Poisonings, especially where intentional, invariably involve access to the particular agent(s) as well as knowledge of the expected toxicity. Over the last 20 years, the internet has provided individuals with a source of information in relation to this, including forums for discussion especially in relation to means of suicide. Where poisons are involved, there have been trends and evolutions in the manner and types, including carbon monoxide, commercial gases (e.g. helium, nitrogen, argon) and chemicals producing hydrogen cyanide or hydrogen sulphide [1]. Aside from carbon monoxide, these present analytical and interpretative challenges to toxicologists. Recently this has been exacerbated by the increasing involvement of sodium nitrite (NaNO2), sodium nitrate (NaNO3) and the potential return of sodium azide (NaN3) [2,3]. Sodium nitrite is used as a food preservative and as a precursor of many dyes; it is also used as an antidote to cyanide poisoning. Sodium nitrate is used in various industries, as a plant fertilizer and in the production of explosives. Sodium nitrite is the more acutely toxic of the two and causes methaemoglobinemia, whereas sodium nitrate is converted in the stomach to nitric oxide which causes vasodilation and hypotension; a small amount of nitrite is also produced [4]. The analytical requirement is to assess NO2- and NO3- ions, including interconversion considerations [5]. As these are not naturally occurring in the body in high concentrations, the mere presence at a high concentration can be useful to indicate use which provides analytical options including presumptive testing [6]. As MetHb is not always elevated in sodium nitrite cases (and not associated with nitrate), this cannot be used as an indicator of use. Various cases of sodium nitrate/nitrate poisoning will be presented.
Literature:
[1] Schultz BV, Rolley A, Doan TN, Isoardi K. Epidemiology of out-of-hospital cardiac arrests that occur secondary to chemical asphyxiants: A retrospective series. Resuscitation. 2022, 175:113-119
[2] Stephenson L, Wills S, van den Heuvel C, Humphries M, Byard RW. Increasing use of sodium nitrite in suicides-an emerging trend. Forensic Sci Med Pathol. 2022, 18(3):311-318
[3] Le Blanc-Louvry I, Laburthe-Tolra P, Massol V, Papin F, Goullé JP, Lachatre G, Gaulier JM, Proust B. Suicidal sodium azide intoxication: An analytical challenge based on a rare case. Forensic Sci Int. 2012, 221(1-3):e17-20
[4] Hikin LJ, Ho J, Morley SR, Ahluwalia A, Smith PR. Sodium nitrite poisoning: A series of 20 fatalities in which post-mortem blood nitrite and nitrate concentrations are reported. Forensic Sci Int. 2023, 345:111610
[5] Kim M, Kim S, Yang W, Sim J. Determination of nitrite and nitrate in postmortem whole blood samples of 10 sodium nitrite poisoning cases: The importance of nitrate in determining nitrite poisoning. Forensic Sci Int. 2022, 335:111279
[6] Presumptive identification of nitrite by Griess reagent test strips-Case reports of fatal poisoning with sodium nitrite. Zhang M, Truver MT, Hoyer JL, Chronister CW, Goldberger BA. J Anal Toxicol. 2023, 47(8):746-749