AVMA Guidelines for Euthanasia

• Euthanasia, derived from Greek words meaning "good death," is defined by the AVMA as ending an animal's life in a way that minimizes pain and distress.
• The goal of euthanasia is to induce rapid loss of consciousness, followed by loss of vital body functions like respiration, heartbeat, and brain function.
• Veterinarians recognize euthanasia as a humane option in certain situations, complementing their role in improving animal health.

AVMA Guidelines for Euthanasia

• The AVMA has convened a Panel on Euthanasia (POE) since 1963 to create euthanasia guidelines.
• The guidelines have evolved since 1963 to include various animal types, most recently updated in 2020.
• Core principles include prioritizing animal welfare and respect, minimizing pain and distress, and proper handling.
• Owners should be offered the option to be present during euthanasia and informed about the drugs and potential reactions.
• Verifying death is crucial, as is handling the environment, disposal, and euthanasia solutions appropriately.
• Inhumane methods are those that cause slow death or trauma before unconsciousness.
• Personnel involved in repeated euthanasia may experience distress, and understanding the "caring-killing paradox" can help mitigate psychological effects.

Basic Mechanisms of Euthanasia (AVMA Guidelines)

• Euthanasia achieves its effect through direct depression of neurons vital for life, hypoxia, or physical destruction of neurons and brain activity vital for life.

Evaluating Euthanasia Methods (AVMA Criteria)

• Key evaluation criteria include minimizing pain and distress, speed of unconsciousness, reliability, and personnel safety.
• Other criteria include Irreversibility, compatibility with intended animal use, emotional impact on observers, and effects on subsequent tissue use.
• Drug availability, abuse potential, species compatibility, equipment maintenance, scavenger safety, legality, and environmental impact are also considered.

Euthanizing Agents - Injected Agents

• Parenterally delivered injectable agents, especially intravenous (IV), are generally the most rapid, reliable, and preferred euthanasia method.
• Using three to four times the therapeutic anesthetic dose can produce rapid cardiac arrest and death.
• Injectable agents require more handling and restraint, which can be stressful for the animal.

Specific Injected Euthanizing Agents

Barbiturates

• Barbiturates, especially sodium pentobarbital, are the most widely used and accepted IV euthanasia agents.
• Mechanism: They severely depress the CNS by interfering with sodium and potassium transport and blocking postsynaptic transmission; high doses bind to GABA receptors, causing rapid sedation, respiratory depression, and death.
• Advantages: Speed of action, smooth euthanasia, relatively low cost, and FDA-approved availability.
• Disadvantages: Requires IV injection (preferred), animal restraint, strict DEA regulations, potential for terminal gasp/excitatory phase, persistence in remains posing risk to scavengers, and potential tissue artifacts.
• Additives: Chloroquine phosphate may be added to quicken unconsciousness/death; lidocaine can reduce IV injection pain, especially in cats.

Tributame Euthanasia Solution

• Components: Embutramide, chloroquine phosphate, and lidocaine.
• Embutramide: Anesthetic with a strong narcotic effect causing respiratory depression but severe cardiovascular effects.
• Mechanism: Death occurs through CNS depression, respiratory depression and hypoxia, and circulatory collapse.
• Advantages: Rapid onset of action, smooth euthanasia, Schedule III status.
• Disadvantages: Currently discontinued, requires IV injection only, animal restraint, aesthetically objectionable agonal breathing, and persistence in remains.
• Caution should be used in cats due to extralabel use.

T-61 (Tanax®)

• Components: Embutramide, mebezonium iodide (NMB agent), and tetracaine hydrochloride (local anesthetic).
• Use: Euthanasia for dogs (IV), amphibians (dorsal lymph sac), and small birds (IM), with induction similar to pentobarbital.
• Advantages: Rapid onset of action, used in various species, and less likelihood of the terminal gasp seen with barbiturates.
• Disadvantages: Not currently being manufactured, requires slow IV injection to avoid dysphoria, animal restraint, and potential secondary toxicosis in animals consuming the remains.

Controlled Substances and Euthanasia Agents

• Proper storage and diversion control of controlled substances used for euthanasia are essential to prevent abuse.
• Most euthanasia agents have a narrow therapeutic index or excessive side effects, limiting their use in human medicine although, some have been used in suicide attempts.