Neurological Manifestations of Myeloneuropathy in Patients with Nitrous Oxide Intoxication

Nitrous oxide intoxication: systematic literature review and proposal of new diagnostic possibilities

Background

Nitrous oxide (N2O), also called “laughing gas,” is the most commonly used inhalation anesthetic in dentistry. The N2O is no longer used, because of the long-term neurologic and cardiovascular sequelae. Due to its sedative and euphoric properties, N2O is often used for recreational use or in some erotic activities. Accidental deaths are mainly associated with the uses of N2O: death can occur from sudden cardiac arrhythmia or, most commonly, acute asphyxiation due to hypoxia. This paper aims to study the literature concerning deaths due to N2O intoxication and highlight pathological findings useful for diagnosis when the crime scene investigation does not reveal any evidence.

Materials and methods

The authors conducted the literature search by PubMed and Scopus databases, searching for articles from 1 January 1970 to 1 March 2020 using the key terms: “Nitrous oxide,” “Laughing gas,” “Hypoxic damage,” “Nitrous oxide anesthesia,” and “Nitrous oxide death.”

Results and discussion

A total of 244 articles were collected. Only 26 articles were included in the systematic review. Most of the deaths from intoxication are due to asphyxiation; the diagnosis is often difficult and immunohistochemistry could be helpful. Nitrous oxide increases the intracellular adhesion molecule expression, E- and P-Selectin (markers of the early inflammatory response), and HIF-1 α (indicative of oxidative stress during ischemia-reperfusion).

Conclusion

The macroscopic and microscopic signs of N2O intoxication are non-specific, but N2O has been proven to cause hypoxic damage to the brain. The suspicion of the presence of the gas in the environment should guide the pathologist. Tissue analyzes provide important information; immunohistochemical stains can confirm hypoxic damage through the use of markers such as HIF-1 α, E-Selectin, and P-Selectin.

Review article: Clinical manifestations and outcomes of chronic nitrous oxide misuse: A systematic review

Recreational nitrous oxide (N₂ O) use is widespread, and complications associated with its use are increasingly common. We sought to identify risk factors, clinical features and outcomes in individuals presenting with effects of chronic N₂ O abuse to develop an approach to clinical assessment and management. A systemic literature review was completed with searches conducted across EMBASE, MEDLINE, PSYCINFO and Cochrane databases. Our search strategy identified 612 studies, 105 met inclusion criteria, and 10 were added via hand search. Subjects from 24 case series and 91 case reports were typically in their 20s, using over 100 bulbs daily for several months. Neurological presentations, including sensory change, gait disturbance or weakness, were characteristic. Serum Vitamin B12 was normal or raised in 133 out of 243 case series subjects and 37 out of 84 reports. Serum homocysteine and methylmalonic acid were usually raised. Macrocytosis and anaemia were not commonly seen. MRI findings were abnormal with dorsal column change where specified, typically involving the cervical spine. Nerve conduction studies mostly reported a sensorimotor polyneuropathy. B12 replacement was the treatment of choice and partial recovery was most reported. This review highlights the dose-dependent nature of chronic N₂ O toxicity and recognises functional B12 deficiency as the cause. As B12 is often normal, homocysteine and methylmalonic acid are important biomarkers of disease. An approach to diagnosis is offered but requires validation in prospective studies. Research exploring B12 and methionine therapy is required to refine management.

Psychiatric and Other Medical Manifestations of Nitrous Oxide Abuse: Implications From Case Series

BACKGROUND

Nitrous oxide (N2O), a commonly used anesthetic agent in dentistry, has emerged as a global public health threat in young population. Although N2O-related neurological sequelae such as spinal cord degeneration and sensorimotor peripheral neuropathy are well known, psychiatric manifestations of heavy N2O use remain unclear. Here, we presented 7 treatment-seeking patients with severe N2O use disorder to delineate the psychiatric profiles of N2O users in Asia.

METHODS

Seven patients with severe N2O use disorder who sought treatment in Taipei City Psychiatric Center between 2017 and 2018 were enrolled. We used chart review method to retrospectively collect their clinical information including sociodemographics, psychiatric and substance history, urine toxicology findings, and treatment course.

RESULTS

These N2O users all had diagnoses of severe N2O use disorder. They usually initiated N2O use in late adolescence and early adulthood. Six of them had histories of mood disorders; all of them reported other illicit substance use before using N2O. The main reasons for treatment seeking were irritability, psychotic symptoms, self-harm, or violent behaviors as four of them were given a diagnosis of substance-induced psychotic disorder. Urine drug screen showed negative for other illicit drug use except for 1 positive case for cannabis and 1 for amphetamine. Three of 7 cases were hospitalized because of the severity of their psychiatric symptoms and suicidal risk.

CONCLUSIONS

These cases with severe N2O use disorder showed high prevalence of psychotic symptoms and dangerous behaviors such as suicide or violence. This study highlights the addiction potential of N2O and its related adverse consequences in the psychiatric aspect.

A model of lipid dysregulation and altered nutrient status in Alzheimer's disease

INTRODUCTION

Dysregulated lipid metabolism and nutrient status are thought to play a role in the pathophysiology of Alzheimer's disease (AD). However, the precise involvement is not well understood, and it remains unclear exactly how such dysregulated lipid metabolism and altered nutrient status, especially changes in phosphatidylcholine, B12, and folate, are connected to the hallmark pathology in AD (i.e., amyloidogenesis).

METHODS

We have postulated that genetic susceptibility (i.e., APOE ε4/ε4) to environmental exposure to emissions of nitrous oxide (N2O) could underlie the onset of AD and its early neuropsychiatric correlates.

RESULTS AND DISCUSSION

The current theoretical editorial describes, using clinical, preclinical, and in vitro evidences, how this model contributes not only to amyloidogenesis but also other nonopioid effects, specifically altered lipid metabolism, depletion of vitamin B12, and disruption of the folate-mediated one carbon metabolic pathway.