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RUSVM Toxicology > Toxic Gases I and II > Flashcards

Toxic Gases I and II Flashcards

1
Q

What are the 5 toxic gases we are covering?

A 
Ammonia (NH3)
Hydrogen Sulfide (H2S)
Carbon Monoxide (CO)
Nitrogen Oxide gases
Sulfur Oxide gases
Other irritant gases, vapors, fumes, and dusts
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2
Q

What are some of the properties of ammonia (NH3)

A

Soluble in water

Readily reacts with hydroxyl ions in moist mucous membranes to form ammonium hydroxide which is irritant and caustic

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3
Q

What is the toxicity of ammonia?

A

Humans eyes burn at 25-35 ppm, but can detect 10 ppm in the air

Most frequently found in high conc in animal houses- enclosed confinement- 50 ppm during normal operation

Livestock most susceptible- swine and poultry

Exposure to 5000 ppm can cause acute death

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4
Q

What is the MOA of ammonia?

A

Inhalation of large concentrations causes pulmonary edema, and lung congestion due to increased permeability to of lung capillaries

Decrease cell respiration

Death electrolyte and cellular metabolic effects- asphyxia

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5
Q

What are diseases that cause respiratory insufficiency?

A

Inhaled irritants (hydrogen sulfide, nitrogen oxides, sulfur oxides, fumes, dusts, vapors)
OP
Polychlorinated biphenyls
Cardiac glycosides

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6
Q

What are some of the properties of hydrogen sulfide (H2S)?

A

Odor of rotten eggs
Water soluble
Irritant bc converted to sulfuric acid in soln and forms sodium sulfide on contact with moist MM
Sulfide with silver, iron, lead and other metals to form black or dark colored compounds in GIT and tissues

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7
Q

How are animals exposed?

A

H2S, NH3, CO2 and methane are liberated from the decomposition of urine and feces in underfloor waste pits, deep litter, manure packs, sewage, and other organic matter containing sulfur

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8
Q

What is the normal level of H2S? Deadly level?

A

10 ppm

May reach 1000 ppm

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9
Q

True or False. H2S is the most dangerous sewage gas.

A

True.

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10
Q

What are some of the toxicity levels associated with H2S?

A

Humans can detect in air 0.025 ppm
200 ppm- olfactory accommodation - DANGER
Sudden exposure to 400 ppm may be FATAL
1000 ppm causes RAPID UNCONSCIOUSNESS and DEATH IN 1 HR
>2000 ppm RESPIRATORY PARALYSIS AFTER 1-2 BREATHS

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11
Q

What is the acute toxic level in mammals?

A

~500-800 ppm

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12
Q

What is H2S converted to in the blood?

A

Alkali sulfide

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13
Q

What is the MOA of H2S?

A

Inhibition of cell respiration- decreased cytochrome oxidase

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14
Q

What is the treatment for H2S toxicosis?

A

Sodium Nitrite IV may be particularly effective by forming methemoglobin– binds sulfide radicals and reactivates cytochrome oxidase

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15
Q

What is the most effective treatment?

A

Prevention– use H2S monitors!

While manure pit injuries are rare, they are highly deadly

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16
Q

What are some of the properties of carbon monoxide?

A

Odorless, colorless, NOT WATER SOLUBLE

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17
Q

What is the toxicity level?

A

> 1000 ppm (0.1%) can cause clinical signs and death with 1 hour of exposure

18
Q

What is the MOA?

A

CO combines with hemoglobin to form carboxyhemoglobin (COHb) which cannot carry O2
(Hb affinity for CO is 240x greater than for )2)

Carboxyhemoglobin interferes with release of O2 carried by normal hemoglobin

Death is from hypoxia

19
Q

What are some of the lesions associated with CO toxicity?

A

Blood is bight red and the MM are a healthy pink (bc carboxyhemoglobin is bright red and due to hyperventilation)– won’t always see this

20
Q

What are some of the properties of nitrogen oxide gas?

A

Reddish brown (NO2)
Colorless (N2O4)
Mixture of the two gases is yellow or yellow-brown haze
Forms layers on top of silage and settles down the chute
Chlorine like odor
Low solubility in water- the gases form nitric acid (HNO3) and nitric oxide (NO)

21
Q

What is the source of exposure?

A

Nitrogen Oxide poisoning- called “silo filler’s dz”

Nitrogen Dioxide (NO2) is a major pollutant (burning of fossil fuels), not to be confused with nitrous oxide (N2O) which is an anesthetic

22
Q

What is the toxicity of nitrogen oxide gases?

A

50-150 ppm causes mild to moderate irritation of the eyes and upper respiratory mucosa

Acute exposure to high concentrations is MORE toxic than chronic exposure to low concentrations

23
Q

What are the toxicokinetics of nitrogen oxide gases?

A

NO2 and N2O4 gases form nitric acid upon contact with MM

The acid or gases may cross respiratory mucosa and cause cellular damage in the lungs- pulmonary edema

24
Q

What is the MOA?

A

Direct irritation of the MM by nitric acid
Bc they are soluble they can pass via the upper to lower respiratory tract and cause damage in the lungs (bronchi/alveoli)
Lung damage- due to caustic reaction with polyunsaturated fatty acids at cell membrane– this leads to pulmonary edema, hemorrhage
Death is from hypoxia- RESPIRATORY FAILURE

25
Q

What are some of the lesions associated with nitrogen oxide gases?

A

Cyanosis
Methemoglobinemia
Necrosis of skeletal muscles

26
Q

What are the treatments?

A

Diuretics- if pulmonary edema
Methylene Blue IV- methemoglobinemia
Ointments (antibiotic) for MM

27
Q

What are the sources of sulfur oxide gases?

A 
Sulfur dioxide (SO2) and sulfur trioxide (SO3) are industrial pollutants
Fossil fuel combustion at power plants (73%)
28
Q

What are some properties of sulfur oxide gases?

A

Highly soluble in water

Sharply irritant to MM because of the form sulfurous and sulfuric acids on contact with water

29
Q

What is the MOA?

A

Direct irritation of the MM and reflex bronchoconstriction

Death due to hypoxia

30
Q

What are most fire-related deaths the result of?

A

80% are from smoke inhalation and not from the burns

31
Q

True or False. The LD50 of smoke is 9.4.

A

False. There is no LD50 bc smoke is a heterogenous mixture of gases.

32
Q

What is the MOA of a simple asphyxiant? Chemical asphyxiant? Irritant?

A

Simple- inert CO2 gases or vapors that displace O2
Chemical- prevent uptake of )2
Irritants- chemically reactive on contact with MM

33
Q

What are 3 examples of simple asphyxiant?

A

CO2
Methane
Oxygen-deprived environment

34
Q

What are examples of chemical asphyxiant?

A

CO- this is the most serious systemic agent with smoke inhalation– CHANGES O2 CARRYING CAPACITY OF Hb

Hydrogen cyanide
Hydrogen sulfide
Nitrogen oxides

35
Q

What should you not use to treat smoke inhalation and why?

A

STEROIDS- higher mortality and infection rates

36
Q

In order to treat, how long should you monitor the patient? And when should you recheck?

A

Monitor 6-8 hours post-exposure

Recheck in 72 hours

37
Q

What are the 3 high water solubility irritants (upper airway injury)?

A

Acrolein (aldehyde)
Sulfur Dioxide
Ammonia

38
Q

What are the two intermediate water solubility irritants (upper and lower airway injury)?

A

Chlorine

Isocyanates

39
Q

What are the 2 poor water solubility irritants (pulmonary parenchymal injury- alveoli, alveolar ducts?)

A

Phosgene (plasticizer)

Nitrogen oxides

40
Q

What is the mechanism of soot?

A

Binds to the respiratory mucosa allowing other material to adhere and react
Sulfur Dioxide adhere highly to soot

41
Q

What is the most important at determinant of respiratory injury?

A

Solubility

42
Q

Highly soluble particles affect which part of the respiratory system? Low water soluble products?

A

High- Upper airway

Low- lung, bronchiole, and alveoli

RUSVM Toxicology (23 decks)

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