)]; an increase in the quantities consumed (use of cylinders); a negative evolution of the contexts of use with a search for self-therapeutic effects and use in violent contexts; an increasing trend of the severity of cases [78.1% in 2021 vs. 70.0% in 2020 (p = 0.07)].The main effects were substance use disorders and/or associated criteria (82.5%), neurological disorders (75.4%), psychiatric symptoms (15.4%) and cardiovascular events (8.6%). In terms of evolution, we observed a significant increase in cases with a use disorder and an increase in neurological complications. Moreover, new serious effects, notably cardiovascular events were reported.

Discussion

The combination of high availability, varied effects from euphoria to relief of discomfort in a stressful global pandemic context and the development of dependence could explain the rapid growth of consumption and the seriousness of the cases.It must now be taken into account that (i) Substance use disorders are associated with nitrous oxide consumption; (ii) clinicians must consider "nitrous oxide" in young subjects presenting different types of manifestations; and (iii) stopping consumption is imperative and is the first treatment. In this context, an addictological assessment must also be carried out.

Beyond the epidural: Alternatives to neuraxial labor analgesia

Labor creates an intense pain experienced by women across the world. Although neuraxial analgesia is the most effective treatment of labor pain, in many cases, it may not be undesired, not available, or have contraindications. In addition, satisfaction with labor analgesia is not only determined by the efficacy of analgesia but a woman's sense of agency and involvement in the childbirth experience are also key contributors. Providing safe choices for labor analgesia and support is central to creating a tailored, safe, and effective analgesic treatment plan with high maternal satisfaction. Healthcare provider knowledge of various nonneuraxial analgesic options, including efficacy, contraindications, safe clinical implementation, and side effects of various techniques is needed for optimal patient care and satisfaction. Future rigorous scientific studies addressing all of these labor analgesia options are needed to improve our understanding. This review summarizes the current published literature for commonly available non-neuraxial labor analgesic options.

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.

Childbirth Pain and Post-Partum Depression: Does Labor Epidural Analgesia Decrease This Risk?

Post-partum depression (PPD) is a common complication of pregnancy worldwide with a prevalence as high as 15% in some countries. Pain has been identified as a risk factor for major depression; however, the relationship between labor-related pain and PPD is less understood. This article sought out to examine the relationship between pain and PPD, examining whether there is a correlation that reducing pain through epidural analgesia can lower the risk for PPD. A PubMed database search was performed using the keywords “post-partum depression” and “labor epidural”. Multiple articles including 2 meta-analyses were evaluated for the association between post-partum depression and epidural analgesia for labor. Although there is evidence supporting labor epidural analgesia reducing PPD, many studies including the meta-analyses did not uphold the hypothesis. More well-designed studies on this topic need to be investigated in order to substantiate the current evidence in the literature.

Pain Relief During Childbirth in the Context of 50 Years of Social and Technological Change

Pain relief during childbirth continues to stimulate controversy as new treatments emerge and continuing interventions in the birth process invoke concerns about safety, technologic imperatives, and informed consent. In this historical commentary, I identify a complex dissonance between scientific advances and women's needs and expectations regarding childbirth. Evidence-based practice became the standard during the last 50 years and has reinforced a more conservative and parsimonious use of technology to respond to women's needs for pain relief. In reviewing this history, it is apparent that pain relief during labor is inextricably linked to interventions. Nurses can advance evidence-based practice and facilitate robust informed consent as they support women during childbirth.

Pregnancy and Dentistry: A Literature Review on Risk Management during Dental Surgical Procedures

Background: Pregnancy is a unique moment in a woman’s life, accompanied with several physiologic changes that have an impact on oral health. Aim of the study: The purpose of the present study was to conduct a critical review of published literature regarding pregnancy and dentistry, the most frequent oral diseases that are encountered during pregnancy, their correlation to adverse pregnancy events, and safe dental treatments that can be performed during pregnancy. Methods: A Medline/COCHRANE search was carried using specific keywords and MeSH terms, combined with the boolean operators “OR” and “AND”. Results: The search led to 146 publications including guidelines, meta-analyses, systematic and non-systematic reviews, published between 2000 and 2021. Discussion and conclusions: Due to the increased inflammatory and immune body response that characterizes pregnancy, periodontal conditions are often aggravated during pregnancy and periodontal disease encountered frequently in pregnant patients. There are conflicting study results in the literature regarding the association between periodontitis and adverse pregnancy outcomes. Periodontal treatment did not show a significant reduction in the adverse outcomes. Many dentists, often due to lack of information, are reluctant to provide dental treatment to pregnant women. However, preventive and restorative dental treatment is safe during pregnancy. Diagnostic radiographs may be performed after the first trimester if absolutely necessary. Analgesics (such as paracetamol) and anesthetics (such as lidocaine) are also considered safe. In case of infection, antibacterial drugs such as amoxicillin, ampicillin, and some cephalosporines and macrolides can also be prescribed. Organogenesis takes place in the first trimester, the time during which the fetus is susceptible to severe malformations (teratogenesis). The ideal time to perform dental treatment is the second trimester (week 17 to 28). However, acute pain or infections make the intervention of the dentist absolutely necessary and emergency treatment can be performed during the whole pregnancy period.

Nitrous oxide versus lidocaine versus no analgesic for in-office hysteroscopy: a randomised clinical trial

OBJECTIVE

To compare the effect of inhaled nitrous oxide (INO) on pain control during in-office hysteroscopy with 1% lidocaine paracervical infiltration and no analgesic.

DESIGN

Single-blind stratified randomised clinical trial with masked assessment by a third party.

SETTING

Department of Obstetrics and Gynaecology in a Spanish hospital.

POPULATION

Women who underwent hysteroscopy.

METHODS

Patients were stratified into three groups according to the purpose of the hysteroscopy (biopsy, polypectomy or tubal sterilisation) and then assigned to different treatment groups through a permuted-blocks randomisation within strata. Pain scale was provided by a gynaecologist totally blinded to procedures and treatments. Effects were assessed using a one-way analysis of variance following an intention-to-treat approach.

MAIN OUTCOME MEASURES

Visual analogue scale (VAS) from 0 to 100 mm.

RESULTS

A total of 314 women were included: 105 to INO, 104 to 1% lidocaine and 105 to no analgesic. Baseline characteristics were comparable. Mean VAS score after the procedure was 34.7 ± 25.8 mm, 36.1 ± 22.9 mm (P = 1.0) and 47.3 ± 28.2 mm (P = 0.001) for INO, 1% lidocaine and no analgesic, respectively. No adverse events were reported in 91 (86.7%) patients in the INO group compared with 79 (76%) in the 1%-lidocaine group (P = 0.04) and 85 (81%) in the no-analgesic group (P = 0.26).

CONCLUSION

INO was as effective as 1% lidocaine in pain control for in-office hysteroscopy and was better tolerated. The no-analgesic group presented the poorer results, so was the least recommended clinical option.

Comparison of entonox and transcutaneous electrical nerve stimulation (TENS) in labor pain: a randomized clinical trial study

AIM

The aim of performing this study was comparison of Entonox and transcutaneous electrical nerve stimulation (TENS) in labor pain in Zanjan city, Iran.

MATERIALS AND METHODS

This clinical trial study was conducted on 120 pregnant women in Zanjan-Iran, 2016. The patients were randomly divided (by method of 1:1:1) into three groups (each group 40 patients): First group was TENS group; the second group was Entonox group and control group were choose from the patients that had a physiological delivery. They did not want to use analgesia. All the analyses were done using SPSS (version 23).

RESULTS

Before intervention the pain severity between three group was relatively same (p = .78). After intervention, pain score was significantly higher in control group compared to other two groups (p = .005), but the differences between mean Apgar score between three groups was not significant (p = .59). Also, both Entonox and TENS had significantly lower pain compared control group (p = .005), but there was no significant difference between Entonox and TENS in regard of pain score (p = .997).

CONCLUSIONS

Our findings reported that two groups of Entonox and TENS had similar effect on pain relief and decreased significantly pain scores. Therefore, TENS methods as a non-drug pain relief method can propose to women for relief of labor pain.

Integration of MEMS IR detectors with MIR waveguides for sensing applications

Waveguides have been utilized for label-free and miniaturized mid-infrared gas sensors that operate on the evanescent field absorption principle. For integrated systems, photodetectors based on the photocarrier generation principle are previously integrated with waveguides. However, due to the thermal excitation of carriers at room temperature, they suffer from large dark currents and noise in the long-wavelength region. In this paper, we introduce the integration of a MEMS-based broadband infrared thermopile sensor with mid-infrared waveguides via flip-chip bonding technology and demonstrate a proof-of-concept gas (N₂O) sensor working at 3.9 µm. A photonic device with input and output grating couplers designed at 3.72 µm was fabricated on a silicon-on-insulator (SOI) platform and integrated with a bare thermopile chip on its output side via flip-chip bonding in order to realize an integrated photonic platform for a myriad range of sensing applications. A responsivity of 69 mV/W was measured at 3.72 µm for an 11 mm waveguide. A second device designed at 3.9 µm has a 1800 ppm resolution for N₂O sensing.

Pain management during labor and vaginal birth

Neuraxial analgesia provides excellent pain relief in labor. Optimizing initiation and maintenance of neuraxial labor analgesia requires different strategies. Combined spinal-epidurals or dural puncture epidurals may offer advantages over traditional epidurals. Ultrasound is useful in certain patients. Maintenance of analgesia is best achieved with a background regimen (either programmed intermittent boluses or a continuous epidural infusion) supplemented with patient-controlled epidural analgesia and using dilute local anesthetics combined with opioids such as fentanyl. Nitrous oxide and systemic opioids are also used for pain relief. Nitrous oxide may improve satisfaction despite variable effects on pain. Systemic opioids can be administered by healthcare providers or using patient-controlled analgesia. Appropriate choice of drug should take into account the stage and progression of labor, local safety protocols, and maternal and fetal/neonatal side effects. Pain in labor is complex, and women should fully participate in the decision-making process before any one modality is selected.

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.

Analgesia effect of premixed nitrous oxide/oxygen during the rehabilitation after total knee arthroplasty: a study protocol for a randomized controlled trial

Background

The morbidity of knee arthritis is increasing among aged people and total knee arthroplasty has been its mainstream treatment to date. Postoperative rehabilitation is an important part of the procedure. However, the intense pain during the functional exercise involved has always been a challenge for both patients and health care professionals. The aim of this study is to test the analgesic effect of a mixture of nitrous oxide/oxygeb (1:1) inhalation for patients who are doing functional exercise 1 month after total knee arthroplasty.

Methods/design

This double-blind, randomized, placebo-controlled study will be implemented in the Rehabilitation Department in the General Hospital of Ningxia Medical University. Patients aged between 50 and 75 years who underwent a primary unilateral total knee arthroplasty are eligible for inclusion. The key exclusion criteria include: epilepsy, pulmonary embolism, intestinal obstruction, aerothorax. The treatment group (A) will receive a pre-prepared nitrous oxide/oxygen mixture plus conventional treatment (no analgesics), and the control group (B) will receive oxygen plus conventional treatment (no analgesics). Patients, physicians, therapists, and data collectors are all blind to the experiment. Assessments will be taken immediately after functional exercise begins (T0), 5 min (T1) after functional exercise begins, and 5 min after functional exercise has finished (T2). Patients will be randomly allocated between a treatment group (A) and a control group (B) in a ratio of 1:1. Primary outcome, including pain severity in the procedure, will be taken for each group. Secondary outcomes include blood pressure, heart rate, oxygen saturation, side effects, knee joint range of motion, Knee Society Score (KSS), rescue analgesia need, and satisfaction from both therapists and patients.

Discussion

This study will focus on exploring a fast and efficient analgesic for patients who are doing functional exercise after total knee arthroplasty. Our previous studies suggested that the prefixed nitrous oxide/oxygen mixture was an efficacious analgesic for the management of burn-dressing pain and breakthrough cancer pain. The results of this study should provide a more in-depth insight into the effects of this analgesic method. If this treatment proves successful, it could be implemented widely for patients doing functional exercise in the rehabilitation department.

Trial registration

ChiCTR-INR-17012891. Registered on 6 October 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3472-7) contains supplementary material, which is available to authorized users.

A qualitative analysis of parturients' experiences using nitrous oxide for labor analgesia: It is not just about pain relief

BACKGROUND

A vast majority of women who choose nitrous oxide for labor report high satisfaction despite variable analgesic effectiveness. We analyzed comments provided by women who used nitrous oxide for labor, to identify determinants of satisfaction in this population, and to better understand reasons for continuing with nitrous oxide despite variable analgesic effectiveness.

METHODS

We conducted qualitative content analysis of comments in a quality improvement database of routine follow-up assessments of women who delivered vaginally, using nitrous oxide as the sole labor analgesic. An inductive grounded approach was used and emergent themes and subthemes were identified.

RESULTS

Of 6507 vaginal deliveries over 34 months in 2011-2014, 753 (12%) used nitrous oxide as their sole analgesic. Analysis of 264 clarifying comments yielded six emergent themes. Parturients cited nonanalgesic benefits of nitrous oxide use (relaxation, distraction, focus on breathing), as well as partial analgesic effects that they deemed to be sufficient, or consistent with their expectations. Numerous women described their nitrous oxide experience as consistent with their birth plan, including 14 who equated it with natural childbirth. Several comments described nitrous oxide as a vital component of the parturients' birth experience. Some described using nitrous oxide when neuraxial analgesia was not possible. Side effects were identified, as were difficulties using the apparatus/mask. Analysis highlighted importance of timely administration upon request and attention to technical aspects.

CONCLUSIONS

Among parturients who choose nitrous oxide as their sole labor analgesic, determinants of satisfaction are more variable than previously understood, and extend beyond analgesia.

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.

Implementation of an Evidence-Based Practice Change to Offer Nitrous Oxide During Labor

OBJECTIVE

The aim of this evidence-based practice change was to implement use of nitrous oxide as a pain management option during labor and to examine women's satisfaction with that option.

DESIGN

Evidence-based practice change guided by the model for evidence-based practice change.

SETTING

Labor and delivery unit in a tertiary medical center in the southwestern United States.

PARTICIPANTS

Laboring women who met eligibility criteria were offered the option of nitrous oxide during a 2-month period.

MEASUREMENTS

Process indicators to measure compliance with the practice change among staff, uptake of nitrous oxide among women, and women's satisfaction with the choice to use nitrous oxide.

RESULTS

Nitrous oxide was offered to 26% (n = 55) of eligible women. Most of the 55 women who used nitrous oxide during the implementation period reported satisfaction with it and indicated that they would consider nitrous oxide for a future labor.

CONCLUSION

Our experience implementing a practice change to offer nitrous oxide to laboring women indicated that use of nitrous oxide was feasible in this setting and that women were receptive to this option, were satisfied with its use, and would use nitrous oxide for a future labor.

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.

Past, present, and future of nitrous oxide

INTRODUCTION

For a drug that has been omnipresent for nearly 200 years, nitrous oxide's (N2O) future seems less certain than its illustrious past. Environmental concerns are coming to the fore and may yet outweigh important clinical benefits.

SOURCES OF DATA

After determining the scope of the review, the authors used PubMed with select phrases encompassing the words in the scope. Both preclinical and clinical reports were considered.

AREAS OF AGREEMENT

The analgesic and anaesthetic advantages of N2O remain despite a plethora of newer agents.

AREAS OF CONTROVERSY

N2O greenhouse gas effect and its inhibition of key enzymes involved in protein and DNA synthesis have provided further fuel for those intent on eliminating its further clinical use.

GROWING POINTS

The use of N2O for treatment-resistant depression has gained traction.

AREAS TIMELY FOR DEVELOPING RESEARCH

Comparative studies for N2O role in combatting the prescription opioid analgesic epidemic may well provide further clinical impetus.

The Effect of Epidural-Spinal Anesthesia on Labor Outcome and Satisfaction in Parturient Mothers: A Randomized Controlled Trial

Introduction: One of the health system concerns is the use of medications for pain relief during labor and its side effects. Therefore, the aim of this study was to investigate the effect of epiduralspinal anesthesia (combined anesthesia [CA]) on labor outcome and satisfaction in pregnant women. Methods: In this randomized controlled trial study, we included 80 nulliparous women who had been admitted to Fatemieh hospital (Hamadan, Iran) during 2015-2016 due to spontaneous onset of labor. They were randomly assigned into 2 groups of 40, one group with CA versus normal vaginal delivery (NVD) group. Data were collected by using of demographic questionnaire, satisfaction questionnaire, and baby truck scales. Data were analyzed by descriptive and analytical statistics in SPSS version 16.0. Results: Average maternal age (mean ± SD) in the CA group was 26.94 ± 4.34 and in the NVD group was 25.89 ±5.18, respectively. There was a significant difference between the 2 groups in terms of length of second stage of labor (P=0.001), headache (P=0.04), and Apgar score (first minute) (P=0.001). Chi-square test showed a significant difference between the 2 groups in terms of satisfaction with childbirth (P=0.004). Conclusion: In this study, labor pain relief by using the spinal-epidural anesthesia (CA) increased the labor satisfaction. Nevertheless, this approach was associated with some maternal and neonatal complications such as: headaches, length of third stage of labor, and low Apgar score. It seems that the use of this method for painless delivery requires further studies.

Perinatal and neonatal use of sedation and analgesia

Optimal obstetric and neonatal care requires the provision of adequate analgesia for painful procedures. However, anesthetic and analgesic agents have the potential to adversely impact the developing fetal/neonatal brain. In this setting, clinicians must assess the risks and benefits of pharmacologic anesthesia and analgesia for specific indications in this population. General anesthesia is required for non-obstetric surgery and cesarean section in the absence of neuraxial anesthesia for the health of the mother and fetus. Although experimental data raise concerns, human data are reassuring and future research may focus on neuroprotective adjuncts in the setting of repeated or prolonged anesthetic exposures. Opioid analgesia is standard of care for preterm infants undergoing major procedures including invasive surgery and endotracheal intubation. The use of opioids for agitation resulting from mechanical ventilation is controversial, but prevalent. Randomized and retrospective studies detect short-term toxicity with inconclusive long-term impact, suggesting the need to explore alternative therapies.

Practice Bulletin No. 177: Obstetric Analgesia and Anesthesia

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

Nitrous oxide versus oral sedation for pain management of first-trimester surgical abortion - a randomized study

OBJECTIVE

The objective of the study was to compare nitrous oxide with oxygen (N₂O/O₂) to oral hydrocodone/acetaminophen and lorazepam for analgesia during first-trimester surgical abortion.

STUDY DESIGN

This double-blind randomized trial assigned women undergoing first-trimester surgical abortion at<11 weeks' gestation to inhaled N₂O/O₂ vs. oral sedation for pain management. The N₂O/O₂ group received up to 70:30 ratio during the procedure and placebo pills preprocedure; the oral group received inhaled oxygen during the procedure and oral hydrocodone/acetaminophen 5 mg/325 mg and lorazepam 1 mg preprocedure. The primary outcome was maximum procedural pain, assessed on a 100-mm visual analog scale (VAS; anchors 0=no pain and 100=worst pain) at 2 min postprocedure. A difference of 13 mm on the VAS was considered clinically significant. Satisfaction with pain management was measured on a 100-mm VAS (anchors 0=very unsatisfied, 100=very satisfied).

RESULTS

We randomized 140 women, 70 per study arm. Mean age of participants was 26±6.6 years; mean gestational age was 7.3±1.5 weeks. Mean maximum procedure pain scores were 52.5±26.7 and 60.8±24.4 for N₂O/O₂ and oral groups, respectively (p=.09). Satisfaction with pain management was 69.3±28.4 and 61.5±30.4 for N₂O/O₂ and oral groups. respectively (p=.15).

CONCLUSION

We found no difference in mean procedural pain scores between women assigned to N₂O/O₂ vs. those assigned to oral sedation for first-trimester surgical abortion. Satisfaction with both options was high.

IMPLICATIONS

Women undergoing early surgical abortion experienced no differences in pain and satisfaction between those who used inhaled nitrous oxide and oral sedation. Nitrous oxide, with side effects limited to the duration of inhalation and no need for a ride home, is a viable alternative to oral sedation for first-trimester abortion pain management.

[Pain therapy during labour]

To date the gold standard of treating labour pain is regional analgesia by application of epidural analgesia. When offering epidural analgesia, the programmed intermittent epidural bolus (PIEB) is more effective in terms of pain reduction, less motor blocks and higher satisfaction of the parturient compared to continuous application via perfusor pump. An upcoming alternative to epidural analgesia is remifentanil, a short acting and potent opioid. Remifentanil, however, requires haemodynamic monitoring as cardiac and respiratory impairment has been described. Nitrous oxide has been used for decades in the Anglosphere but it is a greenhouse gas, and interactions with Vitamin B₁₂ are possible. Using novel extraction systems, nitrous oxide has become more attractive for treatment of the initial phase of labour pain in Central Europe. In order to provide the parturient with the best possible and with a tailored pain concept an interdisciplinary approach with obstetricians, midwives and anaesthesiologists is required.

Patient-controlled analgesia with remifentanil versus alternative parenteral methods for pain management in labour

BACKGROUND

Multiple analgesic strategies for pain relief during labour are available. Recently remifentanil, a short-acting opioid, has recently been used as an alternative analgesic due to its unique pharmacological properties.

OBJECTIVES

To systematically assess the effectiveness of remifentanil intravenous patient-controlled analgesia (PCA) for labour pain, along with any potential harms to the mother and the newborn.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (9 December 2015), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), handsearched congress abstracts (November 2015), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and cluster-randomised trials comparing remifentanil (PCA) with another opioid (intravenous (IV)/intramuscular (IM)), or with another opioid (PCA), or with epidural analgesia, or with remifentanil (continuous IV), or with remifentanil (PCA, different regimen), or with inhalational analgesia, or with placebo/no treatment in all women in labour including high-risk groups with planned vaginal delivery.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, extracted data, and appraised study quality.We contacted study authors for additional information other than incomplete outcome data. We performed random-effects meta-analysis.To reduce the risk of random error in meta-analysis we performed trial sequential analysis. We included total zero event trials and used a constant continuity correction of 0.01 (ccc 0.01) for meta-analysis. We applied the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

Twenty RCTs with 3569 women were included. Of those, 10 trials (2983 participants) compared remifentanil (PCA) to an epidural, four trials (216 participants) to another opioid (IV/IM), three trials (215 participants) to another opioid (PCA), two trials (135 participants) to remifentanil (continuous IV), and one trial (20 participants) to remifentanil (PCA, different regimen). No trials were identified for the remaining comparisons.Methodological quality of studies was moderate to poor. We assessed risk of bias as high for blinding issues and incomplete outcome data in 65% and 45% of the included studies, respectively.There is evidence of effect that women in the remifentanil (PCA) group were more satisfied with pain relief than women in the other opioids (IV/IM) group (standardised mean difference (SMD) 2.11, 95% confidence interval (CI) 0.72 to 3.49, four trials, very low-quality evidence), and that women were less satisfied compared to women in the epidural group (SMD -0.22, 95% CI -0.40 to -0.04, seven trials, very low-quality evidence).There is evidence of effect that remifentanil (PCA) provided stronger pain relief at one hour than other opioids administered IV/IM (SMD -1.58, 95% CI -2.69 to -0.48, three trials, very low-quality evidence) or via PCA (SMD -0.51, 95% CI -1.01 to -0.00, three trials, very low-quality evidence). Pain intensity was higher in the remifentanil (PCA) group compared to the epidural group (SMD 0.57, 95% CI 0.31 to 0.84, six trials, low-quality evidence).Data were limited on safety aspects for both the women and the newborns. Only one study analysed maternal apnoea in a comparison of remifentanil (PCA) versus epidural and reported that half of the women in the remifentanil and none in the epidural group had an apnoea (very low-quality evidence). There is no evidence of effect that remifentanil (PCA) was associated with an increased risk for maternal respiratory depression when compared to epidural analgesia (RR 0.91, 95% CI 0.51 to 1.62, ccc 0.01, three trials, low-quality evidence) and no reliable conclusion might be reached compared to remifentanil (continuous IV) (all study arms included zero events, two trials, low-quality evidence). In one trial of remifentanil (PCA) versus another opioid (IM) three out of 18 women in the remifentanil and none out of 18 in the control group had a respiratory depression (very low-quality evidence).There is no evidence of effect that remifentanil (PCA) was associated with an increased risk for newborns with Apgar scores less than seven at five minutes compared to epidural analgesia (RR 1.26, 95% CI 0.62 to 2.57, ccc 0.01, five trials, low-quality evidence) and no reliable conclusion might be reached compared to another opioid (IV) and compared to remifentanil (PCA, different regimen) both with zero events in all study arms (one trial, very-low quality evidence). In one trial of remifentanil (PCA) versus another opioid (PCA) none out of nine newborns in the remifentanil and three out of eight in the opioid (PCA) group had Apgar scores less than seven (very-low quality evidence).There is evidence that remifentanil (PCA) was associated with a lower risk for the requirement of additional analgesia when compared to other opioids (IV/IM) (RR 0.57, 95% CI 0.40 to 0.81, three trials, moderate-quality evidence) and that it was associated with a higher risk compared to epidural analgesia (RR 9.27, 95% CI 3.73 to 23.03, ccc 0.01, six trials, moderate-quality evidence). There is no evidence of effect that remifentanil (PCA) reduced the requirement for additional analgesia compared to other opioids (PCA) (RR 0.76, 95% CI 0.45 to 1.28, three trials, low-quality evidence).There is evidence that there was no difference in the risk for caesarean delivery between remifentanil (PCA) and other opioids (IV/IM) (RR 0.63, 95% CI 0.30 to 1.32, ccc 0.01, four trials, low-quality evidence) and epidural analgesia (RR 1.0, 95% CI 0.82 to 1.22, ccc 0.01, nine trials, moderate-quality evidence), respectively. Pooled meta-analysis revealed an increased risk for caesarean section under remifentanil (PCA) compared to other opioids (PCA) (RR 2.78, 95% CI 0.99 to 7.82, two trials, very low-quality evidence). However, a wide range of clinically relevant and non-relevant treatment effects is compatible with this result.

AUTHORS' CONCLUSIONS

Based on the current systematic review, there is mostly low-quality evidence to inform practice and future research may significantly alter the current situation. The quality of evidence is mainly limited by poor quality of the studies, inconsistency, and imprecision. More research is needed on maternal and neonatal safety outcomes (maternal apnoea and respiratory depression, Apgar score) and on the optimal mode and regimen of remifentanil administration to provide highest efficacy with reasonable adverse effects for mothers and their newborns.

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.

Nitrous Oxide Utility in Labor and Birth: A Multipurpose Modality

The use of nitrous oxide (N2O) for labor and birth has very recently emerged as a viable modality in the United States, despite a long history of use in Canada and Europe. Usually associated with dental procedures, there are significant differences between dental and parturition utility, efficacy, and staff exposure. In addition to using it for pain relief and anxiolysis, those centers utilizing it have noted it to be multipurpose and useful for such situations as: external cephalic version, manual removal of placenta, intravenous starts, during placement of urinary catheters and intracervical Foley bulbs. Nitrous oxide has proven to be especially helpful for repair of lacerations under local anesthesia and is a multiuse modality that should be available to women in all birth settings. This article explores the history of N2O use, provides a comparison of obstetrical use to use in the dental industry, examines the contraindications to, and implications for usage, and discusses logistical points of consideration for clinicians working with women using N2O for labor and birth.

Occupational exposure to nitrous oxide during procedural pain control in children: a comparison of different inhalation techniques and scavenging systems

BACKGROUND

Nitrous oxide (N2 O 50% in oxygen) is commonly used for painful procedures in children. Potential negative health effects associated with chronic workplace exposure limit its use. Safe occupational N2 O exposure concentrations are below 25 ppm environmental concentration as a time-weighted average (TWA) and below 200 ppm as a short-time exposure level (STEL) of 15 min.

AIM

The aim was to assess occupational exposure of staff during nitrous oxide administration to children using different inhalation delivery devices and scavenging systems.

METHODS

Staff nitrous oxide exposure during use of a double face mask (DFM) with or without a demand valve (DV) was compared with a conventional single face mask (FM). We also compared exposure using the hospital central scavenging system with a portable evacuation system. N2 O concentrations, representing exposure values, were monitored within proximity to staff. Urine N2 O concentration was measured in staff administering the N2 O at the end of the procedural session.

RESULTS

The mean and median values of TWA and STEL within the working area were lower than recommended values in the DFM (10.8, 11.6 ppm for TWA; 13.9, 11.0 ppm for STEL) and DFM-DV groups (2.3, 2.8 ppm for TWA; 4.4, 3.5 ppm for STEL) using the portable evacuation system. The N2 O urine exposure in DFM-DV group was lower than DFM group: a mean difference of 9.56 ppm (95% CI 2.65-16.46). Staff N2 O urinary concentrations were within safe biological limits in both the DFM and DFM-DV groups. High exposure concentrations to N2 O were recorded in all FM and FM-DV environmental and biological samples.

CONCLUSIONS

The DFM system, with or without a DV, connected to a portable evacuation system during N2 O administration to children for painful procedures kept N2 O levels within the local environment below recommended limits.

A randomized controlled trial of nitrous oxide for intrauterine device insertion in nulliparous women

OBJECTIVE

To evaluate the effectiveness of inhaled nitrous oxide for pain management among nulliparous women undergoing intrauterine device (IUD) insertion.

METHODS

A double-blind, randomized controlled trial was conducted among nulliparous women aged 13-45years who underwent IUD insertion at a US center between October 1, 2013, and August 31, 2014. Using a computer-generated randomization sequence, participants were randomly assigned to inhale either oxygen (O₂) or a mixture of 50% nitrous oxide and 50% oxygen (N₂O/O₂) through a nasal mask for 2minutes before insertion. Only the person administering the inhalation agent was aware of group assignment. The primary outcome was maximum pain assessed 2minutes after insertion via a 100-mm visual analog scale. Analyses were by intention to treat.

RESULTS

Forty women were assigned to each group. Mean maximum pain score at the time of insertion was 54.3±24.8mm for the N₂O/O₂ group and 55.3±20.9mm for the O₂ group (P=0.86). Adverse effects were reported for 6 (15%) women in the N₂O/O₂ group and 7 (18%) in the O₂ group (P=0.32).

CONCLUSION

N₂O/O₂ did not reduce the pain of IUD insertion among nulliparous women. ClinicalTrials.gov: NCT02391714.

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.

Inhalation analgesia with nitrous oxide versus other analgesic techniques in hysteroscopic polypectomy: a pilot study

STUDY OBJECTIVE

To show the decrease in pain and better tolerance to inhalation analgesia with a 50% equimolar mixture of nitrogen protoxide and oxygen in hysteroscopic polypectomy compared with paracervical anesthesia and a control group.

DESIGN

One hundred six patients scheduled for office hysteroscopy and polypectomy were divided into the following 3 groups: the control group, the nitrous oxide group, and the paracervical infiltration group. Patients were assigned sequentially (Canadian Task Force classification II-1).

SETTING

The study took place in a hysteroscopy outpatient clinic under the supervision of a gynecologist and 2 nurses trained to cooperate in the trial.

PATIENTS

One hundred six women from Area III of Madrid Community, Spain, who had been diagnosed with endometrial polyps at a gynecology office and were scheduled for office hysteroscopy and polypectomy agreed to participate in the study.

INTERVENTIONS

Patients in group 1 (control group) received no treatment. Group 2 received inhaled nitrous oxide and group 3 paracervical infiltration with 1% lidocaine.

MEASUREMENTS AND MAIN RESULTS

Pain was assessed using the visual analog scale (0-10). Pain perceived by patients was lower in the nitrous Oxide group (mean: 3.55 ± 0.60, median: 3) versus the control group (mean: 5.49 ± 1.88, median: 6, p < .05) and the paracervical infiltration group (mean: 4.22 ± 1.73, median: 5). Tolerance to pain, assessed by the medical staff using qualitative variables, was bad for the control group, very good for the nitrous oxide group, and good for the paracervical infiltration group (p < .05). There were no complications in 82% of the patients in the nitrous oxide group, whereas in the paracervical infiltration group, there were complications in more than 50% of the patients. No severe complications occurred.

CONCLUSION

Nitrous oxide is a safe and effective analgesic technique for polipectomy office hysteroscopy compared with the paracervical infiltration and control groups.