A Systematic Review of Recreational Nitrous Oxide Use: Implications for Policy, Service Delivery and Individuals

Multidisciplinary rehabilitation following recreational nitrous oxide (N2O) misuse: evaluating service provision and rehabilitation outcomes in a cohort with serious disability

Purpose: Recreational nitrous oxide (N2O) misuse is increasing globally. Chronic misuse can cause neurological impairments that require rehabilitation, though literature characterising rehabilitation is limited. This study aimed to evaluate rehabilitation service provision for impairments resulting from N2O misuse. Methods: A retrospective audit of hospitalised patients referred for rehabilitation for N2O toxicity was conducted between 2015 and 2022 at a single metropolitan hospital. Data were collected via medical record audit and analysed via descriptive and non-parametric statistics. Results: 16 eligible cases were identified, aged 18-43 years (50% female/male), with increasing case frequency. 12 cases received inpatient rehabilitation episodes for multifactorial sensorimotor, cognitive and psychosocial impairments. Cases articulated diverse rehabilitation goals and received intervention from a median of 6 clinical disciplines. All cases required assistance to mobilise or perform self-care activities on admission. Functional Independence Measure (FIM) scores significantly improved with rehabilitation (median FIM 84[75-93] to 117[112-123], p < .001). Despite gains in independence, all cases required referral for ongoing rehabilitation post-discharge. Conclusions: Demand for inpatient rehabilitation for disabling N2O toxicity appears to be increasing. In this series, cases were young, exhibited serious impairments, and had multidisciplinary rehabilitation needs. Inpatient rehabilitation led to significant functional improvements, though ongoing disability was evident post-discharge.

Evaluation of an ambulatory care pathway for patients with nitrous oxide-induced myeloneuropathy

Introduction

Cases of nitrous oxide (N2O)-induced myeloneuropathy are increasing at UK hospitals. At our centre, a dedicated ambulatory care pathway, endorsed nationally, was established to treat and monitor patients with N2O-myeloneuropathy in 2021 and refined through three audit cycles. We analysed the outcomes of patients on this pathway to better understand factors associated with non-engagement. Alongside, a novel approach using WhatsApp for questionnaire delivery was trialled in an attempt to improve engagement with treatment.

Methods

Patients on the N2O ambulatory care pathway were identified from MDT meeting lists from 9 September 2022 to 25 April 2023. Clinical data were collected via electronic clinical records, including the most recent neurological examination and reason for discharge from the pathway. Patients identified from MDT lists from 27 January 2023 to 14 March 2023 were approached to participate in weekly 12-item surveys, delivered via WhatsApp. This was approved as a service development project with approval for WhatsApp use given by the chief clinical information officer.

Results

35/56 (62.5%) patients were discharged from ambulatory care due to non-attendance and 17/56 (30.4%) completed their treatment course. The median time from initial presentation to discharge was 49 days. 24/40 (60.0%) of patients with a final neurological examination documented had a residual deficit, with objective sensory deficits most common. 12 patients were approached to receive weekly questionnaires via WhatsApp. 5/8 who expressed interest returned a consent form. All participants were withdrawn due to non-response or participant choice. 1/5 returned more than two surveys.

Conclusion

Despite poor participation in surveys delivered via WhatsApp, novel approaches are needed to improve engagement with patients on the N2O ambulatory care pathway.

Longitudinal follow-up and prognostic factors in nitrous oxide-induced neuropathy

BACKGROUND AND AIM

Recreational use of nitrous oxide (N2O) has been associated with the development of severe nitrous oxide-induced neuropathy (N2On). 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 N2On patients to identify prognostic factors for persistent disability after 6 months.

METHODS

We gathered demographic, clinical, biological, and electrophysiological data from N2On 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 N2On 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 N2O 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.

Nitrous oxide-induced myeloneuropathy in a Thai adolescent: a case report

Nitrous oxide, an inhalational anaesthetic, is popular with adolescents worldwide as an accessible recreational drug which induces a euphoric effect. However, chronic abuse leads to serious complications such as myeloneuropathy and bone marrow suppression by inactivation of vitamin B12. A 17-year-old girl presented with nitrous oxide-induced myeloneuropathy. She reported chronic nitrous oxide inhalation for 10 months and was admitted to the emergency department on account of repeated falls for 2 weeks. She also had ascending paraesthesia in both legs and urinary incontinence. Neurological examination demonstrated bilateral lower extremity weakness [motor power: proximal muscles 4/5, plantar flexion and extensor hallucis longus (EHL) 3/5], decreased sensation, proprioception and vibration of the lower extremities. Deep tendon reflexes were absent in the ankles and knees. Laboratory results demonstrated mild anaemia [Hb 11.2 g/dL (12.0-16.0), haematocrit 35.4% (36-50), MCV 89.4 fl (78-102)] with significant hypersegmented neutrophils in a peripheral blood smear. Serum vitamin B12 was 340 pg/mL (197-771), but serum homocysteine was increased at 65.8 µmol/L (5-15). A nerve conduction study was prolonged, and F-waves were absent from the bilateral perineal and tibial nerves, indicating diffuse demyelinating motor polyneuropathy. Magnetic resonance imaging of the whole spine demonstrated faint T2 hypersignal intensity and an inverted V-shape appearance at the posterior column of the upper thoracic cord (around T2-T6), a pathognomonic sign of vitamin B12 deficiency or subacute combined degeneration of the nitrous oxide-induced myeloneuropathy. A 7-day course of 1000 µg cyanocobalamin was given intramuscularly, followed by weekly doses for 4 weeks. Supplements of daily oral vitamin B1, B6 and B12 (65 µg vitamin B12) were administered, along with rehabilitation. At the 6-months outpatient follow-up, there were a few residual neurological abnormalities: weakness of the left EHL (grade 4/5) and an absent deep tendon reflex in the left ankle. This case emphasises the significant health consequences of chronic abuse of nitrous oxide, myeloneuropathy and megaloblastic anaemia, by inactivation of vitamin B12. The myelopathy is noticeably improved by cyanocobalamin.Abbreviations: EHL: extensor hallucis longus; MRI: magnetic resonance imaging; NCS: nerve conduction study.

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.

How to distinguish Guillain-Barré syndrome from nitrous oxide-induced neuropathy: A 2-year, multicentric, retrospective study

BACKGROUND

Recreational use of nitrous oxide (N2 O) has dramatically increased in recent years, resulting in numerous cases of acute sensorimotor tetraparesis secondary to nitrous oxide-induced neuropathy (N2 On). Challenging clinical features can mimic Guillain-Barré syndrome (GBS), the main differential diagnosis upon admission. The most sensitive biomarkers for distinguishing between these two conditions remain to be determined.

METHODS

Fifty-eight N2 On patients from three referral centers were retrospectively included over a 2-year period and compared to GBS patients hospitalized during the same timeframe (47 patients). Collected demographic, clinical, biological, and electrophysiological data were compared between the two groups.

RESULTS

The typical N2 On clinical pattern included distal sensorimotor deficit in lower limbs with absent reflexes, proprioceptive ataxia, and no cranial involvement (56.7% of our cohort). Misleading GBS-like presentations were found in 14 N2 On patients (24.1%), and 13 patients (22.4%) did not report N2 O use during initial interview. Only half the N2 On patients presented with reduced vitamin B12 serum levels upon admission. A slightly increased cut-off (<200 pmol/L) demonstrated 85.1% sensitivity and 84.5% specificity in distinguishing N2 On from GBS. Only 6.9% of N2 On patients met the criteria for primary demyelination (p < 0.01), with only one presenting conduction blocks. A diagnostic algorithm combining these two biomarkers successfully classified all GBS-like N2 On patients.

CONCLUSIONS

Vitamin B12 serum level < 200 pmol/L cut-off and conduction blocks in initial electrophysiological study are the two most sensitive biomarkers for rapidly distinguishing N2 On from GBS patients. These two parameters are particularly useful in clinically atypical N2 On with GBS-like presentation.

Pushing boundaries or adding a gimmick to the party? Young people's experiences of nitrous oxide use in Denmark

Nitrous oxide (N₂O) use for intoxication among young people has increased in many parts of the Western world, including Denmark. The literature, however, primarily focusses on harms related to N₂O use, and not on other aspects, for example modes of administration or effects such as different forms of pleasure or fun. Therefore, despite this increase, we still know very little about how and why young people use nitrous oxide for intoxication, including their experiences of N₂O intoxication. Based on 45 qualitative interviews with young Danes age 18-25 years, who all were former or present N₂O users, we explore their experiences of N₂O intoxication. We do this by analyzing in-depth descriptions of where, how and with whom they use N₂O. When analyzing these descriptions in relation to different modes of administration, intensity of use, combination with other substances (e.g. alcohol, cannabis), and use in different settings, we argue that N₂O intoxication is experienced differently by the young participants. Some of the participants also searched for particular intoxication experiences with N₂O. We unfold the participants' various descriptions of intoxication by differentiating between moderate and intensive use. Overall, our study shows that these differences in N₂O use for intoxication are not equally risky or harmful. In general, young people's own perspectives and experiences with (illegal) drug use is increasingly emphasized as important to include when developing preventive interventions. Our analysis of the young participants' differing experiences with N₂O for intoxication can inform future prevention initiatives in relation to harms of N₂O intoxication.