Downeast Dog News
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“Need to Breathe”

Laryngeal Paralysis in Dogs
By Gail D. Mason, DVM, MA, DACVIM | May 31, 2019

The larynx or “voice box” can be considered an under-appreciated organ until its function is impaired. Besides producing sound, the larynx is a very talented gatekeeper of the airway. It closes while the dog swallows food or water to keep airways clear. During the respiration cycle, it opens and closes to allow air in and out of the lungs. A common dysfunction of the larynx in dogs (rare in cats) is when the abductor muscles which pull the laryngeal folds open become weak or flaccid. “Lar par”, as its known, usually comes on gradually in elderly dogs which may be incorrectly assumed to be normal aging. Most common in Labrador retrievers, the symptoms include excessive panting, gagging after drinking water, exercise intolerance, “hoarse” bark, loud breathing sounds, and respiratory gasping or distress. Warm, humid weather and heavy exercise increase the risk for sudden onset symptoms. In severe cases, it is a life-threatening emergency!

The cause of lar par in many patients cannot be specifically identified. However, it should be noted that it can be an important symptom of neurological disorders such as myasthenia gravis or polyneuropathy.

How is the diagnosis made?

In order to assess laryngeal function, light to moderate sedation is required. This allows the veterinarian to directly observe the structure and function of the organ. The arytenoid cartilages should symmetrically and crisply open upon inspiration and close snugly on expiration. If the functionality is not obvious, a respiratory stimulant (doxapram) can be given intravenously to the patient to briefly stimulate respirations. Though lar par can be bilateral, it most commonly presents as a unilateral issue. In that case, one cartilage opens normally, and the other sits “idle.” This decreases the amount of air that the dog can inhale which can lead to increased respiratory effort, swelling of the laryngeal tissues, and anxiety of the patient. If the dog is already in respiratory distress, immediate sedation and intubation (insertion of a breathing tube) to maintain an open airway is crucial to survival. Once the patient is stabilized, the diagnosis can be confirmed by removing the breathing tube and examining the larynx. Complete baseline blood testing, as well as chest radiographs (xrays) are indicated as some dogs develop a dilated esophagus and/or aspiration pneumonia as well.

How is lar par treated?

Effective treatment for laryngeal paralysis involves surgical intervention in most cases. If symptoms are mild or the patient is not a suitable candidate for surgery, you can help your dog by 1) changing from a collar to a harness to avoid pressure on the larynx; 2) avoid excessive heat and strenuous exercise; 3) reduce anxiety and stress that increase respiratory the rate. This may require using anti-anxiety agents (which are very safe in dogs) or tranquilization. Short term corticosteroids can reduce swelling of the airway tissues.

Surgical treatment for lar par is the most effective over time but should be considered carefully. The most common procedure is called an “arytenoid lateralization” or laryngeal tieback surgery. It involves the surgeon tethering the cartilage of the affected side to the wall of the pharynx or throat. Just like tethering a tent flap open, this permanently allows the dog to have more airway space and certainly can be life-saving. However, this permanent tie back prevents complete closure of the larynx during swallowing. A reduced bark sound and coughing after drinking or eating are expected outcomes. Additionally, post-operative patients have an elevated risk of having material from the mouth inadvertently enter the lungs (aspiration pneumonia) since there is no longer complete laryngeal closure. The onset of this type of pneumonia ranges from intermittent and mild to sudden and severe. Most dogs with aspiration pneumonia do survive the illness unless they have a concurrent esophageal dysfunction.

This surgery requires specific veterinary surgical expertise in a 24-hour setting to improve the odds of a favorable patient outcome. It is recommended that surgical patients be treated as necessary to avoid excessive barking or anxiety for 2-3 weeks following surgery. Lar par tie back patients should not be allowed to swim as the risks are too great. Fun with a water hose or kiddie pool can is allowable. The patient is usually released the day following surgery and most greatly appreciate the ability to breathe more freely!

Addendum:

We are pleased to announce that the talented and trusted teams of Portland Veterinary Specialists and Animal Emergency & Surgical Care have united into one veterinary health team under the ownership of surgeon Dr. Marta Agrodnia. Our new name is Portland Veterinary Emergency & Specialty Care (PVESC)!

Dr. Gail D. Mason

Chief Medical Office/staff internist