Toxic Gases 1 Flashcards
How are animals usually exposed to ammonia (NH3) ?
Inhalation
Burning plastic/nylon
Agricultural fertilizer
What are the properties of ammonia?
Sharp odor (olfactory accommodation)
Heavier than water
Soluble in water
What is the MOA of ammonia?
Reacts with hydroxyl ions —> ammonia hydroxide —> irritant and caustic (dermal and mucosal )
What effect does ammonia have on the respiratory system?
Disrupt cell integrity —> increased permeability of lung capillaries —> edema and congestion
Inflammation/irritation —> susceptibility to secondary infections
Death due to ammonia gas results from?
Asphyxia, and partly due to electrolyte and cellular metabolic effects
Humans can detect ammonia at ________ppm in the air, and their eyes burn at ______ppm
10; 25-35
Where are high concentrations of ammonia usually found and who is must suspecptible
Animal houses
-livestock: swine and poultry
What are the acute signs of ammonia toxicity?
Red mucous membranes Lacrimation Coughing Sneezing Nasal discharge
What are the chronic clinical signs of ammonia toxicity?
Decreased growth rate, decreased egg production in birds
What are the terminal signs of ammonia toxicity?
Cyanosis, CNS stimulation, and clonic convulsions
How can you make a diagnosis of ammonia toxicity?
History
Clinical signs
Lesions and the odor of ammonia make diagnosis obvious
What is your DDX for inhaled irritants causing respiratory insufficiency?
Hydrogen sulfide Nitrogen oxide Sulfur oxide Fumes Dusts
How do you treat ammonia toxicity?
Removal of NH3 source Ventilation Fresh air for dyspnea Soothing ointment for eyes Antibiotics for secondary infection Diuretic for edema
What is usually the source of exposure to hydrogen sulfide?
Waste pits/manure packs/sewage
- normal levels 10ppm
- agitated —> deadly at 100ppm
What are the properties of hydrogen sulfide?
Colourless and odor of rotten eggs
Heavier than air
Flammable
What is the MOA of hydrogen sulfide?
Converted to sulfuric acid in solution and forms sodium sulfide when contacts moist mucus membranes —> irritant
Inhibit cellular respiration by inhibition cytochrome oxidase
Stimulate carotid body chemoreceptor —> depress respiratory drive
Reacts with silver, iron, lead, and other metals —> dark or black coloured compounds in GI tract
what is the most dangerous sewage gas?
Hydrogen sulfide
Where is hydrogen sulfide absorbed, metabolized, and excreted?
Absorbed in lungs and GI tract
Converted to alkali sulfides in blood —> oxidized to sulfate and is excreted in urine
Some sulfide excreted in feces as iron sulfide (dark/blood appearance )
What are the acute clinical signs of hydrogen sulfide?
Large concentrations
Sudden collapse, cyanosis, dyspnea, anoxic convulsions
Rapid death
What are the chronic clinical signs of hydrogen sulfide?
Lower concentrations
Irritation to ocular, respiratory mucosa, and lungs
What lesions do you see in hydrogen sulfide toxicity?
Blood is dark and may not clot
Tissue dark/greenish purple
Odor of H2S
GI contents dark and odorous
How do you treat hydrogen sulfide toxicity?
Remove source
Sodium nitrate IV - forms methemoglobin that binds radicals and reactive cytochrome oxidase
Oxygen, ventilation, and supportive care
What are the sources of exposure of CO?
Fires, space heater, engines in confined spaces
What are the properties of CO
Odorless and colourless
NOT water soluble —> not an irritant like the other gases
CO > __________ppm can cause clinical signs and death in 1hr
1000 (0.1%)
What is the MOA of CO ?
Combines with hemoglobin to form carboxyhemoglobin (COHb) which cannot carry oxygen and interferes with O2 release
—> anoxemia/hypoxia
—> interfere with cellular respiration
What are the clinical signs associated with CO?
Low exposure (30-60%) - hypoxia, drowsiness, incoordination, dyspnea, lethargy, coma
High expire (60-70%). - death
Moderate concentrations (<250ppm) of CO can have what affect on lambing/farrowing?
Increase number of stillborn fetuses
What are the lesions seen in CO toxicity?
Blood is bright red and the mucous membranes are healthy pink
Chronic- brain edema, hemorrhage, and necrosis
How can you diagnose CO toxicity in the lab?
Measure CO in air
Measure % of carboxyhemoglobin in the blood or in fetal thoracic fluid
first gas that has a laboratory diagnosis
How do you treat CO toxicity?
Oxygen or 5%CO2 in oxygen administered with positive pressure
Blood transfusion
Recovery may or may not occur
