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the most challenging issue because it needs to be tailored to the individual patient. Too high of a dose can have deleterious effects on renal perfusion and electrolytes, especially in a dog or cat with hypotension. Conversely, too low of a dose can lead to unnecessary hospitalization, expense, and potential euthanasia because of refractory or recurrent pulmonary edema. Additionally, in patients with severely decompensated HF, the best route of administration is IV because of its quicker onset of action and more predictable bioavailability.42 The current debate about furosemide in human medicine is on the use of repeated bolus dosing versus continuous rate infusions (CRI).43, 44, 45 The author uses a combination of repeat bolus dosing and CRIs to manage hospitalized patients with decompensated HF (see Table 5). The combination of a furosemide bolus followed by a CRI may have a better diuretic effect.45 The initial emergency furosemide dose is usually higher than the discharge dose, and the best dose to administer chronically is the lowest effective dose. Generally, renal parameters and electrolytes are reevaluated with 1 to 3 days in inpatients with HF and 3 to 7 days in outpatients with HF. Another loop diuretic of possible use in acute severe refractory canine HF is torsemide (Demadex).46 Torsemide has a longer duration of action, decreased susceptibility to diuretic resistance, and adjunctive aldosterone antagonist properties compared with furosemide. Generally, the torsemide dosage is one-tenth of the daily furosemide dosage divided into twice-daily oral dosing. In addition to furosemide, in patients with severely dyspneic HF, the addition of either nitroglycerin (Nitro-Bid ointment) or nitroprusside (Nitropress) is recommended because of their vasodilator actions. Nitroglycerin, a venodilator, is commonly used in a transdermal formulation in veterinary medicine. Nitroprusside, a potent IV venous and arterial vasodilator, is given by a variable dosage, starting at a low dosage of 1 or 2 ug/kg/min in dogs and even lower in cats (0.5 mcg/kg/min) and titrating upward based on blood pressure, targeting a mean blood pressure of 70 mm Hg or systolic blood pressure of 90 to 100 mm Hg.47 Because of its potent vasodilatory effects, direct arterial blood pressure monitoring is recommended; however, if an arterial catheter cannot be placed (eg, smaller dogs and cats), continuous indirect blood pressures (eg, Doppler) should be measured. Other vasodilators useful in the management of HF include amlodipine (Norvasc), sildenafil (Viagra), and angiotensin-converting enzyme inhibitors (ACE-I), specifically enalapril (Vasotec) or benazepril (Lotensin). Many previous studies in dogs have shown that ACE-I improve survival and quality of life in dogs with congestive HF secondary to both DCM and MVD.48, 49, 50 Although the two ACE-I are very similar, benazepril is less dependent on renal clearance. The benefit of ACE-I seems to involve more than just their vasodilator effects. It is proposed that the inhibition of the local renin-angiotensin-aldosterone system may protect the myocardium from deleterious remodeling effects. Although enalapril has been shown to reduce pulmonary venous pressures acutely in HF,51 ACE-I are typically withheld in the peracute management of severely decompensated HF because of the possibility of lowering intrarenal perfusion and the glomerular filtration rate. ACE-I should also be used cautiously in any patient with HF with concurrent azotemia by either dose reduction or withholding ACE-I if creatinine is greater than 2.0 g/dL. ACE-inhibition is recommended in the chronic management of all patients with HF (cats and dogs) once patients are stable and eating. After the initiation of an ACE-I, reevaluation of serum urea nitrogen, creatinine, and electrolytes is recommended in 3 to 7 days. Sildenafil is a useful adjunctive vasodilator in the setting of symptomatic and severe pulmonary hypertension and in refractory HF associated with pulmonary hypertension.52, 53 Sildenafil is a phosphodiesterase inhibitor with greater affinity for certain vascular beds, including the pulmonary arteries. Because sildenafil is now available in a generic formulation in the United States, it can be a realistic option financially. Amlodipine, a calcium channel blocker, acts primarily as an arterial vasodilator. Amlodipine can also be used in patients with refractory or recurrent congestive HF, especially if systolic blood pressure is maintained or high (eg, >120 mm Hg systolic). Amlodipine is especially helpful in dogs with severe refractory HF caused by MVD. The most important recent advancement in HF management is the addition of an inodilator, pimobendan (Vetmedin). Pimobendan has a dual mechanism of action; therefore, it is labeled as an inodilator. Specifically, it is a calcium-sensitizing drug that improves contractility (positive inotrope) with minimal effects on myocardial oxygen consumption. The other mechanism of action is phosphodiesterase inhibition, primarily leading to a balanced vasodilation (arterial and venous).54 The favorable pharmacokinetic and pharmacodynamic actions of pimobendan make it essential in the management of most canine HF and possibly feline HF. Several prospective canine studies and one retrospective feline study have shown improved survival and quality of life with pimobendan either in combination or compared with ACE-I and furosemide.55, 56, 57 In addition to its Food and Drug Administration–labeled indications for the management of HF secondary to canine DCM and MVD, it is also used to manage dogs with HF from other causes, such as heartworm disease, primary or secondary pulmonary hypertension with secondary right HF, infectious endocarditis, and some congenital heart diseases.58 The role of pimobendan in feline HF is still evolving. Although not licensed for use in cats (or humans in the United States), pimobendan is being used more frequently in the management of feline HF. Pimobendan is typically added when a cat with HF has left ventricular systolic dysfunction identified echocardiographically, significant pleural effusion, renal insufficiency, or severe refractory pulmonary edema. There are