Laser Surgery of the Upper Respiratory Tract

Take Home Message  

The diode laser (980nm) is most commonly used. Laser surgery offers a less invasive alternative  to conventional surgery and can alleviate the need for general anesthesia. However, the laser  must avoid contact with laryngeal cartilage.  

Introduction  

Laser surgery through videoendoscopic control has gained widespread use in horses during the  last 20 years. Initially CO₂ (0.01 mm) and Nd:YAG (neodymium-doped yttrium aluminum  garnet; 1054 nm) lasers were widely used until replaced by smaller and more portable diode  lasers. Although the laser is very effective for cutting and ablation they require experience to  handle them safely; avoidance of contact with cartilage is important to minimize morbidity.  

Technique and Methods  

Laser surgery can be performed with the animal standing and sedated with detomidine (5-6 mg  /1000lbs IV) and butorphanol (4mg/1000lbs IV) followed by topical anesthesia. If re-sedation is  needed re-dosage with 2mg of detomidine is given. The most useful laser fiber is the 600µm dual  contact and non-contact fiber. When used under general anesthesia the use of nitrox, heliox or  compressed air is needed. Under general anesthesia the placement of the endotracheal tube  affects the region of the larynx that is accessible: nasotracheal intubation interferes with  procedure in the dorsal aspect of the larynx while endotracheal intubation interferes with the  ventral aspect of the larynx. Finally smoke evacuation is important under general anesthesia. In  both cases the control of the tip of the laser is critical; the user must, at the same time, control  both the wheel of the videoendoscope that affects the lateral, medial and dorso-ventral movement  of the laser and the rostro-caudal movement of the laser. In contact mode the laser is used to  transect tissue (Fig. 1) while in non contact mode it is used to ablate the area (Fig. 2). Finally, all  safety regulations must be followed.  
 

Results  

Laser assisted ventriculo-cordectomy, removal of ary-epiglottic folds, and treatment of  aryepiglottic entrapments are the most common treatments. Data in experimental animals  confirms that laser assisted ventriculo-cordectomy is an effective treatment of abnormal upper  respiratory noise and partial laryngeal obstruction.^1,2 The actual laser setting is variable and most  authors use between 12-25 watts for upper airway surgery.³ Although effective in the treatment  of epiglottic entrapment, this is the modality that is most susceptible to complications because of the cartilage response to inadvertent laser trauma (Fig. 3). On the contrary, collateral damage to  the nasopharyngeal mucosa seems to heal without complications (Fig. 4). Non healing ulcers  seem to respond to ablation of the surface of the ulcer at low energy (1-3 watts). Post-operative  recovery ranges from 2-6 weeks post treatment. Most authors recommend the use of anti inflammatory agents in the early postoperative period.
 

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