New Techniques In Laser Treatment

Just as laser surgery has become commonplace in human medicine, lasers are playing a larger part in equine surgery. A laser--which stands for Light Amplification by Stimulated Emission of Radiation--generates and concentrates light of different wavelengths. Focused light can make an incision, while a defocused beam will ablate (evaporate) tissue or, depending on the distance, function in place of a cautery (an agent used to burn, sear, or destroy tissue). The surgical procedure determines how the laser is used and which type is best suited to the job.

Laser equipment and the fibers it utilizes to create light are expensive, so their use is often confined to the larger veterinary hospitals and clinics. There are no special training requirements to own a surgical laser, but, "It would be foolish to try to do this without any kind of training at all," says Ken Sullins, DVM, Dipl. ACVS, of the Marion duPont Scott Equine Medical Center (EMC) in Leesburg, Va.

Since 1989, Sullins and others have used CO2 and ND:YAG lasers to improve or replace some conventional surgeries. For example, with the CO2 laser, a surgeon is able to ablate a tumor on the surface of the cornea, while an ND:YAG or diode laser used endoscopically makes it possible to evaporate a formerly unreachable uterine cyst or correct an upper airway problem such as an entrapped epiglottis. In fact, many cases that formerly required a large incision and general anesthesia can now be done while the horse is sedated and standing, using an endoscope inserted through a natural opening or a small incision.

Sullins has recently adapted two new laser procedures. One dramatically shortens recovery time and minimizes discomfort for a horse with bladder stones; the other, if used early on problem arytenoid cartilage (relating to small muscles or unpaired muscles of the larynx), might be career-saving for high-performance horses such as racehorses.

Blasting Bladder Stones

Until now, owners of horses with bladder stones (urinary calculi) had two choices. They could opt for immediate surgery or continue to work the horse, hoping that the discomfort caused by the stone would not impair performance until a break in his schedule made the surgery and its four- to six-week recovery period convenient.

Conventional surgery is difficult because of the location of the bladder. The surgeon makes a midline incision, then opens the bladder with another incision and stretches it forward so that the stone is accessible, being careful not to shatter the stone in the process. "Some stones tend to crumble," adds Sullins, "so you have to be really careful." If the stone is broken into smaller pieces, each must be searched for and removed. This greatly extends the time that the horse must remain under anesthesia and increases the risk that a small piece will fall into the abdominal cavity or be left in the bladder, where it will grow into another irritating stone. After surgery, a four- to six-week recovery is necessary to allow the midline incision to heal and return to full strength.

Sullins has been able to shorten recovery time to a matter of days by avoiding any incision, instead introducing the laser into the bladder via a videoendoscope inserted through the urethra. The procedure is called non-invasive removal of uroliths using pulsed dye laser lithotripsy. Sullins finds the pulsed dye laser not only effective on the calcium carbonate stones, but safer, as it poses little danger to the surrounding bladder tissue.

Laser lithotripsy can be done on a horse either standing while sedated or under general anesthesia. "I did one standing at the request of the owner, but it was clumsy and awkward, and it took three hours instead of two," says Sullins. Once the bladder is inflated with sterile saline, he touches or taps the stone with the contact tip of the laser, dissolving it into powder or breaking it up into smaller fragments. This buildup of debris periodically clouds the view through the videoendoscope, requiring the veterinarian to remove the endoscope and insert sterile tubing to lavage (wash) out the debris. The process is repeated--10 to 20 times, depending on the size of the stone--until each fragment is destroyed or small enough to wash out. "Using the scope makes it possible to be sure you got everything," says Sullins.

The horse is discharged from the hospital the day after surgery and allowed to return to work. Because inserting the endoscope and sterile tubing numerous times can irritate the urethra, phenylbutazone and antibiotics are recommended for five days. The cost of non-invasive laser lithotripsy is comparable to conventional abdominal surgery.

Salvaging Arytenoid Cartilage

Arytenoid chondritis (inflammation of the arytenoid cartilage) isn't the same as "roaring" (laryngeal hemiplegia), but it appears very similar. Both conditions prevent normal airflow when the cartilage fails to open properly, and are often first noticed when the horse breathes loudly and with difficulty during work. The arytenoid cartilage is part of the larynx, which is located in the back part of the pharynx. The arytenoid opens when the horse inhales, but when infected, it thickens and won't open properly. A granulating mass might form and obstruct airflow completely.

Conventional surgical treatment requires general anesthesia with an endotracheal tube inserted through an incision in the neck rather than through the mouth. Another incision is made in the throat and, depending on their condition, one or both of the arytenoid cartilages are removed. The incision is left open to drain. After surgery, the tracheostomy tube is left in place for several days, as swelling at the surgical site impairs breathing. The horse must remain hospitalized for a week, and the ones which can return to work require many weeks of convalescence. Often the horse is unable to continue a career where maximum airflow is essential and must be retired or find a less strenuous job.

"There haven't been any real studies," says Sullins, "but it's generally understood that a horse is done with racing if both the left and right cartilages are removed."

Sullins has developed a new treatment for early-stage arytenoid chondritis. During this stage, there is swelling and immobility of the cartilage, a granulating mass on the cartilage surface, and often an abscess in the cartilage. The procedure is done with the horse sedated, but standing. A videoendoscope inserted through the nose allows the surgeon to view the area where he will be working, and a very small incision is made in the throat for the free beam (no contact) diode laser. This laser is similar in properties to the ND:YAG, but uses a different wavelength.

The laser is used to vaporize the mass and infected areas, leaving the underlying structure of the cartilage intact.

"The heat from the laser has the added advantage of killing bacteria that may be present," says Sullins.

The horse is kept overnight in the hospital for observation, allowed to return home the following day, and is back to work in three to four weeks, making this laser treatment for arytenoid chondritis both cost-effective and career-saving.

From one end of the horse to the other, these new developments in laser surgery are adding up to great savings in time and expense for owners, and less down time trauma for their horses.

About the Author

Susan Konkle

Susan Konkle is a freelance writer from Rockville, Va., whose primary horse interest is show hunters. With her horses spending more time in surgery than showing, she became interested in researching and writing about veterinary care and treatments.

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