Not long ago, compassionate and well-meaning veterinarians believed some things about animal pain that we now recognize as completely wrong.
For instance, it was "common knowledge” that animals do not feel pain the way humans do. We believed that some post-operative pain was a good thing to assist with keeping an animal quiet after a surgery.
Because it is often difficult to assess pain in animals, we often unintentionally overlooked animal pain because we simply did not know how to recognize it.
Now we know better.
All Pain is Not Created Equal
We used to believe that there were many different kinds of pain—acute, chronic, post-operative, cancer/malignant—and we had a limited number of treatment options. We also used to believe that monotherapy (treatment with a single agent) was the strategy of choice.
Clifford Woolf, M.D., set us straight with his identification of pain as a continuum from "adaptive” pain—pain that helps us—to "maladaptive” pain—pain that hinders us. An example of adaptive pain is transient physiologic pain. Examples of maladaptive pain include phantom pain following an amputation and the altered sensation that results from unmanaged or undermanaged acute or chronic pain.
Because the pain phenomenon is very complex, we have many potential targets for our pain management efforts. Ongoing research and clinical studies continue to expand our treatment options.
The most effective pain management plans incorporate multiple targets. Multiple targets mean multiple modalities, hence the term "multi-modal” pain management.
Start with Assessment
While we are still chasing the one perfect pain scoring tool, a thorough pain palpation is a skill every veterinarian and veterinary technician can learn and incorporate into every examination (Downing, 2011).
The AAHA/AAFP Pain Management Guidelines for Dogs & Cats clearly articulate the need for pain to be elevated to the fourth vital assessment, and for a pain assessment to be performed on every single patient every single time that patient comes into the practice.
Once pain is identified, it can be investigated, a complete diagnosis made, and an appropriate pain management plan constructed. Chronic pain patients (e.g. those with osteoarthritis) need ongoing regular assessments and revisions of their pain management strategies. Chronic maladaptive pain is the gift that keeps on giving, and it is up to the veterinary health care team to partner with the family to stay ahead of the changing pain management landscape.
Pharmacology is a foundational piece in any multimodal pain management plan. The non-steroidal anti-inflammatory drugs decrease inflammation as well as provide analgesia in their own right. Both acute pain and chronic pain patients can benefit from treatment with NSAIDs.
It is important to perform a thorough baseline metabolic profile both to screen for patients for whom NSAIDs may not be a good choice, as well as provide a point of reference in case the animal experiences an adverse event. NSAIDs are most effective in the presence of inflammation so they work very well in the post-operative period or following an acute injury.
The most common cause of chronic maladaptive pain in animals is osteoarthritis. OA is a chronic inflammatory condition, making it an excellent target for NSAIDs. There is no "best” NSAID, only the best one for each patient, and regular reassessments will help to determine if the choice is a good one.
Several drugs have been identified to work well clinically alongside the NSAIDs for pain. In the acute adaptive pain setting, narcotics (e.g. µ opioids) provide potent pain relief.
For chronic maladaptive pain, gabapentin and pregabalin target the dorsal horn of the spinal cord to modulate neuronal firing. Amantadine targets the NMDA receptor in the spinal cord to counteract the effects of central sensitization—a phenomenon resulting in enhanced transmission of pain impulses.
Tricyclic antidepressants have been used for years in humans with chronic maladaptive pain. It appears that for some animal patients with chronic maladaptive pain, this class of medication offers effective relief.
Tramadol works on µ receptors (like morphine and fentanyl), and along serotonin and norepinephrine pathways. But there are several disadvantages to tramadol, including:
• We do not yet have good safety data about tramadol in dogs and cats.
• The half-life of tramadol in the dog is very short, which makes consistent delivery difficult for many clients.
• Tramadol is exceptionally bitter and that can cause dosing difficulties.
Tramadol may be best positioned for short-term use for acute pain (e.g. post-op) or pain flares superimposed on an effective chronic pain management strategy.
Physical therapy techniques have been applied to animals beginning in the early 1900s. Physical rehabilitation is a relatively new formal field in animal medicine that is becoming better recognized and evidence-based. There are many benefits to applying physical medicine techniques to animals, which include:
• Increased function and quality of movement
• Reduced pain and swelling
• Reduced rate of post-operative complications
• Increased overall recovery rate from injury or surgery
• Increased strength, range of motion, endurance, and performance
• Improved and prolonged quality of life
• A focus on prevention
Physical medicine techniques include:
• Cold/heat therapy
• Medical massage
• Therapeutic exercise
• Therapeutic ultrasound
• Myofascial trigger point release
• Chiropractic adjustment
• Medical acupuncture
• Therapeutic laser
To elaborate on a couple of these techniques:
• Medical massage techniques can reduce pain, muscle spasm, anxiety, edema and tissue restrictions. Massage facilitates arterial, venous and lymphatic flow, relaxes skeletal muscle and mobilizes tissues abnormally adherent to adjacent structures.
• Therapeutic exercise includes a variety of activities including balance and proprioceptive exercises, strengthening, range of motion, endurance activities and functional activities.
Medical acupuncture focuses on neuromodulation to decrease pain and improve neurologic function. To cite one application, electro-acupuncture has been demonstrated to be beneficial in its application to intervertebral disk disease in dogs with neurologic deficits (Joachim 2010). There are many strategies for applying acupuncture to painful patients, both for treating pain locally (e.g. the pain from canine hip dysplasia and OA) as well as modulating nervous system function more globally.
Therapeutic lasers allow for the delivery of "light packets” into painful tissues to normalize tissue function. Most of the basic science to date on therapeutic laser has been conducted in rodent models or cell culture, and most clinical studies have been conducted in humans.
Fortunately, data is emerging from clinical studies conducted in animal patients. For instance, Colorado State University College of Veterinary Medicine is evaluating the use of therapeutic laser to treat dogs with rattlesnake bite.
The preliminary data are compelling. Therapeutic laser provides a photobiomodulatory effect on tissues to decrease inflammation, increase microcirculation, increase angiogenesis, increase beta endorphins, and increase nerve cell action potentials (thus decreasing pain).
Good post-graduate training programs are available in the various areas of physical medicine should you choose to add physical medicine modalities to your practice.
Physician and humanitarian Albert Schweitzer stated, "Pain is a more terrible lord of mankind than even death.” Surely animal patients need and deserve the full attention of the veterinary health care team to identify and then banish pain.
Pain is insidious and can show up in unexpected circumstances as well as when we anticipate it.
Every patient needs and deserves to be evaluated for pain every single time it is seen in the veterinary practice. Pain really is the fourth vital sign. We need to look for it, and we need to know what to do when we find it.
Fortunately, veterinarians and their health care teams now have an impressive number of pain management tools from which to choose.
Abbott’s OroCAM Is First Oral Spray NSAID
OroCAM (meloxicam) Transmucosal Oral Spray, the first veterinary nonsteroidal anti-inflammatory drug with transmucosal oral delivery, recently received U.S. Food and Drug Administration approval and is shipping the product, manufacturer Abbott Animal Health reported in February.
The drug, indicated for the control of pain and inflammation associated with canine osteoarthritis, is rapidly absorbed into the bloodstream after being sprayed onto a dog’s gums or inner cheek, Abbott reported.
"The challenge with administering a tablet, or even a chewable pill, is reported so often that we saw a need for veterinarians to help pet owners address this challenge,” said Andrea Wainer, divisional vice president and general manager.
The spray allows for accurate dosages and eliminates the risk of improper swallowing or digestion, uneaten treated food and expelled pills, Wainer added.
Abbott conducted a masked, placebo-controlled, multisite field study involving more than 250 client-owned dogs diagnosed with osteoarthritis. Dog owners reported successful management of osteoarthritis pain by Day 28 in 73 percent of the OroCAM group, compared to 47 percent of the placebo group.
The use of OroCAM was not evaluated in dogs younger than 6 months or weighing less than 5.5 pounds, in dogs used for breeding, or in pregnant or lactating dogs.
AAHA/AAFP Pain Management Guidelines for Dogs & Cats; J Am Anim Hosp Assoc 2007; 43: 235-248.
Downing R. "Managing Chronic Maladaptive Pain”; NAVC Clinician’s Brief. August 2011.
Gaynor J, Muri W. Handbook of Veterinary Pain Management, 2e. St Louis, MO: Elsevier Publishing, 2008.
International Veterinary Academy of Pain Management – www.ivapm.org
Joachim JG, et al. "Comparison of decompressive surgery, electroacupuncture, and decompressive surgery followed by electroacupuncture for the treatment of dogs with intervertebral disk disease with long-standing severe neurologic deficits”; J Am Vet Med Assoc. 2010 Jun 1: 236(11): 1225-9.
Woolf CJ. "Pain: Moving from Symptom Control toward Mechanism Specific Pharmacological Management”; Ann Intern Med. 2004; 140: 441-451.