Severe methemoglobinemia due to ingestion of toxicants

Toxin-induced methemoglobinemia is seen in poisoning with oxidizing agents. We report the clinical features and outcome of patients admitted with severe methemoglobinemia due to intentional ingestion of toxicants.

In this observational case series, patients admitted with toxin-induced methemoglobinemia between September 2011 and January 2014 were identified from the institutional poisoning database. Clinical profile and outcome of patients with methemoglobin concentration greater than or equal to 49% is reported.

Of the 824 patients admitted with poisoning, 5 patients with methemoglobin concentration greater than or equal to 49% were included. The implicated compounds were nitrobenzene, benzoylphenylurea, flubendamide and Rishab(TM). One patient refused to name the compound. All patients were managed in the intensive care unit. Altered sensorium [Glasgow coma scale (GCS) < 10] was common (80%); 2 patients presented with a GCS greater than 4. All patients manifested cyanosis, low oxygen saturation and chocolate-brown-colored blood despite supplemental oxygen therapy. The median methemoglobin concentration was 64.7% (range 49.8-91.6%); 2 patients had methemoglobin concentration greater than 70%. One patient needed inotropes. Four patients required mechanical ventilation for 4-14 days. All patients were treated with methylene blue; 4 received more than one dose. Three patients also received intravenous ascorbic acid 500 mg, once daily, for 3 days. Following treatment, there was evidence of haemolysis in all patients; 2 required blood transfusion. All patients survived.

Patients with severe toxin-induced methemoglobinemia present with altered sensorium and cyanosis and may require ventilatory support and inotropes. Though methemoglobin concentrations greater than 70% are considered fatal, aggressive management with methylene blue and supportive therapy can lead to survival.