Methemoglobinemia caused by sodium nitrite overdose
===================================================

* Dana Saleh
* Scott Lucyk
* Eric McGillis

A 20-year-old man who was comatose and centrally cyanotic arrived at the emergency department 1 hour after ingesting 21 g of sodium nitrite that was purchased online as part of a “suicide kit” found by the patient’s family; it included a measurement scale, a flask for dissolution in water and antiemetics (metoclopramide and famotidine). The patient’s heart rate was 60 beats/min, systolic blood pressure was 80 mm Hg, body temperature was 36.5°C; and oxygen saturation as measured by pulse oximetry (SpO2) was 85%, despite oxygenation by way of a supraglottic airway with a fraction of inspired oxygen (FiO2) of 1. We observed conjunctival, nail bed and palmar pallor. Arterial blood was dark and chocolate coloured (Figure 1A). We intubated the patient after initiating fluid resuscitation and vasopressor support. We performed decontamination by gastric lavage and activated charcoal (1 g/kg) by way of an orogastric tube. We administered empiric methylene blue (1 mg/kg) intravenously. The patient’s methemoglobin level was later reported as greater than 29%, the upper limit reporting cut-off for our laboratory. The patient clinically improved within hours after receiving a total of 4 mg/kg of methylene blue; hemolysis was not noted. He was alert and oriented at discharge from the intensive care unit 2 days later.

![Figure 1:](http://www.cmaj.ca/https://www.cmaj.ca/content/cmaj/194/30/E1066/F1.medium.gif)

[Figure 1:](http://www.cmaj.ca/content/194/30/E1066/F1)

Figure 1: 
(A) Arterial blood gas sample from a 20-year-old man with methemoglobinemia showing dark, chocolate-coloured blood and (B) from a healthy patient for comparison.

Sodium nitrite is readily available online as it is used in meat curing and as a laboratory reagent. It oxidizes the ferrous iron in hemoglobin to ferric iron, which cannot bind oxygen. This impairs oxygen transport to tissues.1 The lethal dose of sodium nitrite is between 0.7 and 6 g. Ingestion should be suspected in comatose patients with chocolate-coloured blood and hypoxemia that does not respond to supplemental oxygen; pulse oximeters are calibrated to the specific wavelengths of oxyhemoglobin and deoxyhemoglobin only.2,3

A recent rise in intentional ingestions and deaths from sodium nitrite poisoning has been reported in multiple countries, including Canada.2,4,5 This has been attributed to websites that promote its use for suicide and sell suicide kits.2,5 The United Kingdom now requires that sodium nitrite suppliers refuse “suspicious transactions” when people pay in cash or appear nervous.2,6 Enhanced employee training and legal scrutiny are needed in Canada to restrict the sale of sodium nitrite and ban dangerous websites.

Clinical images are chosen because they are particularly intriguing, classic or dramatic. Submissions of clear, appropriately labelled high-resolution images must be accompanied by a figure caption. A brief explanation (300 words maximum) of the educational importance of the images with minimal references is required. The patient’s written consent for publication must be obtained before submission.

## Footnotes

*   **Competing interests:** None declared.

*   This article has been peer reviewed.

*   The authors have obtained patient consent.

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY-NC-ND 4.0) licence, which permits use, distribution and reproduction in any medium, provided that the original publication is properly cited, the use is noncommercial (i.e., research or educational use), and no modifications or adaptations are made. See: [https://creativecommons.org/licenses/by-nc-nd/4.0/](https://creativecommons.org/licenses/by-nc-nd/4.0/)

## References

1.  Wright RO, Lewander WJ, Woolf AD. Methemoglobinemia: etiology, pharmacology, and clinical management. Ann Emerg Med 1999;34:646–56.
    
    [CrossRef](http://www.cmaj.ca/lookup/external-ref?access_num=10.1016/S0196-0644(99)70167-8&link_type=DOI) 
    
    [PubMed](http://www.cmaj.ca/lookup/external-ref?access_num=10533013&link_type=MED&atom=%2Fcmaj%2F194%2F30%2FE1066.atom) 
    
    [Web of Science](http://www.cmaj.ca/lookup/external-ref?access_num=000083384200010&link_type=ISI) 

2.  McCann SD, Tweet MS, Wahl MS. Rising incidence and high mortality in intentional sodium nitrite exposures reported to US poison centers. Clin Toxicol (Phila) 2021;59:1264–9.
    
    

3.  Nelson L, Howland M, Lewin N, et al. Methemoglobin inducers. In: Goldfrank’s toxicologic emergencies. 11th ed. New York: McGraw Hill Education; 2019: 1703–12.
    
    

4.  Hickey TBM, MacNeil JA, Hansmeyer C, et al. Fatal methemoglobinemia: a case series highlighting a new trend in intentional sodium nitrite or sodium nitrate ingestion as a method of suicide. Forensic Sci Int 2021;326:110907.
    
    

5.  Durão C, Pedrosa F, Dinis-Oliveira RJ. A fatal case by a suicide kit containing sodium nitrite ordered on the internet. J Forensic Leg Med 2020;73:101989.
    
    

6.  You can make a difference: sell chemical products responsibly! London (UK): Home Office; 2017. Available: [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment\_data/file/696156/Selling\_chemical\_products\_responsibly\_leaflet.pdf](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment\_data/file/696156/Selling\_chemical_products_responsibly_leaflet.pdf) (accessed 2022 Apr. 16).