This is a very common laser technique used in many hospitals. Advantages over conventional techniques include improved hemostasis compared to sharp dissection but also latent thermal necrosis of the resected margins. Laser energy interacts with tissues in one of four methods: transmission, absorption, scattering and reflection of the laser energy, resulting in vaporization, with a surrounding area of carbonized tissue. Beyond this region, thermal necrosis will generate a margin of tissue destruction beyond the plane of resection; this may be desirable during the removal of invasive tumors.
Dorsal displacement of the soft palate consists of the displacement of the soft palate on top of the epiglottis. This causes exercise intolerance and abnormal respiratory noise in performance horses. Several techniques have been described with varying success for the treatment of dorsal displacement of the soft palate. One therapy in conjunction with traditional surgical techniques is application of a laser in several small areas at the free edge of the soft palate. The theory behind this treatment is to produce scar tissue and stiffen the edge of the soft palate to prevent further displacement. The laser can also be used to resect the free edge of the soft palate (Staphylectomy) under video endoscopic guidance. Previously, this type of surgery was only done with the horse under anesthesia and through a skin incision into the throat.
Neurectomy (removing a section of nerve) is a treatment in large animals to reduce pain from progressive, debilitating disease processes. Removal of a small piece of the nerve supplying sensation to the painful area eliminates the sensation of pain the animal feels. Although this does not treat the disease, it does relieve pain to the animal allowing a more comfortable life. The most common complication of a neurectomy is regrowth of the nerve or formation of a painful neuroma (swelling at the nerve end). Using a laser to remove the nerve seals the end of the nerve tissue decreasing the occurrence of neuroma formation.
Laser treatment has been advocated for treatment of progressive ethmoid hematoma, which may in part be due to the lack of a definitive treatment protocol. The use of lasers is restricted as with other methods by access, but may be useful for lesions in the middle nasal conchae.
Reasonable success can be achieved with laser surgery in the treatment of respiratory masses, even those deep within the bronchi. Care must be taken to minimize the risks of thermal necrosis of adjacent structures, and it is important to remember that even the locally heated air may reach sufficient temperatures to result in mucosal discomfort. Some highly specialized endoscopy systems have a second channel to allow for removal of the smoke plume and heated gases by suction. Alternatively, the application of laser energy should be intermittent to minimize this heating effect.
Masses within the upper airway (trachea, pharynx, larynx) as well as cysts in the epiglottis, pharynx, and nasal passages can all be treated with laser surgery. Laser surgery can be used to remove the masses/cysts with minimal trauma to the surrounding tissue, decreased bleeding, and decreased recurrence when compared to traditional surgical approaches.
It should be noted that upper respiratory surgeries performed under standing sedation are considered significantly safer than those performed under general anesthesia. This is in part due to the inherent risks of general anesthesia, but also due to the risk of working near pure oxygen with its inherent fire risks.
The surgical laser can be used to create this opening or it can be used to create an opening from the pharynx into the affected pouch. Either approach can be performed through the video endoscope on an outpatient basis with the foal standing under sedation.
Guttural pouch empyema is a condition that occurs when the guttural pouch is filled with fluid or somewhat solidified purulent material. It is extremely difficult to resolve the infection with flushing and antibiotic treatments alone. The laser can be used to create a surgical opening from the throat area directly into the guttural pouch (salpingopharyngeal fistula) allowing the infectious material to drain passively.
Lasers can be used to prepare the healing wound bed (granulation tissue) for skin grafting. They can be used to remove the exuberant healing tissue that is often seen in horses and to sterilize the wound bed. The use of the laser also allows for less bleeding in the highly vascularized tissue and less swelling when compared to other methods. The laser creates an ideal environment for the new tissue to grow.
Most surgical skin diseases in large animals are neoplastic (cancer) in origin. Removal or destruction of the diseased tissue is the goal of any therapy. Laser surgery for these lesions both alone and in conjunction with chemotherapy can decrease recurrence rate and speed recovery. Laser excision of tissue causes less swelling to surrounding tissue and less spread of neoplastic cells to
surrounding areas when compared to excision with sharp instrumentation. Typical skin tumors removed with laser surgery include sarcoids, squamous cell carcinomas, and melanomas.
Following cutaneous tumor removal, this is probably the most common application of laser surgery in most animal hospitals. This technique is preferred to the standard surgical technique for ventriculectomy (sacculectomy) via a laryngotomy incision as it is noninvasive and requires no general anesthesia. During the procedure, hemorrhage is the most commonly encountered complication and it is important to take care not to extend the incision to the abaxial surface of the vocal fold where there are many blood vessels. This procedure may be combined with prosthetic laryngoplasty. As a sole procedure, laser ventriculocordectomy has been shown to be effective at reducing airway noise and improving performance in horses with recurrent laryngeal hemiplegia. It should be noted that laryngeal swelling may occur post-operatively, and it is important to have close monitoring and tracheotomy equipment available if necessary.