Today's Veterinary Practice

NOV-DEC 2018

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CLINICAL INSIGHTS NOVEMBER/DECEMBER 2018 65 seizures could indicate noncardiogenic pulmonary edema, while wet lung at the site of blunt trauma may indicate pulmonary contusion or hemorrhage. The distribution of pulmonary changes is best assessed using survey thoracic radiographs, which should be used subsequent to Vet BLUE to evaluate the entire lung fields, pleural space, extrathoracic structures, cardiovascular structures, and mediastinum. Vet BLUE assessment of the pulmonary parenchyma involves the bilateral evaluation of 4 windows: the caudodorsal lung lobe region, the middle lung lobe region, the perihilar lung lobe region, and the cranial lung lobe region ( FIGURE 8 ). At each position, the transducer is oriented cranially so that the company logo on the image is to the viewer's left, between ribs, such that the pulmonary–pleural interface in association with the adjacent rib shadows resembles a partially submerged alligator with eyes peering above the water (referred to as the gator sign; FIGURE 7 ). Horizontally oriented hyperechoic A-lines are equidistant lines caused by reverberation artifacts of the lung margin, or reverberation artifact from the normal pulmonary–pleural interface ( FIGURE 7 ). The presence of A-lines in conjunction with a normal glide sign indicate normal, dry lung. Wet lung is indicated by the presence of B-lines, which are hyperechoic lines running perpendicular to A-lines that oscillate with respiration ( FIGURE 9 ). These lines are sometimes referred to as ultrasound lung rockets or ring-down artifact. Etiologies for the presence of B-lines by distribution are listed in TABLE 1 . Assessing for Pericardial Effusion and Tamponade The probe position for identifying pericardial effusion has been described as the pericardial site: ventrolateral along the thoracic wall, within the 5th to 6th intercostal spaces, bilaterally ( FIGURES 6 AND 10 ). 4 Pericardial effusion appears as anechoic or echogenic material surrounding the ventricular and/or atrial free walls, bordered by a thin curvilinear echogenic structure representing the pericardium ( FIGURE 10 ). If a large volume of effusion (accumulated over a long time) or a small volume of effusion (accumulated over a short time but creating elevated intrapericardial pressure) is present within the pericardial sac, cardiac tamponade might be present. Tamponade is characterized by collapse or inward motion of the right ventricular and right atrial free wall throughout the cardiac cycle, particularly during early diastole, when pericardial pressures exceed intracardiac pressures. If pericardial effusion is identified in a hemodynamically unstable patient (e.g., cardiac tamponade), ultrasound- guided pericardiocentesis is indicated. Scant pericardial effusion may not be immediately life threatening but always warrants further investigation. Focused Echocardiography With appropriate training and practice, focused echocardiography can aid the emergency clinician in early identification of functional or structural cardiac disease. Full descriptions of specific TABLE 1 Considerations for B-lines (Wet Lung) by Distribution CONSIDERATION AFFECTED AREA Cardiogenic pulmonary edema Perihilar lung lobe region (dog); variable (cat) Noncardiogenic pulmonary edema Caudodorsal lung lobe region Aspiration pneumonia Middle and cranial ventral lung lobe regions Contusion Variable/associated with trauma AFAST and TFAST require limited anatomic study, and nonradiologist veterinarians can achieve proficiency with training.

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