Surgery and PBM are the two biggest areas of laser use by veterinarians. However, there are other areas where lasers have become an integral part of the veterinary armamentarium.
Veterinarians, as a rule, tend to be resourceful practitioners. They readily adapt and are willing (and sometimes compelled!) to explore alternative methods to improve the health of their patients. In addition, with many owners considering their pets more and more a part of the family, the level of care demanded has driven the incorporation of many technologically advanced modalities for routine diagnostic and therapeutic procedures. These include ultrasound, endoscopy, MRI, CT, chemotherapy, radiation therapy, orthotics, organ transplants, open heart surgery and, of course, lasers.
The most wide spread use of lasers in the veterinary field is for laser therapy; to reduce pain and inflammation and to enhance tissue healing. And it is the healing effect that is most beneficial. Laser therapy directly stimulates tissue repair, regeneration, and remodeling. It allows practitioners to resolve conditions that were traditionally less responsive. In addition, it helps many common conditions heal much faster and much better.
Laser light in the red and near-infrared range is absorbed by specific chromophores in the body (cytochrome C oxidase/hemoglobin/water) and this has a positive effect on specific biological reactions. This photochemical reaction increases blood flow to tissue, stimulates the release of O2 from the hemoglobin delivered, and enhances the conversion of O2 to useful energy by cytochrome C oxidase in the production of ATP. This leads to improved cellular function and/or an increase in cell growth, replication, repair, or production of beneficial biochemical compounds – enzymes, proteins, cytokines, immunoglobulins, DNA/RNA. There is a cascade of secondary and tertiary affects which enhance/accelerate/improve the following physiologic reactions.
Therefore, laser therapy has been advocated for a broad range of clinical applications for pain management, wound healing, reducing inflammation/swelling/edema, and rehab in both large and small animals. Measurable positive results can be seen consistently in the following conditions:
The two most important features that determine the optimum response of a laser are wavelength and power. Laser light in the red and near-infrared range has biostimulatory properties. Roughly, this corresponds to wavelengths between 600nm and 1100nm. The shorter wavelengths are absorbed more superficially and therefore do not have the ability to penetrate as readily as the longer wavelengths. Wavelengths in the visible red range (650nm-660 nm) are highly absorbed by melanin and other superficial receptors. These can enhance wound healing. They may also stimulate trigger points, acupuncture points, and/or cause release of secondary messengers that may improve other deep-seated conditions. From absorption spectra data we know that the wavelengths near the 970nm range have moderate increased absorption by water. With the higher-powered lasers, this can create some thermal gradients and increase circulation in these areas. It is also near the peak of the Hb absorption curve. However, the 905 nm wavelength is even closer to the peak of the hemoglobin absorption curve. Recent studies have indicated that this wavelength creates as much as a 30-50% increase in O2 release to the tissue over the 970-980 nm wavelengths. The most important discovery was related to wavelengths nearer the 800nm range (750-830). These are at the peak of absorption for the cytochrome-C oxidase enzyme. This is the rate-limiting step in the conversion of O2 to ATP within the electron transport cycle. These wavelengths will accelerate the production of ATP within the mitochondria. Utilizing all 4 wavelengths can give you a synergistic effect and/or a wider range of treatment options across a broader spectrum of clinical conditions and patients which will result in better clinical outcomes.
Laser power is the rate at which the Laser energy is delivered. Although seemingly straightforward, the power question seems to raise the most discussion regarding appropriate parameters. The physics associated with laser penetration within non-pigmented tissue is well established and quantified by the rate of decay of an incident beam as it moves through tissue.
Classification of all lasers is dictated by the FDA, based on the maximum power the laser can deliver. It is used for guidance when discussing safety and the potential to cause harm/damage, especially to the eye. Most therapeutic lasers are class IIIa, IIIb, or IV. Class IIIb lasers produce < 500 mW of power (1/2 watt). Class IV Lasers are anything over 500mW of power. Class IV therapy lasers are extremely safe. The main benefit of higher power is the ability to deliver enough photons at the surface (a larger total dose) to compensate for the power loss (decreased number of photons) reaching deeper tissues. This allows for a more direct photochemical response on these tissues. Lower dosages are used when treating superficial wounds/lesions and for acupuncture point or trigger point stimulation. Adjustable power output can make a Class IV laser effective for superficial dermatologic lesions, deep musculoskeletal conditions, and anywhere in between!
Notwithstanding years of research on the bio-stimulatory effects of laser light, we are just starting to realize all the clinical applications for veterinary patients (and humans!). Exciting new possibilities include help with OCD (osteochondritis dessicans), chronic rhinitis/bronchitis, insect/ snake bites, allergic reactions, chronic intestinal or urinary tract inflammation, bacterial/viral infections, and adjunct therapy to improve stem cell results. Laser therapy is becoming standard of care for the control/palliation of many secondary effects related to chemo and radiation therapy in cancer patients. There is optimism for neurologic trauma including concussions, brain ischemia and stroke, peripheral nerve damage, IVDD, and stenosis. It’s worth emphasizing again that laser therapy does not just accelerate healing; it actually improves repair, regeneration, and remodeling of tissue. Post-op complications are reduced. Muscle atrophy can be reversed. Type 1 collagen production yields better tendon and ligament strength and elasticity. There is a positive effect on neurologic function and axonal sprouting. The joint capsule, synovial lining/fluid, and cartilage all benefit. Therefore ROM, function, flexibility and mobility are all enhanced. The potential for re-injury is greatly reduced. Performance animals not only recover quicker but they can regain their competitive edge. Pets can get back to their daily routines and become an active member of the family again.
These are exciting times. Like all technology, lasers have become smaller, safer, more efficient and easier to use. Their broad range of applications makes them not just affordable but profitable. It’s no wonder that lasers are rapidly becoming an indispensable tool in thousands of veterinary hospitals.
