Controversial Euthanasia Methods - Definitions, Policies And Guidelines

DEFINITIONS:
Euthanasia - The term euthanasia is derived from the Greek term 'eu' meaning 'good' and 'thanatos' meaning 'death'. A ‘good death’ would be one that occurs without pain and distress. In the context of this report, euthanasia is the act of inducing humane death in an animal. Euthanasia techniques should result in rapid unconsciousness followed by cardiac or respiratory arrest and ultimate loss of brain function. In addition, the technique should minimize any stress and anxiety experienced by the animal prior to unconsciousness. Stress may be minimized by technical proficiency and humane handling of the animals to be euthanised.

Humane is defined as ‘Characterized by kindness, mercy, or compassion, marked by an emphasis on humanistic values and concerns’; Synonyms: humane, compassionate, humanitarian, merciful. The central meaning shared by these adjectives is ‘marked or motivated by concern with the alleviation of suffering’.

1. Inhalant Agents
Ether:
Ether is not a good agent for either euthanasia or anaesthetic purposes.
· It is stressful to the animal
· It has high explosive potential
· There are problems with storage and disposal of remains

Carbon Dioxide (CO2)
Prolonged carbon dioxide inhalation is an effective and approved method of euthanising rodents and small birds when it is done in accordance with the following guidelines. In fact, CO2 euthanasia has several advantages over other methods of euthanasia. For example, carbon dioxide is a potent central nervous system depressant and thus causes rapid unconsciousness and anaesthesia. Carbon dioxide exposure has also been shown to induce analgesia that begins within a few minutes of exposure and lasts for as long as an hour. Carbon dioxide is a relatively inert, inexpensive and easily procured gas that is not very hazardous for exposed humans. Finally, carbon dioxide does not accumulate in or contaminate tissues and has minimal effects on tissue architecture (with the exception of the lungs). Nonetheless, since inhalation of carbon dioxide is known to cause mucosal irritation and thus may cause short-term stress in animals exposed to this gas, a few precautions are warranted.

a. Carbon dioxide concentration in the chamber should be maintained in excess of 70% (it takes at least 50% to cause unconsciousness and some animals, especially diving mammals and other vertebrates, can withstand even 70% without being anaesthetised).

b. It is better to pre-fill the chamber prior to introduction of the animals so that unconsciousness will be induced in the shortest amount of time (rodents will be unconscious in about 30 sec in pre-charged chamber, vs. 150 sec in chambers filled slowly by continuous flow).

c. Either 100% CO2 or 70% CO2: 30% O2 may be used (no differences in stress reactions have been observed between inhalation of 70% or 100% CO2 ; although, it takes significantly longer to induce unconsciousness with the mixture.)

d. Dry ice may be used as a carbon dioxide source; however, the animal must be placed on a platform above the dry ice so that the animal does not have direct contact with the ice (dry ice can burn the tissue).

e. It is best to leave the animals in the euthanasia chamber for at least 5 minutes to assure death.

Note: The above guidelines apply to rodents and small birds. Larger animals such as rabbits are better euthanised by another method.

See also: Euthanasia – The Carbon Dioxide Debate

Acceptable Inhalant Agents
Halothane, methoxyflurane and isofluorane are acceptable agents with or without prior anaesthetic use.

Acceptable Non-Inhalant Agents
Sodium pentobarbital is the most commonly used non-inhalant agent.

Unacceptable Non-Inhalant Agents
Injectable agents ‘(strychnine, nicotine, caffeine, magnesium sulphate, potassium chloride, and all neuromuscular blocking agents), when used alone, are unacceptable and are absolutely condemned for use as euthanasia agents.’

2. Physical Methods
Some consider physical methods of euthanasia aesthetically displeasing. However, some of these methods cause less fear and anxiety, and may be more rapid, painless, humane, and practical than other forms of euthanasia when properly used by skilled personnel with well-maintained equipment.

It is strongly advised that anaesthesia be used prior to use of a physical method. Guidelines on some of the specific methods follow:

Cervical Dislocation
This method is primarily reserved for neonatal euthanasia. However, ‘when properly executed, manual cervical dislocation is a humane technique for euthanasia of poultry, other small birds, mice, rats weighing <200 g, and rabbits weighing <1 kg. In heavier rats and rabbits, the greater muscle mass in the cervical region makes manual cervical dislocation physically more difficult; accordingly, it should be performed only with mechanical dislocators or by individuals who have demonstrated proficiency euthanising heavier animals.’ As stated above, it is strongly advised that anaesthesia be used prior to use of a physical method.

See also: My Views on Different Methods of Euthanasia

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