Page 177 - Veterinary Laser Therapy in Small Animal Practice

Considering laser therapy for your practice 163

to wait the biological half-life of the drug (usually about The take-home message is: try not to aim at the
7–10 days) after the injection to treat over the site. thyroid area or focus a high dose specifically over the
Treating before an injection has no contraindication gland, and don’t treat the neck of hyperthyroid patients,
since the light is absorbed within nanoseconds of treat- but otherwise treat cervical conditions whenever laser
ment, so if you want to inject, do the laser treatment is indicated.
first.
10.2.6 Other extra precautions
10.2.5 Thyroid
• As obvious as it may seem, do not laser over active
It has been advised to avoid laser over the thyroid gland. bleeding: laser will stimulate blood flow into the
This organ is delicate, already very metabolically active, area, which will increase the bleeding. If the bleed-
and the number of people being diagnosed with thyroid ing is minimal, this may not have consequences, for
nodules is growing, so there are some concerns about example right after closing a spay incision, but to
potential uncontrolled stimulation of thyroid function improve the situation you should apply some cold
both in medical and veterinary practice. and light pressure to the wound first, then consider
Could you send a patient into a thyroid storm? We LT after bleeding has completely stopped.
are not aware of any single such report. There are a few • Be extra cautious in epileptic patients: it is known
animal studies on the effect of LT on thyroid activity, that pulsing visible red light as an aiming beam can
though. A dose of 4 J/cm over the thyroid of mice trigger epileptic seizures in humans (make sure the
2
increased their thyroid hormone production, without pet owner and other people in the room are not epi-
morphological changes, [415] but higher doses had pre- leptic themselves), and although most of the energy
viously been reported to potentially increase vessel will be delivered using invisible light (infrared), LT
diameter and numerical density of pinocytotic vesicles. devices generally use a visible pulsing red light.
[416] On the other hand, a study in 6-month-old rabbits Laser can be considered in some epileptic patients
found after repeated treatments that the effect was a provided the patient does not see the flashing red
decrease in total T3 and T4 serum concentrations, and light at all, we are not working around the head, and
an increase in serum TSH. [417] Another study showed the matter has been discussed with the owner. Why
a variable effect of infrared laser irradiation depending the head? When treating over the temporal, frontal,
on age: laser increased the size of the thyroid capillaries parietal, and occipital areas (brain projection areas),
in very young Wistar rats and had the opposite effect in be aware of the fact that the skull is relatively trans-
older ones. [418] parent to the laser. It has been proposed that a
One of the most interesting reports in this field was power density of 1.6 W/cm applied transcranially
2
2
a study in people with chronic autoimmune thyroiditis. is equivalent to 1.1 W/cm applied directly to an
In a randomized, placebo-controlled clinical study, LT exposed cortex. [172] I had two personal communica-
was able to dramatically decrease the need for thyroid tions from colleagues describing epileptic episodes
replacement therapy and decreased some of the auto- after laser treatments for two wounds over the skull,
immunity markers. [419] The potential for this use had in patients who had not previously been diagnosed
been previously pointed out in the chronic autoim- as epileptics. So it is possible that the changes in
mune thyroiditis pilot study. [420] The same authors also cerebral blood flow unmask a cryptogenic/second-
found LT increased the levels of transforming growth ary epilepsy. I would also be especially cautious if
factor (TGF) [421] and improved thyroid parenchyma I had to treat the neck of an epileptic patient with
vascularization. [422] high power, since it can also affect cerebral blood
LT may have an impact on thyroid function even flow.
if laser is not directly applied over the thyroid area. • Refer to section 9.2.1, “Laser therapy in growing
Researchers have found some protocols applied to the animals”; again, it is not an absolute contraindica-
mandible have no effect on thyroid activity, [423] while tion, just a particular type of patient that can benefit
others demonstrated an effect on serum levels of T3 a great deal from LT but already has a higher meta-
and calcium – which nevertheless remained within the bolic rate, so dosing and frequency of treatment
normal range. [424] should be adjusted.

REDONDO PRINT (4-COL BLEED).indd 163 08/08/2019 09:48