Presentation The patient presented with an acute severe desaturation to 74% on room air. Initial management included 15 litres of oxygen via non-rebreather mask and continuous monitoring. Despite this, he remained markedly cyanosed and tachycardic. 

Diagnosis Arterial blood gas (ABG) analysis revealed methaemoglobinemia and a characteristic dark brown discoloration of the blood. Figure 1.  Methylene Blue was considered, but conservative management was continued due to clinical improvement.  

Treatment After one hour, cyanosis and tachycardia had improved, and an ABG showed decreased methaemoglobinemia. A fourth ABG at 4 hours showed a methaemoglobinaemia less than 3%.

Discussion It was later discovered that the patient had ingested a bottle of “poppers”, a commonly abused drug containing amyl nitrite.