Nitrous oxide abuse direct measurement for diagnosis and follow-up: update on kinetics and impact on metabolic pathways.

Recreational use of nitrous oxide (N2O) has become a major health issue worldwide, with a high number of clinical events, especially in neurology and cardiology. It is essential to be able to detect and monitor N2O abuse to provide effective care and follow-up to these patients. Current recommendations for detecting N2O in cases of recreational misuse and consumption markers are lacking. We aimed to update current knowledge through a review of the literature on N2O measurement and kinetics. We reviewed the outcomes of experiments, whether in preclinical models (in vitro or in vivo), or in humans, with the aim to identify biomarkers of intoxication as well as biomarkers of clinical severity, for laboratory use. Because N2O is eliminated 5 min after inhalation, measuring it in exhaled air is of no value. Many studies have found that urine and blood matrices concentrations are connected to ambient concentrations, but there is no similar data for direct exposure. There have been no studies on N2O measurement in direct consumers. Currently, patients actively abusing N2O are monitored using effect biomarkers (biomarkers related to the effects of N2O on metabolism), such as vitamin B12, homocysteine and methylmalonic acid.

Calcium state estimation by total calcium: the evidence to end the never-ending story.

Background Total blood calcium (TCa) is routinely used to diagnose and manage mineral and bone metabolism disorders. Numerous laboratories adjust TCa by albumin, though literature suggests there are some limits to this approach. Here we report a large retrospective study on agreement rate between ionized calcium (iCa) measurement and TCa or albumin-adjusted calcium measurements. Methods We retrospectively selected 5055 samples with simultaneous measurements of iCa, TCa, albumin and pH. We subgrouped our patients according to their estimated glomerular filtration rate (eGFR), albumin levels and pH. We analyzed each patient's calcium state with iCa as reference to determine agreement rate with TCa and albumin-adjusted calcium using Payne, Clase, Jain and Ridefelt formulas. Results The Payne formula performed poorly in patients with abnormal albumin, eGFR or pH levels. In patients with low albumin levels or blood pH disorders, Payne-adjusted calcium may overestimate the calcium state in up to 80% of cases. Similarly, TCa has better agreement with iCa in the case of hypoalbuminemia, but performed similarly to the Payne formula in patients with physiological albumin levels. The global agreement rate for Clase, Jain and Ridefelt formulas suggests significant improvement compared to Payne calcium adjustment but no significant improvement compared to TCa. Conclusions Total and albumin-adjusted calcium measurement leads to a misclassification of calcium status. Moreover, accurate calcium state determination depends on blood pH levels, whose measurement requires the same pre-analytical restrictions as iCa measurement. We propose that iCa should instead become the reference method to determine the real calcium state.

Bile acid alterations in nonalcoholic fatty liver disease, obesity, insulin resistance and type 2 diabetes: what do the human studies tell?

PURPOSE OF REVIEW: The purpose of this review is to discuss the influence of obesity, insulin resistance, type 2 diabetes (T2D), and nonalcoholic fatty liver disease (NAFLD) on bile acid metabolism and to analyze whether these findings reinforce current beliefs about the role of bile acids in the pathophysiology of these diseases. RECENT FINDINGS: Discordant results on plasma bile acid alterations in NAFLD patients have been reported. Obesity, insulin resistance, and T2D, common comorbidities of NAFLD, have been associated with bile acid changes, but the individual bile acid species variations differ between studies (summarized in this review), perhaps because of clinicobiological differences between the studied patient populations and the heterogeneity of statistical analyses applied. SUMMARY: The regulatory role of bile acids in metabolic and cellular homeostasis renders bile acids attractive candidates as players in the pathophysiology of NAFLD. However, considering the complex relationship between NAFLD, obesity, insulin resistance and T2D, it is difficult to establish clear and independent associations between bile acid alterations and these individual diseases. Though bile acid alterations may not drive NAFLD progression, signaling pathways activated by bile acids remain potent therapeutic targets for its treatment. Further studies with appropriate matching or adjustment for potential confounding factors are necessary to determine which pathophysiological conditions drive the alterations in bile acid metabolism.

[An alarming health check-up: what a bloody plasma!] / Un bilan alarmant : un plasma sanglant !

A 35-year-old patient with a metabolic pathology was hospitalized for programmed fibroscopy under general anesthesia for investigation and management of portal hypertension. Following the operation, he showed signs of sepsis and was transferred to intensive care unit. Biological analyzes carried out and generated automaton alarms for certain parameters. A visual check of the appearance of the sample revealed an unusual color of plasma. Additional informations obtained from the clinical department did not provide any explanation for this coloration. Additional assays confirmed an overdose of vitamin B12 related to the treatment of his pathology and which is responsible for the interference observed. Hence the interest of checking the reaction curves in the event of suspected interference and, if necessary, of making dilutions in order to reduce the effects on the biological assays.

Understanding Neuropathy Features in the Context of Nitrous Oxide Abuse: A Combined Electrophysiological and Metabolic Approach.

BACKGROUND: The incidence of neurological complications associated with nitrous oxide (N2O) abuse, including N2O-induced myelopathy and neuropathy, has risen in the past decade. N2O-induced neuropathy often presents as a subacute axonal pathology; however, demyelinating patterns mimicking Guillain-Barré syndrome have also been observed. This study explores the metabolic pathophysiology of N2O-induced neuropathy, focusing on the alteration in metabolism to provide a deeper understanding of the biochemical pathways influencing the diverse electrophysiological patterns observed. METHODS: We conducted a combined metabolic and electrophysiological exploration of 35 patients who underwent electromyographic exams at our referral center over a three-year period for sensorimotor symptoms linked to recreational N2O use. We collected demographic, clinical, radiological, electrophysiological, and biological data. Patients were categorized into axonal or demyelinating groups based on their electrophysiological patterns, and metabolic parameters were compared. RESULTS: Our cohort predominantly exhibited a length-dependent sensorimotor axonal symmetrical neuropathy affecting the lower limbs. Among the patients, 40% met the demyelinating criteria, with four patients exhibiting conduction blocks. The demyelinating group had a significantly higher peripheral neuropathy disability (PND) score at diagnosis. Elevated homocysteine and methylmalonic acid (MMA) levels were noted in all patients, but these were lower in the demyelinating group. CONCLUSIONS: This study highlights the diverse electrophysiological manifestations of N2O-induced neuropathy and underscores the potential role of metabolic parameters as biomarkers to understand its pathophysiology. Lower hyperhomocysteinemia and MMA levels were observed in demyelinating patterns. In this study, we did not observe further improvement, but it is well-known that demyelinating features have a better prognosis related to the further remyelination. These findings contribute to a better understanding of N2O-related neuropathic damage and could guide future therapeutic interventions based on biochemical-neurophysiological stratifications.

Enhancing Differential Diagnosis Related to Oxidative Stress, Nitrous Oxide, and Nutrition by Rapid Plasma Homocysteine Measurement.

BACKGROUND: Historically used as a marker for inherited disorders, the current interest in plasma homocysteine measurement lies in its ability to provide valuable information about the metabolic and nutritional status of patients. Specifically, nitrous oxide (N2O) abuse can lead to functional vitamin B12 deficiency by oxidation and increase oxidative stress, resulting in elevated plasma homocysteine levels, which mimic neurological conditions such as Guillain-Barré syndrome. Rapid identification of hyperhomocysteinemia is crucial for timely intervention and avoiding costly, unnecessary treatments. OBJECTIVE: This study evaluates the performance of a rapid immunoassay technique (Snibe) compared to mass spectrometry (LC-MS/MS) for measuring plasma homocysteine levels in patients with nitrous oxide abuse and non-inherited caused of elevated homocysteine, aiming to enhance differential diagnosis related to oxidative stress. METHODS: 235 patients from Lille University Hospital were included. EDTA blood samples were collected and analyzed using both rapid immunoassay (Snibe) and LC-MS/MS. Neurological assessment was performed using the peripheral neuropathy disability (PND) score. RESULTS: Firstly, significant elevations in plasma homocysteine levels were observed in patients abusing nitrous oxide measured by LC-MS/MS. Secondly, the immunoassay provided rapid results, essential for early clinical decision-making, but tended to underestimate high values compared to LC-MS/MS. A good correlation was found between the methods for low and moderate values. CONCLUSION: The immunoassay tended to underestimate high-value samples compared to LC-MS/MS, which is a common problem with the competitive methodology. The rapid immunoassay technique is effective for initial screening and early intervention, aiding in the differential diagnosis of conditions related to oxidative stress. Therefore, it is recommended to use the CLIA method for initial screening and confirm with mass spectrometry if there are abnormal samples. Integrating both techniques can enhance diagnostic accuracy and improve patient outcomes.

[SFBC Working Group on sources of errors in laboratory medicine: objectives and key areas of work]. / Groupe de travail SFBC Sur les sources d'erreurs en biologie clinique: Objectifs et axes de travail.

Laboratory medicine plays a crucial role in patient care, contributing to approximately 70 % of clinical decisions. In collaboration with clinicians, laboratory medicine specialists perform analyses that are useful for diagnosis, screening and prevention. Laboratories are known for their efficiency, which is reached through a rigorous quality system. However, errors can occur, especially given the complexity of the total testing process. These errors may lead to severe consequences, such as incorrect diagnoses or delays in treatment. Errors can occur at every stage of the total testing process, those related to the pre-analytical phase being the most prevalent. To reduce medical errors related to laboratory processes, it is essential to provide training for medical and paramedical staff, optimize production automation, and leverage technological advancements. These considerations have led to the creation of a French Working Group on Sources of Errors in Laboratory Medicine, under the aegis of the French lean society of clinical chemistry and laboratory medicine (Société Française de Biologie Clinique - SFBC). The objectives of this working group are to produce an educational handbook on sources of errors in laboratory medicine, provide training for clinical chemists, and conducting applied research projects to better understand the mechanisms behind specific errors. Ultimately, the aim is to minimize errors and enhance the quality of laboratory tests.

Biomarkers for the diagnosis and monitoring of nitrous oxide intoxication: objectives and methodology of the SFBC Working Group.

The recreational use of nitrous oxide (N2O) is an emerging public health issue. Chronic N2O abuse may result in various clinical symptoms, encompassing neurological, psychiatric and cardiovascular outcomes. Despite the difficulties for the laboratory investigation of N2O intoxication, there is currently no guidelines in France to help both clinicians and biologists use appropriate biomarkers for the diagnosis and monitoring of patients with clinical symptoms potentially related to N2O intoxication. A multi-disciplinary Working Group, carried out under the auspices of the French Society of Clinical Biology (SFBC) and in collaboration with the French Societies of Emergency Medicine (SFMU), Analytical Toxicology (SFTA), Hemostasis and Thrombosis (SFTH), Vitamins and Biofactors (SFVB), and the French Federation of Neurology (FFN), was recently implemented to elaborate practical guidelines. The methodology of the Working Group is based on the critical analysis of the literature, and raising concerns and objectives are grouped into five working packages. The present manuscript primarily aims to expound upon the methodology and objectives of the ongoing SFBC Working Group on N2O.

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.

Targeted Metabolomics Analysis Suggests That Tacrolimus Alters Protection against Oxidative Stress.

Tacrolimus (FK506) is an immunosuppressant that is experiencing a continuous rise in usage worldwide. The related side effects are known to be globally dose-dependent. Despite numerous studies on FK506, the mechanisms underlying FK506 toxicity are still not well understood. It is therefore essential to explore the toxicity mediated by FK506. To accomplish this, we conducted a targeted metabolomic analysis using LC-MS on the plasma samples of patients undergoing FK506 treatment. The aim was to identify any associated altered metabolic pathway. Another anti-calcineurin immunosuppressive therapy, ciclosporin (CSA), was also studied. Increased plasma concentrations of pipecolic acid (PA) and sarcosine, along with a decrease in the glycine/sarcosine ratio and a tendency of increased plasma lysine was observed in patients under FK506 compared to control samples. Patients under CSA do not show an increase in plasma PA compared to the control samples, which does not support a metabolic link between the calcineurin and PA. The metabolomics changes observed in patients under FK506 highlight a possible link between FK506 and the action of an enzyme involved in both PA and sarcosine catabolism and oxidative pathway, the Peroxisomal sarcosine oxidase (PIPOX). Moreover, PA could be investigated as a potential biomarker of early nephrotoxicity in the follow-up of patients under FK506.