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IACUC Training
Minimizing Pain or Distress

There are numerous means of minimizing pain or distress to animals used in research, testing and training. In fact, over 90% of animals used in research in this country do not experience significant pain or distress. Good science and animal welfare are not mutually exclusive concepts; they are dependent on one another. Some methods of minimizing pain or distress are listed below.

Alternatives

Alternatives to painful or distressful procedures performed on live animals should be used whenever possible. Concepts such as refining experimental design and procedures to minimize the impact on animals, reducing the number of animals used to only those which are necessary, and replacing live vertebrate animals with invertebrate in vitro, mechanical, mathematical or computer models must be considered whenever planning to perform procedures that may cause more than momentary or slight pain or distress. The use of alternatives has had a significant impact on animal use. While there has been little change in the total numbers of animals used over the last 30 years, there has been a significant increase in the amount of research performed. The difference is made up for in alternatives to animals. Likewise, there has been a significant shift toward the use of less sentient animals.

Husbandy/Housing

As previously described, the environment an animal lives in and the care it receives can have significant impacts on its health and well-being. Guidelines for husbandry and housing must be followed at all times, unless specific approval is given by the IACUC for exceptions. These guidelines include the amount of cage space needed for animals; temperature, humidity and ventilation requirements; guidelines for the quality of, and the frequency of providing feed and water; frequency of and methods for sanitation; and the need for environmental enrichment and social behavior.

Recognizing Problems

It is essential to carefully design experimental procedures to prevent them from causing disease, pain or distress to animals. However, it may not be possible to anticipate all problems. This is, after all, research. We are delving into the unknown. Therefore, it becomes necessary to plan for the unexpected. What problems are likely to occur based on the procedures? How will they be recognized? What will be done if they occur?

Experiment Guidelines

Aseptic technique must be followed whenever performing invasive procedures to prevent infection. Specific methods for achieving asepsis may vary among procedures as detailed under Experimental Surgery.

Immunization

Inflammation from immunization with adjuvants can result in pain or distress.

Tumor Induction

Tumors can result in pain or distress when they reach an advanced stage. Unless necessary for the experiment, animals should be euthanized before the tumor begins having adverse effects, such as anorexia, depression, weight loss, ulceration of the skin, internal bleeding or interference with the animal's locomotion.

Blood Collection

Blood collection can result in anemia or hypovolemic shock. Certain methods, such as orbital sinus collection or intracardiac blood collection, can be painful and normally require use of anesthesia.

Toxicity Testing

Toxicity testing has great potential for causing pain or distress to animals. This can be alleviated by defining the endpoint of the experiment at the earliest point at which toxicity can be detected. In the case of LD50 studies, it may be possible to perform a pilot study on a limited group of animals to establish a set of criteria that correlate with an irreversible progression to death. For example, in one study a drop in body temperature preceded death by a specific time interval. For future studies, the endpoint could be defined as a drop in body temperature, which normally occurred before any clinical signs of pain or distress were seen.

Food or Water Restriction

Food and water restriction are known to cause stress in animals. Therefore, it is essential that measures be taken to prevent serious complications. First know what normal amounts of food or water are required for the animal species of the size and life stage (i.e. growth, pregnancy, lactation, geriatric). Restriction should be modest and should be based on something measurable (e.g. a percentage of ad lib consumption or ad lib body weight). It is critical to monitor animal well-being during times of food or water restriction. As physiological or environmental conditions change, an animal's food and water requirements will change. A previously acceptable level of food or water restriction may suddenly become a source of distress. Adapting animals slowly to changes in diet can help prevent problems. Monitor for signs of distress during food or water restriction such as rapid weight loss, poor body condition (i.e. muscle wasting, prominence of bones, sunken eyes, poor hair coat), loss of appetite, lethargy or clinical signs of dehydration (lack of urine, constipation, dry mucous membranes, sunken eyes, crusting around eyes and nose, loss of skin elasticity). Daily monitoring of food and/or water consumption and weekly weight monitoring are recommended.

Restraint & Handling

Proper handling procedures can minimize stress to both the handler and the animal. If restraint devices are used, it is important that animals be adapted to the device (place them in the device several days in a row for gradually increasing intervals). If prolonged restraint is to be performed (over 1 hour), it may be necessary to provide food, water, and the opportunity for the animal to exercise during the restraint period.

Analgesia

Analgesics, or pain relievers, are drugs that can be used to prevent or relieve pain. Analgesic considerations between humans and animals are similar, as the ability of humans and other vertebrate animals to experience pain are similar. We have the same general components to our nervous system.

Types of pain - the intensity and character of pain differs depending on the location and source of the pain stimulus

Superficial - refers to pain transmitted by somatic efferent nerves from skin and muscles. Generally less intense than deep pain.
Deep - often referred to as visceral pain. Transmitted by visceral efferent nerves from viscera, the pleura and peritoneum, and the periosteum. Generally the most intense pain.
Nociceptive - the type of pain detected by receptors sensitive to pressure, heat or electrical stimulus.
Inflammation - the type of pain stimulated by release of intercellular messaging molecules such as substance P, prostaglandin's and leukotrienes.
Chronic - some types of pain tend to last longer than the inciting stimulus. This includes neuropathic pain, chronic inflammation, and others

Drugs Used to Relieve Pain
Methods of Administration

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