Today's Veterinary Practice

MAY-JUN 2018

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27 MAY/JUNE 2018 ‚óŹ TVPJOURNAL.COM CONTINUING EDUCATION is an oxygen cage with the ability to vary the oxygen content and control temperature. Oxygen cages have the additional benefit of reducing activity, hence reducing oxygen use by the muscles. However, some larger dogs can become hyperthermic in small oxygen cages. If an oxygen cage is not an option, flow-by oxygen, masks, and nasal prongs may be used. In dogs with a diagnosis of acute congestive heart failure, oxygen should be used in conjunction with a potent loop diuretic, such as furosemide. Ideally, an intravenous catheter is placed and furosemide is given IV. If the patient is too unstable, furosemide can be administered IM and the patient returned to the oxygen cage, pending improvement. Exact doses depend on the severity of the presenting signs; furosemide 2 to 4 mg/kg IV or IM is used initially. Response to treatment should be closely monitored over the next 1 to 2 hours.1 Ideally, after 1 hour, the respiratory rate and effort should start to decline; however, some severely affected dogs require several doses before improvement is noted. However, if the patient has not responded after oxygen and furosemide have been administered, referral consultation with a specialist should be considered. Close monitoring of respiratory rate is a noninvasive way to tailor diuretic therapy. The production of large amount of dilute urine is an encouraging sign that furosemide is having an effect. If there is no improvement, the dose can be repeated as a bolus, or the patient can be placed on a constant- rate infusion (CRI). CRI doses of furosemide 0.6 to 1 mg/kg/hr IV have been suggested; this high dose should be carefully monitored and decreased by 50% as the patient improves, or major electrolyte disturbances will be seen.1 Pimobendan should also be administered as soon as CHF is diagnosed. This inodilator causes vasodilation via phosphodiesterase 3 inhibition and augments contractility of the heart, supporting the failing heart by promoting calcium binding to troponin C within the cardiomyocyte. Left atrial pressure declines with pimobendan in experimental models and likely in the clinical setting.2 If the patient appears stressed as a result of dyspnea, opioids can be beneficial to reduce anxiety and provide mild sedation. This must be balanced against the potential to depress the respiratory centers. Butorphanol at 0.1 to 0.2 mg/kg IV or IM is often used. Second-Line Options Following these treatments, the next parameter to evaluate is blood pressure. Due to the sympathetic drive, these patients may be normo- or hypertensive, and this afterload is an extra burden on the failing myocardium. If the patient is hypertensive, arterio dilators can be used to decrease the afterload for dogs with severe mitral regurgitation to achieve a systolic blood pressure of about 100 mm Hg. FIGURE 1. (A) Lateral and (B) dorsoventral thoracic radiographs of an 8-year-old Doberman pinscher with DCM in CHF. Note the cardiomegaly with a straightened caudal border, prominent left atrium, and tracheal elevation. There is a diffuse alveolar/interstitial pattern in the lung fields with air bronchograms and dilated pulmonary veins. A B

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