Rebound paediatric methemoglobinemia from nitroethane ingestion: a case report

Methemoglobinemia is a potentially life-threatening hematologic condition characterized by the oxidation of hemoglobin iron, which impairs oxygen delivery. While acquired methemoglobinemia in children is commonly associated with direct oxidizing agents, accidental ingestion of industrial solvents like nitroethane presents unique management challenges. Nitroethane, found in products such as paint hardeners, metabolizes into nitrites, causing potent oxidative stress. Unlike many other causes, nitroethane ingestion is specifically associated with "rebound" methemoglobinemia due to the toxin's continued metabolism and the relatively short half-life of the antidote, methylene blue.

We report the case of a 6-year-old boy who presented with vomiting, abdominal pain, and progressive central cyanosis following the accidental ingestion of a mouthful of paint chemical hardener (AkzoNobel) that had been stored in a reused drinking water bottle. Upon arrival, he exhibited cyanosis refractory to high-flow oxygen, with oxygen saturation (SpO₂) fluctuating between 88% and 93% on room air. Venous blood gas analysis confirmed severe methemoglobinemia with levels exceeding 30%. The patient was treated with intravenous methylene blue (1 mg/kg), resulting in a rapid reduction of methemoglobin to 9% within 1 hour. However, 8 hours post-treatment, he developed clinically significant rebound methemoglobinemia (16.6%) accompanied by desaturation, necessitating a second dose of methylene blue. He was monitored in the intensive care unit and general ward for delayed complications and was discharged well on day 8.

This case illustrates the severe toxicity of small volume nitroethane ingestion and highlights the critical risk of rebound methemoglobinemia. Because the oxidative effects of nitroethane metabolites can outlast the therapeutic duration of methylene blue, a single dose of antidote is often insufficient. Clinicians must ensure prolonged observation and serial co-oximetry monitoring for these patients. Furthermore, this case underscores the vital public health need for keeping hazardous chemicals in original, child-resistant containers to prevent accidental pediatric poisonings.