Page 72 - Veterinary Laser Therapy in Small Animal Practice

58 Veterinary Laser Therapy in Small Animal Practice

can often be noted within minutes; if you don’t believe experimental groups differed both in the dose and the
it, just try it on yourself next time you get bitten or power density. In another in vitro study, fibroblasts pro-
scratched. Wounds are a great way to start in the LT liferated more under 3 J/cm but not under 5 J/cm .
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world, since more than 90% of them will show a posi- In her experiment with wounded fibroblasts, Houreld
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tive change with just 1–2 sessions. This does not mean found that 5 J/cm stimulated proliferation while 16 J/
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they will be closed with one treatment, of course, but cm was damaging. [115, 202] A similar result was described
the following effects are generally seen. by Hawkins and Abrahamse, [117] who found 0.5 to 5 J/
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cm to be stimulating for the in vitro growth of fibro-
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• Acute wounds that are becoming more instead of blasts, while 10 and 15 J/cm were inhibitory.
less inflamed after the first 48 h, which would be the But the same doses (10–30 J/cm ) that seem to be too
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physiological process, will evolve from this inflam- much for in vitro cultures have been found to be stim-
matory/catabolic state to an anabolic/proliferative ulating in vivo, [106, 123] and in fact, several peaks of stim-
one, and produce new tissue and less inflammation ulation have been obtained in vitro with both low and
(Fig. 7.1). higher doses [203] ; dose may not necessarily be propor-
• Chronic wounds that are stuck in an underactive tional to effect. Even higher doses may be beneficial: a
metabolic state will change to a more reactive phase, murine model of healing by secondary intention found
where new tissue can be created. even more collagen and glycosaminoglycan synthesis,
cellularity, vascular density, and faster wound closure
Since the required penetration is less than for mus- with 30 J/cm than with 3 J/cm doses [121] and 36 J/cm
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culoskeletal tissue, for example, and there are hygiene improved random skin flap survival in a rat model. [204]
and patient comfort considerations, treatment is Again, the different parameters used in each study
usually performed in non-contact mode. The exception make it difficult to compare results. Most in vitro
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could be when we treat the periphery of the wound studies use a dose of 0.5 to 4.0 J/cm , but of course in
and the patient is comfortable enough; in this case, we vivo treatments may require and tolerate higher doses.
could also combine a non-contact treatment directly A review including 47 studies with mice and rats con-
over the wound with a soft contact treatment over the cluded that there was a consistent benefit for wound
periphery. healing. [128] The average dose in those studies was 4.2
It is highly recommended to take pictures of the J/cm .
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wounds and measure them at different stages (or at To summarize, the usual starting dose for wounds
every visit) to help evaluate progression objectively. is 1–4 J/cm . But we have also learned from clinical
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Always include a distance reference (ruler or index experience that high doses (10–30 J/cm ) may be ben-
card) when taking pictures of wounds, and whenever eficial to treat some chronic wounds, and remember
possible, take the picture from the same angle in similar dose is just a part of a bigger picture that includes other
lighting conditions. Pain assessment should also be important factors, such as power density and time:
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performed. taking 1 hour to deliver 4 J/cm may not be as efficient
Dose (J/cm ): the range of appropriate doses or (or practical) as doing it in 3 minutes.
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energy densities can range from 1 to 30 J/cm , and Table 7.1 has suggestions about dose, power, and
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if you try to find literature to support the choice of a power density when treating soft tissue. Rather than
lower or higher value, please note factors such as how considering these figures as something rigid you have
a monolayer of in vitro cells behaves differently from a to abide by, take them as a general framework, but
real, full thickness wound, or how an acute experimen- always be aware of the values you are using.
tal wound over the back of a mouse can be different When treating wounds, you need to include not just
from a chronic ulcer on a dog’s footpad. the wound bed, but a margin of healthy tissue. And of
Some in vitro studies have suggested that high doses course, that area needs to be included in your calcu-
can be damaging, but where is the point where energy lations. Let’s imagine an example: if you had a wound
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density becomes “high” or “too much”? An in vitro with an area of 150 cm , and you wanted to use 4 J/cm ,
model with a keratinocyte culture found that doses of applying 600 J is NOT what you need. If you were to
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0.1–1.2 J/cm increased cell proliferation and migra- include a 2 cm margin, your area of treatment would
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tion, while 10 J/cm was inhibitory [125] ; however, the be 266 cm , and if you wanted a margin of 5 cm around

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