Controversial Euthanasia Methods - Definitions,
Policies And Guidelines
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 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
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
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
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:
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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