The Hurt Unlocker

Jasper falters and then collapses several times as she enters the exam room. The years have not been kind to the 11-year-old yellow Labrador retriever. Complications from a seizure condition have left her rear legs unsteady, and like many older dogs (and people), she suffers from arthritis. A couple of years ago, Jasper twisted a hock while wrestling with a canine playmate.

Her owner, Paul Schnaittacher of West Brookfield, Mass., uses a towel sling to get his pet upstairs at night. He carries the 70-pound dog downstairs in the morning. “I put her in my lap, and we slide down the steps,” he says. “She needs help with just moving around, period, and I don’t know how much fun that is for her.”

Like many owners of an aging pet, Schnaittacher wishes Jasper could simply tell him where it hurts and what would make her life easier. To get those answers, he brought his pet to Alicia Karas, N85, V89, head of the Pain Consultation and Referral Service at Tufts’ Foster Hospital for Small Animals.

One of only two veterinarians in Massachusetts who focus their practice on the treatment of chronic pain—and one of about 30 such experts nationwide—Karas’ job is a tricky one.

Human pain medicine is complicated enough, given that the causes of chronic pain are still poorly understood, and pain medicine as a specialty emerged just after World War II. And there is no test for pain. Physicians depend on their human patients to rate their discomfort on a scale of 1 to 10, or indicate the intensity of their pain by pointing to a chart of increasingly unhappy stick-figure faces—hardly the most precise diagnostic tools. Veterinarians face an additional hurdle: Their patients can’t put words to their discomfort.

But what can’t be conveyed verbally might be evinced in more subtle ways—a look, for example, or the turn of an ear. To advance her work in diagnosing and managing pain, Karas has collected hundreds of gigabytes of digital video and photographs (and before those, scads of film and stacks of VHS tapes) over two decades in an effort to document what animals in pain look like.

Her work mirrors two relatively new pain-assessment techniques used in human and lab animal medicine. In 2006, a scientist at Missouri State University developed the Classification of Pain Expressions, software that uses facial recognition to compare elements of a baby’s expression against a database of 60 photographs of infants undergoing a heel-prick blood draw, a standard procedure believed to be painful. Four years later, Canadian researchers announced the development of a Rat Grimace Scale and Mouse Grimace Scale, which teach laboratory technicians how to evaluate five features of a rodent face to determine whether it is hurting.

So what does a pet’s “pain face” look like?

“Well, if I told you to pretend that you have awful, crushing abdominal pain, you’d stiffen up. You wouldn’t breathe as deeply,” says Karas. “You’d start thinking about yourself, not about the outside world, and appear inwardly focused. You might squint. You might frown. If you could move your ears, you might move them back. When I look at all my videos and photos, I see a lot of these types of grimace faces.”

Jasper was able to telegraph her pain to Karas. The dog lies down in the exam room, but she looks anything but relaxed. Her neck is stretched out, her graying muzzle hovering just above the floor. Her brow is furrowed, and she seems disinterested in her surroundings. If she were a person, you’d assume she had one awful headache.

Karas thinks the dog looks pretty uncomfortable, but she wants to “ask” the Lab herself. She lowers herself to the floor and sidles up to Jasper. “You’re so gorgeous,” she tells her patient. She slowly massages the dog’s shoulders, back and legs, digging her fingers into Jasper’s muscles, which jump in response. The twitches tell Karas that there’s pain there—most likely because Jasper is straining the few muscles that are working well to compensate for weakness and more pain elsewhere.

As she continues this combo physical exam and massage, Karas asks Schnaittacher about Jasper’s habits: Does the dog sleep soundly (yes), still beg for table scraps (yes), want to hang out with family members (yes, as much as ever). The dog is on three anti-seizure medications, which, when coupled with many traditional pain relievers, can cause an adverse reaction. Karas says the good news is that Jasper still appears to enjoy many aspects of her life and should benefit from acupuncture and a few changes to her daily routine.

As Jasper enjoys a dog treat, Karas taps several hair-thin needles into place: one on the dog’s head for calming and pain relief and others along her back, hindquarters and rear legs. Before all the needles are in, Jasper stretches out comfortably and snoozes for the rest of the 90-minute appointment.

Karas suggests a special harness so that Schnaittacher can help Jasper up and down stairs. Because Jasper prefers lying on hardwood floors to the rugs her owners have put down to keep her from slipping, Karas says a rosin spray applied to the dog’s pads will provide traction. She’s optimistic that Jasper’s pain will subside.

Advances in veterinary medicine mean that animals are living longer—and are therefore more likely to experience pain as a result of cancer, arthritis, dental disease, glaucoma or injury. While geriatric pets like Jasper often have medical issues that can’t be fixed, Karas says that veterinarians are finally beginning to assemble a toolkit to treat pain as its own problem—instead of accepting it as an unavoidable side effect of other conditions.

The Pain We Share

Pain medicine as a veterinary specialty is relatively new. As recently as a decade ago, most veterinarians assumed that animals didn’t feel pain, or at least experienced it differently from humans. It was thought that pain helped keep a pet inactive so it wouldn’t cause further harm.

“Just imagine a doctor telling a mother, ‘We are going to let your toddler go without pain relief after surgery so he doesn’t move around and hurt himself,’ ” Karas says. “It’s basically the same thing.”

Now all evidence points to the contrary. Research has shown that animals and humans have similar neural pathways for the development, conduction and modulation of pain, making it pretty likely that our pets experience pain in much same the way we do.

Even in people, pain is often undertreated. Fifty percent of chronic pain sufferers who had visited a physician got what they felt was sufficient relief, according to a 2005 survey by Stanford University Medical Center.

“If we’re looking at practically half of the human population that’s in pain getting undertreated, I have to believe that over 95 percent of animals in pain are not getting proper treatment,” says Michael Petty, president of the International Veterinary Academy of Pain Management, founded in 2003 to advance pain management in animals. “This should be considered an epidemic.”

As recently as a decade ago, most veterinarians assumed that animals didn’t feel pain, or at least experienced it differently from humans. Illustration: Vivienne Flesher

Chronic pain in pets—the kind that builds slowly over months and years—is largely untreated because its symptoms are insidious. Acute pain that results from an accident or surgery, say, is easier to spot, “because there often is an abrupt change in the animal’s behavior—whether it’s crying out or not using a leg,” notes Petty, who runs an animal pain center in Michigan and frequently lectures on pain at national veterinary conferences. “Chronic pain is more of a challenge, because most animals adapt to it by curtailing their activities.”

To determine whether your pet is in pain, think about the animal’s daily routine—and compare what your cat or dog does now versus two or three years ago. Arthritis, for example, commonly goes undiagnosed in cats, Petty says, and may be discovered only when the animal appears to be wasting away. “I’ll ask the owner, ‘Where do you feed your cat?’ And the answer comes back, ‘On top of the washing machine because otherwise the dog will eat the food.’ Well the cat just can’t jump up there anymore. It’s virtually starving.”

Age is never the sole reason an animal stops doing something. “Old dogs like to play, go for car rides and eat,” says Petty. “They just do things a little bit more slowly because they have decreased muscle mass. They don’t have the energy of youth, but they still like to do all those things.” If pets are not showing an interest in daily activities, more often than not, he says, it’s due to pain.

Dogs in pain may appear agitated, lose their appetite, act “dull,” experience lapses in housebreaking or start licking a specific area of their body, notes Karas, while “cats are really, really good at pretending that nothing is wrong.” But if you took a hard look at your cat, you might see signs that indicate pain: rapid and shallow breathing, poor or no grooming, decreased appetite, lapses in litter box training and retreating to quiet areas of the house for long periods.

Cascade of Problems

Aside from the fact that no pet owner wants an animal companion to suffer, you should be vigilant to signs of pain for other reasons.

Pain in cats and dogs (as in humans) causes other complications and can impede recovery from illness, surgery or injury. Pain spurs the body to release the hormone cortisol, which increases the heart rate, slows digestion, impairs sleep and reduces blood flow needed for healing.

Over time, pain also disrupts the nervous system, causing changes in the spinal cord and brain that make people and pets more susceptible to pain. Chronic pain affects the region of the brain that modulates human and animal responses to pain, creating more sensitivity, which in turn destroys still more brain matter that regulates pain—a vicious cycle. Chronic pain also gives the nervous system way too much practice at transmitting pain. The longer that nerves carry pain messages along their routes, the more efficient those pathways become at conveying that message.

“Chronic pain is like water damage to a house,” says Daniel Carr, a professor at Tufts University School of Medicine and director of its Pain Research, Education and Policy degree program. “If it goes on long enough, the house collapses. By the time most patients make their way to a pain clinic, it’s very late.”

Such was the case for Linus, a 4-month-old kitten that went into a downward spiral after being declawed. The kitty seemed a little off when he first got home from the clinic, recalls Lynn Crystoff of Worcester, Mass. Within a couple of months, though, Linus was in such agony that he couldn’t walk or use the litter box.

“I felt horrible. It was like I had stolen his kittenhood away,” says Crystoff. “His days consisted of me taking him off the bed, him limping to eat and then me carrying him to the couch, where he spent the day sleeping.”

Crystoff took Linus to three veterinarians, but none could figure out how to help him. Eventually, Linus was referred to Karas, who says she had never seen an animal with such severe nerve damage. That meant that none of the pain relievers commonly used in cats would work, she says. Linus ultimately got relief with a combination of gabapentin, an antiseizure drug also used to treat shingles pain in people; amantadine, a human antiviral medication used to relieve some of the symptoms of Parkinson’s disease; and Prozac, which, like many antidepressants, seems to ease pain by elevating serotonin levels in the brain and spinal cord.

In-home physical therapy also helped the kitten’s recovery. Although the pain relievers allowed Linus to comfortably put weight on his paws again, the cat’s chest muscles had atrophied so much that he had to rebuild his furry pecs before he could walk. With Karas’ help, Crystoff trained Linus to touch her hand with his paw—in a way that strengthened his muscles—to receive a treat.

Linus still takes medications three times a week, but otherwise is a normal cat. The chatty part-Siamese loves to roam the house and jump onto windowsills, from which he carries on “conversations” with the neighbors. “I only hope he’s able to forget everything he went through,” says Crystoff.

He probably has, says Karas, who notes that when it comes to pain, our pets’ cognitive differences from us are a blessing and a curse. People can be reluctant to seek help when they hurt, she says. “One problem with humans is that there’s an idea that suffering brings you closer to God. Or we worry we’ll get hooked” on pain drugs.

“Our pain is also worse in certain circumstances,” adds Karas. “For example, pain from a C-section probably won’t hurt as much as pain from the same incision for cancer surgery to remove your uterus, because it is a happy event to have a baby and a sad one to have cancer.

“Animals don’t know any of that stuff,” says Karas. “Animals just know, ‘I hurt.’ Maybe their pain is worse because they can’t know if they are ever going to feel better.”

This story first appeared in the Winter 2013 Tufts Veterinary Medicine magazine.

Genevieve Rajewski can be reached at genevieve.rajewski@tufts.edu.

Don’t Play Veterinarian

When it comes to easing your pet’s pain, never give any medication without first consulting your veterinarian. Drug dosages and their risks largely depend on an animal’s size and organ function. And if you’re thinking about giving your dog or cat some of your over-the-counter pain medications, close the medicine cabinet door, says Alicia Karas, head of the Cummings School of Veterinary Medicine’s Pain Consultation and Referral Service.

In 2011 alone, the ASPCA Animal Poison Control Center fielded more than 165,000 phone calls about pets exposed to poisonous substances—with over-the-counter human medications being the third most common toxin reported.

Anti-inflammatory drugs such as ibuprofen and naproxen are the most common causes of poisoning in small animals. Even small doses of such pain relievers as Advil, Bayer aspirin and Motrin will cause stomach and intestinal ulcers and kidney damage in cats, Karas says.

And “Tylenol will kill cats,” she warns, because acetaminophen, the active ingredient, damages feline red blood cells and interferes with their ability to transport oxygen.

It’s not just human medications that need to be handled with care. Pets can be poisoned by veterinary medications if they receive more than the prescribed dosage or are given a drug prescribed for another animal.

If your pet ingests a potentially toxic medication, call your veterinarian or the ASPCA Animal Poison Control Center’s 24-hour hotline at 888-426-4435.