The University of Arizona Institutional Animal Care and Use Committee Handbook

IV. PAIN

"What level of pain do we allow?" is a question facing all animal care committees. The IACUC must somehow reconcile the research's physical and psychological consequences to the animal with the objectives of the proposed investigation. It is the goal of the IACUC to limit the pain and distress of experimental animals to the absolute minimum necessary.

The following information is used by the Committee in considering painful and stressful procedures, and these guidelines should also be used by those submitting protocols for review. By mutual understanding of terminology, there can be no confusion as to the definitions and standards used by the Committee in the review process. Animal Care Facility personnel will also follow these same guidelines.

A. PAIN AND DISTRESS: DEFINITIONS

  1. Pain is an awareness of acute or chronic discomfort, occurring in varying degrees of severity, and resulting from injury, disease, or emotional distress as evidenced by biological and/or behavioral changes.
  2. Acute Pain results from a traumatic, surgical, or infectious event that is abrupt in an onset and relatively short in duration. It is generally alleviated by analgesics.
  3. Chronic Pain results from a longstanding physical disorder or emotional distress that is usually slow in onset and has a long duration. It is seldom alleviated by analgesics but frequently responds to tranquilizers combined with environmental manipulation and behavioral conditioning.
  4. Distress is an undesirable physical or mental state resulting from pain, anxiety, or fear. Its acute form may be relieved by tranquilizers. Sustained distress, however, requires environmental change and behavioral conditioning and does not often respond acceptably to drug therapy.

B. ANALGESICS AND ANESTHESIA: DEFINITIONS
  1. Analgesia refers to relief from pain.
  2. Tranquilization is a state of behavioral change in which the patient is relaxed and unconcerned by its surroundings. In this state, the animal is often indifferent to minor pain.
  3. Sedation is a mild degree of central depression in which the patient is awake but calm.
  4. Narcosis, in man, is defined as a drug-produced state of deep sleep accompanied by analgesia. In veterinary medicine, the narcotized patient is seldom asleep but is sedated and oblivious to moderate pain.
  5. Hypnosis is a condition of artificially induced sleep, or a trance resembling sleep, resulting from moderate depression of the central nervous system.
  6. Local Anesthesia is the loss of sensation in a limited area of the body.
  7. Regional Anesthesia is insensibility in a larger but limited area of the body.
  8. Basal Anesthesia is a light level of general anesthesia usually produced by preanesthetic agents. It serves as a basis for deeper anesthesia on administration of other agents.
  9. General Anesthesia is complete unconsciousness.
  10. Surgical Anesthesia is unconsciousness accompanied by muscular relaxation to such a degree that surgery can be performed painlessly and without struggling on the part of the patient.

C. SIGNS OF PAIN
  1. An animal in pain, regardless of species, usually displays one or more of the following signs:

D. SIGNS OF ACUTE PAIN

E. SIGNS OF CHRONIC PAIN

F. SPECIES SPECIFIC SIGNS

 In compiling general guidelines it has become clear that there are species specific signs of pain which should be taken into account when making a practical assessment. Experience has taught that such signs are often associated with what is believed to be a painful condition, although no sign can by itself be regarded as diagnostic of pain and may also occur in conditions in which pain is unlikely to be a feature.

Although a comprehensive description of species specific signs has not been produced, the following notes and comments might be helpful.

1. Primates

Monkeys often show remarkably little reaction to surgical procedures or to traumatic injury. Obvious signs of pain are not readily seen. Loud and persistent vocalization is unlikely to be an expression of pain, but it is more likely to signify alarm or anger. Pain causes a general appearance of misery and dejection. The animal may be huddled in a crouching posture with a 'sad' facial expression and glassy eyes; it may moan, avoid its companions and may stop grooming itself. A monkey in pain may also attract increased attention from its cage mates. This can vary from social grooming to attack. Acute abdominal pain may be shown by facial contortions, clenching or teeth, restlessness and shaking accompanied by grunts and moans. Food and water are usually refused.

Contact Training Coordinator for Primate Module

2. Horses

The following signs are associated with pain: periods of restlessness; interrupted feeding with food held in the mouth uneaten; anxious appearance with dilated pupils and glassy eyes; increased respiration and pulse rate with flared nostrils; profuse sweating and a rigid stance. In prolonged pain, behavior may change from restlessness to depression with head lowered. In pain associated with skeletal damage, limbs may be held in unusual positions and there is reluctance to move with head and neck 'fixed'. In abdominal pain, a horse may look at, bite or kick its abdomen; it may get up and lie down frequently; walk in circles; roll and injure itself as a result of these activities. This state may progress and can last for several hours. When near collapse, the horse may stand very quietly rigid and unmoving. Horses in pain generally show a reluctance to be handled.

3. Cattle

 Cattle in pain often appear dull and depressed with little interest in their surroundings. There is inappetence, weight loss and, in milking cows, a sudden drop in milk yield. Severe pain often results in rapid, shallow respiration. On handling, they may react violently or adopt a rigid posture designed to immobilize the painful region. Grunting and grinding of teeth may be heard. Generally signs of abdominal pain are similar to those seen in the horse but are less marked. Rigid posture may lead to a lack of grooming because of an unwillingness to turn the neck.

Link to Cattle Module

4. Sheep and goats

In general, signs of pain in sheep and goats are similar to those in cattle. Changes in posture and movement are apparent and a change in facial expression may be indicative of pain. Goats in particular are more likely than cattle to vocalize in response to pain. Grinding of teeth and grunting are also heard.

Link to Sheep and Goat Module

5. Pigs

Pigs in pain may show changes in gait and posture. Pigs normally squeal and attempt to escape when handled but these reactions may be accentuated when in pain. Pigs will often be unwilling to move and may hide in bedding, if possible.

Link to Swine Module

6. Dogs

Dogs in pain generally appear quieter and less alert with stiff body movements and an unwillingness to move. In severe pain, the dog may lie still and adopt a crouching attitude. In less severe states, it may appear restless. There may be inappetence, shivering and increased respirations with panting. Spontaneous barking is unlikely, the dog is more likely to whimper or howl, especially if unattended and may growl without apparent provocation. A dog may bite or scratch at painful regions and may become more vicious when handled.

7. Cats

 Cats in pain are generally silent, but may growl or hiss if approached. There is inappetence and a tendency to hide. Posture becomes stiff and the cat may sit hunched in sternal recumbency being reluctant to stretch out. A cat in severe pain may howl and show demented behavior with desperate attempts to escape. Incessant licking is sometimes also associated with pain. More usually, the cat has a generally miserable, un-groomed appearance with a change from its normal temperament. There may be panting with an increased pulse rate and dilation of the pupils.

8. Rabbits

 Rabbits in pain may be apprehensive, dull, inactive and assume a 'hunched' appearance. They sometimes, however, show aggressive behavior, and activity may be increased with excessive scratching and licking. Reactions to handling are exaggerated, and acute pain may result in vocalization. Respiratory rate may be increased, and there may be inappetence.

Link to Rabbit Module

9. Rodents

Pain in rodents usually results in decreased activity, piloerection and an un-groomed appearance, or there may be excessive licking and scratching. They may adopt an abnormal stance with ataxia, but rats and mice may become unusually aggressive when handled. Acute pain may cause vocalization. Inappetence or a change in feeding activity may be noted and, if housed with others, a change in the normal group behavior may be apparent.

10. Birds

 Birds in pain may show escape reactions with vocalization and excessive movement. There may be an increase in heart and respiratory rates. Prolonged pain will result in inappetence and inactivity with a drooping, miserable appearance. When handled, the escape reaction may be replaced by a state of tonic immobility.

11. Fish

 It is difficult to determine the nature of the response to pain in fish. Responses to harmful stress include an increased ventilatory pattern with excessive movement of fins.

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