Respiratory distress in cats and dogs (Proceedings)

Respiratory distress is common and challenging. Cats often compensate well for pulmonary diseases, and some conditions can rapidly fulminate. Dogs are often more "honest" although they can decompensate rapidly as well. It is crucial to balance the equal goals of limiting stress on the patient with respiratory distress, and to work to identify the specific cause of the distress so that appropriate therapy can be provided.

Phone triage

Home care of the pet with respiratory distress is not advised. Pets with respiratory distress should be evaluated by a veterinarian as soon as possible. Pets with known pre-existing therapy may receive additional therapy at home immediately before leaving to come to the hospital, such as an additional dose of furosemide to a known heart failure patient, or albuterol/terbutaline and prednisone to a known lower airway disease cat.

Initial examination and stabilization

Initial physical examination should focus on the major body systems (heart, brain and lungs) and include an assessment of respiratory rate and effort, with a specific focus on evaluation increased airway sounds, or dull/absent sounds with increased effort. Auscultation of the heart may document a murmur or gallop, although it should be recalled that that murmurs may be hard to hear in the ER at times. Rectal temperature should be recorded, as hypothermia is common in cats with congestive heart failure. Temperature is much less commonly low in dogs with heart failure. Following rapid assessment, supplemental oxygen should be provided, and a history obtained from the cat's family. Care should be taken to inquire about past diagnosis (including auscultation of a heart murmur), possible trauma/exposure to the outdoors, and any other changes, such as decreased appetite, cough (or suspected "hairballs"), current heartworm status or PU/PD. Following a brief physical examination and assessment of the pet's medical history, an initial attempt at therapy should be provided, including continuing oxygen therapy, diuretics, glucocorticoids, or thoracocentesis. In a growing number of hospitals, ultrasonography (US) is readily available. Used of US is vital for rapid assessment of pleural effusion with minimal training, with more advanced training and practice, other assessments, such as left atrial size, evidence of LV hypertrophy, or mediastinal masses may also be provided. In my experience, the use of ultrasound has largely negated the need to perform a "diagnostic" thoracocentesis, and limits unnecessary discomfort and eliminates the possibility of iatrogenic pneumothorax.

Thoracic radiographs are ultimately required to (well at least HELP..) determine the cause of respiratory distress in most animals. Ideal positioning is NOT required when pets are in respiratory distress. It may be wise to start with a single view, and then to allow the patientt to recover for a few minutes before taking a second view.

A standard approach to interpretation of the thoracic radiograph includes evaluation of the pulmonary parenchyma, the pleural space, the cardiac silhouette, ribs and diaphragm. Tips for evaluation of chest film include
     1) When looking for pleural effusion, small volumes will obscure the lung/diaphragm interface on a DV or VD projection.
     2) Cardiomegaly may be subtle, even in fulminate heart failure in cats.
     3) Patchy infiltrates are most often heart failure in cats,; dogs tend to have cardiomegaly with perihilar edema.
     4) Bronchial disease can look like metastatic disease in cats
     5) Rib fractures can accompany coughing/respiratory distress in all species
     6) If films look normal, consider upper airway disease.

Other diagnostic testing may include echocardiography, pleural effusion cytology, transoral tracheal wash, and/or computed tomography. Common differentials include consideration of a)upper airway disease b) lower airway disease c)Parenchymal disease d) pleural space disease or e) trickery. Hypoventilation may cause hypoxemia or hypercarbia, but these will not be easily appreciated on physical examination.

Initial therapy

Pets that have respiratory distress should be promptly treated with supplemental oxygen. An oxygen cage is very appealing to the cat, although it may be challenging to evaluate a cat in a closed cage. Recall that oxygen does not "rush" out of the cage if opened, but does equilibrate quickly with room air. Supplemental oxygen in dogs reflects the pet's size and temperament. I typically try to determine if there is any pleural effusion present, because if it is, and may be removed, if can provide immediate clinical improvement. Pleural effusion may be appreciated on FAST ultrasound, or by radiographs. If no effusion is present, then it is important to try to determine if there is pulmonary edema (eg. Left sided -heart failure). Important clues include hypothermia in cats, and the presence of a gallop. Dogs will often have a loud murmur with mitral disease, or atrial fibrillation and a gallop with dilated cardiomyopathy. A single dose of furosemide is warranted if heart failure is not able to be excluded. In the normothermic cat, particularly with a history of cough, lower airway disease is highly likely and 2-4 mg of dexamethasone should be administered, perhaps coupled with injectable or inhaled Beta-2 agonists. In dogs with a history of vomiting, antimicrobials for potential aspiration should be administered.