Page 14 - BSAVA Guide to Pain Management in Small Animal Practice

2 | Physiology of pain

VetBooks.ir ndings led to the development of scales such other medical concerns. entle, respectful
palpation of or around presumed painful
as numerical rating scales, simple word
descriptive scales and visual analogue scales.
presence of pain, and validated pain scales
hese scales were adapted for the veterinary areas is also very useful in detecting the
setting from human pain scales such as the such as the lasgow Composite easure Pain
c ill pain uestionnaire el ack, 197 . Scale see below specify palpation cm away
Unfortunately, these scales tend to be from the wound as direct wound manipulation
unreliable in the treatment of acute pain in a is undesirable. ther potential signs of pain,
hospital setting, mainly due to wide operator such as vocali ation and changes in
variability, the sub ective nature of the scales physiological parameters, may contribute to
and the inherent need for, and capacity of, the prediction of pain but cannot be used in
animal patients to hide pain. his is evidenced in isolation. In fact, in a study in cats undergoing
a study in which behavioural assessments, but onychectomy, physiological parameters did
not a numerical scoring system, identi ed dogs not di erentiate between cats that had surgery
given analgesics versus those given placebo and those that were simply anaestheti ed and
drugs ardie et al., 1997 . In addition, these bandaged without any painful procedure
scales are simple one dimensional Cambridge et al., . urthermore, stress
measurement tools that may indicate the to collect physiological data may cause
presence, and perhaps even intensity, of pain changes in these parameters, confounding
but do not include a ective and behavioural results. hus, many of the most useful pain
components that describe the impact of that scoring systems used to assess acute pain in
pain on the patient. Since pain is a complex conscious patients do not include
multidimensional stimulus, assessment of pain physiological parameter changes as a
should be done with multidimensional tools. component of the score. Physiological
his reali ation led to more advanced changes are more useful in anaestheti ed
scales being developed that encompass patients where unconsciousness alleviates the
physiological data such as heart rate, respiratory impact of stress on the parameters.
rate and cortisol levels, as well as behavioural Change in behaviour from before the painful
scales which focused on the ethnology of incident i.e. pre surgery or pre trauma to after it
animals experiencing pain e.g. urrell and is ideal for identifying pain but the patient s
ohnson, 6 . Currently, the most advanced behaviour pre pain may be unknown to the
veterinary pain scales available are composite veterinary sta . he owner may be able to
based scales such as those produced by provide insight on normal behaviour for their pet
orton and ri ths 198 , ellyer and aynor but this is often more useful for chronic pain
1998 , irth and aldane 1999 , Reid et al. where the pet is at home and the behaviour has
7 , and Brondani et al. 1 . he important changed. ospitali ation itself can change
feature of the multidimensional scales is that behaviour, which confounds the identi cation of
they take into account not only the pain pain versus stress. he presence or absence of
intensity, but also the sensory and a ective behaviours associated with pain can also be
components of pain i.e. not ust how bad the useful and are the premise for most of the
pain is, but how it a ects the patient. multidimensional composite pain scales
Since sensory and a ective components of described in this chapter. he observer is not
pain impact patient behaviour, it is recogni ed asked to decide whether the behaviour is
that change in behaviour is the most normal abnormal for the pet, but to state
predictive indicator that the patient may be in whether it exists or not. his simpli es the pain
pain athews et al., 14 . f course, change evaluation and makes it more robust, at least for
in behaviour is predictive for many maladies so the general population. As stated, however,
the change must be e uated to a painful individual patients should still be treated if they
incident and the patient must be examined for exhibit what the clinician presumes to be pain,

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