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What is this thing called pain?

Posted Jun 30 2011 5:04pm

As I’m busy writing up research papers for publications to “count” towards my research productivity, I’m reminded of one reason I keep on blogging – and it’s this: blogs are open to anyone.  People can comment on what I write.  When someone comments, whether they agree, disagree, or simply pose a question, it’s an opportunity for dialogue and reflection. That’s not nearly as easy to do in a peer-reviewed journal!

As a result of comments from my post yesterday, I’m musing on ways to explain the distinction between acute and chronic pain that will make sense to someone who experiences fluctuations in pain intensity. I think I’m clear in my own mind between the two, but perhaps things are not as distinct as I’ve made them – or maybe I haven’t explained things well.

There are several ways that acute pain can be distinguished from chronic pain, none of them particularly satisfactory except, maybe, one.  We can think of the association between pain and tissue damage or threat of tissue damage.  In acute pain, tissue damage or the potential to damage tissue is often present – but not always.  Think of a typical “tension” headache.  It’s usually short term, but not associated with muscle damage.

We can consider duration – how long does this pain persist?  Acute pain is typically short-term, it does end at some point – sometimes well after the need for a “warning” alarm is necessary – but what about chronic hip osteoarthritis?

Some of the other factors I see used to distinguish acute pain from chronic include – quality of the sensation, how quickly the pain comes on, whether psychosocial factors are relevant, whether disability or illness behaviour is present, even the location or specificity of the pain can be used as an identifying factor.

We can also think of usefulness – acute pain is usually useful.  It tells we need to do something, take action to reduce the threat to our body’s integrity.  I think this is probably the most useful definition of the lot, even in the case of a “tension” headache – when it  might simply be an indication we need to have some time out, drink more water or get some new glasses.

Chronic pain has a bad rap.  There are many clinicians who consider that chronic pain is almost entirely influenced by psychosocial factors – therefore the person with pain needs to simply “get over it” and they’ll recover.  Then there are those who think chronic pain is simply pain that hasn’t had the “source” of the pain identified yet – find that source, burn it or cut it or otherwise remove it, and the pain will be gone.  And for some kinds of ongoing pain, like an osteoarthritic hip, that’s the case.

Over the years I’ve worked in chronic pain management, I think I can confidently say that chronic pain can be sharp, stabbing, dull, burning, deep, aching – all the same kinds of sensations that acute pain can be.  Its onset can be pretty rapid, but also insidious or gradualBoth acute and chronic pain are strongly influenced by psychosocial factors – things like attention, general alertness level, “threat value” or beliefs about what the pain means, attention from others, past learning – all of these things influence our experience of both acute and chronic pain, although it’s probably true to say that as pain persists, many of these psychosocial factors play an increasingly important role in the disability associated with pain.

There are other definitions of chronic pain.  One is duration – pain that persists beyond “normal healing time” (whatever this is).  Alternatively, pain that has been present for three to six months.  My problem with this definition is that it’s common for people to have pain around a fracture site for up to 12 months even when bony union is progressing normally.  Is this chronic pain?  What about instances where the pain is intermittent – migraine? Noncardiac chest pain? Abdominal pain?

So, what about chronic pain that fluctuates?  This seems to be the case more often than not.  It’s very very rare for me to hear someone say their chronic pain is at exactly the same intensity day in, day out.  When I do hear it, I like to spend some time exploring this experience in more detail.  Without fail, with gentle enquiry, fluctuations of pain intensity are there but may be subtle.

Why is recognising this so important?  Well, let me first put to bed any idea that I think people with chronic pain are immune to acute pain – that’s so not true.  What is arguable is whether fluctuations in pain, particularly when they’re the “same old, same old” pain, need to be managed using acute pain treatments.

And this is important because

  • so many acute pain treatments are passive,
  • take time away from living,
  • put the person getting the treatment at risk of yet another diagnosis or explanation,
  • reduce the opportunity to gain confidence with using self management strategies,
  • in the case of medication can put the person at risk of addiction or inappropriate use of this,
  • and, often unrecognised, can train the person to begin to fear (& then avoid) experiencing pain – leading to increased distress and continued treatment seeking

Am I advocating never using adjuntive intervention? See yesterday’s post in answer to that! But at the same time, I’d suggest that it’s pretty important to be aware of the risks.

So far, in answer to the question posed in my title, one of the best descriptions of the various types of pain and of the distinction between “normal” pain and “pathological” pain there is, Clifford Woolf’s paper is my choice.  Actually, the whole issue of this journal (which is – fabulously! – completely open access online!) could be required reading for anyone wanting to be informed about advances in our knowledge of pain.  I particularly love the examples he provides for each type of pain problem and how they arise.  That’s great stuff.

But even this set of wonderful papers doesn’t really explore some of the aspects of pain that don’t really get mentioned – disability and the effects of social, family, community attitudes and responses.  Yes, I know they’re messy to research.  They’re complex. They differ across countries, cities, villages and families.  But oh how powerful they are in our experience of pain.

Woolf, C. (2010). What is this thing called pain? Journal of Clinical Investigation, 120 (11), 3742-3744 DOI: 10.1172/JCI45178

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