Cyanide poisoning

Question 1

Cyanide is also known as…

Answer 1

hydrogen cyanide (HCN)
hydrocyanic acid
prussic acid

Question 2

What cyanogenic plants do large animals most commonly get poisoned from?

Answer 2

Wild cherry (prunus spps)
Sudan grass, johnson grass, and sorghums
***these contain cyanogenic glycosides that can liberate toxic amounts of HCN

Question 3

What cyanide plants or products may small animals be exposed to?

Answer 3

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)

Question 4

Clinical signs of cyanide poisoning are similar to poisoning from what toxic gas?

Answer 4

Carbon monoxide

**both will make the blood BRIGHT red

Question 5

What kind of gas is HCN?

Answer 5

Volatile

**has a characteristic odor: bitter almond or ammoniacal

Question 6

T/F: HCN is irritating to MM

Answer 6

TRUE

Question 7

T/F: Cyanide has antithyroid effects

Answer 7

FALSE

Thyiocyanate (SCN) has antithyroid effects but not cyanide

Question 8

What does the CN- radical bind with and form complexes with in the blood?

Answer 8

ferric iron, cupric, and molybdenum

*very active binding

Question 9

Greater than _____ppm in a plant is toxic

Answer 9

200ppm

Question 10

The acute oral MLD of HCN is ____ mg/kg in all species

Answer 10

2 - 2.3 mg/kg = highly toxic

Question 11

What species factors will affect the degree of cyanide toxicity?

Answer 11

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

Question 12

What plant factors will increase cyanide toxicity?

Answer 12

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

Question 13

What cyanogenic plant parts of the most toxic?

Answer 13

SEEDS

then leaves, bark, stems, fruit (highest to lowest)

Question 14

What plant stage is the most toxic (HCN)?

Answer 14

Young and growing plants bc they contain more glycosides

Question 15

What soil condition may increase HCN accumulation in plants?

Answer 15

High nitrogen and low phosphorus may increase glycoside

Question 16

How is cyanide absorbed?

Answer 16

Through the GIT, inhalation, and via skin contact – then distributed throughout the body

Question 17

In the presence of thiosulfate, CN- is metabolized to what in the serum and liver?

Answer 17

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

Question 18

What is the MOA in acute cyanide poisoning?

Answer 18

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

Question 19

What is the MOA in chronic cyanide poisoning?

Answer 19

Neuronal degenration and demyelination of the spinal cord and brain

low levels of cyanide are goitrogenic due to thiocynate

Question 20

What clinical signs are associated with acute cyanide poisoning?

Answer 20

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)

Question 21

What clinical signs are associated with chronic cyanide poisoning?

Answer 21

posterior paralysis, urinary incontinence, cystitis, constipation, goitrogenic effect

Question 22

What lesions are associated with cyanide poisoning?

Answer 22

Bright red blood and MM - blood may not clot
GIT and lungs - petechiation
Plants may be in rumen contents
+/- the smell of cyanide

Question 23

what specific test can be used to detect cyanide in rumen contents or in plants?

Answer 23

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

Question 24

What is the specific treatment for cyanide poisoning?

Answer 24

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

Question 25

T/F: Activated charcoal is effective for adsorption of cyanide

Answer 25

FALSE

Question 26

T/F: There is a specific and effective treatment for chronic cyanide poisoning

Answer 26

FALSE

no treatment - prognosis will depend on have severe the neuronal degeneration and demyelination
*damage is usually irreversible