Nitrate Poisoning: What You Need to Know

Nitrate poisoning might not be on your radar unless you've encountered it or heard about it from a colleague. Although not the most common emergency, it can be dramatic, with patients showing severe cyanosis that can make rescuers think the situation is futile. This isnt always the case however as there is an effective and accessible reversal agent. So, do you know what methemoglobinemia is? Do you know how to manage it? And do you know how to protect yourself as a rescuer? Let's dive in so you’re prepared if you ever encounter nitrate poisoning.

Why it’s relevant:

• Increased reports of nitrate poisoning cases.

• Media exposure about suicide kits containing sodium nitrite.

• Potential hazards to rescuers in cases of chemical suicides.

What is Sodium Nitrate?

Sources and Uses:

• Nitrates are essential for life, found naturally in our diet.

• Commonly used as preservatives in food and in products like instant cold packs.

• Used in cardiovascular medications and as an antidote for cyanide poisoning.

Difference Between Nitrates and Nitrites:

• Nitrites are more reactive and toxic. Nitrates are converted into nitrites in the body.

• For our purposes, we can consider them similar, but nitrites are more dangerous and often present as a volatile or vapour.

Epidemiology

• Exact numbers of nitrate poisoning cases are hard to find.

• Significant increase in the use of sodium nitrite for suicides globally.

• Reports from the US, Canada, South Korea, Japan, Australia, and Europe.

Pathology: How Nitrate Poisoning Works

Mechanism:

• Nitrates convert to nitrites in the GI tract, entering the bloodstream.

• They oxidize haemoglobin, converting it from Fe2+ to Fe3+, creating methaemoglobin, which can’t bind with and carry oxygen.

• This leads to cellular hypoxia, as blood can’t transport oxygen to tissues.

• Methemoglobin causes normal hemoglobin to hold onto oxygen more tightly, worsening hypoxia.

Symptoms:

• Anxiety, headache, lightheadedness, and tachycardia at 30-50% methemoglobin levels.

• Fatigue, confusion, dizziness, seizures, and potentially fatal outcomes at higher levels.

• Cyanosis (bluish skin) is a key indicator, with blood appearing chocolate-colored.

Scene Safety for Rescuers

• Risk of topical absorption or inhalation.

• Dynamic risk assessments are crucial.

• Remove the patient from exposure and seek senior support if needed.

• Remember Remove, remove remove principles in cases of gross contamination.

Management and Treatment

Immediate Actions:

• ABC approach.

• Provide high-flow oxygen, although it won’t reverse cyanosis.

• Administer fluids for hypotension if necessary.

• Rapid transport to the hospital is critical.

• Pre-alert with the suspected agent and early request for Methylene blue, as this may not be kept in the dept.

Hospital Treatment:

• Blood gas analysis and methemoglobin levels.

• Methylene blue administration is the antidote.

• Blood transfusions may be considered in severe cases.

Takeaways

• Rare but Serious: Nitrate poisoning and methemoglobinemia are rare but potentially severe emergencies.

• Scene Safety: Rescuers must be aware of the potential exposure hazards.

• Signs and Symptoms: Look for low oxygen saturation and cyanosis unresponsive to oxygen therapy.

• Critical Care: Provide good ABC care, high-flow oxygen, and rapid transport to the hospital with a clear pre-alert about the need for methylene blue.

Stay informed and prepared, and you won't be caught off guard if you encounter a case of nitrate poisoning.

References

1. NHS England. Risk of death from unintended administration of sodium nitrite. August 2020. Available at: https://www.england.nhs.uk/2020/08/risk-of-death-from-unintended-administration-of-sodium-nitrite/

2. National Center for Biotechnology Information. Sodium nitrite toxicity. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10611400/

3. BBC News. Increase in sodium nitrite suicides. Available at: https://www.bbc.co.uk/news/uk-68347415

4. Wiley Online Library. Rising sodium nitrite suicides in the US. Available at: https://onlinelibrary.wiley.com/doi/abs/10.1111/sltb.13043

5. National Center for Biotechnology Information. Sodium nitrite poisoning. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10611400/