ALAT Chapter 14 Euthanasia PDF

ALAT Chapter 14 Euthanasia • The term “euthanasia” is derived from Greek words eu, meaning “good,” and thanatos, meaning “death.” In the laboratory animal science field, euthanizing an animal means ending its life in a way that minimizes pain and distress. • Another way to express the meaning of e...

ALAT Chapter 14 Euthanasia • The term “euthanasia” is derived from Greek words eu, meaning “good,” and thanatos, meaning “death.” In the laboratory animal science field, euthanizing an animal means ending its life in a way that minimizes pain and distress. • Another way to express the meaning of euthanasia is to give the animal a gentle death. • Some common terms used to describe euthanasia are “put down,” “put to sleep,” or “sacrifice;” however, the word “euthanasia” is the preferred term. • In the research setting, euthanasia of laboratory animals must meet both humane standards and the needs of the research study. In the research field, there are several reasons why animals may have to be euthanized. • Most studies require that the animals’ organs and tissues be examined to obtain research data. • Studies may make animals ill, so they are euthanized before they experience a significant amount of pain or distress. • Once an animal has been on a study, it may not be possible to transfer it to a different study due to the effects from experimental treatments received. In addition, laboratory animals may develop illnesses unrelated to the experimental treatment, such as changes caused from aging, which may not be responsive to veterinary treatments. These animals should be euthanized so that they do not experience unrelieved pain or distress. • It is the ethical responsibility of all personnel to ensure that the most humane standards are followed in performing euthanasia. AVMA Guidelines for the Euthanasia of Animals • The AVMA Guidelines for the Euthanasia of Animals, published on the AVMA’s website, is accepted by the research community as the standard for the euthanasia of animals. • Animal care staff and researchers who perform, observe, or train others in euthanasia practices should familiarize themselves with the AVMA Guidelines for the Euthanasia of Animals and follow the recommendations carefully in order to treat the animals humanely. These guidelines take into consideration • • • • general animal welfare principles, the physiology and anatomy of each species, The characteristics of each method of euthanasia Personnel safety. • The euthanasia method chosen should produce a rapid loss of consciousness followed by cessation of the heartbeat, respiration, and ultimately brain function. In addition, the technique should minimize distress and anxiety experienced by the animal prior to the loss of consciousness. Most facilities have a policy to euthanize animals in an area apart from the colony in case sounds or smells generated by animals undergoing euthanasia cause distress to the other animals. • Equipment used in euthanasia must be kept clean and be well maintained to ensure the animals are not subjected to unnecessary pain and distress. • Regardless of the method of euthanasia, it is essential to confirm that the animal is dead before disposing of the carcass. For each species covered, the AVMA Guidelines identify the euthanasia methods that are acceptable, acceptable with conditions, and unacceptable. • These classifications are based on many factors, including whether the method consistently leads to a humane death for the animal and is safe for the individual performing the procedure. • Acceptable methods are preferred for use in animal research. • Methods that are acceptable with conditions are appropriate for animal research provided certain conditions are met, such as weight limits on animals and specific personnel training requirements. • Adjunctive methods are procedures used to assure death after an animal has been made unconscious. Typically, these are physical methods such as exsanguination, decapitation, and pithing. • All euthanasia methods must be specified in the animal use protocol and approved by the IACUC. • It is important to remember that the acceptability of a method is specific to the species and age of the animal. • Some amphibians and reptiles can hold their breath for long periods, so inhaled anesthetics are usually not advisable for euthanasia of these species. • Cervical dislocation is acceptable only for rodents weighing less than 200 grams and other small mammals. • Neonates of some species are resistant to carbon dioxide, so other methods are preferred for these animals. • All technicians should know what methods can be used with the species kept in their facility. • In every situation, the method used must comply with the animal use protocol and facility SOPs, which are based on the AVMA Guidelines. Summary tables of information on the methods that are appropriate according to species can be found in the AVMA Guidelines Methods of Euthanasia Euthanasia can be performed using chemical agents or physical methods. Staff must be trained on euthanasia procedures prior to performing them. Responsible personnel must remain with the animals at the site where euthanasia is performed throughout the entire process. Having SOPs approved by the facility managers and veterinarians for each procedure ensures that proper and consistent techniques are used. Methods of Euthanasia: Chemical Agents • Use of chemical agents as a method to euthanize animals is preferable to physical methods of euthanasia. • Chemical agents may be • inhaled (CO2, anesthetic gasses), • injected (eg barbituates), or • absorbed (Eg. Ms-222 for aquatics) Methods of Euthanasia: Inhalant Agents • Inhalant agents are either compressed gases (typically carbon dioxide) or anesthetics that are administered at a high concentration to induce oxygen starvation (hypoxia) These anesthetics are liquids which evaporate rapidly when exposed to room air, generating a gas or vapor, and are referred to as volatile. The animal breathes in the gas and loses consciousness, just as it would in preparation for a surgical procedure. Overdose of the gas then causes hypoxia, the cessation of breathing and the heartbeat, and then, brain death. • Inhalant agents may be administered to animals individually or in groups, as in a euthanasia chamber. • Euthanasia chambers must be an appropriate size for each species. Ideally, these chambers should be transparent so that the animal inside may be observed in case any problem arises in their reaction to the agent. Animals must not be overcrowded in the euthanasia chamber; facilities typically have SOPs specifying how many animals may be placed together. Chambers should be cleaned between groups of animals to keep conditions sanitary and to minimize residual odors that may distress animals subsequently euthanized. • When using inhalant euthanasia, minimizing stress to the animals being euthanized should be a priority. To do so, institutional SOPs should be followed. Examples of good practice for inhalant euthanasia are:  Euthanasia should be performed in the home cage. Rather than transferring animals to a dedicated euthanasia chamber; they should be euthanized in a familiar environment.  Overcrowding should be avoided.  Euthanasia chambers should be cleaned and cleared of waste gas between groups of animals to prevent distress caused by exposure to a high initial gas concentration Automated euthanasia processes can also be a good way to minimize animal stress. • Automated euthanasia apparatus may be attached to mouse IVC racks or use a large chamber that can accommodate multiple standard cages. This allows animals to receive the required gas concentration, in their home cage, at an appropriate stocking density. • Euthanizing mouse or rat neonates requires significantly longer exposure to inhalant euthanasia than for adults. This is because neonates are resistant to the effects of hypoxia. Adequate time of exposure should be provided (for example, up to ~ 50 minutes).3,4 Once animals are deeply anesthetized, an adjunctive method (such as cervical dislocation or decapitation) should be performed. Methods of Euthanasia: Inhalant volatile anesthetics • Overdose of volatile anesthetics such as isoflurane and its equivalent compounds, desflurane, and sevoflurane, is commonly used for euthanasia of laboratory animals in the United States. • Volatile anesthetics may be used for euthanasia in the induction chamber of an anesthesia machine. • The animal is placed in the induction chamber, which is closed tightly, and the concentration of anesthetic is slowly increased past the level used for surgical anesthesia. Your institution’s SOPs should specify the exact concentration and amount of time that the animals must remain exposed to the anesthetic. • Waste gas is drawn into an approved waste collection system, where it can be absorbed or exhausted safely. This process is called waste gas scavenging. Commonly used scavenging equipment includes use of activated charcoal canisters which absorb anesthetic (passive scavenging), and use of suction, fume hoods, and downdraft stations which pull away gas containing the volatile anesthetic (active scavenging) and exhaust them outdoors. • Rodents can be euthanized by using an overdose of inhalant anesthetic in a bell jar, which is a clear glass or plastic chamber with a reservoir and wire mesh on the bottom. A cotton ball or other absorbent material is soaked with the anesthetic and placed below the wire mesh, out of reach of the animals. Animals should be separated from the absorbent material because the anesthetic’s fast evaporation rate makes it cold to the touch, which would chill the animals’ paws and cause pain. This procedure must be conducted in a fume hood to protect the personnel from breathing the anesthetic vapor when the bell jar is opened to remove carcasses. Methods of Euthanasia: Inhalant Carbon dioxide (CO2) • Carbon dioxide CO2 is a gas that rapidly produces loss of consciousness when inhaled in a high concentration. • It is one of the most commonly used chemical agents to euthanize rodents and other small mammals in laboratory animal research. • CO2 is an effective and inexpensive method of euthanasia for these animals • it poses minimal risk to the operator. • Animals inhale CO2 and lose consciousness due to a reduced oxygen level in the brain and other tissues in the body (hypoxia). • A compressed gas cylinder must be used as the source of the CO2 gas. No other source of CO2 is permitted. • A low-pressure regulator must be used to control the flow of gas so that animals are not distressed by a turbulent inflow of gas. • The flow rate must provide for a gradual displacement of 10% to 30% of the air inside the euthanasia chamber per minute for conscious rodents to minimize aversion and distress. • After the rodents become unconscious, the CO2 flow rate may be increased to shorten time to death. • The CO2 flow should be maintained for at least 1 minute after the animals cease to breathe, to assure death. • Following with an adjunctive method, such as cervical dislocation, is recommended. Methods of Euthanasia: Chemicals for injection Injectable euthanasia agents are generally administered to produce a rapid loss of consciousness followed by death. The use of injectable agents requires skill and experience on the part of the technician. These agents are typically solutions containing barbiturates, like pentobarbital, which are approved by the Food and Drug Administration for this purpose. • In small mammals, these agents may be administered intraperitoneally due to the large volume required and the size of the blood vessels. • In larger animals (rabbits, cats, dogs, nonhuman primates, ruminants, swine, and horse) injectable barbiturate solution is typically given intravenously. • Most injectable euthanasia solutions are controlled substances because of the potential for human abuse. The federal government’s Drug Enforcement Administration (DEA) has strict requirements for handling, inventory control, and recordkeeping of these controlled substances. • Disposal: The drugs in these euthanasia solutions remain chemically intact in the body after death and can kill scavenger animals that eat the carcass of a euthanized animal. Therefore, the remains of euthanized animals must be disposed of in ways that prevent either their consumption by wild animals or entry into the food chain. Typically, carcasses are destroyed by incineration. Methods of Euthanasia: Chemicals for Immersion • Fish and aquatic amphibians can be euthanized by immersing them in a water bath containing an overdose of buffered MS-222 or other appropriate anesthetic. • The anesthetic is absorbed through the gills of fish and the thin skin of the amphibians. • An adjunctive method of euthanasia is required. • Disposal: The drugs in these euthanasia solutions remain chemically intact in the body after death and can kill scavenger animals that eat the carcass of a euthanized animal. Therefore, the remains of euthanized animals must be disposed of in ways that prevent either their consumption by wild animals or entry into the food chain. Typically, carcasses are destroyed by incineration. Methods of Euthanasia: Physical Means • While chemical methods of euthanasia should be used whenever possible, there are times when scientific requirements may necessitate use of physical methods of euthanasia. Physical euthanasia methods are generally acceptable with conditions, and personnel using these methods must be trained and proficient in their use. Using a physical method of euthanasia avoids contaminating the animal’s tissues with chemicals that could interfere with a study. • Physical methods of euthanasia either destroy the brain or stop its functioning, thus euthanizing the animal quickly. • Physical methods may involve the use of equipment to apply a force or a cutting action with speed and precision, while safeguarding the operator. Examples of such equipment include the use of a guillotine device or a captive bolt. • If properly done, physical methods are humane because the animal rapidly loses consciousness. However, as physical methods involve trauma, there are risks for both the animals and personnel. • Animals may be distressed by the restraint necessary to position them in equipment • Animals may be injured in a failed procedure. • Personnel may be injured by a struggling animal or malfunctioning equipment. • Even when carried out humanely, a physical method of euthanasia may cause emotional distress in observers. • The proper functioning of the equipment is an important factor in determining whether the method is humane for animals and safe for personnel. • Knowledge and skill to restrain the animal and perform the procedure appropriately are essential to ensure that the animal rapidly loses consciousness and dies with minimal pain and distress. Methods of Euthanasia: Physical Means • Cervical dislocation: the dislocation of the vertebrae in the neck, which is the cervical area of the spine. • In cervical dislocation, the spinal cord is quickly separated from the skull, thus preventing transmission of nerve impulses in either direction between the brain and the body. • When properly done, the animal quickly ceases to breathe and the heart stops beating. There may be muscle contractions continuing for some time, which causes motion of the limbs. However, since the body’s nervous system is disconnected from the brain, this motion is only a result of an automatic reflex and not the sensation of pain. • Cervical dislocation is acceptable with conditions for mice, small rats weighing less than 200 grams, immature rabbits, and some bird species. • Decapitation: Uses a special instrument called a guillotine to sever the head from the body. The guillotine must be cleaned between animals, and the blade must be kept sharpened. • In neonatal rats and mice, appropriately-sized scissors or a scalpel may be used for decapitation. • The person performing physical means must be properly trained and comfortable with the technique used. Verification of Death • After euthanasia is performed, the death of the animals must be verified. • Animals may stop breathing in a CO2 chamber, but they may not be dead. In these cases, the effect of the CO2 can wear off, allowing the animals to recover and wake up. Verification confirms death by making sure that the heart has completely stopped beating and respiration has ceased. • For large animals, technicians may monitor the animal to verify the lack of a pulse, heartbeat, and breathing. • In small animals, especially rodents, these vital signs are difficult to assess, making it necessary to use an adjunctive method to ensure that death has occurred. • Cervical dislocation can be performed on rodents removed from a CO2 chamber to ensure that the animals are dead. Under the effects of prolonged high levels of CO2, a live animal would be unconscious and unable to feel any pain related to this second procedure. • Another adjunctive method that can be used in large and small mammals is to open the chest cavity on both sides with scissors or a scalpel, thereby creating a bilateral pneumothorax. This collapses the lungs and ensures death by preventing the resumption of breathing. Learning to Perform Euthanasia • Because proper euthanasia technique is critical for animal welfare and occupational safety for personnel, individuals who perform euthanasia must be thoroughly trained in the methods used at their institution. This training includes • • • • • • the proper restraint and handling of the animals the physiological processes involved with the euthanasia method use and maintenance of equipment handling and administration of euthanasia agents verification of death in euthanized animals the method of carcass disposal • Practicing on animals that are either anesthetized or already euthanized helps technicians develop proficiency with any method. • Movements and vocalizations that are similar to those made by animals in distress may accompany even the most humane methods of ending an animal’s life. These involuntary reflexes of the unconscious animal may be uncomfortable for the technician to witness. It is normal to experience discomfort and anxiety when performing euthanasia procedures. Learning to Perform Euthanasia – Compassion for Staff • Everyone must understand the emotional distress that can be experienced by the personnel involved in these procedures. Regardless of the reason, terminating the life of an animal can be a difficult task. A good way to learn to deal with such feelings is to learn all you can about the procedures, train with those who have a lot of experience, and perform the techniques in the most humane way. • Taking the life of any animal can affect people in many different ways. • Personnel should never minimize the emotional impact of performing euthanasia on the animals that had been under their or others’ care. Anyone may experience grief or bereavement over the loss of the animals. Sadness, depression, disinterest in work, and compassion fatigue can be signs of grief associated with the sense of loss. • Suppressing or minimizing these feelings may lead to difficulty performing the task again, detachment toward the other animals in the facility, anxiety in the workplace, and conflict with coworkers. • Sharing these feelings with coworkers, a supervisor, or a veterinarian can help technicians deal with these normal reactions. The AALAS publication “Compassion Fatigue: The Cost of caring” offers suggestions to staff and management on strategies for coping with grief over the death of animals in the workplace. This information can be downloaded for free from the AALAS website. Summary • The AVMA Guidelines for the Euthanasia of Animals describes the methods of euthanasia that are acceptable, acceptable with conditions, and unacceptable for each animal species. • The method of euthanizing laboratory animals must comply with this document and be described in the approved IACUC protocol for the animal research. • Acquiring the knowledge and skills to competently perform euthanasia is essential for safeguarding both animal welfare and personnel safety. • Laboratory animal technicians should be aware that euthanizing animals they care for may cause them to grieve, which is a normal reaction shared by many individuals involved with animal research. Taking pride in having attained the technical competence to humanely care for laboratory animals, even at the time of their death, can help ease the grief felt at the loss of these animals. • It is true that laboratory animals often have short lives because of their contributions to biomedical research. However, if quality of life is valued, then laboratory animal technicians who are caring and competent make great contributions to these animals throughout their lives.