B-300 Importance of Clinical Chemistry and Metabolism Parameters for the Management of Patient With Chronic Nitrous Oxide Intoxication

Abstract Background Recreational use of nitrous oxide (N2O) has increased exponentially recently and leads to severe neurological disorders. A recent report from European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) showed that the recreational use of N2O is a growing and became a major health issue in Europe. For biological monitoring, serum or urine N2O assays are not routinely performed because they do not allow to ensure a real exposure due to the very short half-life of this gas in the body. Functional disorders of vitamin B12 metabolism, characteristic of N2O intoxication, could be explored by two markers: homocysteine (Hcys) and methylmalonic acid (MMA). We experimented here, management of N2O abused patient thanks to functional markers as Hcys and MMA. Methods We collected clinical and biological data from patients with declared chronic N2O consumption. The patients treated in Lille University Hospital between september 2020 and december 2022 were included in the study. The clinical evaluation included the Peripheral Neuropathy Disability (PND) score which was evaluated by a neurologist. Results Our study included 202 patients with N2O abused, Globally, plasma functional markers concentration are increased in case on consumption (Table). We noticed that clinical sign of patient evaluated by PND score correlated with plasma MMA (P-value < 0.01) but not with plasma hcys (P-value > 0.05). Conclusion The use of functional markers as Hcys and MMA makes it possible to follow the metabolic disturbances of nitrous oxide abused patients and evaluated clinical outcomes. However, in view of the thrombotic risk related to high Hcys and the need to quickly adapt the nutritional treatment, biological and in particular Hcys, current reporting time is not satisfactory using mass spectrometry method. Hence, our medical laboratory aim to improve our method evaluating immunoassay techniques in order to reduce the turnaround time while maintaining analytical reliability.