[An unusual cause of cyanosis]

A case is reported of a 37 year old man who was involved in an accidental shell blast. He was admitted with black tattooing of his face, forearms, hands and legs. Repair of the severe ocular lesions and the surgical debridement of his burns required general anaesthesia. This lasted for 6 h; throughout, haemodynamic and respiratory parameters remained stable. The Pao2 was 130 mmHg. During recovery, cyanosis was noted despite a Pao2 of 65 mmHg with 92% Sao2, a normal chest X-ray and stable normal haemodynamic parameters. This paradoxical situation suggested a toxic haemoglobinopathy. Biochemical investigations revealed severe methaemoglobinaemia (40%) due to percutaneous absorption of dinitrobenzene (DNB), a constituent of the 1917 bomb. The amount of DNB absorbed had been unknowingly reduced by the surgical brushing of the burned skin. The classical treatment of methaemoglobinaemia, associated with two plasmaphereses to remove the toxic substance, were successful. Normal arterial blood gases associated with chocolate brown coloured arterial blood should make one suspect methaemoglobinaemia.