We’ve all experienced pain. We generally do what we can to avoid it. And when it comes to our loved ones, the thought of them being pain is often unbearable.

Most of our loved ones can tell us when they’re in pain and then we have the opportunity to do something to alleviate it. But that’s not always the case when it comes to our pets. Yes, they can yelp or cry out, but this is actually not a common way for them to express pain, especially chronic pain. We need to look at what they do, not so much what they say.

Here we’re going to look at the behaviours that indicate a pet is in pain. But we’re going to do more than that. We’re going to put aside the overly simplistic explanations of pain and get to grips with some of the complexities of pain in a little more sophisticated way. Because those overly simplistic views lead to inadequate pain management. And no one wants that.

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What is pain?

Much of our understanding of pain comes from its study in people. And the more we come to understand pain in people, the more complex the picture becomes. Here’s the definition of pain from the International Association for the Study of Pain (IASP):

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

A sensory and emotional experience – not a disease, not a condition – an experience. And it’s well recognised in human medicine that people have difficulty communicating their pain experience. They’re often frustrated and distressed by not having the words to express what they’re going through. What does that mean for our pets when they can only communicate pain through behaviour?


the pain experience

When I went to uni, we learned about pain in terms of basic stimulus and response. That is: something (heat, pressure, pinprick etc) stimulates a pain receptor, which sends signals along pain (sensory) nerves up to the spinal cord and then the brain, which drives an appropriate response – pulling away, yelping… that sort of thing. There was no recognition that pain is also an emotional experience (because if you can’t express emotions, you mustn’t have them, right?!)

Pain management was all about finding the right drugs to block the pain receptors and nerves. Simple! Yeah, not so much.

Although much of veterinary medicine still thinks about pain using this stimulus–response (biomedical) model, we now know from human studies that each individual’s pain experience is affected by a complex combination of biomedical, psychological and social factors.

This means that the degree of pain, disability and distress experienced in relation to similar physical injury varies (a lot). Things like personality type, genetics, diet, having supportive family and friends, sleep, other illnesses and previous experiences (even in utero!) can affect how much pain is felt and how it affects you.


types of pain

We often classify pain in terms of time: acute versus chronic. This classification is important but it tends to give the false impression that chronic pain is just acute pain that doesn’t get better. Acute pain and chronic pain are quite different beasts.

Pain management network (a resource for people with chronic pain) has a great introductory video on pain.

As well as knowing the difference between acute and chronic pain, it’s also important to classify pain in terms of pathophysiology (or what’s happening in the body). Currently, pain classifications include:

  • nociceptive pain – this is where the stimulus–response pain model comes from. Throughout the body, there are pain receptors called nociceptors, which when stimulated, send pain signals via the nerves up to the spinal cord and brain, which in turn, drive an appropriate response. Nociceptive pain guards against tissue injury (eg warns of potentially damaging stimuli such as heat) and supports healing and repair (eg increases pain to normally innocuous stimuli to aid protection/immobilisation of injured tissue). Typically, nociceptive pain only lasts as long as the tissue is injured and goes away when things have healed

  • neuropathic pain – this sort of pain occurs when there is something wrong with the nerves that sense pain. The nerves might have been injured or be affected by disease (eg diabetes, infection). It can occur at the same time as nociceptive pain but it tends to last longer and be harder to control with medications

  • nociplastic pain – this one is a bit harder to explain (although that introduction to pain video with the concept of ‘gates’ helps). Basically, think of this one as an adaptation of how nociceptive pain is processed – the pain experience can get ramped up, dialled down or extended depending on what else is going on (or has gone on in the past). Examples of this type of pain in people include fibromyalgia, irritable bowel syndrome, chronic pelvic pain and bladder pain syndrome (see the cat version of this – FIC). Osteoarthritis is probably a good example of this in dogs

While I’m not going to do this to you, I could write pages and pages on this. Actually, I’ve already done it and if you are interested (or you’re looking for a sleep aid) you can read more about (human) pain and pain management here. Although it’s written for GPs, anyone can read it.

 
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How can you tell if a dog is in pain?

acute pain

When we have a dog in hospital, one of the parameters we measure and monitor (just like heart rate, respiration rate and temperature) is pain. We do this using something called the Colorado State Pain Scale, which is a way we can read various behaviours and translate them into a measurement of pain.

Here is what the scale looks like:

chronic pain

This scale is very useful for measuring acute pain (ie post injury, post surgery, during painful metabolic conditions such as pancreatitis). But it’s not so good for chronic pain. Chronic pain signs are often quite subtle and tend to be put down to other things like getting old or becoming cranky or just being a ‘sook’. They can also vary day to day and week to week.

Here are some signs of chronic pain:

  • not doing usual activities – look for things like not wanting to jump up into the car or onto the couch (he may refuse or hesitate or climb up rather than jump)

  • not keeping up on a walk – he may be slow or refuse to walk or not bring back the ball, or he seem to prefer to pottering around rather that striding out

  • limping – unless there is a physical explanation (ie one leg shorter than the other or a joint being surgically fused), limping means he is feeling pain when he puts weight on the leg

  • changes to routine – he may stay in bed downstairs rather than follow you upstairs at night, or he may not get excited around usual walk times (although he might still seem keen to go)

  • changes to sleep – he may seem to sleep more or he may be unsettled and get up frequently

  • change to personality – he may become snappy or grumpy with other pets or family members or seem to have become anxious or antisocial

  • going off food – pain can reduce appetite or change appetite so only some foods will be eaten (eg human foods or wet foods will be eaten by dry kibble is left)

  • excessive licking – lots of dogs lick at the paws due to allergies, but we can also see licking over sore joints

  • increased vocalisation – while chronic pain doesn’t cause as much yelping, crying out or growling as acute pain, you still might notice more groaning or perhaps yelping with certain activities

These signs can be due to things other than pain too. If you see any of these, it’s important to get a veterinary assessment.

 
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Assessing pain

If you bring your dog in with possible signs of pain, we need to do a pain assessment. This starts with taking a history that includes the different aspects of the pain experience. Depending on how well we know your dog, we might ask questions like:

  • When did the signs start and was there anything that might have triggered them (eg a fall, a car accident, a dog fight)?

  • Have there been any previous accidents or injuries?

  • How does your dog generally respond to pain?

  • How does your dog generally respond to stress?

  • Does your dog have any other illnesses or conditions (eg separation anxiety)?

  • Is your dog on any medication? Has he had pain medication before and did it work?

  • Does the pain seem better or worse at certain times?

  • What are his activity levels and have these changed?



During a physical examination, we’ll look for:

  • the primary location of the pain (plus any radiation)

  • the pain response during movement (eg worse when limb straightened or flexed)

  • effect of pain on movement (eg reluctance to sit down or jump up)

  • associated symptoms (eg nausea with abdominal pain)


Depending on what we find, we then need to create a pain management plan.

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How do we manage pain?

Along the same lines of how we understand individuality of the pain experience, we now know that there is individual variation in response to pain management. Studies now tell us that most analgesics work well only in a small proportion of human patients. And, no analgesic drug works well in all human patients with chronic pain.

There are some differences in pain receptors in dogs and people, but there’s no reason to assume that all dogs respond the same to all analgesics. Nor is there a reason to think that pain drugs are the answer to everything. But let’s look at the drugs first, because that’s what most people expect.

pain drugs (analgesics)

The most commonly used pain drugs for dogs are non-steroidal anti-inflammatories (NSAIDs). These modify the body’s production of inflammatory prostaglandins, thereby reducing inflammation (ie swelling, redness, warmth and pain) in affected tissues. They are generally safe and work well… but only for inflammatory pain, which is generally nociceptive pain and maybe some neuropathic pain (eg if due to injury-based tissue damage).

The most common NSAIDs are:

  • meloxicam (Loxicom®, Metacam®)

  • carprofen (Rimadyl@)

  • firocoxib (Previcox®)

  • robenacoxib (Onsior®)

The possible side effects of NSAIDs are due to them acting on ‘good’ protective prostaglandins found in the stomach and kidneys. Hence, the main side effects are gastrointestinal (eg going off food, vomiting, dark diarrhoea) and renal (eg vomiting, changing to drinking and urinating). Liver effects are also possible,

The next most common drug type we use are opioids. Unlike with people, opioids are mostly only used in hospital or for very short periods at home (such a fentanyl patch applied post surgery). We don’t usually prescribe opioids for chronic pain in pets unless it’s for palliative care. The majority of oral opioids taken by people are ineffective in dogs.

Other pain medications used include:

  • gabapentin (Neurontin®) – which is an anticonvulsant drug that has been shown to be one of the few things that works for neuropathic pain

  • tramadol – this is considered a type of opioid inasmuch as it acts as on opioid receptors (at least in people) but it’s weak in its opioid effect. It also acts on serotonin and noradrenaline and due to its combined effects, it’s described as an ‘atypical centrally acting analgesic’

  • amantadine – was developed as an antiviral medication but was also found to partially block a receptor in the central nervous system that is associated with pain pathways

These pain medications tend to be used in conjunction with each other and/or with NSAIDs and help modify the pain experience (more than stopping the thing causing the pain). We may find that antidepressant and anti-anxiety medications will play a role in dog pain management as they do in some human pain plans.

non drug things that can help pain

Along with physical comforts like a warm bed, there are things that can dampen down the pain experience. These are often quite simple:

  • social interaction – not every dog wants to be cuddled, but most find comfort in company even if that just means being near you or another companion. Being isolated can increase anxiety and heighten the pain experience

  • exercise – this is good for the circulation and muscles as well as for the mind. Specific physiotherapy may be good for some pets but just getting out in some fresh air is therapeutic

  • diet – a balanced diet with a good amount of health fats (eg omega 3 fatty acids) can help reduce inflammation and maintain healthy muscles, bones and joints

  • stress reduction – this one tends to go hand in hand with social interaction but can also mean avoiding known stressors like car trips or noisy places

  • acupuncture – this can make a huge difference for some pets and is extremely well tolerated (despite what you might think!)

More and more alternate therapies are becoming available. I suggest you keep an open mind about these but don’t let go of all skepticism – some are completely bogus!