SHM Converge Scientific Abstract ePoster Gallery-Pulse Ox Paradox

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This case describes a 23-year-old woman with a history of anxiety, depression, and suicidal ideation who was found unconscious at home near bottles of bupropion and hydroxyzine. In the emergency department, she was profoundly cyanotic, hypotensive, tachycardic, hypothermic, and unresponsive, with refractory hypoxemia despite high-flow oxygen and eventual intubation. Her blood was noted to be “dark chocolate” colored, raising concern for methemoglobinemia.<br /><br />Laboratory testing confirmed severe acquired methemoglobinemia with a methemoglobin level of 57%. Toxicology consultation was obtained, and she was treated with activated charcoal, orogastric lavage, and three doses of methylene blue. Her oxygen saturation improved after treatment, reaching 95% after the third dose, and her cyanosis gradually resolved. After extubation, she disclosed ingesting sodium nitrite shortly before EMS arrival.<br /><br />The report emphasizes that acquired methemoglobinemia occurs when an oxidizing agent converts heme iron from the ferrous (Fe2+) to ferric (Fe3+) state, reducing hemoglobin’s oxygen-carrying capacity and causing functional anemia. Common causes include local anesthetics, antibiotics, antineoplastics, nitrites/nitrates, and some pharmaceuticals or recreational drugs. A key clinical clue is the “pulse oximetry paradox” or saturation gap: low SpO2 that does not improve with oxygen, despite discordant arterial blood gas findings.<br /><br />The authors stress that clinicians should maintain a high index of suspicion for methemoglobinemia in patients with unexplained cyanosis and hypoxemia unresponsive to supplemental oxygen, especially given the rising incidence from intentional sodium nitrite ingestion (“suicide kits”). First-line treatment is intravenous methylene blue at 1 mg/kg for severe cases, up to a cumulative 7 mg/kg, with hematology consultation for possible exchange transfusion if the patient does not respond.

Asset Subtitle

Avi Prajapati

Meta Tag

Author List Avi Prajapati, Kingshuk Mazumdar

Category Clinical Vignettes

Concept Methemoglobinemia

Concept Methylene Blue

Concept Functional anemia

Concept Sodium nitrite

Concept Blue-Gray Skin Discoloration

Distinguished Non-Finalist

Presenter Organization University of Rochester Medical Center

Presenting Author Avi Prajapati

Track Adult

Keywords

methemoglobinemia

sodium nitrite

cyanosis

methylene blue

hypoxemia

suicide attempt

toxicology

bupropion

pulse oximetry paradox

oxidizing agent

Methemoglobinemia

Methylene Blue

Functional anemia

Sodium nitrite

Blue-Gray Skin Discoloration