Page 100 - Small Animal Internal Medicine, 6th Edition

72 PART I Cardiovascular System Disorders

sustained-release preparations may be useful, but they have Dietary changes are best instituted gradually and when
not been systematically evaluated in small animals. Trans- the patient is not in acute CHF; for example, mix the new
VetBooks.ir dermal patches (0.2 mg/h [5 mg/24 h] nitroglycerin trans- with the old diet in a 1 : 3 or 1 : 4 ratio for several days, then
gradually increase the proportion of new diet over a week or
dermal system), applied for 12 hours per day, have been used
with anecdotal success in large dogs. Large doses, frequent
some areas can contain high sodium concentrations. This
application, or long-acting formulations are most likely to be so until the new diet alone is being fed. Drinking water in
associated with drug tolerance. Whether intermittent treat- might become important for animals with end-stage CHF
ment (with drug-free intervals) prevents nitrate tolerance that is difficult to control. Nonsoftened water or (where
from developing in dogs and cats is unknown. Isosorbide water from the public water supply contains > 150 ppm of
dinitrate and mononitrate are orally administered nitrates. sodium) distilled water can be recommended to further
Their efficacy in dogs is unknown. They occasionally have decrease salt intake. Supplementation of specific nutrients is
been used in refractory (stage D) heart failure or in combina- important in some cases (discussed later).
tion with an arteriolar dilator for patients unable to tolerate Inappetence is a common problem with advanced heart
an ACEI. failure, even though energy needs are increased. Fatigue,
increased respiratory effort, azotemia, adverse medication
DIETARY CONSIDERATIONS effects (including digoxin toxicity), and low diet palatability
A good-quality diet with adequate calories and protein, as all can contribute to poor appetite. At the same time, poor
well as moderate salt restriction, is recommended for most splanchnic perfusion, bowel and pancreatic edema, and sec-
patients with chronic heart failure. Progressive weight loss ondary intestinal lymphangiectasia may reduce nutrient
can be problematic, especially as heart failure advances, so absorption and promote protein loss in advanced CHF.
diet palatability and calorie content are important. Protein Hypoalbuminemia and reduced immune function may
restriction is not recommended unless there is concurrent develop. Such factors, as well as renal or hepatic dysfunction,
renal disease. Heart failure can interfere with the kidney’s also can alter the pharmacokinetics of certain drugs.
ability to excrete sodium and water loads. Therefore moderate Strategies that can help improve appetite include warming
dietary salt restriction is recommended to help control fluid the food to enhance its flavor, adding small amounts of more
accumulation. However, very low salt intake can increase palatable human foods (e.g., nonsalted meats or gravy, low-
RAAS activation. It is unclear whether reduced-salt intake is sodium soup) or canned reduced-sodium cat food. Sprin-
necessary before overt CHF develops; however, at minimum, kling on a salt substitute (KCl) or garlic powder, handfeeding,
refraining from feeding the patient high-salt table scraps or and providing small quantities of the diet several times a day
treats is prudent. High-salt foods include processed meats, also can help. In some cases, a drug with appetite-stimulating
canned fish, cheese, canned vegetables and soups, breads, properties (such as mirtazapine or capromorelin, or cypro-
salty processed snack foods, as well as many dog treats. heptadine for cats) might help, although their effects in
A moderate degree of salt restriction entails a sodium patients with CHF are not well reported.
intake of about 30 mg/kg/day (about 0.06% sodium for Cardiac cachexia is the syndrome of progressive muscle
canned food or 210-240 mg/100 g of dry food). Although wasting as well as fat loss associated with advanced chronic
diets for senior animals or those with renal disease usually CHF. Increased energy requirements, metabolic abnormali-
provide this level of salt, their protein restriction is a draw- ties, and reduced food intake are contributing factors. Cardiac
back for many cases. Supplementing with additional protein cachexia usually is identified only after CHF develops and
(such as hard-boiled eggs or cooked chicken) is a strategy. becomes most evident in cases with more chronic, refrac-
Other commercial diets that provide reduced-salt, adequate tory heart failure. It is seen in dogs more often than cats,
protein, and omega-3 fatty acid (FA) supplementation are especially those with right-sided CHF signs and/or DCM.
available (including Royal Canin Veterinary Diet Canine Muscle loss over the spine and gluteal region usually is noted
Early Cardiac, Hill’s Prescription Diet j/d, Purina Veterinary first. Weakness and fatigue occur with loss of lean body
Diets JM Joint Mobility, or Purina’s CV Cardiovascular mass; cardiac mass also can be affected. Cardiac cachexia is
Feline Formula); a good source for additional information thought to be a predictor of poor survival. It also is associated
and updates can be found at www.tufts.edu/vet/heartsmart. with reduced immune function in people. The pathogen-
Prescription cardiac diets (such as Hill’s Prescription Diet esis of cardiac cachexia involves multiple factors, especially
h/d) usually have greater sodium restriction (e.g., 13 mg proinflammatory cytokines, TNF α , and interleukin-1. These
sodium/kg/day, or about 90-100 mg sodium/100 g of dry substances suppress appetite and promote hypercatabolism.
food, or 0.025% sodium in a canned food), but also can have Dietary supplementation with fish oils, which are high in
more protein restriction. Although possibly helpful in man- omega-3 fatty acids (eicosapentaenoic [EPA] and docosa-
aging refractory CHF, an additional protein source may be hexaenoic [DHA] acids) can reduce cytokine production,
needed. Severe sodium restriction (e.g., 7 mg/kg/day) can may improve endothelial function, and appear to have
exacerbate NH activation and contribute to hyponatremia. antiarrhythmic effects, among other benefits. Oral doses of
Recipes for homemade low-salt diets are available but pro- 40 mg/kg/day EPA and 25 mg/kg/day DHA have been sug-
viding balanced vitamin and mineral content may be gested. Over-the-counter fish oil capsules containing 180 mg
difficult. EPA and 120 mg DHA in each 1-g capsule can be used at a