Severe hypoxaemia due to methaemoglobinaemia and aspiration pneumonia

The authors report a case of a previously healthy 40-year-old man who was admitted to the emergency department due to severe hypoxaemia after emesis. He vomited after a cup of coffee with the milk at his office. On admission, he showed cyanosis and oxygen saturation measured by pulse oximetry was extremely low (86%) in spite of the administration of 10 litres of oxygen. The authors suspected pneumonia, but oxygen saturation was disproportionately low to pneumonia severity. Oxygen saturation measured by pulse oximetry was significantly different from oxygen saturation calculated from arterial blood gas analysis, suggesting the existence of haemoglobin abnormality. The level of methaemoglobin was 9.3% (reference range, 1-2%). The patient was treated by antibiotics for pneumonia, and his methaemoglobinaemia was spontaneously ameliorated. The authors later found that the patient drank bleach containing hypochlorous acid instead of milk by mistake. To conclude, the patient's hypoxaemia was due to pneumonia and drug-induced acquired methaemoglobinaemia.