Page 376 - Small Animal Internal Medicine, 6th Edition

348 PART II Respiratory System Disorders

animal’s condition to maintain systemic hydration, which is Prognosis
necessary to maximize the effectiveness of airway clearance Animals with mild signs of disease and a correctable under-
VetBooks.ir mechanisms. However, overhydration must be avoided worse for animals with more severe disease or uncorrectable
lying problem have an excellent prognosis. The prognosis is
because of a tendency for pulmonary edema.
underlying problems.
Oxygen supplementation (see Chapter 25) is initiated
immediately in compromised animals. Positive-pressure
ventilation is required for animals in severe respiratory dis-
tress that is unresponsive to oxygen therapy. EOSINOPHILIC LUNG DISEASE
Bronchodilators can be administered to decrease bron- (EOSINOPHILIC
chospasms and ventilatory muscle fatigue. They are most BRONCHOPNEUMOPATHY)
̇ ̇
likely to be effective in cats. Bronchodilators can worsen V/Q
mismatching, exacerbating hypoxemia. They are discontin- Eosinophilic lung disease, or eosinophilic bronchopnue-
ued if no improvement is seen, or if clinical signs appear to mopathy, is a broad term that describes inflammatory
worsen after their administration. lung disease in which the predominant infiltrating cell is
The antiinflammatory effects of glucocorticoids can be the eosinophil. Eosinophilic inflammation can involve pri-
beneficial, but glucocorticoids can interfere with normal marily the airways or the interstitium. Allergic bronchi-
host defense mechanisms in tissues that have already been tis and idiopathic bronchitis are by far the most common
severely compromised. This author reserves the use of eosinophilic lung diseases seen in cats and are discussed
glucocorticoids for patients that have severe respiratory in Chapter 21. Interstitial infiltration, with or without
compromise and a deteriorating clinical picture despite concurrent bronchitis, was historically referred to as pul-
appropriate antibiotic therapy and supportive care. Low monary infiltrates with eosinophils (PIE) and is typically
(antiinflammatory) doses of short-acting preparations are seen in dogs. Eosinophilic pulmonary granulomatosis is a
administered for up to 48 hours. severe type of eosinophilic lung disease of dogs and char-
Animals with a large airway obstruction can benefit from acterized by the development of nodules and often hilar
bronchoscopy and foreign body removal. However, routine lymphadenopathy. It must be differentiated from mycotic
bronchoscopy is not indicated because of the risk associated infection and neoplasia. These names are descriptive only
with the general anesthesia needed during the procedure and and likely encompass a variety of hypersensitivity disorders of
the infrequency of large airway obstructions. the lung.
Antibiotics are administered immediately in animals that Because eosinophilic inflammation is a hypersensitivity
are presented in severe distress or with overt systemic signs response, an underlying antigen source is actively pursued
of sepsis. Selected antibiotics should have a broad spectrum in affected animals. Considerations include heartworms,
of activity and be administered intravenously. Such drugs pulmonary parasites, drugs, and inhaled allergens. Food
include the combination of a fluoroquinolone or an amino- allergy could play a role in these disorders, but this associa-
glycoside with ampicillin with sulbactam (see the earlier tion has not been explored. Potential allergens are discussed
section on bacterial pneumonia). further in the section on allergic bronchitis in Chapter 21.
A tracheal wash is ideally performed in stable patients Bacteria, fungi, and neoplasia can also induce a hypersensi-
before antibiotics are initiated, to document the presence of tivity response, but this response often is not the predomi-
infection and to obtain antibiotic sensitivity data. This infor- nant finding. In many cases no underlying disease can be
mation is particularly valuable because prolonged treatment found. Eosinophilic pulmonary granulomatosis is strongly
is often needed, and also because research in human medi- associated with heartworm disease.
cine has amply demonstrated that resistant secondary infec-
tion can develop after aspiration in patients given antibiotics Clinical Features
initially or on an empirical basis. As discussed for bacterial Eosinophilic lung diseases are seen in young and older dogs.
pneumonia, the high incidence of gram-negative and mixed Affected dogs are evaluated because of progressive respira-
infections makes assumptions regarding antibiotic sensitiv- tory signs such as cough, increased respiratory efforts, and
ity prone to error. Pending results of culture, it is reason- exercise intolerance. Systemic signs such as anorexia and
able to initiate treatment in stable patients with penicillin weight loss are usually mild. Lung sounds are often normal,
with a β-lactamase inhibitor (e.g., amoxicillin-clavulanate or although crackles or expiratory wheezes are possible.
ampicillin with sulbactam). Because infection can occur as
a later complication in these patients, frequent monitoring Diagnosis
with physical examination, CBC, and thoracic radiographs The finding of peripheral eosinophilia is not present in all
is necessary to detect any deterioration consistent with sec- animals with the eosinophilic lung disease, nor is it a specific
ondary infection. Tracheal wash is repeated if infection is finding. A diffuse interstitial or bronchointerstitial pattern
suspected. is seen on thoracic radiographs. Eosinophilic pulmonary
Further therapeutic and monitoring considerations are granulomatosis results in the formation of nodules, usually
discussed in the section on bacterial pneumonia. Underlying with indistinct borders. These nodules can be quite large,
diseases are treated to prevent recurrence. and hilar lymphadenopathy may also be present. A patchy