Today's Veterinary Practice

SEP-OCT 2015

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TOday'S VeTerinary PracTice | September/October 2015 | tvpjournal.com TOday'S TecHnician Peer reviewed 72 Electrocardiography electrocardiography (ecG) can also be a useful diagnostic tool, especially when determining the presence of cardiac tamponade. • Low-voltage (small) QrS complexes are common. reduced voltage can also be caused by pneumothorax, emphysema, and infiltrative myocardial disease. 5 • electrical alternans occurs when the size or configuration of the QrS complex, and occasionally the T wave, changes beat-to-beat. This ecG finding may suggest a large volume of pericardial effusion, and results from the heart moving back and forth within the pericardium (Figure 4). • Sinus tachycardia is common in cardiac tamponade; while less frequent, atrial or ventricular tachyarrhythmias may occur as well. 2 MANAGEMENT Pericardiocentesis When cardiac tamponade is present, immediate pericardiocentesis is indicated. reduction of pericardial pressure by removal of fuid results in greater cardiac output and a decreased heart rate, which should improve the clinical condition of the patient. diuresis—which takes place after cardiac tamponade is relieved—typically resolves any ascites. if ascites is severe, it can be removed to make the patient more comfortable and relieve ventilatory compromise. 6 To assist with performing pericardiocentesis, the veterinary technician: • Positions the patient in left lateral recumbency (procedure ideally performed on right side) • Provides sedation with a benzodiazepine and opioid, if necessary • can provide oxygen supplementation via flow by or mask • Places a peripheral iV catheter in the cephalic vein (Table 3 ) • Shaves and scrubs a square over the fourth and fifth intercostal space, where the cardiac apex beat is palpated • Watches the ecG to monitor for any arrhythmias while the procedure is being performed; a critical component to the process. Once pericardiocentesis has been performed, signs associated with right-sided congestive heart failure tend to subside very quickly. When pericardial effusion is secondary to diseases causing congestive heart failure, congenital malformations, or hypoalbuminemia, the patient often improves once the underlying condition has been treated. 3 complications of pericardiocentesis include cardiac injury or puncture resulting in arrhythmias, pneumothorax or hemorrhage due to lung laceration, coronary artery laceration, and potential for dispersion of infection or neoplastic cells into the pleural space. 5 Pericardiectomy When pericardial effusion recurs after one or more pericardiocentesis procedures, pericardiectomy can be considered. Traditionally, median sternotomy and right lateral thoracotomy are pursued. Open thoracotomy allows: • complete removal of the pericardium below the level of the phrenic nerve • accurate identification of masses arising from the right atrium • excision of the right auricular appendage when a mass is isolated to that area of the heart. Thoracoscopic pericardiectomy is an alternative method, with a lower morbidity rate than traditional thoracotomies. However, the inability to visualize the right atrium as a whole is a disadvantage of this technique. Percutaneous Balloon Pericardiotomy a minimally invasive option is available: the application of percutaneous balloon pericardiotomy in which a balloon catheter is inserted percutaneously into the pericardial sac and infated until it tears the pericardium, resulting in drainage of pericardial fuid into the pleural cavity. TABLe 3. equipment needed for Pericardiocentesis 14–18 gauge polypropylene catheter 3-way stopcock 2% lidocaine Clippers Collection vessel EDTA and plain test tubes Intravenous extension set Large syringes (appropriately suited for patient size) Scalpel blade Scrub Sterile gloves FIGURE 4. Electrocardiogram demonstrating electrical alternans, in which the height of the QRS complex alternates with each beat due to the heart swinging within the pericardium. This fnding is rate dependent and more commonly seen at a normal heart rate.

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