Special Report from the CDC: Suicide rates, sodium nitrite-related suicides, and online content, United States.

BACKGROUND: In 2022, suicide ranked as the 11th leading cause of death in the United States with 49,513 deaths. Provisional mortality data from 2022 indicate a 2.8% increase in the number of suicides compared to 2021. This paper examines overall suicide trends, sodium nitrite ingestion as an emerging suicide method, and the role that online forums play in sharing information about suicide methods (including sodium nitrite ingestion). METHODS: Suicides were identified from CDC's National Vital Statistics System (2018-July 2023 provisional) multiple cause-of-death mortality files using International Classification of Diseases (ICD), Tenth Revision underlying cause-of-death codes U03, X60-X84, and Y87.0 and T code T50.6 (antidotes and chelating agents). Google search popularity metrics were captured from January 2019 to January 2023. Case reports of sodium nitrite related suicide and suicide attempts (through February 2024) were identified in the medical and forensic literature. RESULTS: At least 768 suicides involving antidotes and chelating agents (including sodium nitrite) occurred between 2018 and July 2023, set in the context of 268,972 total suicides during that period. Overall, suicides involving antidotes and chelating agents (including sodium nitrite) represent <1% of all suicides, however, numbers are rising. CONCLUSIONS: Suicide methods are known to change over time. These changes can be influenced by, among other factors, online forums and means accessibility, such as internet purchase availability. CDC remains committed to prevention through comprehensive public health strategies that protect individuals, families, and communities. PRACTICAL APPLICATIONS: States and community partners might consider leveraging physicians, emergency responders, and other appropriate crisis response groups to disseminate information on sodium nitrite self-poisoning and its antidote, methylene blue. Efforts should be part of a comprehensive public health approach to suicide prevention.

Fatal methemoglobinemia: A case series highlighting a new trend in intentional sodium nitrite or sodium nitrate ingestion as a method of suicide.

Unintentional exposure to nitrite- or nitrate-containing toxic salts is a recognized cause of acquired methemoglobinemia (MetHb). This systemic alteration of the blood can be fatal if not recognized and treated promptly. The intentional ingestion of sodium nitrite (NaNO2) or sodium nitrate (NaNO3), causing MetHb, is an uncommon and recently identified method of suicide, with the first reported case in the literature occurring in New Zealand in 2010. In this case series we present 28 cases of sudden death of individuals with evidence of MetHb and/or toxic salt ingestion, occurring in the Province of Ontario, Canada, between the years 1980 and 2020, inclusive. Of the 28 deaths in our case series, 25 showed evidence of intentional ingestion of sodium nitrite or sodium nitrate salts. Our year-over-year data demonstrated this is an increasingly used method of suicide in our provincial population, with the majority of cases occurring in the final two years of our study. Postmortem detection of MetHb is typically established via screening techniques such as scene evidence suggesting fatal consumption of a toxic salt in addition to the characteristic grey-purple lividity observed upon the body. The diagnosis can be established via postmortem blood testing demonstrating elevated methemoglobin saturation. Additionally, we have confirmed that postmortem MRI in cases of MetHb demonstrates a T1-bright (hyperintense) signal of the blood; both within intracardiac blood on chest MRIs and postmortem blood samples in tubes.

Direct and specific analysis of nitrite and nitrate in biological and non-biological samples by capillary ion analysis for the rapid identification of fatal intoxications with sodium nitrite.

In recent years, a significant increase of reports about suicidal cases due to intentional sodium nitrite intake has been described. In the forensic pathology context, the strategy to approach intoxication cases by sodium nitrite, without any preliminary information or hint, is not straightforward. Indeed, in a number of cases the lack of crime scene data and/or specific pathological signs makes difficult the identification of nitrite poisoning. Moreover, the analytical determination of nitrite in blood is challenging, due to its rapid oxidization to nitrate by hemoglobin. Although several methods have been proposed for the clinical analysis of nitrate and/or nitrite in biological samples, none of these is specifically focused on the determination of these ions in cadaveric samples. Consequently, the diagnosis of nitrite fatal intoxication is still based on methemoglobin analysis. The present paper reports the optimization and validation of an analytical method of capillary ion analysis (CIA) with UV detection, for the determination of nitrite and nitrate in biological fluids and its application to two authentic cases of death by nitrite intake. The analyses were carried out in a bare fused-silica capillary (75 µm inner diameter) using 100 mM sodium tetraborate (pH 9.24) as background electrolyte and applying a voltage of - 15 kV between the capillary ends. The detection was obtained by direct UV absorption recorded at 214 nm wavelength. Bromide was used as the internal standard. Linearity was established in the range of 0.25-5 mmol/L). Reproducibility (intraday and day-to-day) was characterized by relative standard deviations (RSDs) 14.7% for peak areas. The method was applied to the determination of nitrite and nitrate in two real forensic cases, where high concentrations of nitrate were found in cadaveric blood samples (6.5 and 4.4 mmol/L, respectively). Nitrite was found only in trace amounts, due to the instability of this ion in cadaveric blood where it is oxidized to nitrate. The present method represents a new tool for the direct and rapid determination of nitrite and nitrate in cases of forensic interest, and thus offers a diagnostic tool more sensitive and precise than the need methemoglobin analysis.

Sodium nitrite detection in costal cartilage and vitreous humor - Case report of fatal poisoning with sodium nitrite.

Medico-legal case reports very rarely describe sodium nitrite poisonings, but when they do most often they describe fatal suicide attempts. The case report presents a suicidal attempt with sodium nitrite of unknown provenance and the first attempt to detect nitrite ions in costal cartilage and vitreous humor samples. In February 2020, the corpse of a 23-year-old man was revealed in a student apartment. According to the prosecutor's office, the deceased had an incomplete IT (Information Technology) degree. The onsite inspection revealed the body on the bathroom floor, an opened container with sodium nitrite III in the bathroom cabinet, and a farewell letter in the apartment. The autopsy showed the hypoxia symptoms. The blood and urine of the deceased showed no trace of ethyl alcohol or psychoactive substances. Analyses showed the presence of nitrite ions in the blood (0.2 µg/ml) and urine (24.6 µg/ml) of the deceased. Additional analyses revealed nitrites presence in the gastric contents (2200 µg/ml), liver tissue (0.3 µg/g), kidney tissue (3.6 µg/g) and, for the first time, in costal cartilage (3.4 µg/g) and vitreous humor (57.7 µg/ml). The autopsy concluded that the cause of death was an acute cardio-respiratory failure in the course of suicidal sodium nitrite poisoning. The presented case indicates the need for collecting a wide range of samples for toxicological analyses. It also proves that both costal cartilage and vitreous humor may serve as an alternative forensic material in sodium nitrite poisonings.

Fatal methemoglobinemia in three suicidal sodium nitrite poisonings.

Nitrites are chemicals that are abundant in the environment, widely used as preservatives for meat, and in pharmaceuticals. Volatile products containing nitrites have been used recreationally for the euphoric effect associated with mild hypoxia. Dietary exposure to small amounts is considered harmless. Deaths by ingestion of nitrite salts are not common, but accidental exposure and as suicidal and homicidal agents have been noted. Death is a consequence of oxidation of hemoglobin ferrous (Fe+2 ) iron (Hb) to the ferric (Fe+3 ) form (methemoglobin, MetHb), causing a reduction in the oxygen-carrying capacity of the blood. We report three cases of ingestion of sodium nitrite in two college students (one mildly decomposed) and one adult in early middle age. All of the decedents in these cases developed fatal methemoglobinemia. Sodium nitrite in chemical form was found near the bodies. MetHb was detected in the postmortem blood of each decedent. The MetHb concentrations in the two decedents with a short postmortem interval were less than MetHb concentrations reported in the current literature. The MetHb concentrations reported in the mildly decomposed person were greater than for the other two, but still less than the concentration previously considered lethal. The data from these cases indicate that levels of MetHb can vary widely in fatal cases, and should not be used as the sole criterion for determination of a death caused by sodium nitrite. Following a discussion of the cases, there is a review of the pathophysiology of MetHb production and a current literature review.

A fatal case by a suicide kit containing sodium nitrite ordered on the internet.

Fatal sodium nitrite poisonings are rare in the forensic context. The present work describes a first fatal case of sodium nitrite contained in a suicide kit that the victim acquired over the internet. The results of the autopsy showed general signs of asphyxia, such as intense cyanosis of the extremities, brown-gray-blue-red livor mortis, and some Tardieu petechiae in addition to intense visceral congestion. It is clear that forensic experts must be aware of the proliferation of this market and the risks of improper selling of these substances through suicide support networks available on the internet. The lack of knowledge of this reality may become unidentifiable, when toxicological analysis contemplates only the most classical and frequent substances involved in poisoning and reinforce the importance of a careful analysis of the death scene.

[Autointoxication with 'suicide powder']. / Auto-intoxicatie met 'zelfmoordpoeder'.

We present two patients who were treated for an intentional overdose of sodium nitrite. When ingested sodium nitrite leads to severe methaemoglobinaemia, resulting in severe hypoxia (as methaemoglobin does not transport oxygen), vasodilation and hypotension. Symptoms include cyanosis, headache, nausea, convulsions, coma and death. When measured by pulse oximetry, patients with a sodium nitrite intoxication and severe methaemoglobinaemia generally have an oxygen saturation of around 85%. This value is unreliable as the oxygen content of the blood is often extremely low - this can be confirmed by arterial blood gas analysis. Treatment of sodium nitrite intoxication consists of intravenous administration of methylthioninium chloride 1-2 mg/kg. Methylthioninium chloride converts the methaemoglobin back to haemoglobin. Due to the pharmacokinetics of methylthioninium chloride and sodium nitrite, a rebound effect is not to be expected. The only contra-indication for methylthioninium chloride is glucose-6-phosphate dehydrogenase deficiency, which is extremely rare in the Netherlands.

Sodium nitrite food poisoning in one family.

Sodium nitrite is used as a coloring agent or preservative in food, as well as an antimicrobial agent in meat and fish and some cheeses. In high amounts it can be toxic for humans, causing methemoglobinemia. This is an unusual and potentially fatal condition in which hemoglobin is oxidized to methemoglobin (MHb), reducing the amount of oxygen that is released from hemoglobin, similar to carbon monoxide poisoning. MHb levels of 70% are generally lethal, but the existence of underlying anemia, acidosis, respiratory compromise, and cardiac disease may exacerbate the toxicity of MHb. We present a case of poisoning with sodium nitrite in three family members after eating homemade sausages given to them by their neighbor who was a butcher. According to the findings of the veterinary inspectorate in charge of food control in this case, the concentration of sodium nitrite in the homemade sausages was about 3.5 g per 1 kg of meat, almost 30 times higher than allowed according to legislation. In this case report, a 70-year-old man died about 7 h after consuming the meal, while two women, 53 and 67 years of age, respectively, were admitted to a toxicology clinic the following day due to food poisoning, with the maximum concentration of MHb in blood of 33.7 and 20.4%, respectively. They were discharged 3 days later. The autopsy of the deceased man showed sodium nitrite poisoning with a relatively low concentration of MHb in his blood - 9.87%. Death was attributed to the exacerbation of hypertensive and ischemic heart disease, resulting from accidental sodium nitrite poisoning. The presented cases illustrate the necessity of close cooperation between the authorities, medical staff, veterinary inspectorate, and forensic pathologists in determining the source of poisoning, the cause of death of the victim, and preventing the outbreak of poisoning among a greater number of consumers.

Difference of the clinical course and outcome between dapsone-induced methemoglobinemia and other toxic-agent-induced methemoglobinemia.

CONTEXT: Acquired methemoglobinemia is a potentially fatal condition that leads to tissue hypoxia. Although the clinical features of methemoglobinemia depend on the methemoglobin levels, the clinical course would differ depending on the causative agents. OBJECTIVE: We attempted to clarify this issue by comparing the clinical course of methemoglobinemia caused by dapsone and that caused by other toxic agents. MATERIALS AND METHODS: A retrospective case-control study was performed. All patients with methemoglobinemia and who were admitted to the emergency department (ED) of our hospital from 1 January 2002 to 31 December 2014 were included. RESULTS: Of the 34 patients with methemoglobinemia, 15 ingested dapsone (14 with acute overdose and one with chronic therapeutic use) and 19 had been exposed to other toxic agents, such as sodium nitrites, indoxacarb, primaquine, and lidocaine. The clinical characteristics and the course of dapsone-induced and other toxic-agent-induced methemoglobinemia were compared. There was no significant difference in clinical presentation and methemoglobin level (38.5% vs. 35.0%, p = 0.456) upon their ED arrival between the two groups. However, the methemoglobin level after use of methylene blue and the total dose of methylene blue were higher in patients with dapsone-induced methemoglobinemia than in those with other agent-induced methemoglobinemia (11.9% vs. 1.7%, p = 0.001, 455 mg vs. 144 mg, p = 0.006). The majority of dapsone-induced methemoglobinemia (93.3%) required more than 72 h for normalization of the methemoglobin level, despite the use of methylene blue. Five of the study patients died due to multiorgan failure, and all of whom were inpatients with dapsone-induced methemoglobinemia. CONCLUSION: The clinical course of dapsone-induced methemoglobinemia was worse than that of other toxic-agent-induced methemoglobinemia despite no significant difference in their initial clinical presentation. Continuous treatment with serial monitoring of the serum methemoglobin is necessary for patients with dapsone-induced methemoglobinemia.

Boletus edulis Nitrite Reductase Reduces Nitrite Content of Pickles and Mitigates Intoxication in Nitrite-intoxicated Mice.

Pickles are popular in China and exhibits health-promoting effects. However, nitrite produced during fermentation adversely affects health due to formation of methemoglobin and conversion to carcinogenic nitrosamine. Fruiting bodies of the mushroom Boletus edulis were capable of inhibiting nitrite production during pickle fermentation. A 90-kDa nitrite reductase (NiR), demonstrating peptide sequence homology to fungal nitrite reductase, was isolated from B. edulis fruiting bodies. The optimum temperature and pH of the enzyme was 45 °C and 6.8, respectively. B. edulis NiR was capable of prolonging the lifespan of nitrite-intoxicated mice, indicating that it had the action of an antidote. The enzyme could also eliminate nitrite from blood after intragastric administration of sodium nitrite, and after packaging into capsule, this nitrite-eliminating activity could persist for at least 120 minutes thus avoiding immediate gastric degradation. B. edulis NiR represents the first nitrite reductase purified from mushrooms and may facilitate subsequent applications.

Early administration of isosorbide dinitrate improves survival of cyanide-poisoned rabbits.

CONTEXT: More effective, rapidly delivered, safer antidotes are needed for cyanide poisoning. Previous study has demonstrated a beneficial effect of isosorbide dinitrate on the survival of cyanide-poisoned mice. OBJECTIVE: To evaluate the effectiveness of isosorbide dinitrate compared with that of sodium nitrite in cyanide poisoning. MATERIALS AND METHODS: A comparative animal study was performed using 18 rabbits, randomized into 3 study groups. Animals were poisoned intravenously with potassium cyanide (1 mg/kg). The first group was not given any further treatment. The second and third groups were treated intravenously 1 min after poisoning with sodium nitrite (6 mg/kg) and isosorbide dinitrate (50 µg/kg), respectively. The primary outcome was short-term survival of up to 30 min. Secondary outcomes included time to death, a clinical score, mean blood pressure, pulse, blood pH, and lactate and methemoglobin levels. RESULTS: Rabbits treated with isosorbide dinitrate or sodium nitrite survived while only one untreated rabbit survived. Median time to death of the 5 poisoned and untreated animals was 10 min. All the animals collapsed soon after poisoning, exhibiting rapidly disturbed vital signs and developed lactic metabolic acidosis; average peak blood lactate levels were 15.5-19.1 mmol/L at 10 min after poisoning. The treated animals improved gradually with practically full recovery of the clinical scores, vital signs, and blood gas levels. Sodium nitrite administration raised methemoglobin to an average peak of 7.9%, while isosorbide dinitrate did not change methemoglobin levels. CONCLUSION: Early administration of isosorbide dinitrate improved the short-term survival of cyanide-poisoned rabbits. Isosorbide dinitrate shows potential as an antidote for cyanide poisoning and may exert its effect using a nitric-oxide-dependent mechanism.

Life-threatening methemoglobinemia after unintentional ingestion of antifreeze admixtures containing sodium nitrite in the construction sites.

CONTEXT: Construction workers are exposed to a wide variety of health hazards such as poisoning at the construction sites. Various forms of poisoning incidents in construction workers have been reported. However, studies on methemoglobinemia caused by unintentional ingestion of antifreeze admixtures containing sodium nitrite at the construction sites have not been reported yet. OBJECTIVE: The aim of this study was to evaluate life-threatening methemoglobinemia after unintentional ingestion of antifreeze admixtures containing sodium nitrite at the construction sites and describe similar incidents involving ingestion of antifreeze admixtures in Korea. MATERIALS AND METHODS: Retrospective observational case series study on patients with methemoglobinemia after unintentional ingestion of antifreeze admixtures containing sodium nitrite admitted to the emergency department (ED) from January 1, 2010 to December 31, 2012 and cases reported to the Korea Occupational Safety and Health Agency (KOSHA) was performed. Results. Six victims were admitted to our ED. They had methemoglobin levels ranging from 32.4% to 71.5% and all of them recovered after receiving one (2 mg/kg) or two doses infusion of methylene blue. From the data of the KOSHA, six incidents that caused 27 victims were identified. Of 27 victims, five were included in the ED cases. For all incidents, antifreeze admixtures were not contained in their original containers and all new containers did not have a new label. All workers mistook antifreeze admixtures for water. Among the 28 victims included in this study, four died. CONCLUSION: Unintentional ingestion of antifreeze admixtures containing sodium nitrite at the construction sites can cause life-threatening methemoglobinemia. There is a need to store and label potentially hazardous materials properly to avoid unintentional ingestion at the construction sites.

Investigation of in vivo toxicity of hydroxylamine sulfate and the efficiency of intoxication treatment by α-tocopherol acetate and methylene blue.

OBJECTIVES: Investigation of hydroxylamine sulfate toxicity mechanism in vivo and estimation of α-tocopherol acetate and methylene blue efficiency in poisoning treatments. METHODS: In vivo experiments were conducted on 102 Wistar Han rats. The experiments investigated the hematotoxic and oxidative stress effects of hydroxylamine sulfate in acute and subacute toxicity treatment of animals. Electron Spin Resonance was used for quantitative determination of blood and liver tissue parameters alterations after intoxication. The osmotic fragility of erythrocytes, lipid peroxidation intensity and level of SH-groups in liver of rats were determined by established biochemical assays. RESULTS: Hydroxylamine sulfate cause an acute hematotoxicity and oxidative stress in vivo as demonstrated by the appearance of free oxidized iron in blood, reduced glutathione content and increased lipid peroxidation in liver. The experimental studies showed the formation of Hb-NO, MetHb in erythrocytes and as well of stable complex of reduced iron (Fe(2+)) with hydroxylamine sulfate. Methylene blue treatment does not reduce the Hb-NO or MetHb levels in intoxicated animals while administration of α-tocopherol acetate reduces substantially lipid peroxidation. CONCLUSIONS: Oxidative stress is a key mechanism of acute hematotoxicity caused by hydroxylamine sulfate. Methylene blue is not suitable antidote in case of hydroxylamine intoxication.

[Myocardial electrogenesis in laboratory rats under conditions of acute nitrite intoxication].

In anesthetized male rats the arterial blood pressure in femoral artery and electrocardiogram in standard leads were recorded uninterruptedly for 1-1.5 h under conditions of acute nitrite intoxication produced by a subcutaneous injection of water solution of sodium nitrite (donor of nitric oxide) at concentrations of 10, 30, and 50 mg/kg body mass. Results of the study have shown dose-dependent changes of arterial pressure as well as of time and amplitude characteristics of electrocardiogram under effect of NaNO2. At the threshold hypoxic dose, an increase of amplitude of R and S waves was observed by the 30-45th min, while at the maximal NaNO2 dose, amplitude of all waves rose by the 15th min of intoxication. High nitric doses often caused an increase of the ST segment above the isoelectric line and a rise of the amplitude of the T wave, on which a notch appeared in some cases. The change of the ECG time parameters was expressed in the dose-dependent development of bradycardia for the first 4-7 min; its level correlated with the progressively decreasing arterial pressure in the beginning (the 2-4th min) of nitrite intoxication. Variation analysis of heart rate spectral characteristics by Baevskii has revealed a rise of the total spectral power of pulse oscillations. Under effect of nitrite, in the spectrum of cardiointervals, quent recovery of the normal ECG spectrum in the end of the experimental period. The maximal nitrite dose produced more pronounced shifts of the heart rate spectrum towards the LF and VLF diapasons that were not restored for 1 h of experiment. Transitory processes of readjustment of the cardiac rhythm had discrete character. The nitrite dose of 50 mg/kg body mass increased the RR-interval after 4-7 min with amplitude steps of 3-5 imp/s and the time constant of 20-40 s. The revealed ECG changes had the reflex (enhancement of parasympathetic tonus) and metabolic (the hypoxic and histotoxic damage of myocardium) nature.

[Severe methemoglobinaemia following sodium nitrite ingestion]. / Schwere Methämoglobinämie--Diagnostik, Therapie und Pathophysiologie am Beispiel eines Falles.

We report the case of a patient suffering from a severe methemoglobinaemia following accidental sodium nitrite intoxication, a substance frequently used as a preservation agent for animal feed. On base of this case report, pathophysiology, clinical symptoms, diagnostical and therapeutical options with methylene blue (1-2 mg/kg of body weight) are discussed. Recently, pulse oximeters capable to measure 4 different hemoglobins have been introduced. These may be helpful for diagnosis especially in the prehospital setting.