Page 543 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Fluid and Diuretic Therapy in Heart Failure 531

prescribe carvedilol (starting at 0.1 mg/kg q12h PO and (DHA). Nutraceuticals, such as taurine or L-carnitine,
up-titrating every 2 to 4 weeks to 0.6 mg/kg q12h PO). may be indicated for selected patients 83 with dilated car-
These dosages are well tolerated in “preclinical” disease. diomyopathy (consult a cardiologist).
However, once CHF is evident, initiating ß-blocker ther- Home management of cats with progressive CHF or
apy is contraindicated until failure is well controlled and recurrent pulmonary edema or pleural effusion secondary
dogs taking carvedilol may require a dosage reduction. to cardiomyopathy generally includes furosemide (1 to
Use of these drugs in established CHF is best monitored 2 mg/kg orally every 24 hours or every 12 hours) and
in consultation with a cardiologist. Finally, we do not rou- enalapril or benazepril (0.25 to 0.5 mg/kg every 24
tinely use ß-blockers in small breed dogs at any stage of hours to every 12 hours orally). Spironolactone
valvular heart disease. (6.25 mg orally every 24 hours) also can be added to
Thus the typical home therapy of CHF in dogs the treatment plan. Digoxin (one fourth of a 0.125-mg
includes administration of an ACE inhibitor (generally tablet orally every 48 hours) rarely is used in cats today.
enalapril or benazepril 0.25 to 0.5 mg/kg orally every Once the cat with CHF is stabilized, a cardiologist should
12 hours), furosemide (2 to 6 mg/kg orally every 12 be consulted regarding other drug options, including
to 8 hours), pimobendan (0.2 to 0.3 mg/kg orally every inodilators such as pimobendan, which can provide clini-
12 hours), and spironolactone (2 mg/kg/day orally as cal benefit in some cats with chronic cardiac failure.
7
one dose or in two divided doses). Digoxin (0.005 to
0.0075 mg/kg orally every 12 hours) is reserved for cases REFRACTORY EDEMA AND
with atrial fibrillation or end-stage CHF), with contrain- EFFUSIONS
dications including complex ventricular ectopy, moderate Some patients become refractory to diuretic therapy and
142
azotemia, or sinus node dysfunction. Once CHF is well continue to develop edema or effusions. Three com-
controlled, an up-titration of carvedilol can be considered monly encountered examples of this problem are (1) pro-
in selected cases as discussed above. Importantly, the neg- gressive ascites and pleural effusion in dogs with
ative inotropic effects of carvedilol and other b-blockers biventricular heart failure, (2) progressive pleural effusion
can worsen CHF and these drugs should not be given in cats with cardiomyopathy, and (3) recurrent pulmo-
to “wet” patients. Additionally, the dosage may need to nary edema in dogs with left-sided heart failure. Success-
be reduced if fluid retention worsens despite diuretic ful therapy of some of these patients may be attained by
and inotropic therapy. When CHF is complicated by atrial skillful use of cardiac medications 110 and by addressing
fibrillation, digoxin should be given along with diltiazem the following points:
(starting at 1.5 mg/kg orally daily in two divided doses • Ensure medication compliance, and educate the client
(for the long-acting drug) or three divided doses (for about medications, dosages, and methods of
the standard drug). The total daily dosage can be administration.
increased to a maximum of about 6 mg/kg orally to gain • Consistently enforce a restricted or low-sodium diet.
heart rate control of 100 to 150 beats/min in the hospi- • Enforce rest.
tal. A b-blocker may also help in control of ventricular • Optimize current medication dosages (to full
rate response. Both diltiazem and b-blockers are negative recommended dosages).
inotropes and must be used carefully in CHF. A serum • Improve left-sided heart function with an additional
digoxin concentration is measured after 1 week of treat- afterload reducer such as amlodipine.
ment (trough target concentration of 0.9 to 1.2 ng/mL), • Reduce the dosage of any negative inotropic drugs,
and the dosage of diltiazem adjusted to control heart rate. such as b-blockers or diltiazem.
When severe pulmonary hypertension leads to clinical • Adjust the dosage or route of administration of
signs such as exertional collapse, the phosphodiesterase- furosemide.
V inhibitor sildenafil is added to the treatment regimen • Consider using combination diuretic therapy.
(1 to 3 mg/kg q12h PO). Finally, amlodipine may be • Identify and treat extracardiac complications such as
used for treatment of concurrent hypertension that is hyperthyroidism, anemia, and hypertension.
unresponsive to an ACE-inhibitor and diuretic. Vasodila- • Consult with a cardiologist.
tor drugs such as amlodipine and hydralazine may activate The first three points are straightforward but by no
the RAAS 61 and can lead to additional fluid retention. means easy to achieve. With progressive CHF, the sodium
Dietary measures in treatment of CHF are often intake should be progressively limited unless the patient is
overlooked. Low sodium diets may be beneficial in dogs hyponatremic. Periods of enforced rest are useful in
with CHF. 144 Other dietary measures may be considered. mobilizing edema and decreasing cardiac work. Rest alone
The addition of omega-3 fatty acids found in fish oil may canleadtoconsiderablediuresisinpatients withright-sided
inhibit proinflammatory cytokines and reduce cardiac CHF. The remaining guidelines require some explanation.
cachexia. 50 Typical dosages are 30 to 40 mg/kg orally Modifying the diuretic dosage may be necessary, espe-
daily for eicosapentaenoic acid (EPA) and 20 to cially in dogs with chronic renal failure, in those that
25 mg/kg orally daily for docosahexaenoic acid develop severe polydipsia, and in those with apparent