Toxic methemoglobinemia due to biofertilizers, herbicides

Abstract

Introduction : Methemoglobinemia is an emergency condition which is the result of the oxidization of iron into ferric form. It can be congenital or acquired. Acquired methemoglobinemia due to drug toxicity, in rural areas most commonly due to intentional self-poisoning and the most common compounds, are plant growth enhancers, herbicides and indoxacarb which is a non-organophosphorus insecticide. Methods: This is a retrospective observational study of patients who are admitted in an emergency with methemoglobinemia from 2018 to the present. Results: A total of 10 cases were found in the hospital records with toxic methemoglobinemia and the sex ratio is equally distributed. Farmers were predominant with 60. Ingestion was the mode of consumption in all cases. The most common compound was seaweed extract followed by plant alkaloids all cases presented to emergency initial saturation was less than 80% with the most common presenting feature being breathlessness and cyanosis and irritability in cases presenting late. Out of the 10 cases, 30% cases required mechanical ventilation at initial presentation. Despite 100% oxygen supplementation saturation levels did not improve indicating a problem with oxygen binding and unloading. All the cases were given methylene blue as the antidote of choice. 6 patients required 1 dose. In all cases saturation levels improved after ingestion of methylene blue, but 4 patients required repeat dosing, and 3 patients required exchange transfusion. Conclusion: Methemoglobinemia is a potential complication of ingestion of herbicides, plant growth extracts and plant alkaloid compounds. The presence of breathlessness, cyanosis, and persistent hypoxemia should raise suspicion of the disorder. Early institution of easily available antidote methylene blue can save lives and avert potential complications.