Written by: Chantal Marleau
Discover the therapeutic uses of lasers, and how this technology is leading to incredible breakthroughs in equine medicine.
Undeniably, laser technology has found its way into our lives; it is used in eyesight correction, a wide array of human surgeries and even dentists are beginning to retire drills in favour of specialized lasers. Have lasers also found a home in veterinary medicine? Although expensive equipment makes the technology relatively rare in large animal practices, all five Canadian veterinary colleges have added at least one laser to their respective tool kits – making the technology available in many parts of the country.
“In my opinion, since universities are funded at least in part by public funds, it is a part of our mandate to provide technology and expertise to the general equine population,” said Dr. Renaud Léguillette, DVM, Dipl. ACVIM, associate professor at the University of Calgary’s Faculty of Veterinary Medicine (UCVM). “Laser surgery is definitely an area in which veterinary colleges have an opportunity to shine.”
WHAT IS LASER TECHNOLOGY?
Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. Lasers generate intense beams of light that can cut, seal or vapourize a variety of tissues. “The technology has really evolved in the past decade and there is a vast amount of laser [types] to choose from,” Dr. Léguillette noted. “Basically, there are low-power lasers for rehabilitation [physiotherapy] and high-power lasers for surgical cases.”
TYPES OF LASERS
Each laser concentrates a very precise wavelength of light in order to affect a specific type of tissue. As a result, there are four primary types of high-powered lasers used in equine cases:
- CO2 lasers are used to vapourize soft tissues without risk of damaging the surrounding ones. They have proved very helpful in castrations, eye surgery and in the removal of tumours.
- Neodymium: yttrium aluminum garnet (Nd:YAG) lasers use quartz tips, slipped through an endoscope, to deliver high-power surgical performance. They are designed to be particularly effective in cutting and cauterizing tissues and are primarily used in upper respiratory surgeries. Described as behemoths, these lasers are not portable.
- Diode lasers are a spinoff of the Nd:YAG laser. Affecting similar tissues as their predecessor, diode lasers are smaller, easily portable and highly efficient. In fact, these light scalpels are so powerful that the most common concern is that their highly focused energy causes marked inflammation in the surrounding tissues.
- Holmium: yttrium aluminum garnet (Ho:YAG) lasers are used for lithotripsy (the destruction of hardened masses). These lasers emit a high-frequency pulse that fragments calcium formations such as those sometimes found in the urinary tract.
PROS AND CONS
Since laser procedures are typically done as standing surgeries, the risks associated with general anesthesia, post-operative infection of incisions and scarring are virtually eliminated, making the technology highly advantageous. “Avoiding the risks and costs of general anesthesia is a very important consideration,” said Dr. Sheila Laverty, MVB, MRCVS, Dipl. ACVS, Dipl. ECVS, professor, chief, Equine Surgery service, director, Comparative Orthopedic Research Laboratory at the University of Montreal’s Veterinary Teaching Hospital (UdeM). “Tranquilizing the horse for a standing laser surgery brings costs way down, as well as the risks.”
“The recovery time is very quick – horses are often ready to trailer home within hours after surgery,” added Dr. Léguillette.
However, Dr. James Carmalt, MA, VetMB, MVetSc, Dipl. ACVS-LA, professor, Large Animal Surgery, Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine (WCVM), said an important consideration is the surgeon’s level of skill. “Just because the technology is new, it is not necessarily always better,” he said. “The laser definitely has its advantages, but clients have to understand that a lot of practice is required to use it effectively.
“One of the most common problems resulting from lack of experience is postoperative inflammation. The greater the length of time you’re using the laser, the more energy is going to be transferred to the tissue and the more inflammation you are going to get. You can’t get around that.”
At the University of Prince Edward Island’s Atlantic Veterinary College (AVC), where surgeons perform an average of two upper airway laser surgeries each month, practice has cut some procedure times in half, but inflammation remains a concern. “If inflammation becomes severe, the swelling can actually occlude [obstruct] the airway and prevent breathing,” explained Dr. Aimie Doyle, DVM, MS, Dipl. ACVS, assistant professor, Large Animal Surgery at the AVC. “The horses are medicated with high doses of anti-inflammatory medication before and after surgery and are kept in the intensive care unit for the first twenty-four hours after surgery to ensure they are breathing normally.
“Any signs of stridor [airway noise that might indicate the horse is having difficulty moving air through the larynx] are an indication to perform an emergency tracheotomy. Although this is very rare, we are always prepared and monitor the horses closely.”
One indisputable advantage of lasers is that they have simplified certain airway procedures and allowed new ones to be performed.
Laryngeal hemiplegia (roaring) is one of the disorders most commonly remedied by lasers. This condition occurs when muscles on one side of the larynx are partially or fully paralyzed, impeding airflow into the lungs. The paralysis affects the arytenoid cartilage, the vocal cords and the laryngeal ventricles or parts thereof.
“We used to do the ventriculectomy as a standing surgery in draft horses,” said Dr. Laverty. “These horses are so huge, in some cases, the costs of general anesthesia was often too great.
“We stood underneath their throats and opened into their larynxs; it was trickier and blood fell on your face and it wasn’t as elegant, but that’s how we did it until the laser came along.
“We also did the other procedures through an external incision into the larynx and left those incisions to heal. With the laser, these procedures are now minimally invasive.”
At the University of Guelph’s Ontario Veterinary College, Dr. Judith Koenig, DVM, DVSc., Dipl. ACVS & ECVS, associate professor, Large Animal Surgery & Equine Sports Medicine, shared that she recently made another important discovery in the use of laser surgery in roaring cases. “When we used the laser to remove the vocal cord and ventricle saccules during a ventriculocordectomy, we discovered that inflammation caused by the laser created a web of fibrous tissue at the entrance of the larynx,” she said. “This further blocked the airflow and caused the horse to make an even louder respiratory noise. What we learned from that case was to only remove one saccule/cord at a time.”
Dr. Laverty agrees that figuring out ways to control inflammation in the larynx area is critical. “Because of the small diameter of the larynx, a small amount of inflammation can restrict airflow. As a preventative measure, we also administer anti-inflammatories before and after surgery.”
Other examples of procedures now available on an outpatient basis thanks to laser technology are: transections of epiglotic entrapments, fenestrations (a surgical opening in a structure) and the vaporization of airway tumors.
Laser technology is no longer revolutionary, but it does sometimes play a leading role in rare surgical cases. “One example of the laser being indispensable is with polyps in the pharynx,” explained Dr. Laverty. “These are rare, but there really is no other easy way to remove that type of mass.”
“Finding new ways to improve the health of horses is an important role for veterinary colleges,” concluded the Dr. Léguillette. “We make advances and find new uses for technology by aiming to innovate.” The following case report is an example of how creative thinking saved the life of an Arabian gelding.
Laser Technology Used in Breakthrough Case
The initial prognosis was less than encouraging. Harlequin, an eight-year-old Arabian gelding, whom readers might remember from last year’s Canadian Horse Health Annual, suffered from a chronic guttural pouch infection that seemed impossible to treat; without a significant breakthrough in either techniques or technology, the condition would lead to premature death.
After three years of innovative thinking by the University of Calgary’s Faculty of Veterinary Medicine (UCVM) associate professor, Dr. Renaud Léguillette, DVM, Dipl. ACVIM, Harlequin’s health struggles are finally over.
After a contribution from the Equine Foundation of Canada funded the UCVM’s purchase a high-powered diode laser last year, what began as a desperate case became a success story.
As a yearling, thick yellow discharge sporadically ran from Harlequin’s right nostril. The source of the problem remained undiagnosed until Dr. Léguillette, an internal medicine specialist, began consulting on cases at Moore Equine Veterinary Centre in Balzac, Alberta, as part of the University of Calgary’s Distributed Veterinary Learning Community (DVLC) – an operating model that integrates both faculty and students into private clinics throughout the province to assist on various cases. For Harlequin, the DVLC would prove to be a lifesaver.
“The source of Harlequin’s discharge was difficult to pinpoint and quickly led to a series of complicated challenges,” recalled Dr. Léguillette. “Luckily, resources allocated by the university (along with the Moore Equine facilities) allowed us to experiment with new ways to keep the infection under control. The goal was to permanently ventilate Harlequin’s guttural pouch and eliminate the infection altogether.”
Horses have two guttural pouches located on each side of the throat between the middle ear and the pharynx. The pouches are empty chambers that circulate cool air below the brain. Since these pouches are cavities filled with moist air and sometimes secretions, constant airflow is essential in keeping each pouch clean of debris and infection.
In Harlequin’s case, a thick web of fibrous tissue obstructed the right pouch, allowing infection to thrive; it was only a matter of time before bacteria fed on surrounding blood vessels and nerves, which would have lead to his death.
The first step was to enlist the help of Moore Equine surgeon Dr. Mike Scott, DVM, Dipl. ACVS. A large amount of chondroids (hardened balls of infection) were surgically removed from the pouch, but part two of the surgery, creating an incision between both pouches, had to be aborted.
“We aimed to do a procedure called “fenestration,” sometimes done in foals with similar symptoms, but abnormalities within Harlequin’s guttural pouch made that option impossible,” explained Dr. Léguillette. “The septum between both pouches was too thick to cut through because of chronic infection.”
Unwilling to concede defeat, Dr. Léguillette began improvising other methods to ventilate the pouch. “In this case, inaction meant the end of this horse’s life,” he explained. “We had to do something and we really had nothing to lose.”
Dr. Léguillette fashioned many tools; one of which was a scalpel inserted into an inseminator pipette that he used to cut through granulation tissue. “Despite sedation, this procedure came with a significant risk of accidentally cutting blood vessels in the area,” explained Dr. Léguillette.
“We then used human esophageal balloons that we inflated and slid through the opening, trying to permanently pry the tissues apart.
“When the granulation tissue persisted, we had a custom stent built and inserted it as a second opening into the pouch. This worked for a while, but when tissue eventually invaded the stent’s meshing, we sutured a thick endo-tracheal tube inside the stent, trying to keep the opening patent.”
Despite these innovations, granulation tissue remained the enemy. “We were almost out of options when the laser purchase became reality,” explained Dr. Léguillette. “It has proved to be a lifesaving tool for this horse.”
Inserting the high-power quartz fibers of the new 30-watt laser through the endoscope, Dr. Léguillette was able to simultaneously cut and cauterize the fibrous tissue.
Since heat creates inflammation in surrounding tissues, it was decided that only a portion of the opening would initially be treated. “It is an advantage of the laser that we are able to cut one millimetre at a time,” said Dr. Léguillette. “This allows for tremendous precision and control.”
The standing surgery was repeated four times over the next five months until the laser finally reached the guttural pouch.
“The reason this condition has been untreatable in the past is that the opening is deep within the head (roughly 40cms) and covered by a flap,” explained Dr. Léguillette. “There has never before been a method to safely access the area with an efficient cutting tool. With the long and powerful laser fibers, the procedure is suddenly possible.”
Nine months after the first laser surgery, the opening is made of healthy tissue. Although smaller than normal, it is completely functional.
“Cases such as Harlequin’s allow us to push the boundaries of what we think is possible and to innovate new techniques,” said Dr. Léguillette. “Laser technology was the last hope for Harlequin and it has given him a brand new lease on life.”