Metahemoglobinemia de origen alimentario Serie de casos

Resumen

Introduction: Methemoglobinemia (MetHb) is a life-threatening disorder caused by the oxidation of ferrous iron (Fe2+) in hemoglobin to ferric iron (Fe3+). This process prevents oxygen transport, leading to severe tissue hypoxia. Although some cases are congenital, the acquired form is more common, typically resulting from exposure to oxidizing agents such as nitrates and nitrites found in foods like cured meats and water. Diagnostic signs include oxygen-refractory cyanosis and chocolate-colored blood, with the "saturation gap" being crucial in the ICU: it is a discrepancy between low pulse oximetry SpO2 and falsely normal or high SaO2 readings on standard arterial blood gases.

Case presentation: We describe a couple (female, 23 years old; male, 27 years old) who developed severe MetHb simultaneously 1.5 hours after consuming "special cuts of meat 3/4" (processed meat). Both presented with abdominal distension, nausea, vomiting, respiratory distress, altered mental status, and intense central and peripheral cyanosis. Upon admission, they exhibited hypotension and significant desaturation (SpO2 71% and 65%), which did not improve despite supplemental oxygen and crystalloids.

Findings and diagnosis: The key clinical feature was the persistent cyanosis despite high-flow oxygen. Diagnosis was supported by the notable "saturation gap": SpO2 measured by oximetry was low (88% and 86%), while SpO2 calculated from arterial blood gases was falsely high (99% and 100%), creating an 11% and 14% gap, respectively. Blood samples showed a characteristic chocolate brown color, and co-oximetry confirmed the diagnosis with methemoglobin levels of 17% and 10%. Patients received intravenous methylene blue.

Conclusion: Acquired methemoglobinemia from dietary sources is a toxicological emergency that demands high suspicion. Its hallmark features are refractory cyanosis, chocolate-colored blood, and the "saturation gap." This case highlights the importance of co-oximetry for confirmation and the necessity of prompt diagnosis and treatment with methylene blue to prevent severe complications and death.