Cyanide Presents with arterialization of venous blood (venous blood draw looks like ABG) Reason: o Hemoglobin is not able to offload oxygen o CN poisons cytochrome c oxidase preventing conversion of oxygen to water and thus production of ATP Old antidote: sodium thiosulfate New antidote: hydroxycobalamin binds CN producing cyanocobalamin (Vit B12) When you give it expects a dip in pulse because of its blue color. Remember CN will give you a beautiful 100% pulse all the way to death. Lee J, et al. Potential interference by hydroxocobalamin on cooximetry hemoglobin measurements during cyanide and smoke inhalation treatments. Ann Emerg Med. 2007 Jun;49(6):802-5. Epub 2007 Jan 8.