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General anesthesia (GA) is typically recommended for category 1 emergency cesarean delivery (CD). For categories 2-4 emergencies, either regional or GA can be used. The factors influencing the choice of anesthetic technique in these categories remain poorly understood. We analyzed the association between the type of labor analgesia and subsequent anesthetic techniques employed for intrapartum categories 2 and 3 CD. In a prospective longitudinal cohort study, 300 women were consequently enrolled and categorized according to Lucas's classification of CD urgency. The techniques of anesthesia (GA, spinal, and epidural anesthesia [EA]) employed for CD were analyzed with respect to labor analgesia methods (remifentanil patient-controlled analgesia [remifentanil-PCA], EA, and nitrous oxide [N2O]). EA was the most frequent analgesic option (43.8%), followed by remifentanil-PCA (20.7%) and N2O (5.1%), while 30.4% of parturient women received no analgesia. All anesthetic methods showed a significant relationship with analgesic modalities (P < 0.001). Remifentanil-PCA was associated with a higher incidence of GA. Contraindication to EA was the primary factor related to the transition from remifentanil-PCA to GA. Most parturients who received EA were successfully converted to EA. Spinal anesthesia was the most common technique in women using N2O and those without labor analgesia. GA was associated with lower 5-min Apgar scores. The method of labor analgesia was associated with the anesthesia technique employed for categories 2 and 3 CD. This finding may guide patient counseling and intrapartum anesthetic planning. However, the analysis should be cautiously interpreted as the selection of anesthesia is a complex decision influenced by several clinical considerations.

Competing Interests: Financial Disclosure The authors did not report any potential conflicts of interest.

Introduction: Complex Regional Pain Syndrome (CRPS) is a debilitating neuropathic condition often refractory to conventional treatments. N-methyl-D-aspartate (NMDA) receptor antagonists have a well-established role in the development and modulation of chronic neuropathic pain. Nitrous oxide is widely used and generally safe anesthetic gas with NMDA receptor antagonist activity. We therefore tested the hypothesis that brief periods of nitrous oxide exposure reduce pain in patients with CRPS., Methods: Patients with a diagnosis of CRPS were randomized to either 2 hours of nitrous oxide exposure on three alternating days (Nitrous Oxide) versus a placebo air/oxygen mixture (Air-Oxygen). Our primary outcome was patient-reported pain scores at 1 week and 1 month. Secondary and exploratory outcomes were physical and mental health (PRMOIS-29 v2 survey), specific neuropathic pain symptoms (McGill short-form questionnaire), and opioid consumption., Results: 44 patients participated in the study; 20 were randomized to Nitrous Oxide and 24 were assigned to Air-Oxygen. Pain scores did not differ significantly, with the estimated difference in means (Nitrous Oxide-Air-Oxygen) of -0.57 (95% CI: -1.42 to 0.28) points, p=0.19. There were also no differences detected in secondary outcomes, with the estimated difference in mean Z-scores for physical health (Nitrous Oxide-Air-Oxygen) of 0.13 (95% CI: -0.16 to 0.43), mental health 0.087 (95% CI: -0.31 to 0.48), and Patient Global Impression of Change score -0.7 (95% CI: -1.85 to 0.46)., Conclusions: Compared with air/oxygen, 2 hours of nitrous oxide/oxygen exposure for three sessions did not provide meaningful therapeutic potential for patients with chronic CRPS. Our results do not support using nitrous oxide for the treatment of CRPS., Competing Interests: Competing interests: DIS is a consultant for Edwards Lifesciences, Sensifree, and Perceptive Medical. None of the conflicts are related to the submitted study. AT was a speaker for Pfizer and consultant for Consentric Medical. None of the conflicts are related to the submitted study. None of the other authors declare competing interests., (© American Society of Regional Anesthesia & Pain Medicine 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

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., (© 2024 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.)

Study Objective: Uptake of intrauterine devices (IUDs) in the adolescent population may be limited by anxiety and pain anticipated during the insertion procedure. Our institution offers conscious sedation for IUD insertion to mitigate this concern. The objective of this study was to identify characteristics and outcomes of teens choosing between two types of conscious sedation for insertion of a levonorgestrel IUD., Methods: This was a single-site, retrospective cohort study over a one year period, reviewing the electronic medical records of patients who had undergone an attempted IUD insertion using conscious sedation. Conscious sedation included nitrous gas (termed "light" sedation) or intravenous midazolam and fentanyl (termed "moderate" sedation). Patient demographic characteristics and medical and gynecological histories were analyzed., Results: There were 69 attempted IUD insertions during the study period. Most patients (75.36%) were placed under light sedation, and 92.75% were successfully inserted. The only significant factor associated with choice in the type of conscious sedation was previous sexual activity, which increased the odds by 10.0 that the patient would choose light sedation (95% CI, 1.23-81.34; P = 0.031). Differences between other factors (age, history of sexual assault, tampon use, and gender identity) were not statistically significant between successful and failed insertions., Conclusion: In conclusion, history of sexual activity significantly differed between patients in our cohort who selected light sedation over moderate sedation. No other factors influenced the choice in sedative or success of IUD insertion. Knowing the characteristics of patients who choose nitrous versus intravenous sedation, and how it relates to successful insertion, may help guide pre-procedural counseling for patients regarding sedation for IUD insertion., Competing Interests: Conflicts of Interest The authors have no relevant financial or nonfinancial interests to disclose. The authors have no conflicts of interest to declare., (Copyright © 2024. Published by Elsevier Inc.)

Study Objective: Nitrous oxide affects memory and recall. We aimed to determine if using nitrous oxide during labor affected patients' ability to learn and recall the risks and benefits of neuraxial analgesia., Design: Single-center, prospective cohort study., Setting: Labor and delivery unit in a large academic medical center., Patients: Nulliparous patients with spontaneous or planned induction of labor., Interventions: Parturients chose whether to use nitrous oxide during labor. At the discussion for epidural consent, 4 risks were described: headache, infection, nerve damage, bleeding., Measurements: Labor pain score, time from nitrous oxide discontinuation, and cervical dilation were documented at the discussion of epidural risks. Patients were assessed for unprompted recall and prompted recall of epidural risks on postpartum day 1 and unprompted recall at postpartum week 6. The number and proportion of patients who indicated each true risk (unprompted and prompted recall) or distractor (prompted recall only) were summarized by treatment group and results compared using Pearson χ 2 tests., Main Results: Of the 403 enrolled patients, 294 (73%) did not use nitrous oxide, and 109 (27%) did. The 2 groups were similar except women who used nitrous oxide were more likely to be cared for by midwives and had higher pain scores at their epidural request. Scores for unprompted or prompted recall of epidural risks were not different between women who received or did not receive nitrous oxide. All 4 risks were recalled unprompted by only 3% in the nitrous oxide group and by 6% in the group not receiving nitrous oxide (P = .18)., Conclusions: The use of nitrous oxide for labor analgesia does not adversely influence a parturient's ability to recall the risks of epidural placement. Patients who receive nitrous oxide for labor analgesia should be considered eligible to provide consent for subsequent procedures., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Aims: To describe the clinical features and outcomes of patients with myelopathy and neuropathy due to recreationally inhaled nitrous oxide., Methods: We identified patients presenting with nitrous oxide-associated myelopathy from an electronic database of all discharges in a large tertiary hospital between 2016 and 2023. Demographics, clinical features and the results of investigations were recorded. The primary outcome was modified Rankin Scale score (mRS) at least 3 months after hospital discharge where available., Results: There were 12 patients identified, six women, mean (SD) age 27.5 (5.1) years, range 19-47 years. The most common symptoms were numbness, weakness and mental state changes. Four patients used large amounts of inhaled nitrous oxide and also took over-the-counter vitamin B12 supplements. The median (range) hospital length of stay was 8.5 (2-56) days. Functional independence at last assessment (median [range] of 3 [1-34] months after discharge) was achieved in nine of the patients, with three requiring ongoing support for activities of daily living (mRS ≥3)., Conclusion: Nitrous oxide abuse and its neurological complications are an important public health issue. Clinicians should be aware that some patients who use large amounts of nitrous oxide may self-supplement vitamin B12., Competing Interests: The authors have no conflicts of interest to declare., (© PMA.)

Purpose: The purpose of this study was to evaluate the environmental impact of travel and anesthetic gas emissions associated with treating early childhood caries at a single institution. Methods: Outpatient preventive, treatment, and modeled general anesthesia (GA) cases in children 71 months old and younger were included in this retrospective chart review. The main outcomes were kilograms of carbon dioxide equivalents (kgCO₂e) for travel- and anesthetic gas-related emissions. Descriptive statistics and non-parametric tests were used. Results: Most subjects had a caries treatment visit (n equals 3,630 out of 5,767), and nine percent of treatment visits (n equals 353 out of 3,630) received nitrous oxide (N₂O), which added 29.4 kgCO₂eto the visit emissions. Children without caries treatment had lower travel-related emissions (median equals 7.5 kgCO₂e; interquartile range [IQR] equals 7.6) than children with caries treatment (median without N₂O equals 8.7 kgCO₂e; IQR equals 18.2; median with N₂O equals 8.4 kgCO₂e; IQR equals 10.3). Modeled GA travel emissions were estimated at 16.4 kgCO₂e (IQR equals 21.9) with between 3.8-12.9 kgCO₂e in anesthetic gas emissions. Total emissions were greatest for N₂O treatment visits (median equals 43.3 kgCO₂e; IQR equals 22.8). Conclusions: Travel-related emissions were greatest for children requiring caries treatment. Minimizing patient travel may reduce environmental impact. Nitrous oxide contributes a significant amount to a dental visit???s environmental impact. Community-focused models of care and applying systematic and practical case selection to reduce excess N₂O emissions could reduce dental care-related carbon emissions.

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., (Copyright © 2024 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.)

Climate change represents an urgent global threat. Without action, rising temperatures resulting from human activity will increasingly affect our health and wellbeing through changing patterns of disease, extreme weather events and availability of resources. Expedient decarbonisation of the UK economy is an ambitious goal to which we must all contribute.The NHS aims to be the world's first net-zero health service and reach carbon-neutral status by 2040. Dental services are particularly resource-intensive. Some dental anxiety management techniques have a disproportionately high impact on the environment relative to their usage. Inhalation sedation with nitrous oxide is one such example.Nitrous oxide is a greenhouse gas almost 300 times more potent than carbon dioxide, but its utility to facilitate dental treatment for anxious and vulnerable patients is well-documented. This paper balances the health utility with environmental and social harm of continuing to use nitrous oxide and suggests evidence-based methods we can apply to limit the environmental impact of sedation services., (© 2024. The Author(s), under exclusive licence to the British Dental Association.)

Competing Interests: None declared.

Background: Over the last decade, there has been an emerging trend of recreational misuse of several drugs and inhaled solvent including ethyl chloride. This case report follows CARE guidelines and highlights, with supporting video, the neurological features of ethyl chloride intoxication., Case Presentation: A 48-year-old man was seen for the sudden occurrence of an unsteady gait with dizziness. His only medical history was a chronic and treated HIV infection without any complications. Clinical examination revealed a cerebellar syndrome associated with impairment of short-term memory. Biological and radiological workups were normal. After several days, the patient recalled ethyl chloride inhalation. He fully recovered after being discharged from hospital., Conclusion: Clinicians should recognise the clinical features and neurological manifestations of ethyl chloride intoxication due to the potential fatal cardiovascular complications of this intoxication., (© 2024. The Author(s).)

Background: Pediatric patients undergoing minor, but painful procedures in an Emergency Department (ED) need adequate relief of pain and distress to prevent long term negative effects and adversely impact procedures. Inhaled nitrous oxide (N 2 O) is a needle-free pain management option. We conducted a systematic review to determine whether N 2 O is as effective as local anesthesia in minor procedures. The purpose of this study was to evaluate available evidence regarding analgesic effectiveness of N 2 O in pediatric patients., Methods: We searched MEDLINE, Embase, Cochrane and Cinahl databases for controlled trials published in English with pediatric patients in an ED treated with N 2 O compared to local anesthesia and with pain as primary outcome. Adverse events was one of the secondary outcomes. The GRADE system was used to rate the overall quality of evidence., Results: We included seven studies with a total of 371 patients. Two studies showed N 2 O was equally effective in pain treatment as local anesthesia. Five studies showed N 2 O combined with local anesthesia is more effective in reducing pain than local anesthesia alone. None of the included studies reported major adverse effects. The quality of evidence is low., Conclusions: N 2 O can have an important contribution in pain management, but should be combined with local anesthesia for optimal pain management in pediatric patients undergoing minor, but painful procedures in an ED., Level of Evidence: IV., Competing Interests: Conflicts of interest The authors declare no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: This paper reports a life cycle impact assessment (LCIA) to calculate the environmental footprint of a dental appointment using N 2 O, comparing single-use equipment with reusable equipment. Nitrous oxide (N 2 O) is used successfully in dentistry to provide sedation and pain relief to anxious patients, most commonly in children. However, N 2 O is a powerful climate pollutant 298 times more damaging than carbon dioxide over a 100-year estimate., Methods: The functional unit chosen for this LCIA was 30 min delivery of N 2 O to oxygen in a 50:50 ratio at 6 L per minute flow rate as inhalation sedation to one patient. Two types of equipment were compared to deliver the anaesthetic gas: reusable and disposable items., Results: The use of disposable equipment for N 2 O sedation produces a significantly larger environmental impact across nearly all of the environmental impact scores, but the overall global warming potential is comparable for both types of equipment due to the vast environmental pollution from N 2 O itself., Conclusion: N 2 O sedation is a reliable treatment adjunct but contributes to climate change. Single-use equipment has a further deleterious effect on the environment, though this is small compared to the overall impact of N 2 O. Dental priorities should be to deliver safe and effective care to patients that protects staff, minimises waste and mitigates impact on the environment alongside promoting research into alternatives., (© 2024. The Author(s), under exclusive licence to European Academy of Paediatric Dentistry.)

Background and Aim: Recreational use of nitrous oxide (N 2 O) has been associated with the development of severe nitrous oxide-induced neuropathy (N 2 On). Follow-up of these patients poses challenges, and their clinical progression remains largely unknown. The identification of prognostic factors is made difficult by the lack of standardized longitudinal assessments in most studies. The objective was to document the course of neuropathy through systematic follow-up assessments in N 2 On patients to identify prognostic factors for persistent disability after 6 months., Methods: We gathered demographic, clinical, biological, and electrophysiological data from N 2 On patients hospitalized in the Referral center in Marseille, both at baseline and during a standardized follow-up assessment at 6 months., Results: We retrospectively included 26 N 2 On patients (mean age 22.6 ± 4.4). Significant improvements were observed in all main clinical scores including Rankin, ONLS, and MRC testing (p < .01). Electrophysiological studies (EDX) revealed a predominantly motor neuropathy with marked reduction in CMAP in the lower limbs at baseline, and no significant improvement in motor parameters (p = .543). Rankin score at 6 months correlated with the initial weekly N 2 O consumption (r = .43, p = .03) and the CMAP sum score in the lower limbs at the first EDX (r = -.47, p = .02). Patients with and without myelitis showed similar Rankin and ONLS score after 6 months., Interpretation: The clinical course generally improved favorably at 6 months with notable amelioration in the primary disability scores, sensory deficits, and ataxia. However, distal motor impairment associated with peripheral neuropathy persisted, with distal axonal loss emerging as the main prognostic factor for long-term disability in these young patients., (© 2024 Peripheral Nerve Society.)

Competing Interests: None declared.

The formation of pneumoperitoneum involves the process of inflating the peritoneal cavity during laparoscopic and typically uses CO 2 as the insufflation gas. This review aims to identify ideal gas mixtures for establishing the pneumoperitoneum with animal and human studies undertaken up to the writing of this review. A systematic search of PubMed, OVID, and clinicaltrials.gov was performed to identify studies on the utilisation of mixed gases in laparoscopic surgery, including non-randomised/randomised trials, animal and human studies, and studies with inflating pressures between 12 and 16 mmHg. ROBINS-I and RoB2 tool was used to assess the risk of bias. A narrative synthesis of results was performed due to the heterogeneity of the studies. 5 studies from the database search and 5 studies from citation search comprising 128 animal subjects and 61 human patients were found. These studies collated results based on adhesion formation (6 studies), pain scores (2 studies) and other outcomes, with results favouring the use of carbon dioxide + 10% nitrous oxide + 4% oxygen. This has shown a significant reduction in adhesion formation, pain scores and inflammation. The use of this gas mixture provides promising results for future practice. Several of the studies available require larger sample sizes to develop a more definitive answer on the effects of different gas mixtures. Furthermore, the number of confounding factors in randomised trials should be reduced so that each component of the current suggested gas mixture can be tested for safety and efficacy., (© 2024. The Author(s).)

Background: The recreational use of nitrous oxide (N2O) has increased in recent years with a noticeable surge in the incidence of nitrous oxide-related myeloneuropathy., Objectives: To raise awareness of increasing myeloneuropathy due to recreational nitrous oxide misuse in Israel., Methods: We conducted a case series documenting the clinical and investigative features of eight patients presenting with nitrous oxide-induced myeloneuropathy who were admitted to our departments., Results: Paresthesia was the chief complaint in all patients, with sensory gait ataxia being a common feature, which was often accompanied by Romberg's sign and mild lower limb weakness. Vitamin B12 levels were below the normal range in seven patients, accompanied by elevated homocysteine and methylmalonic acid levels. Magnetic resonance imaging scans revealed hyperintense signals in the dorsal columns of the cervical spine. All patients improved following vitamin B12 injections., Conclusions: Enhancing awareness, prompting the use of appropriate investigations, and advocating for timely treatment are needed to overcome the risks associated with nitrous oxide misuse.

Nitrous oxide is a widely used and well-established form of inhalation sedation in dentistry. Its properties have a wide margin of safety and allow for anxious, paediatric and adult patients to receive dental treatment with minimal impact upon discharge. Nitrous oxide has drawbacks, however, including its environmental impact and need for specialist equipment. Methoxyflurane is another drug which could prove to be an alternative to nitrous oxide. Methoxyflurane's use has proved popular within emergency medicine in Australia and New Zealand for its potent analgesic effects and recognition of its anxiolytic effect. As a result, its use in invasive outpatient procedures has now become popular. Unfortunately, there is very limited evidence of its use within dentistry as a form of inhalation sedation and analgesic. A wider evidence base should be established, as methoxyflurane could prove to be an effective and environmentally friendly alternative to nitrous oxide., (© 2024. The Author(s), under exclusive licence to the British Dental Association.)

Background: Pharmacological methods, specifically sedatives, have gained popularity in managing the behavior of children during dental appointments., Aim: The aim of this study was to compare 1 m/kg intranasal dexmedetomidine, 0.3 mg/kg intranasal midazolam, and nitrous oxide in evaluating the level of sedation, behavior of the child, onset of sedation, physiologic signs, and adverse effects., Materials and Methods: In this cross-over trial, 15 children aged 6-8 years were randomized to receive intranasal atomized dexmedetomidine, intranasal atomized midazolam, and inhalation nitrous oxide at three separate visits. After administering the sedative agent, a single pulpectomy was performed during each appointment, and the outcomes were recorded. The washout period between each visit was 1 week., Results: All three sedative agents were equally effective in controlling overall behavior. Dexmedetomidine showed lower sedation level scores (agitated; score 9) than the other groups. There was a statistically significant difference in the onset of sedation, with dexmedetomidine having the longest onset of 36.2 ± 9.47 min. Coughing and sneezing were predominantly observed after administration of intranasal midazolam. Oxygen saturation levels were statistically lower in the intranasal midazolam group during local anesthesia administration and post-treatment., Conclusion: 0.3 mg/kg intranasal midazolam is as effective as nitrous oxide sedation for controlling behavior and providing adequate sedation in pediatric dental patients. However, 1 m/kg dexmedetomidine did not provide the same level of sedation and had a significantly longer onset. 0.3 mg/kg intranasal midazolam is an effective alternative to nitrous oxide sedation in anxious children., (Copyright © 2024 Copyright: © 2024 Journal of Indian Society of Pedodontics and Preventive Dentistry.)

Abstract: Experimental studies have suggested that nitrous oxide-induced analgesia depends on interactions with opioids. On the basis of these results, we hypothesized that the effects of inhaled nitrous oxide/oxygen (N 2 O/O 2 ) 50%-50% equimolar mixture (EMONO) on patients with neuropathic pain would be higher in those receiving concomitant opioids. To test this hypothesis, we did exploratory post hoc analyses of our recently published ProtoTOP study to compare the effects of EMONO and placebo in patients with or without concomitant opioid treatment. A total of 92 patients of the 221 (ie, 41.6%) included in the ProtoTOP study were concomitantly treated with opioids. In contrast with our previous analyses, average pain intensity was significantly decreased in comparison with placebo one week after the last treatment administration in patients treated with opioids, but not in those treated without opioid, and this effect was maintained over the 4-week follow-up period. Neuropathic pain symptom inventory (NPSI total and subscores) was also significantly more decreased after inhalation of EMONO in comparison with placebo only in patients receiving opioids. The proportion of patients with at least 30% pain reduction and of those reporting an overall improvement with the Patient Global Impression of Change were significantly higher only in this population of patients. In conclusion, these results complement our previous analyses with the identification of a specific population of responders to EMONO inhalation in patients with neuropathic pain. As suggested by experimental studies, we hypothesized that these long-lasting analgesic effects could depend on the anti-N-methyl-D-aspartate properties of N 2 O., (Copyright © 2022 International Association for the Study of Pain.)

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., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 International Anesthesia Research Society.)

Rationale: Epidermolysis bullosa (EB) is an inherited disease characterized by fragile skin with painful blistering, which requires lifelong skin and wound care. This case report describes the use of inhaled nitrous oxide (N2O) for procedural pain control at home during wound care in a young man with severe dystrophic EB. To our knowledge, only 1 case was reported by Ingelmo et al in 2017 regarding the use of N2O at home in a 4-year-old-child. To date, no such attempt has been made in adult patients., Patient Concerns: Our patient was a 28-year-old man. Frequent blisters appear spontaneously, and are often preceded by erythema and itching. Patient required daily treatment daily consisting of lancing blisters with a needle and emptying them by compression., Diagnoses: Severe recessive dystrophic EB diagnosed at the time of delivery., Interventions: Procedural pain control was managed by the auto-administration of an inhaled N2O and air gas mixture., Outcomes: Conscious sedation with N2O leads to beneficial effects, such as reduction in dressing duration, acute procedural pain, local antibiotic needing, medication memory, anxiety, anticipatory pain, and fatigue after the dressing session., Lessons: N2O analgesia is safe and effective, resulting in a significant reduction in procedural pain and an improvement in the quality of life of patients and their caregivers., Competing Interests: The authors have no conflicts of interests to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

The use of cuffed tracheal tubes in paediatric anaesthesia is now common. The use of nitrous oxide in anaesthesia risks excessive tracheal tube cuff pressures, as nitrous oxide can diffuse into the cuff during the course of surgery. The aim of this single-centre, prospective, randomised controlled trial was to compare the effect of saline versus air for the inflation of tracheal tube cuffs on the incidence of excessive intra-operative cuff pressure in children undergoing balanced anaesthesia with nitrous oxide. Children (age ≤ 16 y) were randomly allocated to receive either saline (saline group) or air (air group) to inflate the cuff of their tracheal tube. The pressure in the tracheal tube cuff was measured during surgery and brought down to the initial inflation level if it breached a safe limit (25 cmH 2 O). Post-extubation adverse respiratory events were noted. Data from 48 patients (24 in each group), aged 4 months to 16 y, were analysed. The requirement for reduction in intra-cuff pressure occurred in 1/24 patients in the saline group, compared with 16/24 patients in the air group (p < 0.001). The incidence of extubation-related adverse events was similar in the saline and air groups (15/24 vs. 13/24, respectively; p = 0.770). The use of saline to inflate the cuff of paediatric cuffed tubes reduces the incidence of high intra-cuff pressures during anaesthesia. This may provide a pragmatic extra safety barrier to help reduce the incidence of excessive tracheal cuff pressure when nitrous oxide is used during paediatric anaesthesia., (© 2021 Association of Anaesthetists.)

Background Recreational use of nitrous oxide (N 2 O) is associated with many side effects, of which neurological complications are most common. Nitrous oxide abuse is also associated with psychiatric symptoms, but these have received less attention so far. Vitamin B12 deficiency may play a role in the development of these psychiatric symptoms. Aims To explore the relationship among the occurrence of recreational nitrous oxide-induced psychiatric symptoms, accompanying neurological symptoms, vitamin B12 status and choice of treatment. Methods A retrospective search for case reports was conducted across multiple databases (Pubmed, Embase, Web of Science, PsycINFO and CINAHL). Keywords included variants of "nitrous oxide", "case report" and "abuse". No restrictions to language or publication date were applied. Results The search retrieved 372 articles. A total of 25 case reports were included, representing 31 patients with psychiatric complications following nitrous oxide abuse. The most often reported symptoms were: hallucinations ( n  = 16), delusions ( n  = 11), and paranoia ( n  = 11). When neurological symptoms were present, patients were treated more frequently with vitamin B12 supplementation. Conclusions This review highlights the need to recognize that psychiatric symptoms may appear in association with nitrous oxide use. Approximately half of the cases that presented with nitrous oxide-induced psychiatric complaints did not show neurological symptoms, and their vitamin B12 concentration was often within the hospital's reference range. Psychiatrists and emergency physicians should be aware of isolated psychiatric symptoms caused by recreational nitrous oxide abuse. We suggest asking all patients with new psychiatric symptoms about nitrous oxide use and protocolizing the management of nitrous oxide-induced psychiatric symptoms.

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., (© 2021 John Wiley & Sons Ltd.)

Background: Megaloblastic anemia or bone marrow changes could occur after prolonged nitrous oxide inhalation via vitamin B 12 inactivation related DNA synthesis impairment. Previous researches have studied hematological changes with nitrous oxide exposure, but only in adults or adolescents. Pre-school age children with active hematopoietic red bone marrow are more vulnerable to potential side effects of nitrous oxide and might experience growth impairment. The purpose of our study was to analyze red blood cell morphology changes under nitrous oxide anesthesia in pre-school age children., Methods: One hundred thirty-six children under 5 years old scheduled for hemivertebra resection were analyzed. According to fresh gas type in anesthesia records, 71 children who received nitrous oxide in oxygen during anesthesia maintenance were categorized into the nitrous oxide group and the other 65 who received air in oxygen were the air group. Complete blood counts in perioperative period were assessed for anemia, macrocytosis, microcytosis, anisocytosis, hyperchromatosis and hypochromatosis. The peak value and change percentage were calculated for mean corpuscular volume and red cell distribution width., Results: Forty-two children in the air group (64.6%) and 30 in the nitrous oxide group (42.3%) developed anemia (P = 0.009). None developed macrocytosis in both groups. Postoperative mean corpuscular volume peaked (mean [95% confidence interval]) at 83.7(82.9-84.4) fL, and 83.2(82.4-83.9) fL and postoperative red cell distribution width at 13.8% (13.4-14.2%), and 13.9% (13.6-14.2%) for the air group and the nitrous oxide group. Both the relative change of mean corpuscular volume (P = 0.810) and red cell distribution width (P = 0.456) were similar between the two groups., Conclusions: No megaloblastic red blood cell changes were observed with nitrous oxide exposure for 4 h in pre-school age children undergoing hemivertebra resection.

Nitrous oxide (N 2 O), also known as "laughing gas," is a colorless, nonirritating gas. Clinically, it is widely used as an inhaled anesthetic, analgesic, and anxiolytic. In recent years, recreational abuse of N 2 O has become increasingly common, especially among young adults and adolescents, but many of them lack awareness of the possible side effects associated with this drug. N 2 O abuse can damage multiple systems, especially the nervous system, but the exact mechanism of N 2 O toxicity remains controversial. At present, an increasing number of cases of nervous system damage caused by N 2 O abuse have been reported both at home and abroad. Discontinuation of N 2 O use and timely supplementation with vitamin B12 are essential for a good prognosis. Long-term abuse without timely treatment will eventually lead to irreversible neurological damage. In this article, we discuss the epidemiology of N 2 O abuse, neurotoxicity mechanisms, clinical manifestations, relevant auxiliary examinations, treatments, and prognosis to improve social awareness of N 2 O exposure risk, especially among users and clinicians.

Purpose: A rapid increase of recreational nitrous oxide use (i.e. laughing gas, N2O) has been reported in several countries, while it has received limited attention in scientific research. We aimed to study the association of socio-demographic characteristics, mental well-being, sickness absence, truancy, and substance use with the frequency of lifetime nitrous oxide use among adolescents., Methods: We used self-reported questionnaire data of adolescents (N = 555) attending secondary schools to cross-sectionally assess the frequency of nitrous oxide use and potential factors associated with nitrous oxide use, such as gender, mental well-being, and binge drinking. Ordinal logistic regression models were applied with lifetime nitrous oxide use (never, once, ≥ two times) as the outcome variable., Results: Adolescents were on average 15.6 years old (SD = 0.83, range 14-18), 47.0% were female. In total, 86 (15.6%) adolescents had used nitrous oxide at least once in their life. In the multivariable ordinal regression model, the risk of having a higher category of lifetime nitrous oxide use was associated with a non-Dutch ethnic background (OR = 2.10, 95% CI 1.22; 3.61), attending pre-vocational education (OR = 1.88, 95% CI 1.06; 3.34), a higher score on the scale of externalizing problems (OR = 1.10, 95% CI 1.01; 1.20), binge drinking twice or more in the past four weeks (OR = 2.49, 95% CI 1.25; 4.94), and cannabis use (OR = 1.98, 95% CI 1.03; 3.79)., Conclusions: Youth Health Care professionals should be aware of nitrous oxide use in adolescents, especially among adolescents with a non-Dutch ethnic background, lower education levels, externalizing problems, frequent binge drinking, and cannabis use., Competing Interests: The authors have declared that no competing interests exist.

Abstract: To evaluate the utility of low-concentration nitrous oxide (N2O) anesthesia in ptosis surgeryThis study was a retrospective consecutive case series that included 54 successive patients with blepharoptosis who underwent bilateral levator aponeurosis advancement and on whom skin resection performed by the same surgeon between August 2016 and July 2017. Among these patients, 27 were operated with a local anesthesia injection (air group) and 27 with a local anesthesia injection and low-concentration N2O anesthesia (N2O group). All N2O cases used a total of 6 L of gas comprising 70% oxygen and 30% N2O. Preoperative and postoperative blood pressure (BP) and heart rate (HR) and intraoperative pain, anxiety, nausea, and memory were measured immediately after surgery using visual analog scale score (VASS). Additionally, perioperative side effects were examined.There was no significant difference in age, sex, and preoperative and postoperative margin reflex distance (MRD) between the 2 groups (all P > .05). The intraoperative mean peripheral oxygen saturation was significantly higher (97.5% ± 1.6% vs 99.5% ± .6%, P < .001), intraoperative HR was significantly lower (78.2 ± 12.8 vs 70.7 ± 11.6 bpm, P = .02), and operation time was significantly shorter (33.1 ± 8.1 vs 29.4 ± 10.3 minutes, P = .03) in the N2O group than in the air group.Difference between intraoperative and preoperative systolic BP (BPs) (+15.8 ± 18.0 vs + 3.1 ± 21.7 mm Hg, P = .02), diastolic BP (BPd) (+7.0 ± 17.4 vs -2.3 ± 13.6 mm Hg, P = .04), and HR (3.2 ± 8.5 vs -3.9 ± 9.4 bpm, P = .01) was significantly lower in the N2O group than in the air group.VASS of intraoperative pain was significantly lower in the N2O group than in the air group (49.5 ± 24.7 vs 22.6 ± 14.9, P < .001), whereas intraoperative anxiety and memory did not present significant differences between the groups (P = .09 and P = .45, respectively). Intraoperative nausea score was 0 for all cases in both groups. There was no other side effect.Ptosis surgery with anesthesia using 30% N2O may effectively suppress intraoperative BP and HR along with pain and shorten the operation time without side effects such as nausea., Competing Interests: The authors have no funding and conflicts of interests to disclose., (Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Nitrous oxide may be misused due to its euphoric, dissociative, and hallucinogenic effects. Nitrous oxide misuse has been reported to be increasing. Objective: The objective of this study is to describe nitrous oxide misuse reported to two United States (US) data systems. Methods: Cases were nitrous oxide misuse during 2000-2019 reported to the National Electronic Injury Surveillance System (NEISS), which collects data on consumer product-related injuries treated in US emergency departments (EDs), and the Food and Drug Administration Adverse Event Reporting System (FAERS), which collects reports of adverse events involving drugs and other biologic products. The distribution of cases was determined for selected variables. Results: Of the 26 NEISS cases, the mean annual number of cases was 0.5 (range 0-2) during 2000-2013 and 3.2 (range 1-5) during 2014-2019. The patients were 92.3% age 13-39 years and 76.9% male. The patient was treated or examined and released from the ED in 84.6% of the cases. Of the 128 FAERS cases, the mean annual number of cases was 0.4 (range 0-2) during 2000-2013 and 20.3 (range 10-34) during 2014-2019. The patients were 90.2%% age 13-39 years and 77.3% male. A serious classification was assigned to 97.7% of the cases. Conclusions: Nitrous oxide misuse reported to NEISS and FAERS both increased during 2000-2019, particularly after 2013. The majority of patients were age 13-39 years and male. Most NEISS patients were treated or examined and released from the ED.

There is growing interest in assessing possible immunotoxicological effects in anesthetized patients. There are controversial findings concerning the effect of nitrous oxide (N 2 O) anesthetic gas effect on inflammatory response. We tested the hypothesis that N 2 O associated with desflurane (inhalational anesthetic) was likely to worsen neuro-immune-endocrine effects when compared with desflurane alone in this randomized trial. The primary endpoint of this study was to evaluate the systemic proinflammatory interleukin (IL)-6, and the secondary endpoints included other systemic (IL-1β, TNF-α, IL-8, IL-10, IL-17A and high-sensitivity C-reactive protein - hs-CRP) and genetic inflammatory markers (NF-kB, IL-6 and COX-2) as well as hormones (adrenocorticotropic hormone, cortisol and prolactin) comparing patients undergoing minor surgery with or without N 2 O-desflurane. As a second aim, we assessed whether there were changes in the neuro-immune-endocrine profiles within each group. Blood samples were collected before anesthesia, 90 min after anesthesia induction, and the day after surgery. We assessed serum cytokines using a cytometric bead array and hs-CRP by chemiluminescent immunoassay. Expression of three proinflammatory transcripts was assessed by real-time quantitative polymerase chain reaction, and neuroendocrine hormones were detected by chemiluminescent microparticle immunoenzymatic assay. There were no significant between-group differences for any analyzed biomarkers. However, there was a significant increase in: (a) systemic IL-6 and hs-CRP values one day after surgery in both groups and (b) prolactin levels in the intraoperative period compared to baseline and postoperative period levels for both groups. In conclusion, N 2 O does not impair the inflammatory profile and neuroendocrine response compared to patients who receive only desflurane anesthesia., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Objectives: We report a case series of one-time 4 mcg/kg dose of intranasal dexmedetomidine and 1 mcg/kg of intranasal fentanyl plus inhaled nitrous oxide for procedural sedation in children with otitis media with effusion (OME) for tympanostomy tube placement with a specific handheld device (Solo TTD, AventaMed ®)., Methods: A retrospective review was conducted in a tertiary paediatric teaching hospital on patients with OME referred from December 2018 to December 2019 in need of procedural sedation for myringotomy and ventilation tube insertion (VTI). Sixteen of twenty-four consecutively admitted subjects received a one-time dose (4 mcg/kg) of intranasal dexmedetomidine and 1mcg/Kg of intranasal fentanyl followed by inhaled nitrous oxide (iN 2 O) at 50% with the intended goal to achieve a Ramsay Sedation Score 4 allowing a motionless procedure with adequate analgesia. Parents' satisfaction for the procedure was measured by mean of a Likert scale (from 0 to 5 points)., Results: Sixteen patients underwent procedural sedation for myringotomy with VTI. Sedation was achieved successfully in fifteen patients (93,75%), with a mean induction time of 29 min (range 19-43) and a mean recovery time of 74 min (range 54-110). The patient who did reach an adequate sedation level underwent an intravenous line positioning and a dose of ketamine. No adverse effects were reported, and the parents' judgment average on the Likert scale was 4,93. VTI procedure was successful in all ears., Conclusions: A combination of intranasal dexmedetomidine, fentanyl, and iN 2 O could be considered as a possible option for procedural sedation in children with OME undergoing procedural sedation for tympanostomy tube placement in children with Solo TTD device., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Nitrous oxide (N 2 O) is underutilized in ambulatory urology. Here, we review available data regarding application, efficacy, and side effect profile of N 2 O in ambulatory urologic procedures. Data were available from 11 studies. N 2 O has been described in the setting of transrectal ultrasound-guided prostate biopsies, flexible cystoscopy, ureteral stent placement, and extracorporeal shockwave lithotripsy in adult patients and catheterization in children. Studies showed significant improvements in peri-procedural pain and anxiety relative to alternative (or none) forms of analgesia. Adverse effects were rare and self-limited. More widespread use of N 2 O may result in cost savings and better patient tolerance with outpatient procedures., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: We evaluated the hypothesis that the rate of postoperative decline in global cognition is greater in older adults exposed to general anesthesia with nitrous oxide (N2O) compared to general anesthesia without N2O., Methods: Longitudinal measures of cognitive function were analyzed in nondemented adults, 70-91 years of age, enrolled in the Mayo Clinic Study of Aging. Linear mixed-effects models with time-varying covariates assessed the relationship between exposure to surgery with general anesthesia (surgery/GA) with or without N2O and the rate of long-term cognitive changes. Global cognition and domain-specific cognitive outcomes were defined using z scores, which measure how far an observation is, in standard deviations, from the unimpaired population mean., Results: The analysis included 1819 participants: 280 exposed to GA without N2O following enrollment and before censoring during follow-up (median [interquartile range {IQR}] follow-up of 5.4 [3.9-7.9] years); 256 exposed to GA with N2O (follow-up 5.6 [4.0-7.9] years); and 1283 not exposed to surgery/GA (follow-up 4.1 [2.5-6.4] years). The slope of the global cognitive z score was significantly more negative following exposure to surgery/GA after enrollment (change in slope of -0.062 [95% confidence interval {CI}, -0.085 to -0.039] for GA without N2O, and -0.058 [95% CI, -0.080 to -0.035] for GA with N2O, both P < .001). The change in slope following exposure to surgery/GA did not differ between those exposed to anesthesia without versus with N2O (estimated difference -0.004 [95% CI, -0.035 to 0.026], P = .783)., Conclusions: Exposure to surgery/GA is associated with a small, but statistically significant decline in cognitive z scores. Cognitive decline did not differ between anesthetics with and without N2O. This finding provides evidence that the use of N2O in older adults does not need to be avoided because of concerns related to decline in cognition.

Background: The ideal fraction of nitrous oxide (N 2 O) in oxygen (O 2 ) for rapid lung collapse remains unclear. Accordingly, this prospective trial aimed to determine the 50% effective concentration (EC 50 ) and 95% effective concentration (EC 95 ) of N 2 O in O 2 for rapid lung collapse., Methods: This study included 38 consecutive patients undergoing video-assisted thoracoscopic surgery (VATS). The lung collapse score (LCS) of each patient during one-lung ventilation was evaluated by the same surgeon. The first patient received 30% N 2 O in O 2 , and the subsequent N 2 O fraction in O 2 was determined by the LCS of the previous patient using the Dixon up-and-down method. The testing interval was set at 10%, and the lowest concentration was 10% (10, 20, 30, 40%, or 50%). The EC 50 and EC 95 of N 2 O in O 2 for rapid lung collapse were analyzed using a probit test., Results: According to the up-and-down method, the N 2 O fraction in O 2 at which all patients exhibited successful lung collapse was 50%. The EC 50 and EC 95 of N 2 O in O 2 for rapid lung collapse were 27.7% (95% confidence interval 19.9-35.7%) and 48.7% (95% confidence interval 39.0-96.3%), respectively., Conclusions: In patients undergoing VATS, the EC 50 and EC 95 of N 2 O in O 2 for rapid lung collapse were 27.7 and 48.7%, respectively., Trial Registration: http://www.chictr.org/cn/ Identifier ChiCTR19 00021474 , registered on 22 February 2019.

Study Objective: Intranasal fentanyl and inhaled nitrous oxide are increasingly combined to provide procedural sedation and analgesia in the pediatric emergency setting. This regimen is attractive because of its nonparenteral administration, but is associated with a higher incidence of vomiting than nitrous oxide alone. We seek to assess whether prophylactic oral ondansetron use could reduce the incidence of vomiting associated with intranasal fentanyl and nitrous oxide for procedural sedation compared with placebo., Methods: This was a double-blind, randomized controlled trial of oral ondansetron versus placebo conducted at a single tertiary care pediatric emergency department. Children aged 3 to 18 years with planned sedation with intranasal fentanyl and nitrous oxide were randomized to receive oral ondansetron or placebo 30 to 60 minutes before nitrous oxide administration. The primary outcome was early vomiting associated with procedural sedation, defined as occurring during or up to 1 hour after nitrous oxide administration. Secondary outcomes included vomiting 1 to 24 hours after procedural sedation, procedural sedation duration, adverse events, and quality of sedation across the 2 groups., Results: We recruited 442 participants and 436 were included for analysis. There was no significant difference in the primary outcome, early vomiting associated with procedural sedation, between the groups: ondansetron 12% versus placebo 16%, with a difference in proportions of -4.6% (95% confidence interval -11% to 2.0%; P=.18). Most sedations were reported as optimal by treating clinicians (91%). Only 2 minor adverse events occurred, both in the placebo group., Conclusion: Oral ondansetron does not significantly reduce vomiting during or shortly after procedural sedation with combined intranasal fentanyl and inhaled nitrous oxide., (Copyright © 2019 American College of Emergency Physicians. Published by Elsevier Inc. All rights reserved.)

In the 1940s, Seymour S. Kety and Carl F. Schmidt measured cerebral blood flow in awake humans by means of subanesthetic doses of inhaled nitrous oxide. The inhalation route obviated the need for an arterial injection of the indicator, and nitrous oxide had virtues of metabolic inertness, rapid diffusion through the blood-brain barrier, comparable blood and brain solubility, and ease of analytical detection. The technique was also applied to the heart. Follow-up work by Kety contributed to the development of brain scanning methods., (Copyright © 2020. Published by Elsevier Inc.)

Background: Investigations of the electrophysiology of gaseous anesthetics xenon and nitrous oxide are limited revealing inconsistent frequency-dependent alterations in spectral power and functional connectivity. Here, the authors describe the effects of sedative, equivalent, stepwise levels of xenon and nitrous oxide administration on oscillatory source power using a crossover design to investigate shared and disparate mechanisms of gaseous xenon and nitrous oxide anesthesia., Methods: Twenty-one healthy males underwent simultaneous magnetoencephalography and electroencephalography recordings. In separate sessions, sedative, equivalent subanesthetic doses of gaseous anesthetic agents nitrous oxide and xenon (0.25, 0.50, and 0.75 equivalent minimum alveolar concentration-awake [MACawake]) and 1.30 MACawake xenon (for loss of responsiveness) were administered. Source power in various frequency bands were computed and statistically assessed relative to a conscious/pre-gas baseline., Results: Observed changes in spectral-band power (P < 0.005) were found to depend not only on the gas delivered, but also on the recording modality. While xenon was found to increase low-frequency band power only at loss of responsiveness in both source-reconstructed magnetoencephalographic (delta, 208.3%, 95% CI [135.7, 281.0%]; theta, 107.4%, 95% CI [63.5, 151.4%]) and electroencephalographic recordings (delta, 260.3%, 95% CI [225.7, 294.9%]; theta, 116.3%, 95% CI [72.6, 160.0%]), nitrous oxide only produced significant magnetoencephalographic high-frequency band increases (low gamma, 46.3%, 95% CI [34.6, 57.9%]; high gamma, 45.7%, 95% CI [34.5, 56.8%]). Nitrous oxide-not xenon-produced consistent topologic (frontal) magnetoencephalographic reductions in alpha power at 0.75 MACawake doses (44.4%; 95% CI [-50.1, -38.6%]), whereas electroencephalographically nitrous oxide produced maximal reductions in alpha power at submaximal levels (0.50 MACawake, -44.0%; 95% CI [-48.1,-40.0%])., Conclusions: Electromagnetic source-level imaging revealed widespread power changes in xenon and nitrous oxide anesthesia, but failed to reveal clear universal features of action for these two gaseous anesthetics. Magnetoencephalographic and electroencephalographic power changes showed notable differences which will need to be taken into account to ensure the accurate monitoring of brain state during anaesthesia.

Background: Functional endoscopic sinus surgery is a common procedure for sinonasal disease, frequently performed in the outpatient setting. General anesthesia maintained with total intravenous anesthesia (TIVA) with propofol has been shown to give superior surgical conditions compared to inhaled anesthetics. This study evaluated the effects of TIVA versus a predominantly nitrous oxide (N 2 O)-based anesthetic with a low-dose propofol and remifentanil infusion on sinus surgery., Methods: Patients were randomized to either a N 2 O-based (nitrous oxide with propofol and remifentanil) or TIVA (propofol and remifentanil without nitrous oxide) group. The surgeon was blinded to the anesthetic technique. Surgical field grading was performed in real time by the otolaryngologist every 15 minutes with the Boezaart grading system., Results: There were no statistically significant differences between the Boezaart scores, duration of surgery, or estimated blood loss between the two anesthetic techniques. However, the use of N 2 O provided a statistically significant, 38% reduction in time from surgery end to extubation. The TIVA group had significantly decreased mean and median pain scores in the post-anesthesia care unit (PACU). There was no difference in the rate of postoperative nausea and vomiting between the two groups., Conclusion: A N 2 O-based anesthetic for functional endoscopic sinus surgery provides similar intraoperative and postoperative conditions when compared to TIVA, while being superior in terms of time to extubation. Although the TIVA group had significantly decreased pain scores, this did not lead to a decrease in pain medicine received in the PACU, and there was no difference between groups in time to discharge., Level of Evidence: 1b Laryngoscope, 130:E299-E304, 2020., (© 2019 The American Laryngological, Rhinological and Otological Society, Inc.)

Nitrous oxide is a commonly abused inhalant by adolescents and young adults. There is limited data describing the adverse effects of nitrous oxide abuse, known colloquially as "whippets". We present a 21-year-old female with no medical history who presented to the emergency department for confusion, hallucinations, weakness, and falls. She was accompanied by her roommates, who endorsed significant nitrous oxide abuse. Imaging revealed a large cerebral sinus venous thrombus with extension into the transverse sinus, sigmoid sinus and internal jugular vein. She had no prior history of venous or arterial thrombosis. Hypercoagulability workup demonstrated an elevated homocysteine level, elevated methylmalonic acid level, and normal cobalamin and folate levels. Additionally, she was found to be 11 weeks pregnant, with no prior spontaneous abortions. Genetic testing was significant for methylenetetrahydrofolate reductase polymorphisms. She was managed with enoxaparin, cobalamin and folate supplementation. Homocysteine and methylmalonic acid levels normalized after cessation of nitrous oxide use, with no recurrence of venous thrombosis. This case represents the first reported patient with a venous thrombus associated with nitrous oxide abuse.

Concentrations of 64% to 70% nitrous oxide (N 2 O) provide intra-operative analgesia. Clinically, pulse oximeter estimation (SpO 2 ) of oxygen (O 2 ) hemoglobin saturation (SaO 2 ) was observed to decrease with N 2 O. Absorption atelectasis from breathing O 2 was thought to decrease arterial partial pressure of O 2 (PaO 2 ) below 70 mmHg and reduce SaO 2 and SpO 2 when N 2 O was used. Administering N 2 O from the beginning of the anesthesia might prevent atelectasis development and low PaO 2 . The study was done in 2 parts ( P < 0.05). In Part 1, isoflurane-anesthetized dogs undergoing ovariohysterectomy ( n = 15 each group) breathed N 2 O from anesthesia start (N 2 O early ) or 1 hour later (N 2 O late ). SpO 2 , CO-oximetry values, and PaO 2 were compared to dogs breathing O 2 throughout anesthesia (control). Timing of N 2 O introduction did not affect PaO 2 (lowest = 94 mmHg), SaO 2 , or SpO 2 . With N 2 O, the lowest SpO 2 value was 91% and corresponded to a PaO 2 of 151 mmHg. Carboxyhemoglobin increased (highest = 2.7%) and SaO 2 decreased with N 2 O (lowest = 96.7%). In Part 2, to replicate findings, 10 isoflurane-anesthetized dogs breathed N 2 O, then O 2 . With N 2 O, SaO 2 did not decrease, but carboxyhemoglobin increased and returned to baseline once N 2 O was discontinued. The dog with the highest carboxyhemoglobin (2%) had an SaO 2 of 96.8% (PaO 2 = 93 mmHg). Carboxyhemoglobin and SaO 2 changes were not clinically significant. Pulse oximetry did not reliably estimate SaO 2 but N 2 O was not always a factor., (Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.)

Background: Several recent studies have reported subacute combined degeneration (SCD) induced by nitrous oxide (N 2 O) abuse. However, the association between the evolution of dynamic neuroimaging and clinical manifestations has not been reported in patients with N 2 O-induced SCD., Case Presentation: We described the case of a 24-year-old man who developed SCD with inverted V-sign hyperintensities over the posterior aspect of the spinal cord caused by frequent, excessive N 2 O inhalation. One month after treatment, his weakness and paresthesia resolved and serum vitamin B 12 levels exceeded the normal levels. However, the hyperintensities had extended horizontally and longitudinally on T2-weighted magnetic resonance imaging (MRI), compared to those on the initial scan. Two months after treatment, the patient experienced some residual numbness in the distal limbs, and his serum homocysteine levels were normal, but the abnormal signals seen on cervical T2-weighted MRI had decreased only slightly compared to those seen on the one-month follow-up MRI. The evolution of conventional MRI findings lagged compared to the clinical manifestation, which was suggestive of a clinical-radiological dissociation., Conclusions: Clinical-radiological dissociation might have occurred in this case because T2-weighted imaging was not sensitive enough to reveal cytotoxic edema. Moreover, the serum vitamin B 12 level is not a good indicator of cellular vitamin B 12 . Thus, clinicians should recognize this phenomenon, comprehensively assess the condition of patients with N 2 O-induced SCD, and avoid terminating treatment based on the resolution of clinical symptoms and serological results.