Today's Veterinary Practice

NOV-DEC 2015

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Today's VeTerinary PracTice | november/december 2015 | tvpjournal.com aPProach To resPiraTory disTress Peer reviewed 58 (30–50 mg/kg IV Q 6 H) or ticarcillin + clavulanate (50 mg/ kg IV Q 6 H) » Dual therapy with a beta-lactam antimicrobial (eg, ampicillin, 30–50 mg/kg IV Q 6 H) and enrofoxacin (5 mg/kg IV Q 24 H in cats; 10–20 mg/kg IV Q 24 H in dogs) » Other antibiotic choices may also be appropriate but are beyond the scope of this article. • Interstitial lung disease: These conditions are challenging to treat; some are steroid responsive • Pulmonary neoplasia: Management depends on type, location, and whether neoplasia is primary versus metastatic; surgery, chemotherapy, and radiation therapy are all considerations. PULMONARY THROMBOEMBOLISM Etiology \Causes of PTE are the same as for any thromboembolic disease— essentially abnormalities in Virchow's triad, which include abnormalities of blood fow (turbulence or stasis), endothelial damage, and hypercoagulability. With PTE, it is critical to identify and treat the underlying disease if it is not immediately apparent, so as to reduce the risk of further thromboembolic events. Theoretically, any systemic infammatory state can result in a systemic pro-coagulant state that predisposes the patient to PTE. Table 4 lists diseases and conditions known to predispose veterinary patients to hypercoagulability. 8 Clinical Signs & Diagnostic Approach Diagnosis of PTE can be challenging. While thoracic radiographs may be normal, indications of PTE include (Figure): • Degree of respiratory distress out of proportion with changes on radiographs (ie, a patient in severe respiratory distress with minimal abnormalities on thoracic radiographs) • Demonstration of focal hypolucency or vessel truncation • Evidence of main pulmonary artery and/or right heart enlargement due to pulmonary hypertension, a result of significant PTE. Echocardiography is also a useful diagnostic modality in cases of suspected PTE as it can document pulmonary hypertension that often occurs secondary to PTE; detect right-sided cardiomegaly and main pulmonary artery dilation; and may allow visualization of a thrombus in the main pulmonary artery. Advanced imaging, such as CT angiography or, less commonly, a ventilation/perfusion lung scan with nuclear scintigraphy, are required to confrm the diagnosis. 8,9 Stabilization & Management Stabilization involves oxygen supplementation, and treatment requires anticoagulant drugs as well as addressing the underlying disease. Therapies that can be used include: • Anticoagulants (unfractionated or low-molecular-weight heparin) and/or antiplatelet drugs (eg, clopidogrel) reduce risk of further thrombus formation. Although the ideal antithrombotic strategy for dogs and cats with PTE is unknown, it is reasonable to combine low- molecular-weight heparin (eg, dalteparin, 150 U/kg SC Q 12 H) with clopidogrel (approximately 2 mg/kg PO Q 24 H in dogs; 18.75 mg/day in cats). Dalteparin dosing should ideally be monitored by assessment of anti-Xa activity. • Thrombolytic therapies, such as tissue plasminogen activator (tPA), can also be administered; however, systemic administration of tPA is limited by adverse effects. • Sildenafl is often beneficial TABLE 4. Diseases & Conditions That Predispose Veterinary Patients to Hypercoagulability DISEASES Cardiac disease Disseminated intravascular coagulation Heartworm disease Hyperadrenocorticism Immune-mediated hemolytic anemia Neoplasia Protein-losing enteropathy Protein-losing nephropathy Sepsis CONDITIONS Exogenous corticosteroid administration Indwelling IV catheters FIGURE. Thoracic radiograph demonstrating focal hypolucency in the right middle and caudal lung lobes associated with pulmonary thromboembolism; main pulmonary artery enlargement is also evident. Courtesy Dr. Carol Reinero

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