Podcast 188 - Sodium Nitrite Ingestion & Methemoglobinemia w/ Dr. Brookeman

In this episode of the FOAMfrat Podcast, Dr. Harrison Brookeman (@hbrookeman) joins the discussion to examine methemoglobinemia and the emerging prehospital threat of sodium nitrite ingestion. Often viewed as a rare toxicology concept, this condition is appearing more frequently and can progress rapidly with devastating consequences if it is not recognized early.

The episode focuses on what matters most to EMS clinicians in the field: the physiology of methemoglobinemia, why these patients appear profoundly hypoxic despite adequate ventilation, and the classic clue: a pulse oximetry reading that remains fixed around 85 percent regardless of oxygen delivery.

The conversation also addresses iatrogenic causes such as benzocaine exposure, expected mental status changes, and why oxygen alone does not correct the problem.

Emphasis is placed on prehospital decision-making, including early involvement with poison control, transport destination considerations, and ensuring these patients are taken to the right facility the first time. This episode is intended to sharpen recognition, improve pattern awareness, and prepare providers for a call that does not follow typical patterns of respiratory failure.

Core Physiology Review

Sodium nitrite oxidizes hemoglobin iron from the ferrous (Fe²⁺) state to the ferric (Fe³⁺) state. Once oxidized, hemoglobin can no longer carry oxygen. Ventilation may be intact. Oxygen may be plentiful in the lungs. CO₂ elimination may be regular or even increased. Oxygen delivery to tissues fails anyway. At the same time, nitrites are metabolized into nitric oxide, producing systemic vasodilation. The result is functional hypoxia combined with distributive shock, rapid lactate generation, and global ischemia.

What These Patients Look Like

Common early and late findings include:

• Gray or ashen appearance

• Marked perioral and peripheral cyanosis

• Tachycardia

• Hypotension or impending cardiovascular collapse

• Altered mental status progressing to unresponsiveness

• Vomiting or evidence of ingestion

These patients usually look critically ill very early.

The Pulse Oximetry Red Flag

A classic and high-yield clue is a pulse oximetry reading that stays around 85 percent and does not improve with oxygen.

Non-rebreather, high-flow nasal cannula, or BVM with 100 percent oxygen will not change the number.

This occurs because standard pulse oximeters assume only oxyhemoglobin and deoxyhemoglobin. Methemoglobin absorbs light equally across the wavelengths used, resulting in a fixed ratio that appears as approximately 85 percent.

If a patient looks profoundly hypoxic and the pulse ox is “stuck” in the mid-80s, methemoglobinemia should be high on the differential.

Chocolate-Colored Blood

Dark, chocolate-brown blood may be seen when starting an IV, but this is a late sign. It typically appears when methemoglobin levels are very high, often above 50 percent.

Do not wait for this finding to make the diagnosis.

Mental Status and Dyspnea

These patients do not experience air hunger in the same way hypercapnic patients do.

Because CO₂ elimination is preserved, they may appear confused, euphoric, or abruptly obtunded rather than panicked. The presentation resembles altitude hypoxia or nitrogen narcosis more than asthma or COPD.

Common Causes to Remember

While intentional sodium nitrite ingestion is increasing, methemoglobinemia can also be iatrogenic. One of the most common causes is benzocaine, particularly in infants and children. Teething gels and topical anesthetics can trigger methemoglobinemia, especially in small circulating volumes. A fussy infant with cyanosis and abnormal blood color should raise immediate concern.

Treatment Overview

Oxygen is necessary but not sufficient.

Definitive treatment is methylene blue, which:

• Reduces ferric iron back to ferrous iron

• Restores hemoglobin’s ability to carry oxygen

• Scavenges nitric oxide and improves vascular tone

Clinical improvement is often rapid once administered. Methylene blue is not universally stocked.

Prehospital Priorities

Key EMS considerations include:

• Early recognition based on presentation and pulse ox behavior

• Aggressive supportive care

• Anticipation of rapid cardiovascular collapse

• Early vasopressor readiness

• Airway protection and suction due to vomiting risk

Transport Decisions Are Critical

Destination choice can be life-saving.

If methemoglobinemia is suspected:

• Contact poison control early

• Identify hospitals that stock methylene blue

• Consider bypassing facilities that do not carry the antidote

• Understand that some patients may still require ECMO due to severe shock

High-Yield Takeaway

A patient who appears severely hypoxic with a pulse oximetry reading fixed around 85 percent despite oxygen should immediately trigger concern for methemoglobinemia.

This is not a ventilation problem. This is not a bad probe; this is a hemoglobin problem.

Recognition and destination decisions matter more than anything else.

Episode Focus

This episode emphasizes EMS-level recognition, physiology, and operational decision-making rather than toxicology trivia. The goal is not memorization, but pattern recognition when seconds matter.

References:

Hegedus, F., & Herb, K. (2005). Benzocaine-induced methemoglobinemia. Anesthesia progress, 52(4), 136–139. https://doi.org/10.2344/0003-3006(2005)52[136:BM]2.0.CO;2

Kaubrytė, S. S., Chmieliauskas, S., Salyklytė, G., Laima, S., Vasiljevaitė, D., Stasiūnienė, J., Petreikis, P., & Badaras, R. (2025). Fatal Outcome of Suicidal Multi-Substance Ingestion Involving Sodium Nitrate and Nitrite Toxicity: A Case Report and Literature Review. Acta medica Lituanic, 32(1), 160–172. https://doi.org/10.15388/Amed.2025.32.1.11

Padovano, M., Aromatario, M., D'Errico, S., Concato, M., Manetti, F., David, M. C., Scopetti, M., Frati, P., & Fineschi, V. (2022). Sodium Nitrite Intoxication and Death: Summarizing Evidence to Facilitate Diagnosis. International journal of environmental research and public health, 19(21), 13996. https://doi.org/10.3390/ijerph192113996