Euthanasia:

What is euthanasia?:

• Greek word – “eu” meaning GOOD and “thanatos” meaning DEATH. 

• “Good death” is a death that occurs with minimal pain and distress. 

• The act or practice of killing or permitting the death of hopelessly sick or injured individuals (domestic animals) in a relatively painless way for reasons of mercy 

 

Considerations in the selection of euthanasia method:

• Ability to induce loss of unconscious without causing pain, distress, anxiety, and apprehension 

• Time required to induce unconsciousness 

• Reliability, safety of personnel 

• Irreversibility 

• Compatibility with requirement and purpose 

• Emotional effect on the observers/operators 

• Species, age health status 

• Safety for predators / scavengers should the carcass be consumed 

 

Three basic mechanisms of euthanatizing agents:

• Direct depression of neurons necessary for life function (Brain-spinal core-cardiorespiratory center depression): anesthetics – injectable or inhalant 

• Physical disruption-destruction of brain activity: gun shot, captive bolt, electrocution 

• Hypoxia: CO2, N2, exsanguinations 

 

Direct depression of neurons necessary for life function: 

What agents can be used ? 

• All general anesthetic agents 

• Inhalant anesthetic vs. Intramuscular administration vs. Intravenous administration 

 

What methods are acceptable? 

• Acceptable: 
  • Barbiturate overdose 

 

• Conditionally acceptable: o inhalant anesthetics, CO, CO2, N2, Ar 

 

What methods are unacceptable? 

• Exsanguinations 

• Air embolism 

• Drowning 

• Strychnine 

• Nicotine, magnesium sulfate, potassium chloride, all curariform agents (neuromuscular blocker agents) 

• Chloroform 

• Cyanide 

• Stunning 

 

Acceptable inhalation agents:

All general anesthetic agents

• Considerations 

  • Onset of loss of consciousness 

  • The equipment required 

  • Hazardous to personnel 

  • Noise 

  • Reptiles, amphibians, and diving birds and mammals 

 

• Advantages 

  • Particularly valuable for smaller animals (< 7kg) or for animals in which venipuncture may be difficult 

  • Halothane, enflurane, isoflurane, sevoflurane, desflurane, methoxyflurane and N2O are nonflammable and nonexplosive under ordinary environmental condition 

 

• Disadvantages:
  •  Struggling and becoming anxious during induction of anesthesia 

  • Methoxyflurane is unacceptably slow induction in some species 

  • Nitrous oxide will support combustion 

  • Personnel and animals can be injured by exposing to these agents 

  • A potential human abuse 

 

• Recommendations:

  • Inhalant agents are acceptable for euthanasia of small animals (<7kg). 

  • Nitrous oxide should not be used alone 

  • Although acceptable, these agents are generally not used in larger animal because of their cost and difficulty of administration 

 

Carbon dioxide: 

• Advantages 
  • Rapid depressant, analgesic and anesthetic effect of CO2 
  • Readily available and can be purchased in compressed gas cylinders 
  • Inexpensive, noninflammable, nonexplosive and poses minimal hazard to personnel when used with properly designed equipment 
  • Not result in accumulation of tissue residues in food producing animals 
  • Not distort murine cholinergic markers or corticosterone concentration 

 

• Disadvantages 

  • Heavier than air 

  • Some species such as fish and borrowing and diving mammals, may have extraordinary tolerance for CO2 

  • Reptile and amphibians may breathes too slowly for use of CO2 

  • Take longer 

 

• Recommendations 

  • Acceptable for euthanasia in appropriate species 

  • Compressed CO2 gas cylinders us the only recommended source of CO2 

  • Species should be separated and chambers should not be overcrowded 

  • Loss of consciousness may be induced more rapidly by exposing animals to a CO2 concentration of 70% or more 

  • Gas flow should be maintained for at least 1 minute after apparent clinical death 

 

Nitrogen, argon:

• Advantages 

  • Readily available as compressed gases 

  • Minimal hazard to personnel 

 

• Disadvantages 

  • May distress animals due to hypoxemia and ventilatory stimulation 

  • Reestablishing a low concentration of O2 (6% or greater) in the chamber before death will allow immediate recovery 

 

• Recommendations 

  • Can be distressful to some species (ex. rats) 

  • Animal should be sedated or anesthetized 

  • Effective, but other euthanasia methods are preferable. 

 

Carbon monoxide:

• Advantages 

  • Induce loss of consciousness without pain and with minimal discernible discomfort 

  • Hypoxemia induced by CO is insidious 

  • Death occurs rapidly if concentrations of 4~6% are used 

 

• Disadvantages 

  • Safeguards must be taken to prevent exposure of personnel 

  • Any electrical equipment exposed to CO (ex. lights and fans) must be explosion proof 

 

• Recommendations 

  • Used for individual animal or mass euthanasia is acceptable 

  • CO should be provided with that commercially compressed 

  • CO source and chamber must be located in a well-ventilated environment 

  • CO monitor in the room to warn personnel of hazardous concentration 

 

Non-inhalant pharmaceutical agents:

• Most rapid and reliable method 

• Most desirable method 

• Intraperitoneal administration 

• Intracardiac injection 

• Other non-vascular injections are not acceptable 

 

Barbiturates: 

• Depress the central nervous system 

• With an overdose, deep anesthesia progresses to apnea owing to depression of respiratory center, which followed by cardiac arrest. 

• Intravenous administration 

• Rapid onset of action and loss of consciousness 

 

• Advantages 

  • Speed of action, depend on the dose, concentration, route, and rate of injection 

  • Smooth euthanasia with minimal discomfort 

  • Less expensive 

 

• Disadvantages 

  • Intravenous injection 

  • Trained personnel 

  • Controlled drug 

  • Persist in the carcass and may cause sedation or even death of animals that consume the body 

 

• Recommendations 
  • Intravenous injection is the preferred method for euthanasia of dogs, cats, other small animals, and horses 
  • Intraperitoneal injection may be used 
  • Intracardiac injection must only be used if the animal is heavily sedated, unconscious, or anesthetized 

 

Pentobarbital combinations:

• Usually sodium pentobarbital with added local anesthetic agents (schedule III) 

• Combination with a neuromuscular blocking agent is not an acceptable euthanasia agent

 

Chloral hydrate:

• Depress the cerebrum slowly – restraint may be a problem for some animals 

• Death is caused by hypoxemia resulting from progressive depression of the respiratory center 

• May see gasping, muscle spasms and vocalization 

 

• Recommendations 

  • Acceptable for euthanasia of large animals only when administered intravenously 

  • Use only when animals are sedated to decrease undesirable side effects 

  • Not acceptable for dogs, cats, and other small animals 

 

T-61:

• Injectable, nonbarbituate, non-narcotic mixture of 3 drugs used for euthanasia

• General anesthetic, curariform, and local anesthetic actions 

• Available in Canada 

• Used only intravenously 

• Carefully monitored rate of injection 

 

Tricaine methane sulfonate (TMS): 

• MS 222 

• Amphibians and fish 

• 250 mg/L concentration for euthanasia 

• Fish should be left in this solution for at least 10 minutes following cessation of opercular movement 

• Withdrawal time = 21 days. 

• Not appropriate for euthanasia of animals intended for food 

 

Potassium chloride:

• In anesthetized animals = unacceptable 

• In anesthetized animals, the use of fully saturated solution of KCl IV or intracardially is an acceptable method to produce cardiac arrest and death 

• Potassium ion = cardiotoxic 

• 1~2 mmol/kg of body weight intravenously or intracardially  

• Preferred injectable technique for euthanasia of livestock or wildlife species  

 

• Advantages 

  • Not a controlled substances 

  • Carcass that is potentially less toxic for scavengers and predators

 

• Disadvantages 

  • Rippling of muscle tissue and clonic spasms may occur on or shortly after injection 

 

• Recommendations 

  • Personnel performing this technique are trained and knowledgeable in anesthetic techniques 

  • Animal should be under surgical plane of anesthesia 

  • Effective for causing cardiac arrest 

  • No scavenger toxicoses 

 

Unacceptable injectable agents:

• When used alone – unacceptable 

• Strychnine 

• Nicotine 

• Caffeine 

• Magnesium sulfate 

• Potassium chloride 

•  Cleaning agents 

• Solvents 

• Disinfectants 

• Other toxins or salts 

• All neuromuscular blocking agents 

 

Physical methods to disrupt brain activity:

• Captive bolt 

• Gunshot 

• Cervical dislocation 

• Decapitation 

 

• Electroculation: 

• Microwave Irradiation 

• Kill traps 

• Thoracic compression 

• Exsanguination 

• Stunning 

• Pithing 

 

• Considerations: 

• Most appropriate method for euthanasia and rapid relief of pain and suffering in certain situation 

• Skill and experience of personnel is essential 

 

Penetrating captive bolt:

• Used for ruminants, horses, swine, laboratory rabbits, and dogs 

• Mode of action = concussion and trauma to the cerebral hemisphere and brainstem 

• Adequate restraint 

• A multiple projectile is more effective technique 

 

• Advantages 

  • An effective method 

  • For use in slaughter houses, in research facilities, and on the farm when use of drugs is in appropriate 

 

• Disadvantages 
  •  Aesthetically displeasing 
  • Death may not occur if equipment is not maintained and used properly 
  • Penetrating captive bolt 

 

• Recommendations 

  • An acceptable and practical method for horses, ruminants, and swine 

  • Non-penetrating captive bolt must not be used as a sole method 

 

A blow to the head:

• Must be evaluated in terms of the anatomic features of the species 

• Humane method of euthanasia for neonatal animals with thin cranium 

• Require trained personnel for proficiency 

 

Gunshot 

• Can cause immediate insensibility and humane death 

• Only be performed by highly skilled personnel trained in the use of firearms