Lesson 29 - Euthanasia

What is humane disposition?

ethical and compassionate treatment of animals and euthanasia is a kind way of reducing an animals suffering

What is the humane technique for euthanasia?

rapid loss of consciousness followed by cardiac and respiratory arrest and ultimate loss of brain function

What is humane slaughter?

methods employed to intentionally kill animals raised for food, fur, or fiber production and minimize suffering

What is depopulation?

rapid destruction of large numbers of animals in response to emergencies

What are the criteria for evaluating euthanasia methods?

1. humane end

2. reliability and speed

3. safety and impact

4. compatibility

What are the classifications of euthanasia methods?

1. acceptable

2. acceptable with conditions

3. unacceptable

4. adjunctive methods

What are acceptable methods?

methods that consistently produce a humane death when used as the sole means of euthanasia

What are acceptable methods with conditions?

methods that require certain conditions to be met to consistently produce a humane death

What are unacceptable methods?

methods deemed inhumane under any conditions or pose a substantial risk to the human operator applying the technique

What are adjunctive methods?

those that should not be used as a sole method but can be used in conjunction with others to bring about euthanasia

What are the three steps of euthanasia?

1. loss of consciousness

2. cardiac or respiratory arrest

3. loss of brain function

What are the three basic mechanisms of euthanasia?

1. direct depression of vital neurons

2. hypoxia

3. physical disruption of brain activity

What agents cause direct depression of vital neurons?

barbiturates

What agents cause hypoxia?

carbon dioxide or nitrogen

What agents cause physical disruption of brain activity?

penetrating captive bolt and gunshot

Once consciousness is lost, what can occur that is attributed to the excitement phase of anesthesia?

seizures, vocalization, reflex struggling, breath holding, tachypnea

How do we confirm death?

1. lack of pulse and breathing

2. absence of corneal reflex

3. absence of response to firm toe pinch

4. graying of mucous membranes

5. presence of rigor mortis

What is the only single definitive sign of death?

presence of rigor mortis

How do we dispose of remains?

follow laws, incineration or cremation is preferred with deep burial or landfilling as alternatives

What are the inhalant methods of euthanasia?

carbon dioxide and isoflurane

What are the non-inhaled methods of euthanasia?

barbiturates and MS 222

What are the physical methods of euthanasia?

gunshot and penetrating captive bolt

A dog with severe, refractory respiratory distress is scheduled for euthanasia. The veterinarian plans to administer an overdose of an injectable barbiturate as the sole method. Which classification best describes this method?

acceptable

A cow with a catastrophic pelvic fracture is recumbent and in severe pain. The veterinarian uses a penetrating captive bolt to induce unconsciousness, followed by exsanguination. How is exsanguination classified in this context?

adjunctive

A farmer intends to kill a conscious chicken by exsanguination alone. How is this method classified as the sole technique?

unacceptable

What animals is carbon dioxide euthanasia is used for?

small mammals

What happens with carbon dioxide euthanasia?

respiratory acidosis and then unconsciousness and anesthesia

What are some negatives to carbon dioxide euthanasia?

1. CO2 mixed with water in airways making carbonic acid which can cause pain

2. animals may experience air hunger

3. can directly trigger fear response in the brain

What are recommendations for using CO2?

1. gradual displacement preferred over prefilling chambers to minimize pain and distress

2. compressed gas cylinders is only acceptable source

What animals show high tolerance to CO2?

1. immature

2. burrowing

3. diving

What is unacceptable use of CO2?

placing conscious rodent into a 100% prefilled chamber

What are important cautions with CO2?

its heavier than air so layering in chamber can happen and must be conducted in a well-ventilated area

What form must the inhaled agents be in?

purified form

What animals are inhalant anesthetics used for?

small animals

What is inhalant anesthetics not suitable for?

1. food producing animals

2. reptiles, amphibians, diving animals

What animals are resistant to hypoxia?

neonatal animals

What is inhalant anesthetics used with?

combination with second method like exsanguination

What is preferred inhalant anesthetic?

isoflurane

What are characteristics of isoflurane?

1. low potency

2. induces anesthesia rapidly

3. pungent odor

What are characteristics of enflurane?

1. effective for euthanasia

2. seizure activity

What are characteristics of nitrous oxide?

up to 70% may be combined with other inhalant gases

What are characteristics of sevoflurane?

1. less potent than isoflurane

2. less odor

3. seizure activity

What are characteristics of desflurane?

1. potent

2. very strong odor

3. least soluble inhalant agent

What are the advantages of carbon monoxide euthanasia?

painless no discomfort in some species and rapid death at low concentrations

What are the disadvantages of carbon monoxide?

1. aversive for lab rodents

2. potential to exposure to personnel

What is the classification for carbon monoxide euthanasia?

acceptable with conditions

What is the preferred method for most animals?

barbiturates

What do barbiturates do?

directly depress the central nervous system

What are the advantages of barbiturates?

1. rapid onset with IV

2. induces euthanasia smoothly with minimal discomfort

3. relatively inexpensive

What are the disadvantages of barbiturates?

1. IV requires trained personnel

2. strict DEA regulations

3. drug persists in the carcass

What are the advantages of pentobarbital?

1. quick onset

2. IV preferred for companion

2. IP, intracelomic, intra-organ, IC accepted with conditions

What are the disadvantages of pentobarbital?

1. alkaline so IP administration associated with peritoneal irritation

2. significant disposal issues

What is T61?

general anesthetic with NMBA agent with local anesthetic

What are the advantages with T61?

rapid onset with no terminal gasp

What are the disadvantages of T61?

1. currently not manufactured in the US

2. slow IV injection necessary to avoid dysphoria

3. trained personnel

4. controlled drug

5. only IV

What is the general anesthetic in T61?

embutramide

What is the NMBA agent in T61?

mebenzonium iodide

What is the local anesthetic in T61?

tetracaine hydrochloride

What is potassium chloride?

adjunctive method for euthanasia that is cardiotoxic

What are the advantages of potassium chloride?

1. rapid onset

2. not controlled substance

3. less residue

4. no artefacts

What are the disadvantages of potassium chloride?

1. possible spasms

2. painful injection

3. no loss of consciousness

Why does potassium chloride need to be used with another method?

no loss of consciousness

What are the advantages of physical euthanasia methods?

inexpensive, humane, painless, no drug residues, less fear and anxiety

What are the disadvantages of physical euthanasia methods?

can be upsetting for operator

What is pithing?

rod is inserted through the skull hole, destroying brain tissue and spinal cord to prevent revival

What can pithing cause?

involuntary muscle spasms

What are the physical methods of euthanasia?

1. penetrating captive bold

2. gunshot

3. cervical dislocation

4. decapitation

5. cerebral electrocution

6. blunt force traume

7. maceration

8. exsanguination

9. stunning

What is the classification of physical methods?

acceptable with conditions

What bullets are preferred?

solid-point bullets

What are major risks of gunshot?

ricochet and over-penetration

What is the acceptable and preferred method for companion animals?

1. IV injection of a barbiturate

2. pre-euthanasia sedation to minimize animal distress

What are the acceptable with conditions companion animals?

1. IP injection of barbiturate when IV is impractical

2. inhaled anesthetics for small mammals

3. intra-organ infections in unconscious or anesthetized animals

4. gunshot/PCB only in remote areas or emergencies

What is the acceptable and preferred method with farm animals?

IV barbiturate overdose but remains cannot enter the food chain

What is the acceptable with conditions for food animals?

gunshot and PCB but PCB requires adjunctive method

What is the site for physical euthanasia of swine?

1. frontal site center of the forehead directing toward the spine

2. behind the ear aiming toward the opposite eye

What is the site for physical euthanasia in equine?

intersection of two imaginary lines drawn from outer of the eye to the center of the base of opposite ear

What are the euthanasia methods for fish?

1. immersion anesthetics

2. rapid chilling

3. physical methods

What are the immersion anesthetics for fish?

MS 222 or benzocaine

What is the method for fish immersion?

remain for at least 10-30 minutes

What is the rapid chilling fish method?

small-bodied tropical fish like zebrafish in 2-4 Celsius water

What is rapid chilling not appropriate for?

cold-water tolerant species

What are the physical methods for fish?

1. concussive blow to the head

2. decapitation followed by pithing

When is depopulation used in shelter medicine?

last resort

What are unacceptable methods for shelter medicine?

1. gunshot

2. inhalation of carbon monoxide

3. intra-organ injections