Euthanasia in Experimental Animals.pptx
- 1. Euthanasia in Experimental Animals Presenter- Dr Arun Singh Senior Resident Department of Pharmacology SMS Medical College, Jaipur
- 2. Overview Introduction Definition Advantage of Euthanasia Classification Chemical Method Mechanical Method Conclusion
- 3. Introduction • Animals are used in experimental pharmacological studies and assessing the drug activity, it requires analyzing the organ (brain, kidney, lung, etc.), blood (plasma or serum), and body fluid (CSF, urine, etc.) to conclude the result. • Hence for this purpose, animals have to be sacrificed to obtain the said part of the body. • Therefore, according to the animal care guidelines they should be euthanized.
- 4. Definition • “Euthanasia means the humane killing (sacrifice) of an animal which produces rapid unconsciousness and subsequent death without or minimal pain or distress to the animal.” • The choice of a method depends on species, age, availability of restraint and skill of the individual's performing euthanasia. • It is very important that, in an experimental setting, the method of euthanasia must be primarily consistent with the experimental goals.
- 6. Advantages of Euthanasia • Reliability and irreversibility • Minimum pain, distress, anxiety or apprehension • Minimum delay until unconsciousness • Safety and emotional effect on personnel • Compatibility with requirement and purpose, including subsequent use of tissue a • Compatibility with species, age and health status
- 7. Classification Euthanasia methods are broadly classified as: (I) Chemical method (Inhalants/Non- inhalants) (II) Physical methods
- 8. (I) Chemical Method Ex. Halothane, enflurane, sevoflurane, methoxyflurane, isoflurane and desflurane
- 9. (a) Inhalant Anesthetics (i) Carbon dioxide (CO2) It is an effective and widely used agent to euthanize rodents due to rapid hypoxia which further leads to depression of vital centers. (Maintain 20% -70% of the chamber volume per minute) This method is preferred in several animals but it is dangerous to use, so precaution should be taken while using it.
- 10. (ii) Nitrous oxide (N2O) It is not preferred due to lack in fast onset of anesthesia but may produce hypoxemia and cardiac or respiratory arrest. However, it may be used in combination with other anaesthetics to speed anesthesia onset.
- 11. (iii) Ether It was formerly used extensively but is now only acceptable conditionally. The reason is being irritant to mucous membranes and risk of fire and explosion. The use of ether is prohibited in many countries.
- 12. (b) Noninhalents Anesthetics (i) Barbiturates Sodium pentobarbital is the most rapid and reliable method of euthanasia for most experimental animals. In non-rodent species, barbiturates are given intravenously to be most effective. Intraperitoneal injection of barbiturates is acceptable for euthanasia in small mammals.
- 13. (ii) Potassium chloride (KCl) • KCl induces immediate cardiac arrest without any significant depression of the central nervous system. • Hence, it must only be used after the animal is deeply anesthetized. (iii) Magnesium sulphate (MgSO4) • MgSO4 produces its action through cardiac arrhythmia, neuromuscular blockade and deep anesthesia, hence ultimately animal gets euthanized due to cardiac arrest and neuromuscular blockade.
- 14. (iii) Neuromuscular Blocking Agents Ex. Succinylcholine, Curare, etc. • These agents induce muscular paralysis and death because of suffocation. Distress onset is more, hence less preferred for euthanasia.
- 15. (II)Physical Methods Physical methods are performed by skilled and experienced personnel with appropriate, well-maintained equipment. (a) Cervical dislocation: Humane technique for euthanasia which is frequently used for mice, rats, guinea pig, rabbits (weighing less than 1 kg) and other rodents. (b) Decapitation: Decapitation may be used to euthanize rodents and small rabbits. Except in neonatal animals, a guillotine is generally used.
- 16. (c) Microwave irradiation • Special instruments designed (appropriate power and microwave distribution) for this purpose, which is used when an experiment requires fixation of mouse or rat brain metabolites in vivo without losing anatomic integrity of the brain. (d) Penetrating captive bolt • This method is conditionally acceptable and made for ruminants, horses, and swine when chemical agents are scientifically contraindicated. • This method is not employed in the laboratory animals.
- 17. Euthanasia of Poikilothermic (Cold-blooded) Animals The euthanasia of poikilothermic animals is different due to differences in the pharmacokinetics, respiration and tolerance to cerebral hypoxia between these species and homeothermic animals. Chemical agents: Pentobarbital, Tricainemethane sulfonate or benzocaine HCl. Intraperitoneal administration of pentobarbital is an effective method of euthanasia in amphibians.
- 18. Tricaine methane sulfonate or benzocaine hydrochloride may be placed in the water of amphibians and fish to produce anesthesia and prolonged contact may produce death. Inhalant anesthetics may be used for amphibians and reptiles but due to the low oxygen requirements for amphibian, the onset of unconsciousness and death will be significantly lengthened.
- 19. • Physical methods: Poikilotherms may be euthanized by stunning followed by decapitation or pithing to ensure death. In frogs and toads, pithing the brain (single pithing) and spinal cord (double pithing) are effective and acceptable methods.
- 21. Conclusion • Euthanasia methods are under constant study, and guidelines often change as new information is gained. • As new knowledge expands understanding of practices best suited for humane euthanasia, revised and new guidelines can be expected. • Veterinarians trained in laboratory animal medicine should use professional judgment to assess whether a proposed euthanasia method is aligned with the goals of the research and will provide valid data. • When necessary, a veterinarian should participate in the assessment and validation of euthanasia methods on a case-by-case basis.