Different Types of Euthanasia Methods for Pets

Different Types of Euthanasia Methods for Pets

Dogs and cats are probably the most popular house pets across the world. While our best companions, there might crop up some unpleasant situations where they might have to be put to death to save them from further misery, a sort of euthanasia or mercy killing. Gradually, many euthanasia methods for pets have been developed over the years. Such methods are categorised on the basis of their way of working and acceptability for the purposes of euthanasia. 

Agents that can be used for euthanising dogs and cats can belong to either of the following categories:

  • Non-inhalant or injectable pharmaceutical agents, such as – barbiturates, other intravenous anaesthetics, T61, potassium chloride, magnesium sulphate, chloral hydrate
  • Inhalant gas mixtures, such as – anaesthetic gases, nitrogen or nitrogen/argon mixtures, carbon dioxide, carbon monoxide, ether
  • Physical methods, such as – shooting using a free bullet, captive bolt, electrocution, decompression, hanging, drowning
  • Poisons, such as – strychnine, cyanide

 Once the decision for euthanasia methods for pets has been made, it is up to the human family of the dog or cat in question as to which method to adopt.

The euthanasia agents bring about death by either one of three modes of action – hypoxia, causing death by reduction of the oxygen available for the tissues and cells of the animal; affecting the nerve cells in the brain, causing unconsciousness followed by death; and directly destroying the brain. As those areas of the brain are targeted that control respiratory and cardiac functions, death is a natural outcome. While there are various methods that can be adopted for euthanising dogs and cats, each method is quite different from the other. Here, we shall find out the difference between them.

  1. Non-inhalant, injectable pharmaceutical agents

Non-inhalant, injectable pharmaceutical agents include the following:

  1. Barbiturate  

Usually recommended by veterinarians, barbiturates work by affecting the central nervous system, causing a quick loss of consciousness progressing to anaesthesia in almost no time. The effectiveness of barbiturates – such as the widely used Pentobarbitone – is based on the fact that no distressing visual side effects are shown outwardly. The dog or cat that the barbiturate is administered to just, kind of, “goes to sleep’. The mode of working of barbiturates involve depressing those centres in the central nervous system that control the respiratory system and the heart. Administration of barbiturates as a euthanasia method is considered to be one of the most humane way of dealing with euthanasia.

  • Other intravenous anaesthetics

The use of other intravenous anaesthetics, though not recommended, is considered acceptable. While working similarly as Pentobarbitone mentioned above, causing unconsciousness leading to death, Propofol and Thiopentone can also be used as agents for painless anaesthesia, provided they are administered intravenously and given in overdoses. The main reasons why Propofol and Thiopentone are not recommended for use are – firstly, as higher doses are required, the cost of the procedure is much higher as compared to the cost incurred when using Pentobarbitone; secondly, if not given intravenously, these agents can bring out tissue reactions at the spot of the injection, leading to immense discomfort and pain.

  • T61

Though not recommended euthanasia methods for pets, T61 is acceptable, but with certain conditions. A mixture of three compounds, T61 contains – mebezonium iodine, embutramide, and tetracaine hydrochloride. These three compounds work in unison to bring about local as well as general anaesthesia effects, along with paralyzing the muscles. As the compounds in T61 have different rates of absorption in the body, there is a certain risk involved where, if the injection is given in a hurry, the animal can remain awake at the time of respiratory collapse. The conditions involved in the administration of T61 are – the T61 injection has to be given intravenously and in a slow and steady manner; and to ensure that the animal is not agitated, T61 should ideally be administered only when the animal is already under sedation. Due to the complications that can arise out of faulty administration, T61 is no longer used in America.

  • Potassium chloride [KCL]

Acceptable if administered under conditions, Potassium Chloride or KCL can also be used as a euthanasia agent. Causing cardiac arrest, KCL can be either given intravenously or as an injection to the heart. With no analgesic or anaesthetic properties on its own, KCL, if used alone, can cause intense pain before death. KCL is only acceptable under the condition that the animal is already under general anaesthesia. One of the easy and effective euthanasia methods for pets.

  • Magnesium Sulphate [MgSO4]

Acceptable with conditions, Magnesium Sulphate or MgS04 is used as a euthanasia agent as it brings about respiratory and cardiac arrest before death. Nevertheless, as MgS04 leads to muscle paralysis while the animal is fully awake, the animal is conscious though unable to move till the time that the brain stops working due to a lack of oxygen. Known to cause seizures and spasms, the use of MgS04 as a euthanasia methods for pets is only acceptable when the animal is already anaesthetised.

  • Chloral hydrate [CH]

Deemed unacceptable for use as euthanasia agent, Chloral hydrate or CH is known to act slowly and takes time to depress the centres of the brain that control respiration. From the time that the injection is administered to the time that death is caused, the animal is in intense pain as is evident by gasping for breath, vocalising and muscle spasms. Even along with the use of anaesthesia prior to administration of CH, it acts too slowly and is required in such large doses as to make it unacceptable for euthanasia methods for pets especially dogs and cats.

  1. Inhalant agents (gas mixtures)

Inhalant agents, or gas mixtures, include anaesthetic gases, carbon monoxide, ether, carbon dioxide and nitrogen/argon. Inhalation agents, when used for causing euthanasia, work by inducing hypoxia or the loss of the concentration of oxygen reaching the lungs and tissues in the body. As, in order to be effective, a certain level of concentration is required in the lungs of the animal, inhalant agents do not cause instant death. Death by inhalant agents is a long drawn out process that is both painful for the animal as well as the person watching the procedure. Usually, inhalant agents produce seizures and convulsions as well.

  1. Anaesthetic gases

The use of inhalant agents such as anaesthetic gases is acceptable, but with certain conditions. Anaesthetic gases such as Enflurane, Sevoflurane, Halothane and Isoflurane can be used as overdoses to euthanise animals. However, as these gases take different amounts of time to act and can smell quite pungent, the use of anaesthetic gases is not recommended. Such agents are vaporised and administered via a face mask or tube, or introduced into a chamber. Mixed with air or oxygen at the time of administration so as to prevent hypoxia, the equipment that is to be used should be clean and well-maintained, ensuring thereby that the humans are not exposed to the fumes as well. As very large doses are required for euthanasia, the procedure can be quite expensive. 

  • Nitrogen or nitrogen/argon mixtures

Though considered unacceptable, nitrogen or nitrogen/argon mixtures can be used as a euthanasia methods for pets. Both argon as well as nitrogen are present in the air that we breathe. Inert, non-explosive and non-inflammable, these gases are odourless and colorless. Putting animals in chambers prefilled with nitrogen or nitrogen/argon mixtures causes unconsciousness followed by failure of the respiratory centres and death. While loss of consciousness takes about 1 to 2 minutes from the time of inhalation, actual death might be as long as 5 minutes later. As lack of consciousness is preceded by hyperventilation and hypoxemia, there are many disturbing side effects of nitrogen or nitrogen/argon mixtures, making it unacceptable as euthanasia methods for pets.

  • Carbon dioxide [CO2]

A non-acceptable method, Carbon Dioxide can still be used to euthanize animals. Inhaling CO2 in large concentration can affect the central nervous system, causing respiratory arrest leading to death by asphyxia. While loss of consciousness takes about 1-2 minutes, actual death takes between 5 to 20 minutes. CO2, when used for euthanasia, has to be released by cylinders into special chambers. As CO2 forms carbonic acid when it comes into contact with the airways in the animal, there is much irritation.

The use of CO2 is unacceptable for euthanasia as the gas causes a great deal of stress in animals and leads to hyperventilation, sneezing, escape attempts, agitation and breathlessness.

  • Carbon monoxide [CO]

Unacceptable for use in euthanasia, carbon monoxide (CO) can be used as a method by generating the gas in two ways – by a chemical reaction between sodium formate and sulphuric acid, or from exhaust fumes that are produced when any petrol engine is idling. The use of CO is seen to cause great distress to the animal. CO, when used, is passed on from cylinders into special chambers. Combining with the haemoglobin of the blood, it reduces the oxygen reaching the cells and tissues. Severe distress caused in the animals can be seen in the form of muscle spasms, vocalisation, convulsions and moaning. These side effects, combined with the fact that using CO for euthanasia is more expensive and takes longer than other methods, is what makes it unacceptable for use in dogs and cats.

  • Nitrous oxide [N20]

Considered unacceptable as euthanasia method, Nitrous Oxide (N2O) when used on its own, does not induce anaesthesia even when used at a 100% concentration. When used on its own, it causes hypoxemia leading on to cardiac and respiratory arrest. The method is deemed inhumane because of the various distressing side effects associated with it.

  • Ether

Also considered unacceptable for use in euthanasia, ether is a volatile liquid which is highly inflammable, and can even be explosive under certain circumstances. Ether has to be vaporized by passing a gas, usually oxygen, over it. Ether is unacceptable for use due to the distress caused in the animals and the extreme risk that the operators are exposed to.

  1. Physical methods

Physical methods that can be used for euthanising dogs and cats include – shooting with a free bullet, captive bolt, decompression, electrocution, drowning or hanging. Generally, physical methods are not recommended as they are considered inhumane, there is greater margin of error on the part of the operator, as well as a high risk of malfunction or equipment failing. Only to be used as a last resort, these physical methods usually cause far too much stress in the operators themselves, making them more liable to be careless when actually handling the animal.

  1. Shooting with a free bullet

Acceptable, but with conditions. A single shot at point-blank range to the head can destroy the brain at once and cause unconsciousness, leading to death. While death is almost instantaneous, the skill of the operator is important as the bullet has to penetrate the brain. Moreover, the operator himself as well as any bystanders nearby are at risk if any bullet ricochets. The conditions for using a bullet for euthanasia include that it should never be done in confined spaces; and only used as the last resort if any emergency situation arises and the animal is in extreme pain, but cannot be moved or anaesthetised.

  • Captive bolt

Considered unacceptable for euthanising dogs and cats. Though a captive bolt is frequently used for putting down large livestock, it is considered to be inappropriate for use in smaller animals. As the captive bolt pistol should be placed in contact with the skull and exact positioning is essential, proper restraining of the animals is very important to maintain the steadiness of the head. Often, the captive bolt is not quite enough and additional procedures are required, such as – pithing or severing the spinal cord of the animal and exsanguination or blood-letting. Causing much blood to be spilled and brain matter to be splayed, there is also a great risk of mis-stunning as well. All these factors make the captive bolt unacceptable for use in dogs and cats.

  • Electrocution

Though considered unacceptable, electrocution is another method for bringing about death. In electrocution, a two-step process is used – firstly, the brain of the animal is spanned to make him lose consciousness, secondly, sufficient current is applied to the heart in order to cause cardiac fibrillation and subsequently death by hypoxia.

Electrocution as euthanasia method is not acceptable because of the following reasons:

  • skill and level of training of the operator might not be up to the mark
  • there is a greater risk of misuse
  • equipment might not be properly maintained
  • can be quite hazardous to the people involved
  • visually objectionable, causing violent extension followed by stiffening of the head, neck and limbs

Owing to the reasons mentioned above, electrocution is regarded as an unacceptable method for putting down animals.

  • Decompression

Though unacceptable as a method, decompression can be used for euthanizing animals. In this method, specially made decompression chambers are used. The lack of additional oxygen and the low air pressure in the chamber leads to cerebral hypoxia, causing loss of unconsciousness, followed by death.

Nevertheless, as gases trapped within the body try to escape, there are – accompanied by convulsions – instances of bloating, vomiting, urination, defecation and bleeding. All these, in addition to causing immense pain to the animal, are also quite visually distressing to watch. Decompression is considered an inhumane method, and is, thus, unacceptable.  

  • Hanging

Unacceptable as euthanasia method, death by hanging occurs due to asphyxiation caused by a constriction of the trachea by strangulation. An inhumane way of putting down animals, causing them much pain and distress, hanging is unacceptable for euthanizing animals.

  •   Drowning

Though unacceptable as euthanasia method, drowning is nonetheless an option. Death by drowning involves asphyxiation brought about by deliberate immersion in water. Causing great fear and panic in animals, death by drowning is considered an inhumane method for euthanasia, hence, unacceptable.

  1.  Poisons

Poisons cause great distress and excruciating pain when ingested into animals.

  1. Strychnine

Unacceptable, but can be used. Death is caused by strychnine as it adversely affects the central nervous system of the animal. Leading to muscle contractions which in turn cause convulsions, the animal retains consciousness throughout. There is much suffering involved, until the animal dies due to suffocation. Death induced by strychnine is considered to be inhumane, and is unacceptable as euthanasia method.

  • Cyanide

Though unacceptable, cyanide can be used for putting down animals. Blocking the intake of oxygen, cyanide leads to death by bringing about a collapse of the respiratory system. Accompanied by violent convulsions before unconsciousness sets it, cyanide is considered unacceptable for use in euthanizing animals. Cyanide also poses extreme risk for the people involved as toxicity of cyanide is the same for animals and humans.

Euthanasia or “good death” is a term used to refer to the act of deliberately putting someone to death. Animal euthanasia, though a discomfiting thought, might be essential in certain situations where the animal has to be put down for its own sake. While there are many methods available for euthanizing animals, the methods chosen ought to be humane, bringing about quick and painless death.