Pain Parameters

Recognizing and Treating Pain In our Pets

By Dr. Mark Silberman, Southwest Animal Clinic

Pain management in dogs and cats has undergone a dramatic evolution in the past decade. Historically it was thought that animals did not feel pain or that they perceived pain differently than humans. The recognition of pain in our pets is now receiving the attention it so deservers.

Because the natural instinct of animals in the wild is to hide their pain symptoms so that they are not perceived as weak by predators, their ability to mask the symptoms makes identifying their pain more difficult. In addition, it was also previously suggested that pain following surgery or injury was beneficial because it limited movement and thus prevented further injury.

Today, we have a much better understanding of pain pathways, types of pain and how to control pain more effectively.  For example, we now know that animals have very similar if not exact neural pain pathways as humans. Also, pain (whether perceived by the animal or not) is not beneficial, rather, it is harmful.

Veterinarians, as advocates for our patients, have a responsibility to recognize, assess, prevent, and treat pain.  Below are some common myths related to pain in animals:

Myth #1.
Animals do not feel pain as people do.

Truth: From a physiologic standpoint, mammals and humans process pain in the same way.

Myth #2.
Animals tolerate pain better than people do

Truth: In many cases animals do “appear” to tolerate pain better than humans. There may be several explanations for this. In contrast to pain-detection threshold, pain tolerance–the greatest intensity of pain that is voluntarily tolerated–varies widely between species and individuals within a species. Like humans, animals likely tolerate pain to a particular level before showing changes in behavior. Knowing that patients may exhibit a wide range of pain tolerances as well as a broad spectrum of behaviors can improve pain recognition and treatment.

Myth #3.
Labradors are made of steel and Yorkies are wimps!

Truth: This myth illustrates our preconceived notions about variations in breed response to painful stimuli. The inherent danger associated with this belief system is that we may fail to treat patients who are stoic or we may undertreat patients whose overt signs seem exaggerated.

Myth # 4.
Pain is beneficial in limiting a recovering animal’s activity

Truth: Although one of the mostly widely held myths about pain, the type of pain produced by tissue injury, inflammation or direct damage to the nervous system is never beneficial. Aside from being morally questionable, there appears to be little evidence to support this idea.

Recognizing Types of Pain:

There are many types of pain.  All tissue injury, including that from elective surgery, may cause pain. Pain induced stress responses, mediated by the endocrine system, are one of the negative consequences of pain. According to the AAHA/AAFP (American Animal Hospital Association/American Association of Feline Practitioners) Pain Management Guidelines, these pain induced responses lead to “Increased cortisol, catecholamines, and inflammatory mediators cause tachycardia, vasoconstriction, decreased gastrointestinal motility, delayed healing, and sleep deprivation. In addition, trauma causes unseen changes in the central nervous system. Inadequate pain prevention or management can lead to magnification of pain perception and a prolonged pain state”.

The old definitions of chronic versus acute pain have been replaced with adaptive versus maladaptive pain.

Adaptive pain is a normal response to tissue damage. Adaptive pain includes inflammatory pain. Inflammatory mediators sensitize neural pathways, increasing the perception of pain.

If adaptive pain is not appropriately managed, physical changes occur in the spinal cord and brain, leading to pain that is termed maladaptive. Also known as “wind up”, it is a heightened sensitivity that results in altered pain thresholds, both peripherally and centrally, such that pain is experienced in areas unrelated to the original source. Examples of maladaptive pain are neuropathic and central pain and in humans would include conditions like Diabetic Neuropathy and Fibromyalgia.

Frequently Overlooked Causes of Pain:

Type of Pain Cause
Cardiopulmonary Congestive heart failure (pulmonary edema and pleural effusion); pleuritis, cerebral vascular accident, thromboembolism (clot).
Oncologic Any and all cancer.
Dermatologic Ear infectons, severe itching, burns, chronic wounds; abscess, skin infection, clipper burns, urine scalding, severe chin acne.
Dental Oral tumors, feline oral resorptive lesions (Dental disease), fractures (no matter how small), tooth abscess, ulcers, mouth inflamation.
Gastrointestinal Constipation, obstruction, megacolon; anal sac impaction; hemorrhagic gastroenteritis, pancreatitis, gastric dilatation, colic, foreign body.
Musculoskeletal Most often overlooked in cats. Muscular soreness, arthritis, degenerative joint disease, tendon or ligament injury, intervertebral disc disease, facet pain of spondylosis (bone spur in spinal column),  dislocations.
Ocular Corneal disease and ulcers, glaucoma, uveitis (inflammation on inside of eye).
Urogenital Bladder stones,ureter stones, queening/whelping, feline lower urinary tract disease/interstitial cystitis (bladder infection), acute kidney failure, enlarged kidneys (capsular swelling), lower urinary tract infections, urinary obstruction, vaginitis (especially in obese cats).
Hospital procedures Restraint (examination, obtaining blood and urine samples, radiographs, and ultrasound; even gentle handling and hard surfaces can increase pain in an already painful animal). Urinary/IV catheterization, bandaging, surgery, chest tube placement and drainage procedures. Manual extraction of stool and anal sac expression (especially in cats).
Surgical procedures Ovariohysterectomy (Spay), castration, onychectomy (Declaw),* growth removal, and all other surgical procedures.
Neurologic Diabetic neuropathy.
* Regardless of method used, onychectomy causes a higher level of pain than spays and neuters.

How is Pain Treated?

There are many medications available to treat the different kinds of pain.  Sometimes an animal has more than one type of pain and therefore requires multiple medications for its control. Since different pain pathways can be involved in the same animal, a combination of medications designed to interrupt these pathways will be prescribed.

For example, we might combine an NSAID like Rimadyl, Deramaxx, or Previcox with Gabapentin and Tramadol to control long standing osteoarthritis. The idea is to “hit it hard” or attack the relief of pain aggressively and then titrate down to the minimal amount of medication that can control the pain. Essential Fatty Acids (Fish Oil), Glucosamine and MSM might also be used.

What are the signs of Pain?

General Signs Specific Signs
Loss of normal behavior Decreased ambulation or activity, lethargic attitude, decreased appetite, decreased grooming (cats).
Expression of abnormal behaviors Inappropriate elimination, vocalization, aggression or decreased interaction with other pets or family members, altered facial expression, altered posture, restlessness, hiding (especially in cats).
Reaction to touch Increased body tension or flinching in response to gentle palpation of injured area and palpation of regions likely to be painful, e.g., neck, back, hips, elbows (cats).
Physiologic parameters Elevations in heart rate, respiratory rate (panting), body temperature, and blood pressure; pupil dilation.

Controlling pain in your pet is imperative to maintaining a good quality of life.  It is our responsibility as veterinarians and your responsibility as a pet owner to address any and all painful conditions in our furry friends.  We owe it to them!