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24 Veterinary Laser Therapy in Small Animal Practice

pressure threshold of treated animals, but had no if doses are too high for an acute case, this could cause
effect in paw thermal threshold responses. [88] On discomfort, despite the anti-inflammatory or tissue
the other hand, reduction of cold hyperalgesia after healing effect. The potential scenarios are very varied,
LT has also been described. [87] LT also improves and so are your patients and their level of tolerance for
nerve functionality and recovery in nerve entrap- discomfort and manipulation, so you will have to make
ment neuropathy. [89] adjustments within this framework.
• Promoting inhibitory mechanisms, such as sero-
tonin [28, 29] and endogenous opioid production. LT I’ll refer you back to the example in Chapter 2,
increases beta-endorphin production in periph- section 2.2, of treating gout in humans, again to
eral inflammatory models, and this mechanism is remind you of the importance of not just bringing
blocked by naloxone, an opioid antagonist. [86, 90, 91] fresh blood to an area, but also creating a drainage
path for the toxin-filled fluid. Now, don’t be silly and
The scientific community does not have the same start treating the inguinal lymph node
degree of agreement about all these mechanisms; for before treating an abdominal wound.
instance, there is a wide consensus on analgesia through These are very localized effects. But
anti-inflammatory mechanisms, but some studies don’t still, the point is that laser therapy is not
agree on the modification of nerve conduction velocity a plug-and-chug modality where you have some
or opioid release, or they find these effects in a narrow “right” parameter-set preprogrammed into the
therapeutic window. [35] An increase in skin substance P machine. Clinical improvement is also dependent on
after LT has also been described. [92] the skill of the therapist (which you will have
Treatment of acute pain can even start before it nurtured by reading this book).
happens, as in premedication for a surgical procedure.
In chronic pain, treatment should start as soon as pos-
sible, both for ethical reasons and because this will
decrease the likelihood of developing neuropathic pain. 4.2 Don’t forget pain assessment
Treatment should be multimodal and LT can poten-
tially help, in both acute and chronic pain manage- If we are going to treat patients in pain with LT and
ment – it was already included in the WSAVA’s 2014 want to find out how effective our treatment is, we’d
Guidelines for recognition, assessment and treatment better assess it. To treat pain, we must first diagnose it
of pain, [93] both as one of the physical modalities used and evaluate its intensity and progression. This evalu-
in rehabilitation and as a supplemental technique after ation can be based on certain physiological param-
ovariohysterectomy/ovariectomy for both dogs and eters (such as heart rate or blood pressure), changes in
cats. Nevertheless, these recommendations are made
in the most part by transposing experimental results,
clinical experience, and human studies, and more clini-
cal studies should be carried out in small animals.
As a general rule, acute pain is treated with lower
doses and power densities than chronic pain (Table
4.1). Pain related to superficial tissues is also treated
with lower doses than conditions affecting deeper
structures. For instance, an acute wound affecting skin
and subcutaneous tissue would need 2–5 J/cm , while
2
pain related to spondylosis may need 8–15 J/cm . In
2
the first case, power density would be around 0.1–1
W/cm , with lower values if the subcutaneous tissue or
2
muscle are exposed (Fig. 4.2). In the second case, we
2
could go up to 2–3 W/cm (Fig. 4.3). Remember LT can
cause vasodilation, and higher parameters are similar Figure 4.2 A laparotomy incision being treated with LT,
to a stronger manual manipulation to some extent; so using 2 J/cm .
2

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