Treatment of Respiratory Inhalant Toxins in Psittacine Birds
Presenting Author: Marla Lichtenberger, DVM, DACVECC
Animal Emergency Center, Glendale, WI
Interpretive Review and comments by Dr. Nemetz:
This paper addressed how a veterinarian may diagnose and then successfully treat an acute inhalant toxicity in a pet bird when it presents to an animal hospital. Most bird owners are aware of Teflon toxicosis in birds as well as paint fume toxicosis. Many other airborne agents can create a critical respiratory event: aerosols, burning candles, incense, cleaning agents, or smoke (tobacco or any other source) and even other birds' feather dust as seen mostly in macaws housed with cockatoos or African grey parrots.
The respiratory system of a bird is unique compared to mammals with a more efficient system that is more susceptible to inhalant toxins. Since the lungs are non-expanding, rigid structures with expanding and contracting air sacs, auscultation with a stethoscope is of limited value in evaluating the respiratory status in a bird. There are basically 4 patterns of respiratory distress in a bird.
1. Upper Airway obstructions typically cause an open-beak breathing pattern with loud inspiratory squeak-like stridor. Emergency treatment may involve an alternate airway created by surgically placing a tube in one of the caudal air sacs. Inhaled seed kernels, mucus plugs, granulomas, or other foreign bodies are possible causes.
2. Small Airway is a disease affecting the primary and secondary bronchi inside the lung tissue. This is caused primarily by irritant inhalant toxins. Signs include open-beak breathing with soft wheeze sound on expiration when the bird is held close to one's ear. These signs are from fluid or blood that blocks the bronchi and occlude the airways. Sudden death is common, but prognosis is better with this new therapy if the cause is from an acute versus chronic pathologic process.
3. Parenchymal-type is a disease of the lungs and air sacs. This is mostly caused by infectious agents like fungi, bacteria, or viruses, but can also occur in aspiration of food-like material. Unfortunately, the breathing pattern usually produces no audible sounds but increased respiratory rate and effort. There are usually other clinical signs of a chronic disease state: weight loss, depression, nasal discharge, or poor body condition
4. Intracoelomic compression of the air sacs. This is caused by air sacs that are filled with fluid or a space occupying mass. The respiratory distress is characterized by increased rate, increased respiratory effort, and usually a distinct distension of the abdomen.
Management of #2 caused by irritant inhalant toxins is aimed at getting those bronchi to open (dilate) and let more air get past to the deeper tissue for oxygen exchange. Dr. Lichtenberger has found that alpha-2 selective smooth muscle bronchodilators that work to relax smooth muscle around the bronchi and inhibit specific inflammatory processes have increased the survival rate in some patients if therapy is enacted quickly.
The use of terbutaline (0.01mg/kg IM q 6-8h) has shown great improvement within 20 minutes in several cases. For more severe cases and those non-responsive to intramuscular administration, terbutaline can be nebulized in the intubated, anesthetized patient by dosing the same (0.01mg/kg) diluted into 5cc saline and the nebulized over a 15 minute interval. The anesthesia actually lowers the anxiety in many patients and can actually increase the survival rate of these patients. Terbutaline is available in 1mg/ml one milliliter ampules, but only sold in units of ten. The cost is several hundred dollars so Dr. Nemetz suggests a veterinarian find others in the area to help share the cost. This is truly an emergency drug and should be kept in a veterinary facility to be prepared Â for these acute cases.
Other dilators like aminophylline cannot be nebulized as they are not water soluble and rapid infusion can cause many side effects undesirable in these critical patients.
Birds can also produce large amounts of mucous with tracheal irritation. Drugs such as acetylcysteine aerosolized can help reduce the mucous viscosity. However this drug can cause a reflex brochoconstriction and should be administered only after the use of a brochodilator like terbutaline. This combination can be considered in severe refractory cases.