Les intoxications graves au monoxyde de carbone (CO) avec atteinte neurologique, étude de 19 cas

Postmortem concentrations for total blood carbon monoxide (TBCO) as a novel biomarker for carbon monoxide (CO) poisonings

Total blood carbon monoxide (TBCO) showed promising results in improving accuracy of CO determinations in blood and presenting better stability to different storage conditions. Therefore, it was proposed as an alternative biomarker to carboxyhemoglobin (COHb) for CO poisoning diagnosis. However, given that current interpretation reference values exist for COHb only, it is difficult to implement TBCO analysis in routine. Therefore, we aimed at determining TBCO reference values for postmortem CO poisoning cases. A previously validated method for TBCO analysis via gas chromatography-mass spectrometry was applied to cardiac, peripheral, cranial and spleen blood samples collected from 92 autopsies. Autopsy cases included 21 non-CO-related and 71 CO-related cases with varying postmortem intervals (PMIs). Statistical analyses were performed using statistical software R Studio. When comparing lower to higher PMIs for non-CO-related cases, no significant differences were found, which suggests that CO formation or degradation at low PMIs does not occur. Spleen blood showed potential as an alternative matrix to CO determinations in cases with sample availability issues but needs to be evaluated for CO-positive cases. Results for cardiac blood in CO-related autopsies showed a positive correlation between COHb and TBCO values (R = 0.78). This value is lower than what is found in the literature, suggesting that even though COHb and TBCO are correlated, a potential underestimation of the true CO exposure might occur if only COHb values are taken into consideration. Samples were divided into CO exposure groups based on COHb concentrations, and with the data obtained, classification into the following TBCO concentration groups is proposed: no significant CO exposure case <6 µmol/mL, medium CO exposure case 6-20 µmol/mL and high CO exposure case >20 µmol/mL. Even if a higher number of samples in each group would enable to increase the confidence, these results are very promising and highlight the importance of TBCO measurement.

Carbon monoxide analysis method in human blood by Airtight Gas Syringe - Gas Chromatography - Mass Spectrometry (AGS-GC-MS): Relevance for postmortem poisoning diagnosis

Carbon monoxide is one of the most abundant toxic air pollutants. Symptoms of a CO intoxication are non-specific, leading to a high number of misdiagnosed CO poisoning cases that are missing in the disease statistics. The chemical nature of the molecule makes it difficult to detect for long periods and at low levels, thus requiring a very accurate and sensitive method. Current methods capable of accurate and sensitive analyses are available, however an inconsistency between results and symptoms are frequently reported. Therefore, an improved method for the analysis of carbon monoxide in blood and in the headspace (HS) of the sampling tube with the use of Airtight Gas Syringe - Gas Chromatography - Mass Spectrometry (AGS-GC-MS) is hereby presented and validated, for CO concentrations in a range of 10-200 nmol/mL HS (2-40 μmol/mL blood). Analytical LOQ is found at 0.9 nmol/mL HS (0.18 μmol/mL blood) and LOD at 0.1 nmol/mL gas. Application to intoxicated samples from autopsies and comparison to previously published methods show that this method is more appropriate, since performed under fully controlled conditions. Results show higher CO concentrations compared to previous approaches, indicating that results might have been underestimating the true blood CO burden. Therefore, this approach has the potential to help reduce the misdiagnosed cases and the gap between measurement and diagnosis of CO poisonings.