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World Society for the Protection of Animals
Methods for the euthanasia of dogs and cats: comparison and recommendations
This document aims to provide guidance on the
euthanasia of dogs and cats by identifying methods
considered humane and methods that might
compromise animal welfare.
The euthanasia of companion animals is a much
debated issue for animal welfare organisations around
the world. Opinions are diverse and are often influenced
by local situations and cultural backgrounds.
The decision to euthanase an animal is a complex
ethical matter involving many factors, and a detailed
discussion of the subject is beyond the scope of this
document. As an animal welfare organisation, it is our
obligation to ensure that when the decision to euthanase
is taken the methods used are truly humane and
administered by responsible and appropriately trained
Methods of euthanasia, scientific knowledge and
opinions evolve over time; this overview is based on
current scientific evidence and will be subject to review.
Author: Louisa Tasker, MSc, BSc (Hons.)Editor: Companion Animals Unit, World Society for the Protection of Animals
World Society for the Protection of Animals 89 Albert Embankment London SE1 7TP T: +44 (0)20 7557 5000 F: + 44 (0)20 7703 0208 E:
[email protected]: wspa-international.org
DISCUSSION OF
Criteria for euthanasia
EUTHANASIA
Reasons for euthanasia
Personnel and training
Non-inhalant, injectable
Signs of pain and distress
pharmaceutical agents
Confirmation of death
Carcass disposal
Other intravenous anaesthetics
Professional and sympathetic conduct
Potassium chloride (KCI)
Magnesium sulphate (MgSO )
METHODS FOR THE
Chloral hydrate (CH)
EUTHANASIA OF
Inhalant agents (gas mixtures)
DOGS AND CATS
General considerations
Anaesthetic gases
Summary table of methods:
Nitrogen or nitrogen/argon mixtures
Recommended
Carbon dioxide (CO )
Acceptable
Carbon monoxide (CO)
Conditionally acceptable
Nitrous oxide (N 0)
Not acceptable
Physical methods
General considerations
PRE-EUTHANASIA DRUGS
Shooting using a free bul et
Sedatives
Combinations of pre-euthanasia drugs
General considerations
REFERENCES
Dosages and routes of
administration of agents
for euthanasia of dogs and cats
Guidelines on the intravenous
injection of Pentobarbitone for
the euthanasia of dogs and cats
Criteria for euthanasia
Even when these components are in place, WSPA
The term euthanasia comes from the Greek ‘eu'
reluctantly accepts that there are circumstances when
meaning ‘good' and ‘thanatos' meaning death, literal y
the euthanasia of healthy animals is required, for
translated it means ‘good death'. There are four
example in the case of animals that cannot be rehomed,
primary criteria that ensure death caused by methods
or to avoid overcrowding in shelters that would
of euthanasia is humane (Beaver
et al., 2001). The
compromise the welfare of animals being held there.
WSPA firmly believes that in al situations when
1 Be painless
euthanasia is deemed necessary, the methods adopted
2 Achieve rapid unconsciousness fol owed by death
should meet al four of the criteria listed at the beginning
3 Minimise animal fear and distress
of this introduction, and hence be truly humane.
4 Be reliable and irreversible
Personnel and training
To meet these criteria, the method should take into
Al methods of euthanasia have the potential to be
account the species, age and health of the animal. In
poorly performed if operators are untrained and
addition the method should be simple to administer,
unsupported. Consequently, it is essential that
safe for the operator, as aesthetical y acceptable to the
operators are provided with suitable training, including
operator as possible, and preferably require smal doses
a period of initial tuition with assessment of proficiency,
of any chemicals used.
fol owed by continuous monitoring of skil s and ability, as well as access to emotional support.
Reasons for euthanasia
A decision to euthanase an animal is a complex ethical
The initial period of instruction should, without
matter involving many factors, and a detailed discussion
exception, include training in both the technical aspects
of the subject is beyond the scope of this document.
of the methods to be used and the recognition of
The World Society for the Protection of Animals (WSPA)
signs of animal distress. Fol owing the instruction,
believes euthanasia is acceptable and necessary when
operators should understand the mechanism by
an animal is suffering due to an incurable il ness or
which that particular method of euthanasia causes
injury, or when an animal presents a significant risk to
unconsciousness and death. They should also receive
human health and safety or the safety of other animals,
direction and practical training in the careful handling
through disease or aggressive behaviour.
required to prevent distress in the animals they wil be restraining for euthanasia. It is essential that operators
It is advisable for WSPA member societies, which may
are taught to recognise the species-typical behaviour
have cause to euthanase animals in their care, to adopt
and physiological responses that indicate an animal is
an agreed euthanasia protocol that clearly outlines the
experiencing fear, distress, pain or anxiety, and how to
reasons for euthanasia and the acceptable methods.
take immediate action to al eviate these states should
they be observed.
WSPA does not condone the mass destruction of dogs and cats as a population control measure.
Signs of pain and distress
Successful control of dog and cat populations requires
The fol owing behaviours or physiological responses
a coordinated strategy that has been agreed by all
may be signs of pain and distress:
stakeholders and includes:
Aggression towards humans or redirected towards self
• Legislation with effective enforcement
or inanimate objects e.g. snapping, biting, growling,
• Registration coupled with a dependable method of
identification for dogs and cats
Vocalisation – whining, whimpering, high pitched
• Reproduction control
barking, howling, or growling in dogs, hissing or yowling
• Measures to reduce the availability of dogs and cats
through the control of breeders, pet-shops and other
Attempting to escape or withdraw from the situation
• Education of owners or guardians so that they act as
responsible carers for their animals
Pupils becoming dilated
Pilo-erection (hair standing on end)
• No animal should be disposed of until death is verified
Increased heart rate (tachycardia)
Shivering, muscle tremors and spasms; these may also
• Disposal should take into account regulations,
result from reflex skeletal muscular contractions
disease control and drug residues
Immobility or freezing (the animal becomes tense and
Once death has been confirmed the animal should
stops moving, but remains conscious and aware of the
be disposed of in accordance with the local and/or
national regulations. These rules should be obtained
Urination
from the local municipality or relevant animal health/
environment departments in advance and all operators
Anal sacs are emptied (foul smel ing liquid is
should comply with the necessary procedures.
This is especial y important for disease control.
Confirmation of death
Moreover, many of the injectable agents used for
Al operators performing euthanasia should be able to
euthanasia may leave residues in animal carcasses.
identify when death has occurred. Indicators include:
These drug residues may pose a threat to other animals in the event that the carcass is eaten and
• No movement of the chest / No signs of respiration
may cause localised contamination upon carcass
The animal's chest has stopped moving up and
down indicating that it has stopped breathing.
DO NOT rely on this sign alone as the animal's
• Suspect rabies cases require cautious handling and
heart may continue to beat for some time after it
compliance with reporting regulations
has stopped breathing
Special precautions should be taken when handling the carcass of any animal suspected of carrying
• No heart beat
rabies, including the use of protective clothing:
Check for this with a stethoscope or by palpating
gloves, overal s, eye goggles and protective shoes.
the animal's chest wal .
The carcass should be sealed in a plastic bag, as
• No pulse
the rabies virus can remain active for some time
Check for this by palpation over the medial
after death. The external surfaces of the carcass can
aspect of the animal's hind limb.
remain infective for several hours after death, and
Not always easy to locate in small animals
the internal organs can remain infective for several weeks depending upon environmental temperature,
• Loss of colour from the mucous membranes in the
so burial is not recommended. National or local
animal's mouth
regulations may require that the carcass, head or
Mucous membranes become pale and there is no
a sample of brain tissue are sent to a public health
capil ary refil if pressure is applied. With time the
authority laboratory for testing and surveil ance.
mucous membrane becomes dry and sticky.
Capillary refill is frequently still evident for
Professional and sympathetic conduct
prolonged periods after an animal has died
Al operators need to show professionalism and respect
for animal welfare, for the value of animal life, and
• Corneal reflex (blink reflex) is lost
for other people involved. The degree of distress that
The corneal reflex is normal y elicited when the
operators and other people experience when euthanasia
eyebal is touched. After death, the animal's eyes
is performed will be affected by their culture, beliefs
remain open and the lids do not move when touched.
and the community in which they live.
• Glazing of the eyes
Operators should be emotional y supported and trained
This occurs rapidly after death. The cornea loses its
to develop coping mechanisms to deal with this stress.
clear, moist appearance and becomes opaque, dry
This is important for many reasons, including the risk
and wrinkled.
that dissatisfied personnel may become careless when
handling animals and performing euthanasia. Ensuring that
• Rigor mortis
the methods used are humane can also help to reduce the
If death cannot be confirmed by a veterinary
distress experienced by operators and other people.
surgeon, or there is any doubt, operators should
wait until rigor mortis has set in before disposing of
the animal's carcass.
METHODS FOR THE EUTHANASIA
OF DOGS AND CATS
The fol owing pages assess the methods of euthanasia
in current use, in terms of the effects on the animal and
additional information regarding usage. The methods are
divided into the fol owing categories:
This method is considered ‘best practice' because it consistently produces a humane death when used as the sole means of euthanasia.
These methods also produce a humane death when used as the sole means of euthanasia. However, there
are practical limitations to their use.
These methods are acceptable only with caveats, due to the nature of the technique, potential for operator
error, or safety hazards to personnel. These methods may not consistently cause death humanely.
These methods are inhumane and are not considered
acceptable for the euthanasia of dogs and cats.
Some methods of euthanasia can be used in combination with pre-euthanasia drugs, and these are
discussed after the summary table. A detailed overview of each euthanasia method, giving rationale for their
categorisation, is provided on pages 15–21.
Intravenous (IV) injection of 20%
• egarded as ‘
best practice'
Pentobarbitone solution
• apid loss of consciousness, followed by cardiac arrest
• ay be used in combination with a pre-euthanasia drug if required for
fearful, fractious or aggressive animals
• o distressing side effects
• equires training
• elatively cheap
• ot licensed for use in all countries
• ost and availability may vary from country to country
• ombinations of high concentrations of barbiturate with a local
anaesthetic may also be available and suitable if given intravenously as a euthanasia agent
ATS
D C
N
S A
G
O
Intraperitoneal (IP) injection of
20% Pentobarbitone solution
• akes longer to take effect than IV injection: 15–30 minutes (dependent
upon the species and size of the animal)
• larger dose may be required than if given intravenously
• ay be used when col apsed or poor venous access precludes IV injection
• ay not be suitable for the euthanasia of larger animals
• he use of pre-euthanasia drugs may prolong the time until death
• ay cause irritation to the peritoneum, particularly with
concentrations >20%C
• an be combined with a local anaesthetic to reduce the risk of irritation
• nimal may become distressed when it starts to lose consciousness
• ay be a practical alternative when IV injection is difficult e.g. for
fractious stray or feral cats, neonatal kittens and puppies. It is advisable to
return cats to a secure cage after injection as they may become distressed while the drug takes effect
Intravenous (IV) injection of
anaesthetic agents, given as an
• apid loss of consciousness
overdose
• ay be suitable if animals are already anaesthetised for surgery and,
on humane grounds, not permitted to regain consciousness
e.g. Thiopentone or Propofol;
• elatively large volumes or high concentrations required to euthanase
Thiobarbiturate or Phenol
animals, potential y making it impractical for routine use depending upon
the commercial availability of the preparationU
• nder-dosing may lead to recovery
• May be used in combination with a pre-euthanasia drug if required
• equires training
• ost may preclude routine use
Intracardiac (IC) injection of 20%
• nly suitable in col apsed, unconscious animals, or very young puppies
• ay be suitable if animals are already anaesthetised for surgery and, on
humane grounds, not permitted to regain consciousness
Only acceptable if animals are
• ntracardiac route may be painful in ful y conscious animals
anaesthetised by other means prior
• equires training, skill and knowledge of anatomy to ensure penetration of
to its administration (page 14)
the heart is successful on the first attemptS
• ame licensing restrictions apply as with IV injection
Oral (PO) administration of
• Takes longer to take effect than IV injection (over 30 minutes) • May be suitable for neonates (within the first few hours/days of life) as
poor venous access precludes IV injection
• Not suitable for the euthanasia of larger/older animals
Only acceptable for neonatal
• May be used to sedate animals prior to euthanasia with intravenous
animals or to sedate animals prior
injection of Pentobarbitone
to intravenous injection of 20%
• Liquid form of the drug may be detected by animals in their food and
ingestion is avoided
• Powdered form may be delivered in gelatine tablets and hidden in food to
encourage consumption
• Animal may become distressed when it starts to become unconscious• Same licensing restrictions apply as with IV injection
Intravenous (IV) injection of T61
in a controlled manner, after prior
• auses death by respiratory col apse due to paralysis of the diaphragm
sedation
and intercostal muscles, resulting in asphyxia
• equires slow, steady rate of injection
Contains 3 drugs: general
• recise rate of injection is required: its use in fractious animals is
anaesthetic, local anaesthetic and
• ntense pain may result if the injection is given too quickly, due to muscle
paralysis prior to loss of consciousness
Only acceptable if animals are
• t should never be used without prior sedation to permit slow rate of
sedated by other means prior to its
administration and injection rate is
• equires training and skil
slow (page 13)
• o longer available for use in the United States
Intravenous (IV) or intracardiac
(IC) injection of potassium chloride
• auses death by cardiac arrest
(KCl) after general anaesthesia
• t should never be used without prior general anaesthesia to achieve
sufficient insensibility and analgesia, to block the painful side effects of
Concentrated electrolyte solution
• equires training to ensure operator can assess suitability of anaesthetic
Only acceptable if animals are
depth prior to use of KCl
anaesthetised by other means prior
• rior use of narcotic and analgesic mixtures adds significantly to the cost
to its administration (page 14)
and prolongs the time of the procedure
Intravenous (IV) or intracardiac
(IC) injection of magnesium
• auses death by cardiac arrest
sulphate (MgSO ) after general
• t should never be used without prior general anaesthesia to achieve
sufficient insensibility and analgesia, to block the painful side effects R
• equires training to ensure operator can assess suitability of anaesthetic
Concentrated electrolyte solution
depth prior to its useL
• arge volumes are required for euthanasia
Only acceptable if animals are
• saturated solution is required but this makes the liquid very viscous and
anaesthetised by other means prior
can result in difficulty of administration
to its administration (page 14)
• rior use of narcotic and analgesic mixtures adds significantly to the cost
and prolongs the time of the procedure
Inhalation of gaseous anaesthetics
such as halothane, enflurane,
• equires high concentrations to be effective
isoflurane and sevoflurane
• nly suitable for small animals (weighing <7kg)
• ay be suitable if animals are already anaesthetised for surgery and, on
Volatile inhalation anaesthetics
humane grounds, not permitted to regain consciousness D
• ifficult to administer to large animals
• n un-anaesthetised animals the smel of the volatile agent may be
unpleasant, such that they try to avoid it or hold their breath for a short timeI
• n un-anaesthetised animals it may cause respiratory distress as many can
act as irritantsC
• an be harmful to operators: risk of narcosis if exposed to the volatile
• ot routinely recommended as there are better alternatives
Shooting a free bullet to the head
• an cause immediate insensibility if done correctly with an accurate shot
Physical method
• eath by physical damage to the central nervous system
• nly acceptable in emergency situations where no other acceptable
methods are possible because the animal cannot be handled or given pre-euthanasia drugs and it is necessary to al eviate the suffering of an
• ot for routine use
• equires training
• equires skill and precision
• ay require a licence: firearm use is likely to be subject to national and
local regulations
• ngerous and unpleasant for operator and any other persons present
Intravenous (IV) injection of T61
• ay produce intense pain and causes death by paralysis of muscles
when used alone
leading to asphyxiation prior to loss of consciousness if the injection rate is too quick
Contains 3 drugs: general
• ot acceptable when used alone for euthanasia
anaesthetic, local anaesthetic and
• o longer available for use in United States
Intravenous (IV) injection of
• Cardiotoxic
– causes cardiac arrest without rendering the animal
potassium chloride (KCl) given
alone or only with prior sedation
• Produces severe cardiac pain as a result• Sedation provides insufficient analgesia to block painful side effects of
Concentrated electrolyte solution
euthanasia agent
• Not acceptable when used alone for euthanasia
Intravenous (IV) injection of
• auses cardiac arrest without rendering the animal unconscious
magnesium sulphate (MgSO )
• ay cause intense pain and distress
given alone or only with prior
• edation provides insufficient analgesia to block painful side effects of
euthanasia agentN
• ot acceptable when used alone for euthanasia
Concentrated electrolyte solution
Oral (PO) or intravenous (IV)
administration of chloral hydrate
• eath results from depression of the central nervous system resulting in
• esults in convulsions, muscular contractions and gasping
Chemical reagent with sedative/
• istressing and painful side effects
• arge volumes are required to be effective
• ot acceptable for euthanasia
Inhalation of nitrogen (N) or
nitrogen/argon mixtures
• eath due to hypoxia from paralysis of the respiratory centre
• ypoxia may occur before loss of consciousness even at high
concentrations, which is distressing for animalsV
• ocalisation, convulsions and tremors have been observed prior to death
• ery young animals (<four months) can take up to 30 minutes to die as
they may be resistant to hypoxia
• elfare aspects not entirely known
• equires special y constructed chambers
• equires a pure source of nitrogen/argon such as cylinder gas
• ot recommended as better alternatives available
Inhalation of carbon dioxide (CO )
• eath by asphyxia
• ppears to be aversive in most species
• cts as an irritant to the mucous membranes
• nimals may experience pain and distress prior to loss of consciousness,
associated with breathlessness, from increased concentrations of CO in
the blood and acidosis Y
• oung animals (<four months) are particularly resistant to hypoxia and
may take longer to dieR
• equires special y constructed chambers
• equires a pure source of CO such as cylinder gas
• ased upon current research to date on humans and other animals there
are sufficient welfare concerns to indicate that this method should not be used for euthanasia
Inhalation of carbon monoxide
• ighly variable time taken to lose consciousness and can take up to two
minutes at 6% concentration
• eath by hypoxia
• ocalisations and agitation observed in dogs and this may occur while
they are still consciousD
• istressing side effects observed in cats during induction
• nimals <4 months of age and sick or injured animals may have some
resistance to hypoxia caused by exposure to COR
• equires special y constructed chambers that are diligently maintained
and are operated to safeguard animal welfare and human safetyR
• equires a pure source of CO such as cylinder gas
• otential danger to operators either through repeated exposure of low
concentrations when operating the chamber or through accidental exposure to a lethal doseS
• ufficient animal welfare and human safety concerns that this method
cannot be recommended for euthanasia
Inhalation of carbon monoxide
• n addition to above these are hot and contain irritant impurities
(CO) exhaust fumes from petrol
• ot acceptable for euthanasia
Inhalation of nitrous oxide (N 0)
• Death results from hypoxia
• Used alone it does not cause anaesthesia• Causes respiratory distress before the animal loses consciousness
• Requires large concentrations
– must maintain 100% concentration for
• equires special y constructed chambers
• equires a pure source of N O such as cylinder gas
• uman health hazard if exposure occurs
• ot acceptable for euthanasia
Inhalation of Ether
• Causes death by hypoxia
Inhalation agent
• May cause respiratory distress
• Irritants to the respiratory system
• Requires large concentrations and rapid exposure to be effective
• Requires special y constructed chambers• Highly inflammable and may be explosive
– dangerous to operators and al
other persons present
• Not acceptable for euthanasia
Captive bolt
• though potential y and theoretical y an acceptable method this is not
Physical method
recommended for routine use due to practical difficulties including:R
• equires skil and knowledge of anatomical variation in dog breeds e.g.
dolichocephalic, brachycephalic, mesaticephalic skull typesA
• nimal's head needs to remain steady to ensure accurate shot (this may
be particularly difficult with cats)T
• he bolt must be placed directly on to the animals skul
• equires the animal to be restrained (this may be particularly difficult with
• equires further procedure (pithing or bleeding)
• isk of transmission of zoonotic disease (e.g. rabies) if exposed to blood/
• ay cause panic in waiting animals
• ot recommended for euthanasia as other methods are more practicable
• lthough it is theoretical y possible to apply a suitable current and voltage
across the skull (so that it passes through the animal's brain) by trained
Physical method
personnel using suitable electrodes, it is WSPA's experience that such conditions are never achieved in practice
• hole body exposure to the electric current in an electrocution chamber is
• inful and inhumane under practical conditions
• ngerous to personnel
• ot acceptable for euthanasia
• Slow acting• Death results from hypoxia
Physical method
• Pain and distress results from expanding trapped gases in the body prior
to the animal becoming unconscious
• Immature animals are tolerant of hypoxia and require longer periods of
decompression before respiration ceases
• Aesthetical y abhorrent as unconscious animals may bloat, bleed, vomit,
convulse, urinate and defecate during decompression
• Total y unacceptable
• eath by asphyxiation from strangulation
• auses fear and distress
Physical method
• otal y unacceptable
Drowning
• rolonged death by asphyxiation caused by immersion in water
Physical method
• auses fear and severe stress
• otal y unacceptable
Strychnine
• rolonged time for the animal to die and this can be highly variable – from
Poison: Neuromuscular blocker
minutes to days depending upon the dose ingested
• auses violent and painful muscle contractions resulting in asphyxiation
• xtreme danger to personnel
• otal y unacceptable
• auses death by hypoxia and cardiac arrest
• esults in violent convulsions and causes pain and distress while the
animal remains conscious
• xtreme danger to personnel
• otal y unacceptable
PRE-EUTHANASIA DRUGS
Pre-euthanasia drugs (tranquil isers, sedatives,
action, hence this drug cannot be recommended for sole
immobilisers or general anaesthetics) may be required
use prior to euthanasia with agents that may cause pain.
to facilitate safe and humane handling of animals
Moreover ACP should not be used alone to calm fearful
prior to euthanasia, particularly if they are fractious,
animals prior to euthanasia with any, even non-painful
aggressive or fearful. Moreover, the prior administration
agent, as it does not alter the animal's perception of the
of suitable pre-euthanasia drugs may be necessary with
situation, merely its ability to respond.
some conditional y acceptable euthanasia agents to ensure they are humane.
Sedatives
These drugs depress the activity of the central nervous
The majority of these drugs require minimal animal
system, resulting in drowsiness and muscle relaxation so
handling during their administration as they are
that animals become uncoordinated. If they are given in
preferably given as a subcutaneous injection (unless
sufficiently high doses an animal may fal into a sleep-like
contraindicated by the manufacturer), or sometimes as
state. However, they may not render the animal insensible
an intramuscular injection or even via oral dosing. The
to pain: the animal general y remains conscious but
operator then withdraws and waits for the drug to take
calm. As with tranquil isers, sedated animals can become
effect before administering the euthanasia agent. Some
aroused by strong stimulation such as a painful procedure,
pre-euthanasia agents, however, wil require intravenous
making their behaviour unpredictable.
administration. An important point is that the use of these drugs can add significantly to the time taken to
Examples of common sedative agents:
perform euthanasia and this should be considered in
Xylazine (Chanazine, Rompun, Virbaxyl, Xylacare)
advance to safeguard animal welfare.
is a common sedative used with both large animals (equines and livestock) and smal (companion) animals.
There are several drugs that are commonly used prior to
It induces muscle relaxation and also possesses some
euthanasia. It is essential that operators understand the
analgesic properties. If used alone this drug may not be
different effects each of these has on an animal, as their
a suitable pre-euthanasia agent for some conditional y
use may not be appropriate or humane as an adjunct to
acceptable euthanasia methods, as it does not induce
potential y distressing or painful euthanasia methods.
sufficient anaesthesia. In addition this drug will cause a
Terms such as tranquil isation, sedation, immobilisation
drop in blood pressure, rendering subsequent intravenous
and anaesthesia describe the actions of these drugs.
injection of euthanasia agents more difficult.
These terms are sometimes incorrectly used as if
they were interchangeable, their specific meaning and
Medetomidine (Domitor) can induce sedation but must
different effects are explained below.
be given in a sufficiently large dose. Its use also results in muscle relaxation and provides some analgesia. As
with Xylazine, if used alone this drug may not be a
These drugs have some effects in decreasing fear and
suitable pre-euthanasia agent for some conditional y
apprehension while the animal remains awake, making
acceptable euthanasia methods, as it does not induce
it calm when exposed to low level stimuli. However,
sufficient anaesthesia. Also as with Xylazine, this
they have no analgesic effects and the animal is readily
drug wil cause a drop in blood pressure, rendering
aroused by painful stimulation. Often they give a false
subsequent intravenous injection of euthanasia agents
sense of security to someone handling an animal, which
more difficult.
appears calm but may then display enhanced and even violent responses to a strong stimulus such as a loud
Butorphanol (Torbugesic, Torbutrol) has some analgesic
noise or an approach by a person. This is potential y
properties. But both its sedative and analgesic effects
dangerous to anyone who has to perform euthanasia.
are dose dependent. However, this drug may not be suitable for sole use with some conditional y acceptable
Example of common tranquil ising agent:
euthanasia methods, as it does not induce sufficient
Acepromazine maleate (ACP) is a common tranquil iser
anaesthesia or analgesia. Its use is unlikely to produce
used in animals, and has some depressing effects
the drop in blood pressure caused by Xylazine or
on the central nervous system. Its principal use is
in combination with other opiate drugs as a pre-medication given before anaesthesia. It wil not
eliminate any pain associated with euthanasia agents,
These drugs render the animal immobile by inducing
and increasing the dosage above what is recommended
paralysis. The animal's body may become rigid and stiff
will have little further effect over the tranquil ising
and the animal appears unresponsive to external stimuli
such as sound. However, the animal can stil feel pain
Oral administration of drugs or combinations of drugs
and therefore the sole use of immobilisers with painful,
as a prelude to euthanasia has been explored for dogs
conditional y acceptable euthanasia agents is not
(Ramsay and Wetzel, 1998) and cats (Wetzel and
Ramsay, 1998; Grove and Ramsay, 2000). For dogs a combination of Tiletamine-Zolazepam/Acepromazine
Example of common immobilising agent:
or Pentobarbitone used alone consistently induced
Ketamine (Ketaset, Vetalar) classed as a dissociative
sedation and lateral recumbency (Ramsay and
anaesthetic, can also be used for restraint. It may
Wetzel, 1998). However, the time taken to produce
induce muscle rigidity when used alone and produces
profound sedation was prolonged (30
–90 minutes)
an altered state of consciousness (catatonia: not a loss
and highly variable between individuals.
of consciousness). Unless combined with other drugs such as Medetomidine, Xylazine and/or Butorphanol to
In addition, the sole use of Pentobarbitone was
produce sufficient analgesia and anaesthesia, it is not
associated with struggling to stand and prolonged
acceptable as a sole pre-euthanasia drug for use with
ataxia during the onset of ful sedation. These
euthanasia agents that may cause pain. Injection by
undesirable effects were not observed for the
intramuscular or subcutaneous routes may be painful
Tiletamine-Zolazepam/Acepromazine combination
and its rate of absorption can be altered.
and they may be ameliorated if Acepromazine is added to the Pentobarbitone dose (Ramsay and
Wetzel, 1998), but this combination was not tested.
These result in loss of consciousness and provide
It is important to note that liquid preparations of the
good analgesia and muscle relaxation, so that surgical
drugs mixed with food were detected and rejected
procedures can be undertaken.
by dogs (Ramsay and Wetzel, 1998). Uptake by dogs was greatly improved when the required dose
Examples of common anaesthetic agents:
of powdered preparations was placed in gelatine
Tiletamine-Zolazepam (Telazol®, Zoletil®). This drug
capsules and hidden in canned (wet) food.
combination offers good anaesthesia and al ows for an intracardiac injection of pentobarbitone or intravenous
The oral administration of Detomidine/Ketamine
or intracardiac injection of conditional y acceptable
combination was successful in sedating cats (Wetzel
methods of euthanasia when properly administered.
and Ramsay, 1998; Grove and Ramsay, 2000)
This drug combination should be injected
in comparison with other drugs tested (Ketamine,
Detomidine, and Xylazine/Ketamine, Medetomidine/Ketamine combinations). This particular combination
Thiopentone and Propofol. These drugs wil result in
produced reliable sedation within 10
–25 minutes
sufficient anaesthesia to al ow for intracardiac injection
of oral dosing (Grove and Ramsay, 2000). However
of pentobarbitone or intravenous or intracardiac
there are several undesirable side effects that may
injection of conditional y acceptable methods of
preclude this from routine use. The oral treatment
of cats with all combinations tested (Detomidine/
euthanasia. However, both of these drugs must be given
intravenously and may be unsuitable for use in animals
Ketamine, Xylazine/Ketamine and Medetomidine/
that are difficult to handle or restrain.
Ketamine) resulted in vomiting and excessive
salivation in some cats (Wetzel and Ramsay, 1998;
Combinations of pre-euthanasia drugs
Grove and Ramsay, 2000) and is likely to cause
Combinations of drugs may enhance their suitability
distress to cats during induction prior to loss of
as a prelude to euthanasia, especial y if they possess
different, complementary analgesic and anaesthetic
properties (e.g. Ketamine and Butorphanol). Such
Food dosed with these types of drug is unpalatable,
combinations should be chosen to render the animal
hence precluding accurate administration via food.
insensible to the pain that may result from some
However, the method of dosing used in these tests
conditional y acceptable euthanasia methods. When
(squirting the liquid medicants directly into the cats'
using a combination of drugs it is vital that a sufficient
mouth) is difficult to perform remotely with any
dose of each drug is used, and that ample time is
accuracy. The handling of fractious or aggressive cats
al owed for them to reach their maximum effect before
for oral dosing is likely to cause stress to the animals,
euthanasia is undertaken. Moreover, animals should be
thus presenting a welfare issue as wel as a potential
maintained in a quiet and calm environment as external
hazard for operators. Furthermore, Detomidine may
stimulation can prolong the time taken for drugs to
not be licensed for use in cats and guidelines for off-
take effect. Both of these factors can be affected
label use should be fol owed.
by an animal's species (dog or cat), age, body size, demeanour and metabolism, so the individual animal's drug requirements must be careful y determined before this course of action.
DISCUSSION OF
The fol owing discussion provides greater detail
expression of pain. In some individuals a terminal
regarding the use and suitability of each method
gasp may occur when the animal is unconscious and
described in the summary table, to explain the reasons
although this may distress some observers, it is not an
for their categorisation. They are arranged by mode of
expression of pain or discomfort, merely a reflex action.
action and their acceptability for euthanasia.
Pentobarbitone is easy to use, relatively cheap and safe for the operator (provided that it is not misused, e.g.
Euthanasia agents are general y classified by their physical
deliberately self-injected).
characteristics: non-inhalant (injectable) pharmaceutical agents; inhalant agents (gas mixtures); physical
When the restraint necessary for giving an intravenous
methods; and poisons. They work by one of three modes
injection would distress an animal or pose undue risk
of action (Close
et al., 1996; Beaver
et al., 2001):
to the operator then prior sedation or anaesthesia (pages 13–14) or other accepted alternative routes of
• Hypoxia – death results from reducing the amount of
administration should be employed (Beaver
et al., 2001).
oxygen available to the animal's cel s and tissues.
In an emergency situation the drug can be injected
• Direct depression of the nerve cel s in the respiratory
directly into the peritoneal cavity (intraperitoneal).
centres of the brain necessary for maintaining life
The time taken for the animal to lose consciousness
function, leading to a loss of consciousness fol owed
and die (15–30 minutes) is longer than if the drug is
given intravenously (a few seconds). A higher dose of Pentobarbitone is required for intraperitoneal
• Physical disruption of brain activity through
euthanasia (Grier and Schaffer, 1990; Sinclair, 2004)
concussion, direct destruction of the brain, or
and it can cause irritation to the peritoneum, but this
electrical depolarisation of nerve cel s, leading to
can be avoided if the drug is combined with a local
rapid unconsciousness. Death occurs owing to
destruction of the areas of the brain that control
cardiac and respiratory functions.
There are no published reports on the use of
intraperitoneal injection in dogs; nevertheless Sinclair (2004) provides anecdotal accounts that dogs
Non-inhalant, injectable
struggle more than cats; repeatedly attempting to
right themselves during the induction phase. For this
Barbiturate, injectable anaesthetic agents,
reason intraperitoneal injection may be unsuitable for
T61, potassium chloride, magnesium sulphate
larger animals.
and chloral hydrate
While most cats, kittens and puppies appear to advance more smoothly to unconsciousness than adult dogs, they
should be closely monitored, and confined to a warm,
dark, quiet place to facilitate distress-free induction.
Barbiturates act by depressing the central nervous
The combination of Pentobarbitone and Phenytoin (a
system, starting with the cerebral cortex, which
cardiotoxic anticonvulsant drug) may be unsuitable
causes rapid loss of consciousness progressing to
for intraperitoneal injection, because of concerns over
anaesthesia (Beaver
et al., 2001). Their efficacy as
the differential absorption rates of the two compounds
anaesthetic agents free from distressing side effects is
(Sinclair, 2004). The effects of Phenytoin on the heart
widely recognised. With sufficient dosages (overdose)
may occur before the Pentobarbitone component has
barbiturates induce respiratory and cardiac arrest
caused unconsciousness (Fakkema, 1999 cited by
by depressing the centres within the central nervous
Sinclair, 2004).
system that control these life-maintaining functions.
The technique for intrahepatic injection of
For euthanasia of dogs and cats, barbiturates that
Pentobarbitone has been reported by Grier and
have been specifical y formulated as euthanasia
Schaffer (1990). When correctly administered,
agents are preferred. The intravenous injection of 20%
its action is considerably faster in comparison to
Pentobarbitone solution is regarded as the most humane
injection via the intraperitoneal route, with cardiac
method of euthanasia for dogs and cats (Reil y, 1993;
standstil being reported within 11–14 minutes.
Close et al., 1997; Beaver et al., 2001; European Food
However, performing accurate intrahepatic injection is
Safety Authority, 2005) (see Annex 2). Dogs and cats
technical y difficult and may cause animals discomfort
are simply ‘put to sleep'; there is no audible or other
(Sinclair, 2004). Administration outside of the target
organ (the liver) is associated with excitement, which
inducing unconsciousness and death. However,
may also be distressing to the operator (Grier and
larger volumes are required for euthanasia (Annex 1)
Schaffer, 1990).
and often this makes their use more cost prohibitive for routine euthanasia than Pentobarbitone. In
Injection of 20% Pentobarbitone directly into the heart
addition these agents should not be given other than
(intracardiac) may be suitable in col apsed, unconscious
intravenously, as they may cause tissue reactions at
animals. However, this requires skil and knowledge of
the site of injection leading to pain and discomfort. As
anatomy because failure to inject into the correct place
with Pentobarbitone, they may be subject to restricted
wil cause pain. It should only be used by experienced
licensing practices.
technicians in an emergency.
It may be appropriate to administer liquid form of a
ACCEPTABLE WITH CONDITIONS
suitable concentration of Pentobarbitone oral y (by
mouth) to neonatal puppies and kittens (within the first
T61 is a mixture of three compounds (embutramide,
few hours/days of life) for euthanasia, as intravenous
mebezonium iodine, tetracaine hydrochloride),
access is difficult. The time taken for effect is longer
which provide a combination of muscle paralysis
than if administered intravenously.
(via curarifrom-like mechanisms), local anaesthetic and general anaesthetic actions (Giorgi and Bertini,
It should be noted that the time taken for oral
2000). The muscle paralysing agent rapidly
administration of Pentobarbitone to reach its maximum
induces respiratory col apse by paralysing the
effect is prolonged (30–90 minutes) and highly variable
animals' diaphragm and intercostal muscles. A
between individuals given the same dose (Ramsay and
local anaesthetic acts to reduce (painful) tissue
Wetzel, 1998). In addition to the lengthy induction
inflammation at the site of the injection, and the
time, other undesirable side effects may make this
general anaesthetic induces loss of consciousness.
method unsuitable for routine use, for instance some dogs may struggle prior to becoming ful y sedated
The three compounds have different speeds of
(Ramsay and Wetzel, 1998).
absorption in the body (Beaver
et al., 2001) and there is a risk that if the injection is given too quickly
Oral administration of Pentobarbitone for euthanasia
the animal wil remain conscious during respiratory
of juvenile or adult dogs and cats is unsuitable.
col apse, which may produce pain (Giorgi and Bertini,
It may, however, be used to produce sedation or
2000) and distress (Hel ebrekers
et al., 1990) prior
light anaesthesia to precede intravenous injection
to death. For this reason T61 should be given by a
of Pentobarbitone for the euthanasia of fractious or
slow and precise rate of intravenous injection (Beaver
aggressive animals (Ramsay and Wetzel, 1998;
et al., 2001). This is likely to be difficult with animals
Sinclair, 2004).
that are anxious when being handled or restrained.
Some euthanasia products have been formulated to use
T61 should therefore only be used with prior sedation
barbiturates combined with a local anaesthetic agent
(page 13) to al ow for close monitoring of injection
or Phenytoin. The pharmacological differences are
rate and to avoid causing pain to the animal. It should
inconsequential when injected intravenously but such
never be given other than intravenously (Annex 1), as
compounds may be more easily obtained in
the onset of action of each of the three constituents
can be altered when administered via alternative routes (Beaver
et al., 2001). T61 is no longer
WSPA considers the use of intravenous Pentobarbitone
available for use in the United States.
for euthanasia of dogs and cats as ‘best practice'
(Annex 1, Annex 2) and its use is strongly
ACCEPTABLE WITH CONDITIONS
recommended provided that it is legal y permissible and operators have been given appropriate training.
Potassium chloride (KCI)
However, suitable barbiturates are not always
The potassium ion is cardiotoxic (has a toxic effect
available and in these circumstances WSPA urges
on the heart muscle) and rapid injection of potassium
veterinary authorities, animal welfare organisations and
chloride (KCI) as a saturated salt solution causes
governments to strive to make these drugs legal y and
cardiac arrest leading to death if given intravenously
easily available to the relevant professionals.
or by the intracardiac route of injection. It has no anaesthetic or analgesic properties so if used alone it causes animals intense pain prior to death. Hence
KCI is only acceptable as the final stage of euthanasia
Other intravenous anaesthetics
in animals given prior narcotic or analgesic agents to
Other barbiturate drugs commonly used as
block its painful side effects (page 14). It is essential
anaesthetics, such as Thiopentone and newer agents
that personnel performing this technique are trained
such as Propofol, wil produce painless euthanasia if
and knowledgeable in anaesthetic techniques. They
given intravenously as overdoses (Annex 1). They work
should be competent at assessing anaesthetic depth
in a similar manner to that described above, rapidly
appropriate for subsequent administration of KCI.
Euthanasia with KCl is only considered to be acceptable
Inhalant agents (gas mixtures)
if animals are under general anaesthesia, characterised
Anaesthetic gases, nitrogen/argon, carbon dioxide,
by loss of consciousness, loss of response to unpleasant
carbon monoxide, nitrous oxide and ether
(including painful) stimuli and an absence of reflex muscle responses (Beaver
et al., 2001). KCI can be
General considerations
easily acquired, transported and mixed with water to
Inhalation agents used for euthanasia include volatile
form an injectable, supersaturated solution (Annex
liquid anaesthetics and gases or gas mixtures that result
1) to kill animals. However, the use of suitable pre-
in hypoxia; delivered at increasing concentrations they
euthanasia drugs wil significantly increase both the
displace oxygen in the air breathed by animals (inspired
time taken to perform euthanasia and its cost.
air) thereby lowering the concentration of oxygen reaching the lungs and tissues (Close
et al., 1996).
ACCEPTABLE WITH CONDITIONS
To be effective, inhaled agents must reach a certain
Magnesium sulphate (MgSO )
(minimum) concentration in the animal's lungs (Beaver
et
Magnesium sulphate (MgSO ) is a neuromuscular
al., 2001). This means they do not induce an immediate
blocking agent. If delivered intravenously as a saturated
loss of consciousness, and death fol ows at some
salt solution it wil lead to cardiac and respiratory arrest
considerable time later (European Food Safety Authority,
fol owed by death (Close
et al., 1996). However, it
2005). The humane induction of unconsciousness is
causes muscle paralysis (inducing respiratory arrest)
important, and any inhalation agents used must not
without prior loss of consciousness (Beaver
et al.,
be unpleasant for the animal to breathe or produce
2001); the animal therefore remains conscious but
pain or distress prior to loss of consciousness (Close
immobile until the brain succumbs to lack of oxygen
et al., 1996, 1997; Leach
et al., 2004; European Food
(European Food Safety Authority, 2005). Moreover
Safety Authority, 2005). In particular, inhalation agents
MgSO has no analgesic or anaesthetic properties
that produce convulsions prior to unconsciousness are
to block the painful side effects and its sole use as
unacceptable for euthanasia and should not be used
an agent for euthanasia is inhumane (Close
et al.,
(Close
et al., 1996; Beaver
et al., 2001).
1996, 1997; Beaver
et al., 2001; European Food Safety Authority, 2005). Dogs have been observed to
Very young animals are particularly resistant to the
experience violent muscle spasms and contractions,
effects of lowered oxygen concentrations (hypoxia/
vocalising, gasping for breath and convulsion seizures
anoxia) because their haemoglobin (the oxygen-
prior to death (Avariez and Caday, 1958), indicating
transporting molecule in red blood cel s) has a higher
that they experience pain and distress. As with
affinity for oxygen than that of adults (Pritchett
et al.,
using KCI for euthanasia, MgSO is only acceptable
2005 cited by European Food Safety Authority, 2005);
as the final stage of euthanasia in animals that are
an adaptation to being in the uterus. Young animals,
anaesthetised (page 14) and hence unconscious and
therefore, take longer to die from hypoxia than adults
unresponsive to noxious (including painful) stimuli (and
(Close
et al., 1996; Beaver
et al., 2001).
their reflex muscle responses can no longer be evoked).
Again, this requirement for pre-euthanasia drugs
Inhaled agents may take longer to build up in the lungs
significantly adds to both the time taken to perform
and be effective in animals that are il , injured or old, as
euthanasia and to its cost. Furthermore, large volumes
these animals may show decreased ventilation (shal ow
of MgSO are required (Annex 1) and an effective
breathing), making agitation more likely before loss of
saturated solution becomes very viscous and difficult to
consciousness (Beaver
et al., 2001).
handle for injection.
In addition to these general considerations for animal
welfare, the health and safety of operators is a major
concern with some of these methods. Both acute and
Chloral hydrate (CH)
chronic exposure to these agents can have toxic effects
Chloral hydrate (CH) acts slowly to depress the brain
on humans (National Institute for Occupational Safety
centres responsible for control ing respiration and
and Health, 1977).
during the time taken to become unconscious animals
display muscle spasms, gasp for breath and vocalise; indicating that they are in distress (Carding, 1977;
ACCEPTABLE WITH CONDITIONS
Close
et al., 1996). This drug has no anaesthetic or
Anaesthetic gases
analgesic properties to block the painful and distressing
Halothane, Enflurane, Isoflurane and Sevoflurane are
side effects and it is unacceptable for use in dogs and
commonly used as anaesthetic agents and can be
cats. Even with prior use of anaesthetics its slow mode
used for euthanasia if they are given as an overdose
of action and the large volume required for it to be
(Annex 1) (European Food Safety Authority, 2005).
effective make it unacceptable for euthanasia (Carding,
However, these agents differ in the speed at which
1977; Beaver
et al., 2001).
they induce unconsciousness and they possess varying degrees of pungency, which animals may find unpleasant (Leach
et al., 2004; European Food Safety
Authority, 2005). In addition, animals may struggle and
loss of consciousness, dogs were observed yelping,
become anxious during induction (Beaver
et al., 2001)
gasping and convulsing, and some develop muscle
because anaesthetic vapours may be irritating (Leach
et
tremors (Herrin
et al., 1978), occurrences likely to
al., 2004). They are therefore not general y considered
be aesthetical y objectionable for human operators
to be suitable as sole agents for euthanasia in larger
(Reil y, 1993; European Food Safety Authority, 2005).
animals (>7kg). Halothane is preferred because it may
Although time to unconsciousness was 1–2 minutes
be less aversive during induction (Leach
et al., 2004)
from initial exposure to the gas, the time to death was
and produces anaesthesia more rapidly than the other
recorded at 5 minutes (Herrin
et al., 1978). Tranquil ising
agents (Beaver
et al., 2001; European Food Safety
dogs with Acepromazine (ACP) prior to exposure with
Authority, 2005).
nitrogen gas for euthanasia (in an attempt to ameliorate the possible distressing side effects of hypoxemia)
Inhalation anaesthetic agents are vaporised and
significantly prolongs the time to death (Quine
et al.,
delivered into chambers, via a face mask or tube from
1988). It is essential that high concentrations of gas
anaesthetic machines; they are combined with air/
are maintained for the duration until death has been
oxygen during induction to prevent hypoxia (Close
confirmed (European Food Safety Authority, 2005), as
et al., 1996, Beaver
et al., 2001). The liquid states
re-establishing concentration of oxygen at 6% or greater
of these agents are highly irritant, and animals
in the chamber will al ow immediate recovery (Beaver
et
should only be exposed to vapours. Chambers and
al., 2001).
anaesthetic machines should be properly designed to ensure that the gas is evenly distributed and that the
In summary, the suitability and humaneness of this
animal is rapidly exposed to effective concentrations
method is not well understood (Beaver
et al., 2001;
of the agent (Close
et al., 1996). It is important to
European Food Safety Authority, 2005). Current evidence
use equipment that is wel maintained and to have
indicates this method is unacceptable because animals
scavenging units (devices used to reduce the pol ution
may experience distressing side effects prior to loss of
in the air) to prevent personnel being exposed to the
consciousness, and there are more humane alternatives
anaesthetic agents, as exposure to trace concentrations
available for the euthanasia of dogs and cats.
of anaesthetic gases is recognised as a human health hazard (National Institute for Occupational Safety and
Health, 1977).
Carbon dioxide (CO )
The large doses required for euthanasia are expensive
Carbon dioxide (CO ) is a non-flammable, non-explosive
and tend to make this method cost prohibitive. With
gas, present in air in smal concentrations (0.04%); as a
the difficulty in administration and human health
separate gas it is heavier than air (Carding, 1977; Beaver
aspects, this means that although this can be an
et al., 2001). Inhalation of CO above 70% depresses
acceptable method of euthanasia for smal dogs and
the central nervous system leading to respiratory arrest
cats there are more suitable methods available (Close
and death from asphyxia (Carding, 1968). Depending
et al., 1997; Beaver
et al., 2001). The greatest value
on the concentration, loss of consciousness may occur
of anaesthetic gases may be for the euthanasia of smal
within 1
–2 minutes but actual death may not fol ow until
animals (<7kg) where intravenous access is difficult,
5–20 minutes after initial exposure (Carding, 1968).
and to al ow for intracardiac injection of other suitable
For euthanasia, CO must be delivered at a control ed
euthanasia agents. In addition, anaesthetic gases may
rate from cylinders into special y constructed chambers
be given as an overdose to animals that are already
(Beaver
et al., 2001).
surgical y anesthetised when, on humane grounds, it is
not desirable for them to regain consciousness.
CO is aversive to most species (European Food Safety
Authority, 2005). Concerns over the humaneness of CO
(European Food Safety Authority, 2005) stem from its
association with breathlessness and hyperventilation
Nitrogen or nitrogen/argon mixtures
(Hewett
et al., 1993; Raj and Gregory, 1995). At high
Nitrogen and argon are colourless, odourless gases
concentrations, CO dissolves in the moisture of the
that are inert, non-flammable and non-explosive.
animal's air ways producing carbonic acid that causes
Both gases are present in atmospheric air (nitrogen at
irritation (Ewbank, 1983, Close
et al., 1996) and pain
78% and argon at <1%). Placing animals in enclosed
in the animal's nose (Beaver
et al., 2001). In cats,
containers that are pre-fil ed with nitrogen or argon
induction to unconsciousness is accompanied by escape
induces unconsciousness and results in paralysis of the
attempts, licking, sneezing and increased movement or
respiratory centres, fol owed by death (Beaver
et al.,
agitation (Simonsen
et al., 1981); indicating exposure is
2001; European Food Safety Authority, 2005).
distressing (Close
et al., 1997). Similarly, in dogs rapid exposure to increasing concentrations of CO produced
There are few studies on nitrogen inhalation for
severe struggling and hyperventilation (Carding, 1968).
euthanasia of dogs, but these suggest that loss of consciousness is preceded by hypoxemia and
Studies conducted in rats have concluded that CO
hyperventilation (Herrin
et al., 1978) which may be
when used in concentrations sufficient to induce loss of
distressing to animals (Beaver
et al., 2001). Fol owing
consciousness are likely to cause considerable suffering
before unconsciousness (Danneman
et al., 1997; Leach
There are several practical limitations associated with
et al., 2004). The cumulative stress associated with the
this method of euthanasia. Firstly, the construction,
induction of unconsciousness when using CO is a serious
diligent maintenance and careful operation of special
welfare concern (European Food Safety Authority, 2005).
chambers are essential to reduce the risk to human
WSPA therefore considers this to be an unacceptable
and animal welfare; and these are likely to be costly.
method for the euthanasia of dogs and cats.
Secondly, use of CO to euthanase certain groups of animals is considered unacceptable (Humane Society
of the United States, undated). In particular, animals under four months old (resistant to hypoxia); those
Carbon monoxide (CO)
with impaired breathing and or low blood pressure
Methods of generating carbon monoxide (CO) gas
(due to systemic disease, injury or old age) wil take
for euthanasia of animals have included chemical
longer to succumb, causing additional distress prior
interaction arising from combining sulphuric acid
to death. Use of CO inhalation to euthanase obviously
and sodium formate and the use of exhaust fumes
pregnant animals is also discouraged as the unborn
produced from idling petrol engines (Carding, 1977).
young wil not be exposed to the gas and wil die slowly
Both of these techniques produce irritants that are
as a result of suffocation, due to death of the mother
likely to result in considerable distress to animals and
(Humane Society of the United States, undated).
are therefore detrimental to the welfare of dogs and
Moreover, unconscious dogs urinate, defecate and
cats (Carding, 1968, 1977; Close
et al., 1996; Beaver
regurgitate (Moreland, 1974) making this aesthetical y
et al., 2001), and hence their use is not acceptable.
objectionable for operators and requiring chambers to
Commercial y compressed CO delivered from cylinders
be thoroughly cleaned, adding to the time of use.
into special y constructed chambers has been used for the mass euthanasia of dogs and cats.
Although considered a conditional y acceptable method of euthanasia by the American Veterinary Medicine
CO combines with haemoglobin in the red blood
Association (Beaver
et al., 2001) and the Humane
cel s, decreasing the oxygen carrying capacity of the
Society of the United States for some dogs and cats,
animal's blood. As a result, less oxygen is delivered
the many limitations of CO may make this method less
to the tissues and cel s (hypoxia), which leads to
practical, considerably slower and more expensive than
unconsciousness, fol owed by death (Chalifoux
lethal injection (Humane Society of the United States,
and Dal aire, 1983). Although the animal becomes
undated). There is also concern over the distressing
unconscious within 1–2 minutes (variable between
side effects of exposure to CO (European Food Safety
individuals), death as confirmed by cessation of
Authority, 2005) while the animal is conscious (Stafford,
heartbeat does not occur until 10–20 minutes after
2006) and over the significant danger to operators. For
initial exposure to CO at concentrations reaching
these reasons WSPA considers this to be an unacceptable
6% (Moreland, 1974; Chalifoux and Dal aire, 1983;
method for the euthanasia of dogs and cats.
Dal aire and Chalifoux, 1985). Although the welfare
aspects of this method have not been wel researched,
a few studies have reported that prior to loss of
consciousness dogs show signs of anxiety, including
Nitrous oxide (N 0)
moaning vocalisations (Carding, 1968; Chalifoux and
This gas is no longer considered appropriate as a sole
Dal aire, 1983; Dal aire and Chalifoux, 1985) and
anaesthetic agent as it does not induce anaesthesia
signs of agitation (Moreland, 1974; Chalifoux and
in animals even at 100% concentrations (Beaver
Dal aire, 1983). Furthermore, there is some concern
et al., 2001). If N 0 is used on its own it produces
that the onset of convulsions (Close
et al., 1996) and
hypoxemia (low oxygen in the blood) (European Food
muscular spasms (Moreland, 1974) may precede loss
Safety Authority, 2005) before respiratory or cardiac
of consciousness (Chalifoux and Dal aire, 1983; Close
arrest (Beaver
et al., 2001) and as a result animals
et al., 1997). Equal y distressing behaviours have been
may become distressed prior to loss of consciousness
observed in cats during the initial phase of euthanasia
(Beaver
et al., 2001). This method is considered
using this method (Simonsen
et al., 1981).
inhumane and not acceptable for euthanasia.
Use of the tranquiliser ACP prior to euthanasia with
CO significantly reduced some of the behavioural and physiological responses of dogs, but sufficient time
must be al owed for ACP to reach its maximum effect
This is a highly inflammable volatile liquid, which may
before exposure to CO (Dal aire and Chalifoux, 1985).
be explosive under some circumstances. It must be vaporised by the passage of a gas, normal y oxygen,
In addition to the risks for animal welfare, CO is
to be used as an anaesthetic. Ether is a relatively
extremely hazardous for humans because it is highly
dangerous substance to use and causes distress by
toxic and difficult to detect. Even chronic low level
irritation to the nasal passages and eyes to both the
exposure is considered a human health hazard and is
animal and the operator (Close
et al., 1996). This agent
associated with cardiovascular disease (Beaver
et al.,
is not suitable for euthanasia, because of extreme risk to
operators and the detrimental effects on animal welfare.
Physical methods
the conformational differences between the skul s of
Shooting using a free bullet, penetrating captive bolt,
individuals and breeds of dogs increase the risk of a
electrocution, decompression, hanging and drowning
mis-stun. The principle skull types are dolichocephalic (long, narrow head), brachycephalic (short, wide heads)
General considerations
and mesaticephalic (medium proportions).
For several reasons physical methods for the euthanasia of dogs and cats are general y not recommended
Use of a captive bolt may be aesthetical y unpleasant
(Close
et al., 1997). Some methods are likely to cause
to the operator, especial y as further measures are
severe pain and suffering to animals and are therefore
necessary (e.g. pithing or exsanguination) to ensure death
considered inhumane, and unsuitable for euthanasia. In
(Beaver
et al., 2001). The bleeding that occurs after
addition the high risk of equipment failure, malfunction
penetration of the skul and after further pithing creates
and operator error when used in practice wil cause
a hazard for the operator, due to the risk of coming into
pain and distress to the animals. The only physical
contact with blood and brain matter. This risk may be of
method considered conditional y acceptable by WSPA
particular concern in rabies-endemic areas.
– shooting with a free bul et
– could be used as a last resort in an emergency situation when no other
As there is a high risk of mis-stunning through inadequate
methods are possible, but not as routine.
use of the penetrating captive bolt, and hence causing pain and distress, WSPA considers this an unacceptable
Many of these methods may be aesthetical y
method for the euthanasia of dogs and cats.
objectionable for personnel, making them distressing to perform and further increasing the stress that
operators may experience. Furthermore, if operators are distressed and dissatisfied themselves, there is an
increased likelihood of them becoming careless when
In theory it is possible to achieve euthanasia by
handling animals.
applying an appropriate electric current and voltage in a two-step process: first, spanning the animal's
ACCEPTABLE WITH CONDITIONS
brain to render it unconscious – producing an effective stun; second, applying sufficient current across
Shooting using a free bullet
the heart to produce cardiac fibril ation and death
An accurate shot to the animal's head wil result
from hypoxia (Beaver
et al., 2001). However, it is
in immediate destruction of the brain and loss of
WSPA's experience that such ideal conditions are
consciousness, fol owed by death (Carding, 1977).
never achieved in practice. There are grave concerns
However, specialist training and considerable skill
over the suitability of the design (Carding, 1977)
is required to ensure that the bul et wil penetrate
and maintenance of equipment, which, coupled with
the brain. In addition there is extreme danger to the
lack of training and misuse (Phil ips, undated), make
operators and any bystanders, and a firearm should
this method inhumane. If an animal is not effectively
never be used in enclosed spaces as there is a risk
stunned, which is often the case with whole body
of ricocheting bul ets. Moreover, the use of a firearm
exposure to electric current in electrocution chambers
is likely to be subject to strict local and national
(Carding, 1977), death results from cardiac fibril ation
regulations. WSPA would only conditional y accept
in a conscious animal, and hence involves excruciating
this method for use in an emergency situation, when it
pain and distress. In addition this method may be
is necessary to al eviate the suffering of an individual
extremely hazardous to personnel, and is aesthetical y
animal but no acceptable euthanasia methods are
objectionable as it causes violent extension and
possible, because the animal cannot be handled or
stiffening of the animal's limbs, head and neck
given pre-euthanasia drugs.
(Beaver
et al., 2001).
WSPA regards electrocution as an unacceptable method of euthanasia for dogs and cats, as the minimum
Captive bolt
conditions necessary for it to be humane are often not
Although widely used and accepted as a stunning
achieved in practice.
procedure for the slaughter of large livestock species, this method is general y considered inappropriate for
dogs and cats (European Food Safety Authority, 2005). The penetrative captive bolt pistol must be placed in
contact with the animal's skull and precise positioning
This method requires the use of decompression
is essential so that the bolt penetrates the correct area
chambers. In theory the low ambient air pressure in
of the brain first time. Animals must be adequately
the absence of extra oxygen results in cerebral hypoxia,
restrained so that the head remains steady (Carding,
leading to loss of consciousness fol owed by death
1977; Dennis
et al., 1988; Beaver
et al., 2001), which
(Carding, 1977). However, expansion of trapped gases
makes this method particularly difficult with fearful and
in body cavities leads to adverse physical effects, pain
aggressive dogs and cats (Carding, 1977). Furthermore,
and discomfort (Close
et al., 1996), and is likely to cause anxiety and stress in animals (Close
et al., 1997).
In addition this method may be aesthetical y unpleasant for the operator as unconscious animals may bloat, bleed, vomit, convulse, urinate and defecate during decompression (Hatch, 1982).
This method is inhumane and therefore not acceptable for the euthanasia of dogs and cats.
Hanging
Death results by asphyxiation from constriction of the
trachea after strangulation, causing the animals fear
and distress. This method is inhumane and its use is
condemned by WSPA.
Drowning
Prolonged death by asphyxiation after immersion in
water (drowning) causes animals fear and severe stress
(Close
et al., 1996). This method is inhumane and its
use is condemned by WSPA.
Poisons
Strychnine and cyanide
General considerationsThese agents cause excruciating pain and distress to animals.
Strychnine
Strychnine acts on the nervous system resulting in
painful muscle contractions and violent convulsions.
The animal remains conscious and experiences extreme
pain and distress before it dies as a result of suffocation
(Lumb, 1985; Close
et al., 1996; Beaver
et al., 2001).
This is an unacceptable agent for euthanasia as its
mode of action is inhumane.
The World Society for
the Protection of Animals
firmly believes that in all
situations when euthanasia
Cyanide blocks oxygen uptake, leading to respiratory
is deemed necessary the
col apse. It is accompanied by violent and painful
methods adopted should be
convulsions prior to the onset of unconsciousness and death (Hatch, 1982). In addition, the use of cyanide
truly humane. They should
represents an extreme danger to people as they are
achieve rapid, painless
equal y susceptible to its toxicity. The use of cyanide is
death and minimise fear
inhumane and should never be a method of euthanasia.
and distress to animals. Our
goal is for all countries to
adopt the humane methods
endorsed by WSPA, and for
this document to be used
to encourage authorities to
make the recommended
Avariez, J.B. and Caday, L.B. 1958. Magnesium sulphate euthanasia in dogs.
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the AVMA panel on euthanasia.
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Association 218: 669–696.
Hewett, T.A., Kovacs, M.S., Antwohl, J.E., Taylor-Bennett, B. 1993. A comparison
Bishop, Y. (Ed). 2005.
The Veterinary Formulary. Sixth Edition. Pharmaceutical
of euthanasia methods in rats, using carbon dioxide in pre-fil ed and fixed flow rate
Press, The University Press, Cambridge, UK in Association with the British
fil ed chambers.
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Statement on
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euthanasia methods for dogs and cats. www.animalsheltering.org/resource_
carbon dioxide; preliminary trials.
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–21.
Leach, M.C., Bowel , V.A., Al an, T.F., Morton, D.B. 2004. Measurement of
Chalifoux, A., and Dal aire, A. 1983. A physiologic and behavioural evaluation
aversion to determine humane methods of anaesthesia and euthanasia.
Animal
of carbon monoxide anaesthesia of adult dogs.
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Welfare 13: S77
–S86.
Research 44: 2412
–2417.
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Close, B., Banister, K., Baumans, V., Bernoth, E.M., Bromage, N., Bunyan, J., Erhart, W., Flecknel , P., Gregory, N., Hackbarth, H., Morton, D., Warwick, C.
Moreland, A.F. 1974. Carbon monoxide euthanasia of dogs: Chamber
1996. Working party report: Recommendations for euthanasia of experimental
concentrations and comparative effects of automobile engine exhaust and carbon
animals: Part 1.
Laboratory Animals 30: 293–316.
monoxide from a cylinder.
Journal of the American Veterinary Medical Association 165: 853–855.
Close, B., Banister, K., Baumans, V., Bernoth, E.M., Bromage, N., Bunyan, J., Erhart, W., Flecknel , P., Gregory, N., Hackbarth, H., Morton, D., Warwick, C.
National Institute for Occupational Safety and Health. 1977.
Occupational
1997. Working party report: Recommendations for euthanasia of experimental
exposure to waste anaesthetic gases and vapours. No. 77
–140. Washington D.C.,
animals: Part 2.
Laboratory Animals 3: 1–32.
Dal aire, A. and Chalifoux, A. 1985. Premedication of dogs with acepromazine
Phil ips, J.M. Undated. RSPCA Information:
Animal Euthanasia.
or pentazocine before euthanasia with carbon monoxide.
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Quine, J.P., Buckingham, W., Strunin, L. 1988. Euthanasia of smal animals with nitrogen: Comparison with intraveneous pentobarbital.
Canadian Veterinary
Danneman, P.J., Stein, S., Walshaw, S.O. 1997. Humane and practical
Journal 29: 724
–726.
implications of using carbon dioxide mixed with oxygen for anaesthesia or euthanasia of rats.
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– 385.
Raj, A.B.M. and Gregory, N.G. 1995. Welfare implications of the gas stunning of pigs: determination of aversion to the initial inhalation of carbon dioxide or argon.
Dennis, M.B., Dong, W.K., Weisbrod, K.A. 1988. Use of captive bolt as a method
Animal Welfare 4: 273–280.
of euthanasia for larger laboratory animal species.
Laboratory Animal Science 38 (4): 459– 462.
Ramsay, E.C. and Wetzel, R.W. 1998. Comparison for oral administration of medication to induce sedation in dogs prior to euthanasia.
Journal of the American
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Veterinary Medical Association 213: 240–242.
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and other scientific purposes. Annex to the
EFSA Journal 292: 1–136.
Reil y, J.S. 1993.
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and New Zealand Council for the Care of Animals in Research and Teaching,
Ewbank, R. 1983. Is carbon dioxide euthanasia humane?
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administration of medication to induce sedation in cats prior to euthanasia.
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Ames, Iowa State University Press, USA.
of the American Veterinary Medical Association 213: 243–245.
ANNEX 1: Dosages and routes of administration of
agents for euthanasia of dogs and cats
The information is from those organisations using drugs for euthanasia in the field. The effects of many of these agents are dose dependent. It is therefore essential that an accurate estimate of the animal's weight is obtained prior to euthanasia. In addition the effects of these drugs may be highly variable and dependent upon the individual animal's physical characteristics and circumstances. Al manufacturers' instructions should be consulted and adhered to.
Use of pre-euthanasia
drugs indicated?
150mg/kg for both dogs and cats
Carcass disposal
– recommend
solutions suitable for euthanasia
Proposed dosage schedule is
Can be an irritant if given by this
2–3 x recommended dose for IV
unless the animal
administration when preparations
containing concentrations of 390
Takes longer to take effect than via
mg/ml of Pentobarbitone are used
IV route: 15
–30 minutes
(Sinclair, 2004: p 397.)
Carcass disposal
– recommend
120–200 mg/kg as necessary
(Bishop, 2005:p 291)
Intracardiac (IC)
150mg/kg for both dogs and cats
Can be painful if attempted in ful y
Yes, this route of
conscious animals
administration is only suitable
Carcass disposal
– recommend
for unconscious,
col apsed animals
Dose for neonatal kittens and
Takes longer to take effect than via
puppies: despite discussion with
animal welfare groups we have been unable to provide suitable
Powdered preparation delivered in gelatine capsules can be hidden
guidance on an acceptable dose
for oral administration to neonates
in food and is less likely to be
at this time.
detected by dogs than mixing the
liquid form with food.
Dose for sedation of dogs: 63mg/kg
(Ramsay and Wetzel, 1998)
Highly variable time to take effect even in dogs given the same dose.
Prolonged time to take effect:
30–90 minutes.
Effective dose is highly variable,
dependent upon the animal's
an overdose.
age, physical status and use of
pre-euthanasia drugs
Thiopentone
Proprofol
This method is time consuming
and costly in comparison to other methods
Carcass disposal
– recommend incineration
Use of pre-euthanasia
drugs indicated?
Dogs and cats: 0.3ml/kg
Slow, steady rate of injection
iodine, tetracaine
Commercial y available as a
pre-prepared euthanasia solution
accept in the USA
Carcass disposal
– recommend incineration
Intravenous (IV)
One proposed dosage schedule
Often available commercial y as
is 100g of KCI dissolved in 1 litre
a powder which is made into an
after anaesthesia
of water; 20–30ml of solution
injectable solution by dissolving
intracardiac (IC)
sufficient for euthanasia of dogs
weighing 15–20kg
Carcass disposal
– recommend
1
–2 mmol/kg of body weight wil cause cardiac arrest (Beaver
et
al., 2001)
Intravenous (IV)
Saturated solution of MgSO . One
Often available commercial y as
sulphate (MgSO )
proposed dosage schedule is:
a powder, which is made into an
after anaesthesia
injectable solution by dissolving
83% solution of MgSO dissolved
intracardiac (IC)
in boiling water:
Saturated solution becomes very
Dosage varies little if given by
IV or IC route of administration (Avariez and Caday, 1958).
Large volumes required to achieve euthanasia
But highly variable dose for individuals; one suggested
Carcass disposal – recommend
published effective dose:
20–38 ml for a 15 kg dog (Avariez and Caday, 1958).
80mg/kg dose (Close
et al., 1996)
Saturated aqueous solution 1g/ml at a dose of 2.5–4.0 mg/kg (Carding, 1977)
Only suitable for small animals or
animals already anaesthetised for
Delivered in a carrier gas (usual y
oxygen) at the minimum alveolar
concentration (MAC)
Requires an anaesthetic chamber
or can be delivered via breathing
for surgery and,
systems and masks applied to
Human health hazard if inhaled
are not permitted to regain
Carcass disposal
– recommend
ANNEX 2: Guidelines on the intravenous injection of
Pentobarbitone for the euthanasia of dogs and cats
and specialist capture and restraint equipment to prevent
The World Society for the Protection of Animals strongly
handlers being bitten and to minimise human contact
recommends the use of Pentobarbitone (also sometimes
with animal body fluids. To facilitate safe handling of
cal ed Pentobarbitone sodium or sodium pentobarbital);
these animals, sufficient sedation (pages 13–14) should
a barbiturate specifical y formulated for euthanasia.
be used prior to injection with the euthanasia agent.
The intravenous (IV) injection of Pentobarbitone 20%
5. Assessment of the animal's temperament
solution is regarded as the most humane method of euthanasia for dogs and cats. The method of
and ease of handling
intravenous injection for dogs and cats can be mastered
Animals that are not used to being handled by humans
easily with training. In most cases animals show
may experience fear when placed in novel surroundings,
little or no resistance, provided that they are handled
which may result in them showing defensive or avoidance
considerately and that they are used to close human
behaviour. Any animals that are likely to be fractious or
contact. In certain countries euthanasia by intravenous
difficult to handle may pose a risk to personnel through
injection may only be performed by a veterinarian or by
aggressive behaviour. In these instances it is both more
operators working under veterinary supervision.
humane and safer for these animals to be sedated prior to euthanasia with sufficient time being al owed for the
1. Personnel
sedative to take maximum effect before euthanasia is
Trained, competent and considerate personnel are
essential for the humane handling of animals for euthanasia.
Some nervous and aggressive dogs may require muzzling to avoid danger to handlers. If no muzzle is available,
A minimum of two people are required for intravenous
a bandage tied around the dog's nose and then behind
injection: one person should be able to restrain the
the head (also known as a tape muzzle) can work in the
animal safely and humanely (referred to hereafter as
‘the assistant'), while the second accurately delivers the intravenous injection for euthanasia (referred to
Feral cats require special consideration as they are
hereafter as the operator).
general y extremely fearful of humans. This presents both a welfare concern for the cat and a safety concern
for the handlers, as the cat's defensive-aggressive
Appropriate preparation must be made for smooth
behaviour can inflict injury. The most satisfactory
induction, and to ensure safe and humane handling of
method of capturing a feral cat is to use a cat trap with a
animals for euthanasia. In the first instance, personnel
squeeze back facility (Figure 1). The captured cat is then
should ensure that al materials are available to hand
pressed against the mesh on the side of the cage so that
and the environment is suitable, as fol ows.
an injection of a pre-euthanasia agent (pages 13–14) can be given. Once suitably sedated/immobilised the cat can
3. The environment
be handled safely.
A quiet room away from other animals is required in
6. Materials
order to avoid dogs and cats becoming excited before
the procedure, which would make them difficult to
The fol owing materials are required for intravenous
handle, requiring additional restraint.
An examination table approximately 90cm in height,
with a non-slip surface, facilitates handling and al ows
• Disposable syringes with eccentric (i.e. off-centre)
for accurate injection.
• For cats, a syringe size of 2ml is recommended.
Good lighting of the area is essential to enable the
• For dogs, syringe sizes of 5, 10 and 20ml wil be
operator to see the site of the injection (usual y the
suitable for most weights.
cephalic vein on the animal's foreleg); therefore facilitating precise delivery of the injection.
Disposable needles
• Needle diameter is measured by the ‘gauge': the
4. Special precautions should be taken for
larger the gauge the finer the needle.
suspect rabid animals
• Needles are usual y supplied in different coloured
Extreme care should be taken when handling and
containers according to gauge for easy identification.
euthanasing animals suspected of having rabies. Special
The size of the needle depends upon the size of the
precautions include protective clothing for personnel,
animal and the substance to be injected. For an
Figure 1.
Figure 2.
Photograph of a squeeze-back cage for use with feral cats.
Photograph showing a dog restrained for intravenous injection. The assistant stands to left of the dog, and
A – Front door to the cage. Once lifted open the cat can be enticed to enter from a cat trap
her right thumb is used to raise the cephalic vein to
B – The external 'arms' are moved towards the assistant and the rear wal of the cage pushes the cat
enable the operator to insert the needle. Her left arm
flat against the facing wall in the squeeze-back mechanism.
restrains the dog under the chin.
intravenous injection of Pentobarbitone the fol owing
equal to the volume of liquid to be withdrawn. Fill the
are recommended: Cats: needle of 22–24 gauge and
syringe with the correct dose, calculated according to
length 0.75 inches (2cm), Dogs: needle of 18–22
the manufacturer's instructions for the animal's weight.
gauge and length 1 inch (2.5 cm) is convenient for
Remove the needle and syringe from the bottle and
most size of dog.
replace the cap on the needle for safety.
(b) Handling and restraint
If permanent plastic cannulae are available for use they
are preferable as they minimise the risk that the needle
Gently lift the animal on to the examination table. The
may slip during the procedure resulting in some or all of
dog should be facing the operator who wil be giving
the drug not being delivered directly into the vein (see
the intravenous injection. Large or fractious dogs may
section 7e). The technique for inserting a plastic cannula
require more than one handler for restraint. If the
is similar to that for giving an intravenous injection, but
operator is right handed, the assistant should stand
may take a little more training and practice; insertion is
on the animals left. Where possible the animal should
especial y difficult in smal er dogs and cats.
be in the sitting or lying position. The assistants' arm passes over the back of the and the other arm holds the
animal under the chin (Figure 2).
Injection of Pentobarbitone, 20% solution is considered as ‘best practice'; however some euthanasia products
have been combined with a local anaesthetic agent
The cat should be gently placed onto the examination
or Phenytoin. The pharmacological differences are
table, facing the operator for intravenous injection. The
inconsequential but such compounds may be more
assistant should hold the cat against their body, making
easily obtained in some countries.
the cat feel secure.
Dose rate
The animal's head should be held under its chin with
Where possible the animal should be weighed. If this
one of the assistant's hands, while the other hand
is not possible, experienced personnel may be able to
raises the cephalic vein (Figure 3). The cat's foreleg
estimate the animal's weight with sufficient accuracy.
should be pushed forward at the elbow, and the thumb
The dose of Pentobarbitone should be determined
and forefinger used to apply gentle tourniquet pressure,
according to the manufacturer's instructions.
as described for dogs in Figure 4.
7. Method
(c) Site of injection
(a) Filling the syringe
The cephalic vein in the animal's foreleg is the most
A new, disposable needle should be attached to the
convenient site for intravenous injection. When the
nozzle of a new, disposable syringe, and then inserted
animal is held correctly the cephalic vein is visible
into the bottle containing Pentobarbitone for fil ing.
on top of the foreleg (Figure 4). Once the animal has
To prevent a vacuum forming in the bottle, resulting
been suitably restrained, it may be necessary to aid
in difficulty with subsequent withdrawal of fluid, it is
visualisation of the vein, particularly in cats and small
advisable first to inject into the bottle an amount of air
dogs, to clip a smal amount of hair on the foreleg where the injection is to be given.
(d) Preparation for the injection
The assistant's thumb and forefinger of the left hand
is used to create a tourniquet effect at the ‘crook' of
the elbow and inflate or ‘raise' the cephalic vein. Mild
pressure is applied: using the thumb with a slight
outward rotation the cephalic vein becomes clearly
visible for injection (Figure 4).
(e) Starting the injection
The cap is removed from the needle and the point
of the needle is gently inserted through the skin up
and into the vein. The needle is then slid up the
vein, paral el to the skin surface. Before injection of
Pentobarbitone, it is essential to confirm that the
Figure 3.
needle is correctly positioned in the vein. In large dogs
Typical restraint of a cat for intravenous injection. The cat is held close to the
blood wil flow natural y back into the liquid within the
assistant's body, the animal's head is held under the chin with one hand and the
syringe. In smal dogs and cats it may be necessary
assistant uses their other hand to raise the cephalic vein.
to draw the plunger of the syringe back slightly: if positioned correctly blood should flow back into the syringe verifying the needle is indeed in the vein. After
the operator has confirmed that the needle is correctly positioned, the assistant releases their thumb pressure so that the intravenous injection can be given.
(f) Ensuring the injection has been delivered
The calculated dose of the agent is injected with care
ensuring that the needle remains in the vein and that
injection into the surrounding tissues is not occurring.
Injection outside of the vein is rare but possible, and causes swel ing around the vein. Should this occur the procedure should be stopped, the syringe and needle
Figure 4.
removed and a new attempt made at a different position
Insertion of an intravenous cannula into the cephalic vein. The operator is right
on the vein or using the vein on the other foreleg.
handed. The assistant stands to the side of the dog, and uses their thumb to raise
Extravascular injection of Pentobarbitone may cause
the cephalic vein, enabling the operator to insert the needle.
pain and irritation to animals and every effort should be
A – Shaved area exposing the cephalic vein
taken to ensure precise delivery into the animal's vein.
B – Raised cephalic vein is clearly visible
C – 'Crook' of the elbow
D – The assistant's thumb and forefinger create a tourniquet effect. The thumb is
Normal y dogs and cats will become unconscious
rotated outward slightly to raise the vein
before the end of the injection and death fol ows almost immediately with complete freedom from pain
the saphenous vein is considerably less convenient to
or distress when using the recommended dose and
use than the cephalic vein, as it is highly mobile when
with a confident but gentle approach. Death should
pressure is applied making accurate injection difficult.
be confirmed using the indicators stated on page 5. Ideal y operators should check for the absence of the
The technique for raising the saphenous vein is similar
heartbeat using a stethoscope, listening to the left side
to that used when injecting into the cephalic vein,
of the chest where the beat is most audible in life or
but it is more awkward for the assistant to achieve
by checking for a pulse, by palpation over the medial
as the animal has to be placed on its side (in lateral
aspect of the animal's hind limb. If there's any doubt
recumbency) and the hind leg is lifted. The assistants
operators should wait for rigor mortis to set in before
thumb is placed on the outside of the animal's hock
disposing of the animal's carcass.
joint, while the forefinger encircles the inside of the
joint. Thumb pressure is applied with a slight outward
(g) Other sites for intravenous injection
rotation to raise the vein for injection. This technique
If injection via the cephalic vein is not possible, other
requires additional skil , and should only be attempted
sites may be used for intravenous injection, but they
by experienced personnel.
may be more difficult and require greater skil .
8. Additional resources
The saphenous vein can be accessed in either of the
Humane Society of the United States, Humane
hind legs. It is easier to locate in larger dogs than in
Euthanasia by Injection: Training Video Series.
cats and smal dogs. The vein runs down the inside
Produced by the Humane Society University,
of the hind leg from the animal's body, until it crosses
to the outside of the leg above the hock, where it is
easiest to reach for intravenous injection. However
Source: https://www.rspca.org.uk/ImageLocator/LocateAsset?asset=document&assetId=1232711400045&mode=prd
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BY DAVID COIL "I'm going to raid the pharmacy, treat you with tetracycline, and then give you a fungal infection." "Oh yeah, I'm going to give you botulism!" "That's fine because I'm going to give myself a fecal transplant." SHORT VERSION OF THE RULES (FOR PEOPLE WHO DON'T LIKE TO READ) 1. You can only play one Microbe per turn, otherwise play as many cards per turn as you'd like.