Written by Dr. Peter H. Eeg, BSc, DVM, CVLF, FASLMS
Poolsville Veterinary Clinic
Safety Consideration for Laser Therapy Devices
Safety is the first and foremost consideration when the use of any laser wavelength(s) as Therapeutic Laser Energy (TLE) are being instituted for patient care. Aside from standard OSHA compliance guidelines for use of Class 3B and Class 4 laser energy use the following guidelines to avoid therapeutic failure or adverse therapeutic events.
- Eye Exposure: all individuals in the TLE theater should be wearing glasses that have the appropriate optical density to reflect diode laser energy. Patients being treated should not have TLE administered directly into or around the eye where the incident angle would produce transmission into the eye proper.
- Neoplasia: In general TLE application over any neoplastic tissue should generally be avoided. If resection of a neoplastic mass has been completed and the margins have been identified as clean by a pathology review, then use of TLE to enhance wound healing and minimize scar formation is appropriate. Use in palliative therapy to reduce cellular edema and minimize necrotizing factors in surrounding tissue may be a consideration.
- Endocrine Glands: It has been historically recognized that direct absorption of TLE by endocrine glandular tissue should be avoided. There is growing evidence that lasers with regenerative potential may be able to re-initialize endocrine cell function and activate production of endocrine molecules in the patient. Due to the vascular enhancing and cellular respiration enhancing properties of TLE endocrine gland production could be altered in a positive manner to achieve these changes. It would be a rational consideration to avoid exposure of normal endocrine tissue to some forms of laser energy for the same reasoning. Treatment to adjacent tissues surrounding the endocrine glands is appropriate provided the device being used has a quantifiable fluency (J/cm2) and focal diameter.
- Gravid Uterus: Fetal tissue has a very high mitotic rate and therefore should not be exposed to TLE.
Long term oral or topical steroid application: High doses of steroid medication used over an extended period (greater than 2 weeks) for Atopic, Immunoresponsive and anti-inflammatory conditions may alter the tissue response to TLE. Steroids alter cell membrane permeability and Na+ ion and K+ ion pumping. These compounds also can alter cell metabolism rates. The true total effect on steroid altered tissues by TLE is not clearly understood. There may be some indications as well as contraindication for its use with steroids in the future.
- NSAID therapy: Here there are conflicting research reports. There does seem to be a generally positive response to reducing inflammation at a faster rate when both NSAID and TLE are utilized in acute (first 24 hours), sub-acute (24-72hours) and chronic (post 72 hours) anti-inflammatory therapy. Special consideration related to the gastrointestinal, renal and hepatic tissues related to potentially ulcerative and toxic cellular effects of these class of drugs should be considered. Since a bi-phasic response curve shift occurs with increasing levels of TLE there is convincing evidence that too high a dose of TLE along with NSAID therapy may delay or damage cellular regeneration and transportation of inflammatory mediators due to an accelerated drug effect. Further research still needs to be done. In my personal experience I routinely utilize TLE and NSAID therapy in tandem when treating sub-acute and chronic inflammatory cases.
- Chronic Renal Failure: It has been commonly understood to avoid direct absorption of TLE into renal tissue if renal damage is present. But more recent applications of Q-switched 1064 nm bio modulatory lasers have returned some cellular function and reversed or at least stabilized organ function. Treatment of very large surface areas may also release cellular by-product components that will require filtering through the kidneys so it is a good consideration to know the renal status and hydration status of the patient when large areas are being considered for treatment.
- Unknown Disease Foci: As always it is important that you have a clinical diagnosis or strong indication of the condition being considered for TLE application. As an example, a swollen stifle and lameness should have radiographs to confirm that bone cancer is not the presiding factor before TLE in instituted.
- Acute Trauma w/Hemorrhage: When there is any evidence during an acute, traumatic injury that vascular flow has been drastically altered (active open bleeding, hemorrhage or petechiation, or cranial trauma), then TLE should not be instituted for at least 12-24 hours after the abnormal vessel or tissue bleeding has been controlled and the patient is not considered in a shock/intensive care state. Avoiding the use of TLE in these cases is associated with the increased vasodilatation and lymphatic peristalsis that is produced by TLE irradiance. While this effect is most beneficial to reduce edema in sub-acute and chronic tissue inflammation and edema cases, in an acute bleed this can be counterproductive or even dangerous to the patient.
- Direct Nerve Root/Ganglion Stimulation: In this situation it is important to know what wavelength of diode energy you are utilizing. Wavelengths such as 800-810nm and 900-920nm produce a photochemical and photomechanical bio modulatory effects only. Within the appropriate bi-phasic curve parameters these wavelengths in Pulsed Wave irradiance enhance nerve function and regeneration. The ultra-short pulsing of 1064 nm diode, Q-switched bio modulation can also benefit Neuronal tissues. 980nm diode energy has a pronounced photo thermal effect. Nerve cells exposed to Continuous Wave exposure of this wavelength at a high enough Fluence may increase intracellular temperatures above 39 degrees C where nerve cells exhibit cellular damage and organelle breakdown. When intra-cellular temperatures exceed 45 degrees C cell disruption, organelle damage and cell death may likely occur.
- Fungal infections: Contrary to earlier beliefs there is good indication that certain wavelengths of TLE can be used to treat certain forms of fugal infections. Reports in human literature, (http://nomirmedical.com/pdf/NCH_Abstract_Presentation_FINAL_08-26-08.pdf), indicate that 870nm and 930nm wavelength near IR laser energies have been successful in 100% eradication of fungal toenail colonies. Further research into eradication of dermal fungal lesions is needed, but indications are that treatment options are possible.
- Photosensitizing compounds and Medications that enhance photosensitivity: Near IR wavelengths 780nm to 1064nm do not pose a great risk to activation of photosensitizing agents. Most of these chromophores are activated by visible light wavelengths of 450nm to 750nm. In the case of guide beams, the 635nm and HeNe beam wavelengths may have some impact. It is important to review all medications that the patient who is potentially undergoing TLE therapy is taking before beginning therapy.
Aural Hematoma: TLE should not be used in an acute or sub-acute aural hematoma as the hemorrhage has not been identified or ligated. TLE is very appropriate once surgical reduction and ligation of the bleeding vessel(s) has been accomplished. Then the TLE will provide reduction in edema and improve and maintain normal vascular flow. The enhancement of fibroblast migration will speed repair of the damaged cartilage portion of the pinna. Incision scar formation well also be reduced and the final appearance of the pinna will appear anatomically correct.
- Active Growth Plates: Since the mitotic rate in epiphyseal plates is high, the use of TLE is contraindicated directly along the plates. TLE can be used adjacent to the areas without complication. If there is any question as to the disposition of the epiphyseal plates radiographs should be taken before TLE is initiated.
- Epilepsy: There is now compelling evidence that high energy magnetic orientation of brain cells can actually change neuronal function and response. Since TLE can modulate the magnetic orientation of cells, the actual energy released during TLE treatment can reduce the seizure threshold in seizure susceptible patients. There is evidence that pulsating lights of differing Hz may optically stimulate seizure activity in susceptible patients. For this reason, consideration of all factors in seizure genic patients and their owners with history of seizure should avoid visual exposure to any aiming beam from TLE application.
- Anticoagulant Therapy/Anemia: Since TLE can enhance vascular flow rates and increase fluid volume in vessels, there is a consideration that TLE may cause a predisposition of vessels to rupture in susceptible patients. Once again it is the 980nm diode wavelength that would have the greatest potential for damage due to its more superficial penetration and photo-thermal effect. Weakening of the vascular walls and cellular degradation can be a factor.
- Implanted monitoring or regulating devices: There is no direct evidence that photochemical or photomechanical effects of TLE would produce damage to circuitry. There may be a potential for photo thermal damage if the circuits get to hot. It is important that any direct TLE application directly over an implanted device that has an MSDS indication for sensitivity to RF discharge be avoided. Treatment to adjacent areas should not impact the devices.
Recognition of the three dimensional physical nature of TLE and the multiple physics effects that occur in tissues treated with TLE is critical to appropriate therapeutic lasing. I would encourage all clinicians to closely review laser physics and review articles pertaining to TLE. The positive treatment potential of this therapeutic modality is significant. Avoiding complications and contraindications is both a matter of education and common sense.