Page 410 - Small Animal Internal Medicine, 6th Edition

382 PART II Respiratory System Disorders

decrease bronchoconstriction. In combination with oxygen, be useful. The diagnosis and treatment of bacterial and aspi-
they are the treatment of choice for cats with signs of bron- ration pneumonia are described in Chapter 22.
VetBooks.ir chitis (see Chapter 21). Subcutaneous terbutaline (0.01 mg/ may be necessary to intubate the patient and institute
If the dog or cat does not respond to this management, it
kg, repeated in 5 to 10 minutes if necessary) or albuterol
administered by metered dose inhaler (MDI) is most often
lished and specific therapy initiated.
used in emergency situations. Due to the airway obstruc- positive-pressure ventilation until a diagnosis can be estab-
tion, drug administered by MDI may not penetrate into
deeper airways and often must be repeated numerous times PLEURAL SPACE DISEASE
before an effect is seen. Heart rate is used to monitor for Pleural space diseases cause respiratory distress by prevent-
toxicity. Bronchodilators are described in greater detail in ing normal lung expansion. Animals presenting in respira-
Chapter 21. tory distress as a result of pleural space disease typically have
Diuretics such as furosemide (2 mg/kg, administered a markedly increased respiratory rate (see Table 25.2). Rela-
intravenously) are indicated for the management of pulmo- tively increased inspiratory efforts may be noted but are not
nary edema. If edema is among the differential diagnoses of always obvious. Decreased lung sounds on auscultation dis-
an unstable patient, a short trial of furosemide therapy is tinguish patients with tachypnea caused by pleural space
reasonable. However, potential complications of diuretic use disease from patients with tachypnea caused by pulmonary
resulting from volume contraction and dehydration should parenchymal disease. Increased abdominal excursions
be taken into consideration. Continued use of diuretics is during breathing may be noted.
contraindicated in animals with exudative lung disease or Paradoxical breathing refers to a breathing pattern in
bronchitis because systemic dehydration results in drying of which the abdominal walls are “sucked in” during inspira-
airways and airway secretions. Mucociliary clearance of tion. Paradoxical breathing has been associated with pleural
airway secretions and contaminants is decreased, and airways diseases in dogs and cats presented for respiratory distress
are further obstructed with mucus plugs. (LeBoedec et al., 2012). The authors of this study attribute
Glucocorticoids decrease inflammation. Injectable for- the paradoxical breathing to decreased inhibition of con-
mulations such as dexamethasone (0.1 to 0.5 mg/kg, admin- traction of the intercostal muscles secondary to increased
istered intravenously) are indicated for animals in severe pleural pressure. The reported sensitivity and specificity of
respiratory distress caused by the following conditions: idio- the finding as a predictor of pleural disease were 0.67 and
pathic feline bronchitis, thromboembolism after adulticide 0.83 in dyspneic dogs, and 0.90 and 0.58 in dyspneic cats,
treatment for heartworms, allergic bronchitis, pulmonary respectively.
parasitism, and respiratory failure soon after initiation of Most patients in respiratory distress resulting from
treatment for pulmonary mycoses. Animals with other pleural space disease have pleural effusion or pneumothorax
inflammatory diseases or acute respiratory distress syn- (see Chapter 23). Other differential diagnoses are diaphrag-
drome (ARDS) may respond favorably to glucocorticoid matic hernia and mediastinal masses. If pleural effusion or
administration. The potential negative effects of corticoster- pneumothorax is suspected to be causing respiratory dis-
oids must be considered before their use. For example, the tress, needle thoracocentesis (see Chapter 23) should be
immunosuppressive effects of these drugs can result in exac- performed immediately before further diagnostic testing is
erbation of an infectious disease. Although the use of short- conducted or any drugs are administered. Where available,
acting corticosteroids for acute stabilization of such cases ultrasonography can be used for rapid, minimally stressful
probably will not greatly interfere with appropriate antimi- assessment of the pleural space for fluid or air. The acronym
crobial therapy, long-acting agents and prolonged adminis- for the examination is TFAST, which stands for thoracic
tration should generally be avoided. Glucocorticoid therapy focused assessment with sonography for trauma. See the
potentially interferes with the results of future diagnostic Lisciandro (2011) reference for probe positions and charac-
tests, particularly if lymphoma or eosinophilic disease are teristic sonographic signs. Oxygen can be provided by mask
differential diagnoses. Appropriate diagnostic tests are per- while thoracocentesis is performed, but successful drain-
formed once the patient can tolerate the stress. age of the pleural space will quickly improve the animal’s
Broad-spectrum antibiotics are administered if there is condition. Occasionally, emergency placement of a chest
evidence of sepsis (e.g., fever, neutrophilic leukocytosis with tube is necessary to evacuate rapidly accumulating air (see
left shift, moderate to marked toxicity of neutrophils) or a Chapter 23).
high degree of suspicion of bacterial or aspiration pneumo- As much fluid or air should be removed as possible. The
nia. Note that airway specimens (usually tracheal wash) exception is for animals with acute hemothorax. Hemotho-
should be obtained for culture if at all possible before broad- rax is usually the result of trauma or rodenticide intoxica-
spectrum antibiotics are initiated to confirm the diagnosis of tion. The respiratory distress associated with hemothorax is
bacterial infection and to obtain susceptibility data. Speci- often the result of acute blood loss rather than an inability
mens obtained after antibiotics are initiated may not be diag- to expand the lungs. In this situation, as little volume as is
nostic, even with continued progression of signs. However, needed to stabilize the animal’s condition is removed. The
airway sampling may not be possible in these unstable remainder will be reabsorbed (autotransfusion) to the benefit
patients. If sepsis is suspected, blood and urine cultures may of the animal. Aggressive fluid therapy is indicated.