By Kenneth E. Bartels
With the increased use of lasers in veterinary medicine during the past 20 years, the perception that the medical laser is a “tool in search of an application” is out of date. Initially, the cost of laser technology for veterinary medicine was a limitation, but this impediment did not prevent wide spread use in general veterinary practice, especially when the advantages overshadowed the disadvantages. Even considering the required learning curve for efficacious use of a new technology, as well as the attendant safety concerns, the use of surgical lasers in both large and small animal veterinary practice increased based, for the most part, on practitioner implementation rather than from objective peer-reviewed research studies originating at academic institutions. That does not mean results of objective controlled and retrospective studies did not appear in veterinary journals, but much of the enthusiasm was promoted through veterinary magazine-type articles often written by veterinarians supported by specific laser companies marketing to the veterinary profession. In addition, many of the laser medicine continuing education venues at international, national, regional and local professional meetings were, and still are, sponsored by respective laser manufacturers. Without that positive commercial impact, albeit somewhat subjective at times, use of lasers in veterinary medicine would have most likely been limited to veterinary schools and larger general practices. High power (Class 4) lasers have been the devices that opened the door to more extensive use of the technology in veterinary medicine.
Laser use in veterinary medicine has revolved primarily around the use of the high power carbon dioxide laser and often initially promoted/marketed for specific procedures including the feline onychectomy and precisely controlled tissue excision of pathologic soft tissue. Use of the articulated arm versus the semi-flexible hollow waveguide for directing the far infrared wavelength (10,600 nm) to the target tissues still creates a great deal of discussion regarding which type of delivery system is superior for veterinary use. Even so, development of smaller, robust CO2 lasers at prices compatible with veterinary economics, as well as successful and knowledgeable marketing, have all played important roles in the growth of CO2 laser use. Advantages that have included excellent hemostasis of smaller blood and lymphatic vessels, as well as a decrease in postoperative pain, presumably due to photothermal sealing of nerves, have contributed to the technology’s popularity in general veterinary practice.
Fiber delivered wavelengths that include Nd:YAG (1064 nm), diode (805 / 980 nm) and Ho:YAG (2100 nm) lasers have been used for both non-contact and contact fiber-directed surgery. A tremendous advantage included the ability to perform minimally invasive surgery through both rigid and flexible endoscopes. Endoscopic approaches have been extremely useful for upper respiratory and urogenital procedures in the horse (Nd:YAG and diode) and lithotripsy (Ho:YAG), as well as thoracolumbar intervertebral laser disc ablation (Ho:YAG), as a prophylactic procedure in the dog. With advances in diode laser technology, use and availability of the Nd:YAG laser in veterinary medicine have been minimized in most practice situations. Limitations of fiber delivered lasers in the near infrared wavelengths for both contact and non-contact procedures have included a potential for increased collateral photothermal effects due to the wavelength absorption characteristics and the increased tissue scatter of laser energy. Using the diode laser as a light scalpel in contact mode probably does require a higher level of practice in most practitioners’ hands to minimize collateral photothermal effects.
Photodynamic Therapy (PDT)
Photodynamic therapy (PDT) has been used in veterinary medicine for certain types of tumors, although the availability and cost of appropriate photosensitizers up to this point has limited its practical application in veterinary oncology. The use of both monochromatic laser and broader band LED or filtered light sources is still being actively investigated.
Low level laser therapy (LLLT) or laser biostimulation has recently exploded in its application for certain conditions in veterinary medicine. Class 2, 3R, 3B and 4 lasers are all now being used as LLLT devices. As was initially observed with high power lasers in surgery, veterinary practitioners first adopted the technology for treatment of various conditions including pain management and enhanced healing of wounds (chronic and acute). LLLT has been used for many years outside the U.S. with many scientific articles published regarding beneficial effects at the cellular level, as well as positive effects related to treatment of clinical conditions related to pain management and wound healing. There is still much to learn about this technology, but it is now accepted as a beneficial treatment modality by more and more practicing veterinarians. Still, more controlled clinical trials must be performed to augment the numerous anecdotal reports often published in the trade magazines.
Considering the history for the use of lasers in veterinary medicine, it is obvious the technology is here to stay and will benefit veterinary patients greatly. The most recent guideline (ANSI Z136.3 – 2011 American National Standard for Safe Use of Lasers in Health Care) now includes veterinary medicine in the nominative portion of the document. It is the inherent responsibility of the profession to provide safe and efficacious use of all classifications of lasers not only to protect the patient, but also the operator and any assistant who works within the nominal hazard zone. Appropriate signage, wearing wavelength specific laser safety glasses, avoiding potential reflection from shiny surgical instruments, protecting non-target tissue, shielding endotracheal tubes with free-flowing oxygen from the laser beam and evacuating the generated laser plume with appropriate smoke evacuation systems are all concerns that must be addressed during the training phase, as well as during every laser surgical procedure. The use of surgical lasers in veterinary medicine may have created an entirely new definition for performing surgery but the devices still must be considered as “tools” to do the procedure more precisely and more effectively. A veterinarian’s knowledge of pathophysiology and surgical expertise must be the primary factors to determine whether a laser should be used for a particular surgical or treatment procedure in lieu of a more conventional approach. Our profession’s practical, economic and objective approach to any new technology, including laser surgery and low level laser therapy, is essential.
Dr. Kenneth E. Bartels is the McCasland Professor of Laser Surgery.