5. Management chronic pain Flashcards
What is chronic pain in animal species
Many different definitions…
‘what their behavioural changes, combined with their motivational states, tells us it is’.
Plus
pain that outlasts the original injury and expected healing time or lasts longer than a specified period – usually pain lasting >3 months in humans
chronic pain states there are changes in central pain processing which may result in the development of hyperalgesia (exaggerated response to a noxious stimulus) and allodynia (non noxious stimulus perceived as painful).
Is chronic pain a continuation of acute?
NO!
It is maladaptive i.e. it has no biological use to the patient. It represents a chronic stressor with all the resulting physiological damage that stems from this.
List different types of chronic pain
Nociceptive/inflammatory Neuropathic Neoplastic e.g. osteosarcoma Mixed Referred Myofascial Sympathetically mediated pain? - not sure if animals experience this
What it nociceptive/ inflammatory pain?
When is it commonly experienced?
Nociceptive/ inflam pain = pain caused by damage to body tissue
commonly experienced with chronic inflammatory conditions and tissue damage arising from muscles, joints, viscera and skin such as osteoarthritis
What it Neuropathic pain?
What do we commonly see with this pain?
Caused by damage/ injury to nerves- compression, inflamm
Commonly see jumping/startled behaviour in animals and bizarre behaviours such as suddenly attacking a limb or the tail. Neuropathic pain can also develop as a result of central sensitisation.
Neoplasia pain
often involves different types of pain including a mixture of inflammatory, neuropathic and cancer-specific pain such as ischaemic pain from local tumour compression of blood vessels or thrombus formation and postsurgical pain such as phantom limb pain following limb amputations. A classical example of neoplastic pain is bone pain secondary to osteosarcoma as bone is highly innervated but many tumours can result in the development of chronic pain.
What is referred pain?
pain that is projected from the source to a distant site and can make identification of the underlying cause of pain more difficult.
What is Myofascial pain?
pain affecting skeletal muscles
It is often a significant component of many chronic pain states but underdiagnosed, therefore untreated in veterinary practice
How does myofascial pain arise?
arise due to ‘wear and tear’ of skeletal muscles. The current theory is that this results in damage to motor end plates which become leaky and release enough acetylcholine to cause local sarcomere contraction only which leads to formation of a distinct knot or taut band within the muscle
What muscles are commonly affected by myofascial pain?
Commonly affects postural muscles in the neck, shoulders, lumbar spine and hip girdle.
How do we detect myofascial pain?
What may it be secondary to?
Detection of myofascial pain requires a specific palpation technique (and is therefore often missed during examination). Palpation or twanging of a knot/taut band in muscle often elicits a dramatic response from the patient (even a placid animal may turn around to bite).
May occur secondary to postural strain, blunt trauma, spinal pain (e.g. nerve root impingement, facet joint disease, spondylosis, intervertebral disc disease), osteoarthritis (OA), visceral pain or chronic otitis
List implications of chronic pain
Sensory - NOT emotional Emotional Cognitive Motor Welfare and quality of Life - animal and owner "Suffering"
What is the most significant implication of pain
Suffering
If animal experiencing other implication e.g. sensory (pain when walking upstairs) and emotional (wants to be with owner) Overall SUFFERING msut be treated more urgently as can have negative impact on quality of life
It is important to differentiate between the sensation of pain and the suffering that it causes e.g. an arthritic dog may climb stairs more slowly and carefully than before due to pain associated with the physical movement of climbing but it may do this without hesitation and as frequently as before. Where as if the prospect of climbing the stairs makes the dog hesitate or even refuse or if the dog goes upstairs less frequently than it used to, even if the owner is upstairs or the dog’s facial expression conveys effort or anxiety then this can be regarded as suffering.
how to assess chronic pain including the approach to a chronic pain consultation
Quantitative sensory testing
Force plate analysis/ gait analysis
Validated chronic pain scales:
What is quantitative sensory testing?
Helps us assess chronic pain
use of mechanical and thermal nociceptive threshold testing which may be useful to identify hyperalgesia (extreme response to pain) and/or allodynia (v sensitive to touch)
Mainly research Many owners would likely object to the application of pressure or heat to their animal to stimulate a pain response.
