Cyanide poisoning Flashcards
Cyanide is also known as…
hydrogen cyanide (HCN)
hydrocyanic acid
prussic acid
What cyanogenic plants do large animals most commonly get poisoned from?
Wild cherry (prunus spps)
Sudan grass, johnson grass, and sorghums
***these contain cyanogenic glycosides that can liberate toxic amounts of HCN
What cyanide plants or products may small animals be exposed to?
Fumigant rodenticide: Hydrogen cyanide gas
fertilizers
sodium nitroprusside - hypotensive drug
Combustion of plastic compounds - produces HCN gas
Plants: Cherris, apples. plumes, apricots, some spps of lima bean and cassava root (tapioca)
Clinical signs of cyanide poisoning are similar to poisoning from what toxic gas?
Carbon monoxide
**both will make the blood BRIGHT red
What kind of gas is HCN?
Volatile
**has a characteristic odor: bitter almond or ammoniacal
T/F: HCN is irritating to MM
TRUE
T/F: Cyanide has antithyroid effects
FALSE
Thyiocyanate (SCN) has antithyroid effects but not cyanide
What does the CN- radical bind with and form complexes with in the blood?
ferric iron, cupric, and molybdenum
*very active binding
Greater than _____ppm in a plant is toxic
200ppm
The acute oral MLD of HCN is ____ mg/kg in all species
2 - 2.3 mg/kg = highly toxic
What species factors will affect the degree of cyanide toxicity?
Ruminants are more susceptible than horses and swine
**hydrolysis by the rumen microflora causes release of cyanide from cyanongenic plants
*sheep are less susceptible than cattle
What plant factors will increase cyanide toxicity?
Damage to the plant will increase and cause hydrolysis of cyanogenic glycosides and release of cyanide (HCN)
*stunting, wilting, trampling, frost, drought, treatment with Phenoxy derivatives of fatty acids herbicides
What cyanogenic plant parts of the most toxic?
SEEDS
then leaves, bark, stems, fruit (highest to lowest)
What plant stage is the most toxic (HCN)?
Young and growing plants bc they contain more glycosides
What soil condition may increase HCN accumulation in plants?
High nitrogen and low phosphorus may increase glycoside
How is cyanide absorbed?
Through the GIT, inhalation, and via skin contact – then distributed throughout the body
In the presence of thiosulfate, CN- is metabolized to what in the serum and liver?
Metabolized by sulfurtansferase to thiocyante (SCN) which is less toxic and is excreted in the urine
- has an antithyroid effect
- small amounts of HCN will be excreted in the urine or in expired air
What is the MOA in acute cyanide poisoning?
Excess CN in the blood and tissues binds with ferric iron and cupric copper of the mitochondrial cytochrome oxidase - This blocks the electron transport chain -inhibits the cells to utilize available oxygen resulting in histotoxic anoxia - particularly to the brain (***since the tissues can not utilize the oxygen - blood will have extra O2 and be bright red)
- decrease cellular energy
- increase anaerobic glycolysis - acidosis
- Vascoconstriction
- irritation to the MM
**this is a similar MOA as hydrogen sulfide - but with H2S blood will be dark brown and have odor
What is the MOA in chronic cyanide poisoning?
Neuronal degenration and demyelination of the spinal cord and brain
low levels of cyanide are goitrogenic due to thiocynate
What clinical signs are associated with acute cyanide poisoning?
extremely rapid onset
Animals may die without manifesting CS
Tachypnea, anxiety, panting, gasping, behavioral alarm, salivation, muscle tremors, lacrimation, urination/defecation, colic, vomiting, convulsions.. sudden death (only takes 4-5mins)
What clinical signs are associated with chronic cyanide poisoning?
posterior paralysis, urinary incontinence, cystitis, constipation, goitrogenic effect
What lesions are associated with cyanide poisoning?
Bright red blood and MM - blood may not clot
GIT and lungs - petechiation
Plants may be in rumen contents
+/- the smell of cyanide
what specific test can be used to detect cyanide in rumen contents or in plants?
Sodium picrate paper test (commercial test kit)
*yellow color will change to red in a few minutes in an airtight jar
other tests: urine for thyiocynate, lactic acidosis and increased ion gap - good indicators
Chemical analysis on many other samples, and forage - not helpful for ER situations
What is the specific treatment for cyanide poisoning?
Sodium Nitrate 20% IV
this will immediately improve perfusion - vasodilation
*causes methemoglobin which can bind the cyanide and reactivate cytochrome oxidase
Sodium thiosulfate 20% IV
This converts CN to thyiocynate (SNC) which is less toxic and excreted in urine
*can be giving orally
OTHER:
- O2 therapy and nitrite thiosulfate
- Vinegar and cold water orally to slow down microbial hydrolysis
- mineral oil laxative
T/F: Activated charcoal is effective for adsorption of cyanide
FALSE
T/F: There is a specific and effective treatment for chronic cyanide poisoning
FALSE
no treatment - prognosis will depend on have severe the neuronal degeneration and demyelination
*damage is usually irreversible
