Page 359 - Small Animal Internal Medicine, 6th Edition

CHAPTER 21 Disorders of the Trachea and Bronchi 331

be examined for signs of degeneration, suggestive of bac- GLUCOCORTICOIDS
terial infection. Slides should be carefully scrutinized for Therapy with glucocorticoids, with or without bronchodila-
VetBooks.ir the presence of organisms, particularly bacteria and para- tors, is necessary for most cats with idiopathic bronchitis.
Results can be dramatic. However, drug therapy can interfere
sitic larvae or ova. Fluid should be cultured for bacteria,
although it is important to note that the growth of organisms
animal to tolerate a delay in the start of drug therapy must
may or may not indicate the existence of true infection (see with environmental testing; therefore the ability of the
Chapter 20). Cultures or PCR for Mycoplasma spp. may also be assessed on an animal-by-animal basis. Glucocorticoids
prove helpful. can relieve the clinical signs in most cats and may protect
Testing for heartworm disease is described in Chapter 10. the airways from the detrimental effects of chronic inflam-
Multiple fecal examinations using special concentrating mation. Short-acting products such as prednisolone are rec-
techniques are performed to identify pulmonary parasites, ommended because the dose can be tapered to the lowest
particularly in young cats and cats with airway eosinophilia effective amount. A dose of 0.5 to 1 mg/kg is administered
(see Chapter 20). Other tests may be indicated for individual orally q12h initially, with the dose doubled if signs are not
cats. controlled within 1 week. Once the signs are well controlled,
the dose is tapered. A reasonable goal is to administer
Treatment 0.5 mg/kg or less every other day. Although not ideal,
outdoor cats that cannot be treated frequently can be admin-
EMERGENCY STABILIZATION istered depot steroid products, such as methylprednisolone
The condition of cats in acute respiratory distress should acetate (10 mg/cat intramuscularly may be effective for up to
be stabilized before diagnostic tests are performed. Success- 4 weeks).
ful treatment includes administration of a bronchodilator, Glucocorticoids, such as fluticasone propionate (Flovent,
rapid-acting glucocorticoids, and oxygen supplementation. GSK), can also be administered locally to the airways by
Terbutaline can be administered subcutaneously—a route MDI, as is routine for treating asthma in people. Advantages
that avoids additional patient stress (see Box 21.4). Dexa- include minimal systemic side effects and relative ease of
methasone sodium phosphate (0.1 to 0.5 mg/kg) is admin- administration in some cats compared with pilling. Theoreti-
istered intravenously. If intravenous administration is too cal concerns about the oronasal deposition of the potent
stressful, it can be given subcutaneously or intramuscularly. glucocorticoid in cats, compared with people, include the
After the drugs are administered, the cat is placed in a cool, high incidence of periodontal disease and latent herpesvirus
stress-free, oxygen-enriched environment. If additional infections and the inability to effectively rinse the mouth
bronchodilation is desired, albuterol can be administered with water after use. Local dermatitis can be caused by mites,
by nebulization or MDI. Administration of drugs by MDI is dermatophytes, or bacteria. However, veterinarians have
described later in this section. (See Chapter 25 for further been using glucocorticoid MDIs to treat idiopathic feline
discussion of cats with respiratory distress.) bronchitis for many years without frequent, obvious adverse
effects.
ENVIRONMENT This author prefers to obtain a clinical remission of signs
The potential influence of the environment on clinical using an orally administered drug first, except in cats
signs should be investigated. Allergic bronchitis is diag- with relative contraindications for systemic glucocorticoid
nosed through the elimination of potential allergens from therapy, such as diabetes mellitus. Cats that require a rela-
the environment (see the section on allergic bronchitis). tively low dose of oral glucocorticoids to control clinical
However, even cats with idiopathic bronchitis can benefit signs, that have no noticeable adverse effects, and that can
from improvement in indoor air quality through the reduc- be pilled without difficulty are often well maintained with
tion of irritants or unidentified allergens. Potential sources oral therapy. Otherwise, once signs are in remission, treat-
of allergens or irritants are determined through careful ment by MDI is initiated and the dosage of oral prednisolone
owner questioning as described in the section on clinical gradually reduced.
features. Smoke can often aggravate signs through its local A spacer must be used for effective administration of
irritating effects. The effect of litter perfumes can be evalu- drugs by MDI to cats or dogs, and the airflow generated by
ated by replacing the litter with sandbox sand or plain clay the cat must be sufficient to activate the spacer valve. Spacers
litter. Indoor cats may show improvement in response to with masks specifically designed for use in cats or dogs are
measures taken to decrease the level of dusts, molds, and available (AeroKat and AeroDawg, Trudell Medical Inter-
mildew in the home. Such measures include carpet, fur- national, London, Ontario, Canada). This design includes a
niture, and drapery cleaning; cleaning of the furnace and plastic tab that moves with each breath, making it easier for
frequent replacement of air filters; and the use of an air the client to determine whether the cat is inhaling the drug.
cleaner. The American Lung Association has a useful Web The cat is allowed to rest comfortably on a table or in the
site with nonproprietary recommendations for improving client’s lap. The client places his or her arms on either side of
indoor air quality (www.lung.org). Any beneficial response the cat or gently steadies the cat’s neck and head to provide
to an environmental change is usually seen within 1 to restraint (Fig. 21.4). The MDI, attached to the spacer, is actu-
2 weeks. ated (i.e., pressed) twice. The mask is placed immediately on