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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice aPProach To resPiraTory DisTress Peer reviewed 57 PULMONARY PARENCHYMAL DISEASE Etiology Pulmonary parenchymal diseases affect the terminal and respiratory bronchioles, interstitium, alveoli, and vasculature. These diseases include pneumonia, pulmonary edema, interstitial lung disease, pulmonary neoplasia, and others. Examples of pulmonary parenchymal diseases are listed in Table 3. Clinical Signs Characteristic signs in an animal with pulmonary parenchymal disease often include abnormally loud breathing sounds on thoracic auscultation, such as harsh lung sounds, crackles, and wheezes. Patients with cardiogenic pulmonary edema may also have obvious cardiac abnormalities on auscultation, such as a murmur or arrhythmia. 5 Animals with infectious causes of pulmonary parenchymal disease (eg, pneumonia) may have a fever; however, fever has only been reported in about ¹⁄ 8 of dogs and ¼ of cats with pneumonia, making it an unreliable abnormality. 6 Initial Stabilization Initial stabilization and therapy usually involve: • Oxygen supplementation: See recommendations in the Initial Stabilization section (page 53) • Diuretic: Depending on index of suspicion for cardiogenic pulmonary edema, a furosemide trial dose may be administered (typically, 2–4 mg/kg IV, IM) • Antibiotics: If there is a high index of suspicion for pneumonia (eg, history of vomiting, regurgitation, fever), the patient should begin receiving broad spectrum empiric antibiotics as soon as possible. 7 Diagnostic Approach Once the patient is stable, if cardiogenic pulmonary edema is suspected, frstline diagnostics should include: • Thoracic radiographs • Echocardiography. When it is unclear whether the etiology is primary cardiac versus primary respiratory disease, other diagnostics can be performed, including: • Measurement of serum NT-pBNP (aminoterminal pro B-type natriuretic peptide)—a biomarker associated with atrial stretch, which is increased in dogs and cats with clinically significant heart disease; in cats, this test can be performed in a point-of-care fashion but, in dogs, is only available as a reference laboratory test at this time. • Airway cytology (depending on radiographic abnormalities identified). Further diagnostics for interstitial lung disease may include: • Thoracic CT • Lung biopsy. If a solitary lung mass is identifed close to the chest wall, percutaneous fne needle aspiration or biopsy may be an ideal diagnostic modality. Additionally, surgical removal via lung lobectomy may be both diagnostic and therapeutic. Management Treatment for pulmonary parenchymal diseases depends entirely on the underlying disease. However, regardless of the underlying cause, judicious fuid therapy is usually appropriate to prevent exacerbation of extravascular lung water and potential diffusion impairment. Intravenous fuid therapy is generally absolutely contraindicated in animals with heart failure; rather, diuretic therapy is a mainstay of treatment. Specifc therapeutic approaches include: • Cardiogenic pulmonary edema: Diuretic therapy and other cardiac drugs • Microbial pneumonia: Antimicrobial administration and supportive care; adjunct therapies, such as nebulization and coupage, may be considered. Empirical antimicrobial drug choices depend somewhat on patient stability. Animals that present in respiratory distress generally warrant broad spectrum coverage with parenterally administered antibiotics, such as: » Monotherapy with a potentiated aminopenicillin, such as ampicillin + sulbactam Table 3. Classifcation & Examples of Pulmonary Parenchymal Diseases CLASSIFICATION EXAMPLES Pneumonia • Infectious (viral, bacterial, parasitic, fungal) • Aspiration Pulmonary edema • Cardiogenic • Noncardiogenic Interstitial lung diseases • Idiopathic pulmonary fbrosis • Eosinophilic bronchopneu- mopathy • Heartworm disease Pulmonary neoplasia • Primary • Metastatic Traumatic pulmonary parenchymal injury • Pulmonary contusions