Methemoglobinemia treated with hyperbaric oxygen therapy: A case report

2023 American Heart Association Focused Update on the Management of Patients With Cardiac Arrest or Life-Threatening Toxicity Due to Poisoning: An Update to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

In this focused update, the American Heart Association provides updated guidance for resuscitation of patients with cardiac arrest, respiratory arrest, and refractory shock due to poisoning. Based on structured evidence reviews, guidelines are provided for the treatment of critical poisoning from benzodiazepines, β-adrenergic receptor antagonists (also known as β-blockers), L-type calcium channel antagonists (commonly called calcium channel blockers), cocaine, cyanide, digoxin and related cardiac glycosides, local anesthetics, methemoglobinemia, opioids, organophosphates and carbamates, sodium channel antagonists (also called sodium channel blockers), and sympathomimetics. Recommendations are also provided for the use of venoarterial extracorporeal membrane oxygenation. These guidelines discuss the role of atropine, benzodiazepines, calcium, digoxin-specific immune antibody fragments, electrical pacing, flumazenil, glucagon, hemodialysis, hydroxocobalamin, hyperbaric oxygen, insulin, intravenous lipid emulsion, lidocaine, methylene blue, naloxone, pralidoxime, sodium bicarbonate, sodium nitrite, sodium thiosulfate, vasodilators, and vasopressors for the management of specific critical poisonings.

Diagnosis and management of nitrobenzene poisoning in a low-resource setting: A case report

Background

and Importance: Nitrobenzenes are aromatic oxidizing nitrate compounds, acute ingestion of which can cause methemoglobinemia (metHb) that impairs oxygen transport. Clinical presentation ranges from cyanosis to asphyxia depending on the level of methemoglobin in the blood. Lack of improvement of hypoxia despite administration of oxygen can also be a clue to the diagnosis.

Case presentation

A 23-year-old male with accidental ingestion of nitrobenzene presented with multiple episodes of vomiting, headache, and dyspnea. His venous blood was dark brown in color and oxygen saturation was not improving despite high-flow oxygen. He was managed with methylene blue and Vitamin C on this background with an appropriate history of nitrobenzene ingestion.

Discussion

Acute nitrobenzene poisoning results in methemoglobinemia which is diagnosed by Co-oximeter but in resource-limited settings, clinical findings such as no improvement in SpO₂ despite supplemental oxygen and chocolate brown appearance of blood aid in the diagnosis. Prompt treatment of methemoglobinemia with methylene blue along with Vitamin C has shown successful and effective outcomes.

Conclusion

Diagnosis of acute nitrobenzene poisoning can be made with proper history, physical and bedside examinations in resource-limited settings even without the aid of a co-oximeter.

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Methemoglobinemia can cause refractory hypoxia in nitrobenzene poisoning.

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Proper history and thorough physical examination can help reach a diagnosis in resource-limited settings.

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Methylene Blue along with Vitamin C can be used safely in suspected cases.

Asymptomatic benzocaine spray-induced methaemoglobinaemia in preoperative sedation for oesophagogastroduodenoscopy

Methaemoglobinaemia is defined as elevated methaemoglobin in the blood which is characterised by conversion of some of the reduced ferrous iron elements [Fe2+] to the oxidised ferric [Fe3+] form which does not have capacity to bind and transport oxygen resulting in functional anaemia. Causes can be genetic mutations or acquired by medications such as dapsone, nitrates or benzocaine. Benzocaine is currently being used as a topical anaesthetic agent before certain procedures. We report a case of benzocaine spray-induced methaemoglobinaemia in a patient who underwent oesophagogastroduodenoscopy for evaluation of upper gastrointestinal bleeding.

Killer hiding under normal oxygen saturation: a case report about methemoglobinemia

BACKGROUND

Inhaled nitric oxide (iNO) is a choice for the treatment of pulmonary hypertension (PH), especially in cases after cardiac surgery. Potential side effects include the formation of higher oxides of nitrogen and methemoglobin (MetHb). Methemoglobinemia is the oxidation of ferrous iron to iron within hemoglobin, impairing its ability to transport oxygen and resulting in tissue hypoxemia. A level of MetHb >10% will induce clinical hypoxia manifestations, and MetHb >70% may be fatal.

CASE DESCRIPTION

Herein we report a rare case of methemoglobinemia due to iNO therapy in a child after cardiac surgery. We found that as MetHb concentrations increased, pulse oximetry overestimated oxygen supplementation without warning clinicians that dangerous hypoxia was developing. Finally, MetHb and oxyhemoglobin (O₂Hb) in arterial blood gas (ABG) provide diagnostic clues. Methylene blue and low dose vitamin C (VC) were used to successfully save the life of the child.

CONCLUSIONS

iNO administration in the intensive care unit should be managed with close monitoring of MetHb levels during treatment. We emphasize the limitations of traditional methods used to assess oxygenation status, especially in the context of methemoglobinemia. In addition, treatment for methemoglobinemia in acute settings should be initiated as soon as possible.

Recommendations for diagnosis and treatment of methemoglobinemia

Methemoglobinemia is a rare disorder associated with oxidization of divalent ferro‐iron of hemoglobin (Hb) to ferri‐iron of methemoglobin (MetHb). Methemoglobinemia can result from either inherited or acquired processes. Acquired forms are the most common, mainly due to the exposure to substances that cause oxidation of the Hb both directly or indirectly. Inherited forms are due either to autosomal recessive variants in the CYB5R3 gene or to autosomal dominant variants in the globin genes, collectively known as HbM disease. Our recommendations are based on a systematic literature search. A series of questions regarding the key signs and symptoms, the methods for diagnosis, the clinical management in neonatal/childhood/adulthood period, and the therapeutic approach of methemoglobinemia were formulated and the relative recommendations were produced. An agreement was obtained using a Delphi‐like approach and the experts panel reached a final consensus >75% of agreement for all the questions.

Primaquine overdose in a toddler

Antimalarial medications carry a risk of rare, but serious side effects. Primaquine in particular is known to cause methemoglobinemia and hemolytic anemia. In patients with underlying glucose-6-phosphate dehydrogenase (G6PD) deficiency, these side effects become amplified and can be life-threatening. This can complicate treatment plans as the recommended first-line management of severe methemoglobinemia, methylene blue, may cause or worsen hemolytic anemia in G6PD deficient patients. We present a case of a toddler with an accidental primaquine overdose who had undiagnosed G6PD deficiency. Over the 2 days following his ingestion he developed severe methemoglobinemia and hemolytic anemia toxicity. He was initially treated with a dose of methylene blue prior to learning of his G6PD deficiency. He was subsequently given additional doses of ascorbic acid and a blood transfusion. His condition gradually improved and he was ultimately discharged in good condition. To our knowledge, this case represents a unique presentation of mixed methemoglobinemia and hemolytic toxicity due to an accidental primaquine overdose in a G6PD deficient pediatric patient. Though cases remain relatively rare, pediatric patients represent the vast majority of known primaquine overdoses. Their diagnosis and treatment require maintaining a high index of suspicion and a good working knowledge of antimalarial toxicities and management options.

Multimodal imaging of a patient with poppers maculopathy

Objective: To describe the findings and the imaging characteristics of a patient with poppers maculopathy.

Methods: The ocular findings were evaluated with fundus autofluorescence imaging, spectral optical coherence tomography and optical coherence tomography angiography.

Results: A 36-year-old man presented with a history of blurring vision after using poppers. Best-corrected visual acuity was 0.9 and intraocular pressure was normal in both eyes. Fundus examination revealed hyperreflective appearence at macula with a faint foveolar reflex. Optical coherence tomography revealed focal hyperreflectivity and irregularity of the ellipsoid zone at the fovea. Fundus autofluorescence was normal. Optical Coherence Tomography Angiography revealed no vascular changes. The patient received hyperbaric oxygen therapy for 10 days. After one month VA increased, and OCT improved.

Conclusion: Inhalation of poppers may be associated with bilateral vision loss due to the disruption of photoreseptors which is clearly demonstrated with OCT.