Methaemoglobinaemia due to nitrobenzene poisoning

Abstract

Abstract Nitrobenzene poisoning presenting as acute methaemoglobinaemia is an uncommon medical emergency. The case of a 17-year-old male with alleged history of consumption of ‘flower all’ (composition-nitrobenzene) is being reported here. At the time of presentation to the emergency department, the patient had cyanosis of lips and feet with Glasgow coma score 12. His pulse was 161/min, blood pressure 70/40 mm Hg and oxygen saturation by pulse oximeter was 72% on room air. His pupils were bilaterally dilated with sluggish reaction. Rest of the physical examination was unremarkable. In view of desaturation, he was intubated and connected to mechanical ventilator. Blood sample taken for arterial blood gas (ABG) analysis was dark brown in colour. ABG showed pH: 7.443, arterial carbon dioxide tension: 27.8 mm Hg, arterial oxygen saturation (SaO2) 95.6% and bicarbonate 18.7 mEq/L. The calculated difference between SaO2 and SPo2 was 23%. Despite being on mechanical ventilation, he continued to have hypoxia. With a suspicion of methaemoglobinaemia, blood samples were sent for methaemoglobin level. Blood methaemoglobin was 13%. The patient was immediately started on injection methylene blue and injection ascorbic acid. Two sessions of haemoperfusion and one session of exchange transfusion were done. He started to improve clinically on day 3. He was gradually weaned off the mechanical ventilator and was discharged in the stable condition after 3 weeks of in hospital stay.