Application of lasers in equine upper respiratory surgery

Surgical Debulking and TransEndoscopic Noncontact Diode Laser Application for Treating a Sinonasal Myxoma in a Horse

Equine sinonasal myxomas (SNM) are very rare; only a few cases/small case series are reported in veterinary literature. The purpose of this report is to describe the diagnostic and surgical procedure adopted to approach the neoplastic mass in a case of equine SNM. A 5 year old, Murgese gelding was presented with mild serous nasal discharge, minimal facial swelling, decreased airflow from the right nostril, and dull frontal sinus percussion. Diagnostic imaging, including endoscopy, revealed a pale mass in the caudal portion of the right middle meatus, which developed inside the right conchofrontal sinus and nasal cavity and deviated the nasal septum to the left side. A large frontonasal bone flap was created with the horse in general anesthesia, aiming to remove the lesion and perform further diagnostic investigation. The mass had the shape of a small orange, the caudodorsal and rostral part having a hard wall, whereas the ventral part being friable; the inside was hollow, containing a viscous and transparent liquid. Surgical excision was broad but incomplete, and therefore after surgery, a standing transendoscopic diode laser irradiation and photoablation of small residual lesions per nasum were performed. Microscopically, the mass consisted of spindle-shaped cells, loosely arranged within an abundant, light blue myxoid matrix. On the basis of clinical and pathologic findings, the diagnosis of sinonasal myxoma was made. Although benign and slowly growing, myxomas usually tend to infiltrate the surrounding tissues; as a consequence, recurrence is very likely after surgical excision. In the case described herein, the combination of a surgical excision, transendoscopic diode laser irradiation, and photoablation provided a positive outcome, until at least 14 months after surgery.

Comparison of two techniques for transpharyngeal endoscopic auditory tube diverticulotomy in the horse

Auditory tube diverticula, also known as guttural pouches, are naturally occurring dilations of the auditory tube in horses that communicate with the nasopharynx through a small ostium. Infection and select other conditions can result in inflammation and narrowing of the nasopharyngeal ostium, which prevents drainage of fluid or egress of air and can lead to persistent infection or guttural pouch tympany. Auditory tube diverticulotomy allows continuous egress from the auditory tube diverticula and is a feature of disease treatment in horses, in which medical treatment alone is not successful. Transpharyngeal endoscopic auditory tube diverticulotomy was performed using a diode laser either at a single dorsal pharyngeal recess location or bilaterally caudal to the nasopharyngeal ostium in 10 horse head specimens. Both methods resulted in clear communication between the nasopharynx and auditory tube diverticula. Diverticulotomy performed in the dorsal pharyngeal recess required less laser energy and activation time and had a shorter surgical duration than diverticulotomy performed caudal to the nasopharyngeal ostium. Further study related to the clinical application of both techniques is warranted.

Performance of the 808-nm diode laser on equine upper airway tissue is enhanced by intravenous administration of indocyanine green

OBJECTIVE

The objective was to develop a protocol whereby 808-nm diode laser irradiation combined with intravenous (IV) indocyanine green (ICG) could be used in non-contact mode with equal surgical efficacy to the Nd:YAG on equine tissues.

BACKGROUND DATA

The 808-nm diode laser, delivering 20-40 W of power, has been produced for veterinary medical applications. This laser's power output is less than that of most neodymium:yttrium-aluminum-garnet (Nd:YAG) lasers. ICG is absorbed at a wavelength of 810 nm, which when concentrated in tissue should be an excellent absorber for the energy produced by the 808-nm diode laser.

METHODS

This study compares the depths and widths of thermal penetration achieved with the 808-nm diode laser in equine respiratory tissue after intravenous injection of ICG. ICG was administered at two doses: 1.5 mg/kg and 3 mg/kg. The 808-nm diode laser and Nd:YAG laser were set to deliver 200 J of energy. The depths and widths of thermal penetration obtained were compared.

RESULTS

Lesion depth and width tended to be greater in the ICG + 3 mg/kg group than in the ICG + 1.5 mg/kg group. Even so, the 1.5-mg/kg dose substantially increased the efficacy of the diode laser. Plasma ICG concentrations peaked at 5 min post-administration and then dropped markedly; lesion depth decreased after peaking at 7 min post-administration.

CONCLUSION

This study demonstrated that the 808-nm diode laser, when augmented with intravenous ICG, will be as effective a surgical tool as the Nd:YAG laser on equine upper airway tissues when applied using a non-contact fiber.

Laser Vocal Cordectomy Fails to Effectively Reduce Respiratory Noise in Horses with Laryngeal Hemiplegia

OBJECTIVE

To report the effect of unilateral laser vocal cordectomy on respiratory noise and airway function in horses with experimentally induced laryngeal hemiplegia (LH).

STUDY DESIGN

Experimental study.

ANIMALS

Six Standardbred horses without upper airway abnormalities at rest or during high-speed treadmill exercise.

METHODS

Respiratory sounds and inspiratory trans-upper airway pressure (P(Ui)) were measured before (baseline) and 14 days after induction of LH by left recurrent laryngeal neurectomy, and again 30, 60, 90, and 120 days after endoscopically assisted laser cordectomy of the left vocal cord. Data were collected with the horses exercising on a treadmill at a speed producing maximum heart rate (HR(max)).

RESULTS

In horses exercising at HR(max), induction of LH caused a significant increase in P(Ui), sound level (SL), and the sound intensity of formant 2 (F(2)) and 3 (F(3)). The sound intensity of formant 1 (F(1)) was unaffected by induction of LH. Laser vocal cordectomy had no effect on SL, or on the sound intensity of F(1) and F(3). At 30, 60, 90, and 120 days after surgery, P(Ui) and the sound intensity of F(2) were significantly reduced, but these variables remained significantly different from baseline values.

CONCLUSIONS

Unilateral laser vocal cordectomy did not effectively improve upper airway noise in horses with LH. The procedure decreased upper airway obstruction to the same degree as bilateral ventriculocordectomy.

CLINICAL RELEVANCE

Currently, laser vocal cordectomy cannot be recommended for the treatment of upper airway noise in horses with LH.

Use of laser rhinoscopy to treat a nasal obstruction in a captive California sea lion (Zalophus californianus)

Laser rhinoscopy was used to treat a nasal obstruction in a captive California sea lion (Zalophus californianus). The rehabilitated, adult, female sea lion developed mucopurulent, intermittent, bilateral nasal discharge and functional nasal obstruction 20 mo after acquisition by the Aquarium of the Pacific in Long Beach, California. A 3-mm-thick soft tissue structure spanning the region between the soft and hard palates, a deviated nasal septum, and several nasopharyngeal polyps were identified. Biopsies and cultures of the obstructive web showed ulcerative granulation tissue with suppurative inflammation, bacterial infection, and a partial section of an arthropod larva (not speciated). Laser rhinoscopy was performed to relieve the caudal nasopharyngeal obstruction and ablate the polyps. The sea lion appeared to breathe through the nares with lessened nasal discharge for a period of 6 wk after laser therapy, but within 8 wk the mucopurulent nasal discharge returned, the obstruction had reformed, and the sea lion was euthanized. Postmortem examination confirmed antemortem diagnoses of caudal nasopharyngeal obstruction secondary to inflammatory tissue; however, no additional sections of arthropod parasites were located microscopically.

The use of lasers for treatment of upper respiratory tract disorders

Lasers have become important tools for the equine surgeon in the treatment of upper respiratory tract disease in the horse. Multiple wavelengths and delivery systems are available. Indications for the use of lasers in the upper respiratory tract primarily include minimally invasive procedures not possible with conventional surgical instrumentation. New applications for the use of lasers to treat upper respiratory disease are likely to evolve with the development and introduction of new wavelengths and delivery systems.

Neodymium:yttrium-aluminum-garnet laser ablation of a urethral web to relieve urinary outflow obstruction in a horse

An 8-year-old Hanoverian gelding was examined because of urine dribbling and urethral obstruction. Mild proprioceptive deficits of the left hind limb were evident during neurologic examination. Ultrasonography per rectum revealed dilatation of the pelvic portion of the urethra. Endoscopy of the urethra revealed 2 webs of tissue: 1 was located 10 cm proximal to the external urethral opening; the other was located 65 cm proximal to the external urethral opening and prevented passage of the endoscope into the urinary bladder. The mass was ablated with a neodymium:yttrium-aluminum-garnet laser, using a transendoscopic noncontact technique. On follow-up examination 6 months after laser surgery, an endoscope could easily be passed into the bladder, and no urethral web was seen. The horse was able to void a stream of urine but continued to dribble urine intermittently. The proximal location of the urethral lesion in this horse would have made use of traditional surgical methods problematic, whereas transendoscopic laser photoablation was easy and effective.

Neodymium:yttrium aluminum garnet laser ventriculocordectomy in standing horses

OBJECTIVE

To develop a technique for neodymium:yttrium-aluminum-garnet (Nd:YAG) laser ventriculocordectomy in standing horses and document healing in horses undergoing laser ventriculocordectomy.

ANIMALS

6 horses between 2 and 32 years old.

PROCEDURE

Under endoscopic guidance, the left laryngeal ventricle was everted with grasping forceps and excised with an Nd:YAG laser, using 60 watts of power in a noncontact fashion (6,403 to 9,197 Joules). Following removal of the ventricle, the vocal cord was photoablated. Horses were examined endoscopically 2, 7, 14, 21, 30, and 47 days after ventriculocordectomy, and 1 horse was euthanatized on each of these days. At necropsy, the larynx was removed intact and examined grossly. Samples were collected for histologic examination of the ventriculocordectomy site.

RESULTS

Endoscopic examination revealed granulation tissue by day 7, the start of epithelialization by day 21, and healing by day 47. At necropsy, 4 horses were found to have a small amount of ventricular mucosa remaining dorsally and 1 additional horse was found to have a mucocele. Granulation tissue was identified grossly and histologically in the horses euthanatized between 7 and 30 days after surgery. Incipient reepithelialization was evident histologically on day 14, and complete reepithelialization of the surgery site was evident by day 47.

CONCLUSION AND CLINICAL RELEVANCE

Results suggest that ventriculocordectomy can safely be performed with an Nd:YAG laser in standing horses.

History, Instrumentation, and Techniques of Flexible Endoscopic Laser Surgery in Horses

There are clearly a number of applications for which flexible endoscopic laser surgery has become the state of the art in equine surgery, and the Nd:YAG laser seems to be the most versatile instrument for this type of surgery. Nevertheless, it is critical to understand the advantages and disadvantages of each laser technique. For example, the Nd:YAG laser used in a noncontact fashion seems to be superior when ablation of tissue is required such as treatment of upper airway masses. Conversely, contact Nd:YAG laser techniques have proven themselves to be superior when more precise cutting is advantageous such as treatment of epiglottic entrapment. Ultimately, it seems that a range of lasers is necessary to ensure selection of the most appropriate technique, adding significantly to the expense of equipment but improving the outcome for a range of equine diseases.

Transendoscopic laser treatment of rostral displacement of the palatopharyngeal arch in four horses

OBJECTIVE

To document the use and clinical outcome of transendoscopic laser techniques for treatment of rostral displacement of the palatopharyngeal arch (RDPA) in horses.

SUMMARY BACKGROUND DATA

Rostral displacement of the palatopharyngeal arch is a rare cause of upper respiratory noise and exercise intolerance in horses, and may be associated with abnormal laryngeal anatomy. There are few reports of successful treatment of this condition, and no reports of the treatment of RDPA using laser techniques.

METHODS

The diagnosis of RDPA was based on the presence of palatal tissue covering the dorsal aspect of the arytenoid cartilages on endoscopic examination. Either a neodymium:yttrium aluminum garnet (Nd:YAG) laser noncontact technique (1060 nm, 100 W continuous mode) or a diode laser contact technique (808 nm, 14 W, continuous mode) was used.

RESULTS

In 3 horses in which the Nd:YAG laser was used, displaced palatal tissue was not fully divided at surgery, but separated after latent thermal necrosis within 3 days. In the horse in which the diode laser was used, tissues were fully divided at the time of surgery. Two horses had abnormal laryngeal anatomy and laryngeal hemiplegia. One of these 2 horses was subjected to arytenoidectomy, and had limited success as a race-horse, while the other was retired as a broodmare. One of 2 horses with no other laryngeal abnormalities raced once unsuccessfully, while the other horse was never raced.

CONCLUSIONS

Rostral displacement of the palatopharyngeal arch may be corrected in standing horses using transendoscopic surgery, but despite successful ablation of displaced tissue the prognosis for athletic performance is poor.

Transendoscopic chemical ablation of progressive ethmoidal hematomas in standing horses

OBJECTIVE

To examine the response of horses with progressive ethmoidal hematoma (PEH) to intralesional injection of 4% formaldehyde solution.

STUDY DESIGN

Nasal passages of horses affected with PEH were examined endoscopically at different intervals to determine the effects of intralesional injection of formaldehyde solution.

ANIMALS

21 horses with PEH.

METHODS

PEHs were injected transendoscopically with 4% formaldehyde solution. Horses were examined endoscopically and retreated at different intervals until the PEH was eliminated or was so small that reinjection was not possible.

RESULTS

Lesions diminished significantly in size or were eliminated after 1 to 18 injections (median, 5; mean, 7.0 +/- 5.62). Seventeen lesions (60.7%) resolved completely after 1 to 18 injections (median, 5; mean, 7.2 +/- 5.71). Five lesions decreased markedly in size but did not resolve after receiving 1 to 18 injections (median, 5; mean, 7.6 +/- 6.66). Injection of these lesions was discontinued 4.0 to 25.1 months (median, 9.5; mean, 11.02 +/- 8.446) after the first injection. The PEH of one horse was removed surgically after one injection. Three horses, one with bilateral PEH, were lost to follow-up. One horse developed signs of laminitis. No other complications were observed.

CONCLUSIONS

Horses with a PEH can be treated effectively by transendoscopic, intralesional injection of 4% formaldehyde solution.

CLINICAL RELEVANCE

Ablation of PEH using formaldehyde solution avoids general anesthesia and problems associated with ablation by conventional surgery or laser.

Standing laser surgery of the head and neck

The use of carbon dioxide and Nd:YAG lasers has expanded the capabilities of equine surgeons. These lasers are used to incise, vaporize, and coagulate tissue with minimal hemorrhage and reduced morbidity to the patient. In this article, practical fundamentals of laser surgery are briefly reviewed, and selected standing laser procedures of the head and neck are discussed.