J. Brad Case, DVM, MS, DACVS
Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
Overview
Diagnosis and indications
Preoperative management
Surgical approach
Postoperative management
Outcome
Diagnosis and Indications
Acquired laryngeal paralysis is a common disease in geriatric large-breed dogs, which results in significant upper airway obstruction.1-4 Major differential diagnoses include: idiopathic acquired laryngeal paralysis, neoplasia, cervical trauma, and neuromuscular disease. Definitive diagnosis is made by sedated laryngoscopy. Because acquired laryngeal paralysis is progressive, surgery is usually indicated. In general, dogs with moderate to severe clinical signs or worsening clinical signs are candidates for laryngeal surgery. The goal of surgery is to reduce laryngeal resistance enough to improve the flow of air through the larynx without overzealous abduction, which may increase the risk of aspiration pneumonia. Although many different surgical options exist, the most commonly performed procedure in the United States is unilateral cricoarytenoid lateralization.
Preoperative Management
The most important preoperative considerations are: systemic, pulmonary, neurological and esophageal health. In addition to a complete physical and orthopedic/neurological exam, a complete blood count, serum chemistry, urinalysis, and survey-thoracic radiographs are indicated. Additionally, an esophagram can be performed to more objectively evaluate esophageal function.2 Megaesophagus is an absolute contraindication for laryngeal tie back due to the risk of aspiration pneumonia. A permanent tracheostomy should be considered and only undertaken after a long conversation with the owners regarding postoperative care and risks. Dogs presenting for surgery are fasted at least 12 to 24 hours prior to the procedure if possible. Use of prokinetic or gastrointestinal modifying drugs is debatable, but my preference is to pretreat with a metoclopramide (Reglan; 5 mg/ml, Pharmaceutical Associates, Inc., Greenville, SC 29605) CRI at 2 mg/kg/d intravenously the day prior to surgery. Use of sedatives and opioid drugs is minimized due to the potential for decreased gastrointestinal motility and aspiration pneumonia. My preference is to perform my laryngeal examination at the time of anesthetic induction prior to surgery. Metoclopramide is continued perioperatively.
Surgical Approach
The patient is positioned in right lateral recumbency with the neck gently flexed. An incision is made over the larynx just ventral to the jugular vein. The platysma muscle and subcutaneous tissues are dissected down to the thyropharyngeus muscle. The thyropharyngeus muscle is then transected along the edge of the thyroid cartilage. I place a stay suture in the thyroid lamina to allow lateral retraction during the remainder of the procedure. The cricoarytenoid joint is palpated at the insertion of the cricoarytenoideus dorsalis (CAD) muscle. An approximate 3–4-mm margin of the CAD is grasped near the muscular process using thumb forceps and the muscle transected distally. I use an 11 blade to incise the cricoarytenoid joint, which allows exposure of the articular surface of the muscular process. A monofilament, nonabsorbable, 2-0 suture on a swaged tapered needle is passed in a simple interrupted pattern through the middle of the muscular process, then through the dorsolateral caudal margin of the cricoid cartilage. The suture is directed in a cranioventral direction towards the cricoarytenoid articulation then tied. The optimal amount of arytenoid abduction is currently unknown and many recommendations have been made. These include: low tension, high tension, radius of endotracheal tube, and subjective adequacy.1,3-6 My preference has been to tension the suture under direct visualization of the larynx, using a rigid 10-mm endoscopic telescope. The operating room staff has been trained to handle and position the telescope for this purpose at our institution. The technique is simple but does require trained technical staff. Once the surgeon places the suture, a loose knot is formed. The surgery technician then places the telescope at the level of the soft palate and the endotracheal tube is removed. The camera head is rotated counter clockwise 90 degrees to obtain a dorsoventral view of the larynx on the surgery monitor (Figure 1). The surgeon then tenses and ties the suture to the desired amount of arytenoid abduction under video observation. An unused endotracheal tube is then replaced under video observation by the anesthesia staff. The surgical site is closed routinely in three layers.
The thyropharyngeus muscle is apposed in a simple continuous pattern using a monofilament absorbable suture. A deep subcutaneous and subcuticular closure is performed in a simple continuous pattern using a 4-0 monofilament absorbable suture. The skin is closed using 4-0 monofilament nonabsorbable suture. The local anesthetic (Bupivicaine; 0.25%, Hospira, Inc., Lake Forest, IL 60045) is administered as an incisional block.
Postoperative Management
Immediate improvement in upper airway signs is seen in most cases, which obviates the need for excessive use of sedatives. Additionally, it is my experience that most dogs are relatively comfortable and do not require injectable opioid drugs postoperatively. Indiscriminate use of sedatives and opioids may increase the risk of postoperative aspiration pneumonia and should be avoided.
Because gastric emptying can be delayed following anesthesia, nothing per os and metoclopramide (as above) are continued for at least 12 hours postoperatively. Once the dog has recovered and is alert and responsive, 1 or 2 small meatballs or ice chips can be offered. If no regurgitation or vomiting is seen, gradual reintroduction to feeding is encouraged. Feeding recommendations vary between surgeons but my preference is to feed the resting energy requirements in the form of meatballs for the first few weeks. I also recommend elevating the water bowl, although the benefits of this are debatable.
Outcome
Prognosis is good following cricoarytenoid lateralization with greater than 90% of dogs experiencing immediate improvement in upper respiratory function. Median survival is approximately 5 years.1 However, the risk of aspiration pneumonia is between 10–20% and exists lifelong.1,3-4
VIN editor: Figure not available at time of publication.
References
1. MacPhail CM, Monnet E. Outcome of and postoperative complications in dogs undergoing surgical treatment of laryngeal paralysis: 140 cases (1985–1998). J Am Vet Med Assoc. 2001;218:1949–1956.
2. Stanley BJ, Hauptman JG, Fritz MC, Rosenstein DS, Kinns J. Esophageal dysfunction in dogs with idiopathic laryngeal paralysis: a controlled cohort study. Vet Surg. 2010;39:139–149.
3. Hammel SP, Hottinger HA, Novo RE. Postoperative results of unilateral arytenoid lateralization for treatment of idiopathic laryngeal paralysis in dogs: 39 cases (1996–2002). J Am Vet Med Assoc. 2006;228:1215–1220.
4. White RAS. Unilateral arytenoid lateralisation: An assessment of technique and long term results in 62 dogs with laryngeal paralysis. J Small Anim Pract. 1989;30:543–549.
5. Bureau S, Monnet E: Effects of suture tension and surgical approach during unilateral arytenoid lateralization on the rima glottidis in the canine larynx. Vet Surg. 2002;31:589–595.
6. Greenberg MJ, Bureau S, Monnet E. Effects of suture tension during unilateral cricoarytenoid lateralization on canine laryngeal resistance in vitro. Vet Surg. 2007;36:526–532.