see also: [Cyanide poisoning and organ donation in Australia: a case report](https://www.tandfonline.com/doi/full/10.1080/24734306.2024.2381869#d1e231) - [pdf](https://www.tandfonline.com/doi/pdf/10.1080/24734306.2024.2381869) , ["B17" killing more than cancer](https://onlinelibrary.wiley.com/doi/10.1111/1742-6723.14450) > [!key points] > - consider cyanide poisoning in [[lactic acidosis]] in pt with sudden collapse > Antidote:: hydroxycobalamin, sodium thiosulfate, amyl nitrite > **pearl:** combination of HAGMA, LOC, sinus bradycardia, in the absence of acute ischemia, points to cyanide poisoning lethal dose 0.5-3.5 mg/kg # Sources - house fires - if you arrive alive following inhalation exposure, usually survive with supportive care (if smoke itself doesn't kill) - often have associated [[carbon monoxide]] poisoning - Amygdalin/"B17" # Toxic mechanism ## kinetics ![[Pasted image 20230828132728.png]] ## dynamics -- Histotoxic hypoxia - potent mitochondrial toxin produces chemical asphyxiation of cells by binding to the ferric ion (FE3+) of cytochrome oxidase a3 , disrupting last step of electron transport chain → ↓ ATP production → anaerobic metabolism - H+ ions no longer consumed by aerobic ATP production → HAGMA - Tissues such as heart and brain that are highly depenent on aerobic metabolism are most affected by cyanide toxicity Also: - accumlate free fradicals - inhibits GABA → seizure risk # Clinical features ![[Pasted image 20230828133131.png]] ![[Pasted image 20230828132547.png]] # Treatments > 1. direct cyanide binding > 2. sulfur donors to enhance thiocyanate excretion > 3. generate alterantive binding-site (methemoglobinemia) ## Hydroxocobalamin -- Direct cyanide binding - precursor of B12 - binds directly to make cyanocobalamin 70mg/kg (usually ==5g==) ; may need 2nd dose (this should bind 100mg of cyanide) Dicobalt edetate also used ; risks of anaphylaxis, seizures, and dysrhythmias, and more severe if pt has only mild cyanide toxicity ## Sodium thiosulfate -- sulfur donors - maximise sulfur donors for rhodanese, enzyme that detoxifies cyanide into thiocyanate for renal excretion. - slower onset of action (30 min) - 3:1 ratio of sodium thiosulfate to cyande required for complete detoxification dose: 50mL of a 25% solution, or 12.5g give in a separate line ![[Pasted image 20230828132728.png]] ## Amyl Nitrite -- methemoglobinemia - Oxidation of the ferrous (Fe2+) in hemoglobin to ferric (Fe3+) form → alternative binding site for cyanide → less toxic cyanmethemoglobin is formed - [[Methemoglobinemia]] itself causes cyanosis, seizures, death - Can make situation worse if not given in conjunction with thiosulfate - Currently sodium nitrite is a popular suicide agent emerging due to internet promotion for euthanasia - Option if **no other treatments are available** - No longer stocking kits including inhaled amyl nitrite # Related Questions ## cyanide toxicity - [ ] 8Q: [Toxic ingestion](x-devonthink-item://EE8AC47E-BE40-4377-885E-FA9C91C8C262?page=16) -- [Answer]()