Page 727 - Small Animal Clinical Nutrition 5th Edition

754 Small Animal Clinical Nutrition

azotemia during the first five weeks of treatment; one of these
Box 36-1. Palatability of Low-Salt Foods.
VetBooks.ir dogs developed clinical signs of uremia (Roudebush et al,
1994). Two of the dogs that developed severe azotemia had
The question often arises whether sodium chloride enhances
palatability of foods for dogs and cats. Sodium chloride and isosthenuria on the initial urinalysis, which suggested some
degree of pre-existing renal insufficiency. Azotemia is a more
other inorganic salts stimulate specific taste chemosensory frequent complication when canine heart failure is treated with
neural groups in these species. This finding suggests that dogs furosemide and enalapril rather than with furosemide alone
and cats can indeed taste sodium chloride and other inorganic (DeLillis and Kittleson, 1992).
salts. These “taste” groups are also stimulated by simple sugars Drug-induced azotemia in heart failure patients is treated by
in dogs and specific amino acids in dogs and cats. Standard
palatability testing indicates that dogs prefer the taste of a moist reducing the diuretic dose (usually at least by half–skip a dose if
food as the level of sodium chloride is increased, whereas there is not active pulmonary edema); if that fails to resolve the
increasing levels of salt in a dry food have no effect on palata- problem, the ACE inhibitor dose can be reduced by half, the
bility of the food. Palatability enhancers added topically to dry sodium intake can be increased to the next level (Tables 36-5
pet foods probably mask any taste effects of sodium chloride or and 36-6) or a combination of these tactics may be used.
other salts. Many foods with reduced sodium chloride levels for
use in patients with cardiovascular disease have comparable or Management of Hyponatremia
better palatability than grocery or specialty brand pet foods. The correction of hyponatremia associated with CHF has been
evaluated in people but not in domestic animals. The combined
The Bibliography for Box 36-1 can be found at administration of an ACE inhibitor and furosemide (but usually
www.markmorris.org.
not of either agent alone) usually reverses CHF-associated
hyponatremia in people, at least in part (Oster et al, 1994). The
reversal of hyponatremia probably results from the combined
effects of the ACE inhibitor (i.e., decreased thirst, decreased
Box 36-2. Use of Low-Salt Foods in proximal tubular reabsorption of sodium chloride, interference
Chronic Respiratory Diseases. with the hydro-osmotic effect of AVP) and the loop diuretic (i.e.,
increased distal delivery of glomerular filtrate, reduction in urine
Avoiding excess sodium chloride may also be important in osmolality) acting to offset the pathophysiologic factors that
patients with some forms of chronic respiratory disease such as impair excretion of water (Oster et al, 1994; Packer et al, 1984).
chronic bronchitis or asthma. Both epidemiologic and experi- Studies are needed to determine whether similar measures are
mental evidence in people suggest that high sodium chloride effective in reversing CHF-associated hyponatremia in animals.
intake may increase airway responsiveness and exacerbate Hyponatremia secondary to severely decreased cardiac output
clinical signs associated with asthma. When some people with and inappropriate secretion of ADH would not be expected to
asthma are subjected to salt loading, clinical signs worsen, lung resolve with either further diuretic therapy, or with ACE inhibi-
function deteriorates and the need for antiasthmatic drugs tion. In this case, increasing cardiac output (generally accom-
increases. However, not all studies in people with asthma show
benefits of avoiding excess dietary sodium. A serum-borne fac- plished by inotropic stimulation, afterload reduction or a combi-
tor in human patients with airway hyperresponsiveness stimu- nation of the two) would be needed, and pimobendan would be
lates increased sodium influx into cells. Reduced sodium levels the most easily available potentially effective therapy.
in food also result in increased levels of vasoactive intestinal
peptide (VIP) in the plasma and lung; VIP acts as a bronchodila- Pimobendan
tor. Although similar canine and feline studies have not been Pimobendan is an inodilator drug (combination positive ino-
completed, foods that avoid excess salt may be helpful in con- trope and vasodilator) approved by the FDA for the treatment
d
junction with other forms of therapy in animals with chronic of heart failure in dogs in 2007 in the United States. This
bronchitis or asthma-like clinical signs. drug, used at an oral dose of 0.3 mg/kg twice daily in combina-
tion with an ACE inhibitor and furosemide, is now part of the
The Bibliography for Box 36-2 can be found at standard medical therapy for dogs in heart failure from either
www.markmorris.org.
chronic valvular heart disease or dilated cardiomyopathy.There
are no known dietary considerations that influence the pharma-
codynamic effects of pimobendan.The drug appears to be asso-
ciated with a dramatic and helpful appetite stimulating effect in
sodium by reducing the diuretic dosage and liberalizing sodium many patients. It is not approved by the FDA for use in cats.
intake (Parker et al, 1987). Renal insufficiency is a potential
complication of ACE inhibitor therapy in dogs with CHF, but Cardiac Glycosides
the role of sodium restriction is unknown (Roudebush et al, Pimobendan has largely supplanted the routine use of digoxin
1994; Longhofer et al, 1993; DeLillis and Kittleson, 1992). in dogs and cats in sinus rhythm, at least until their heart fail-
Four of 10 heart-failure dogs treated with captopril, furosemide ure becomes refractory to standard treatment with pimoben-
and a sodium-restricted veterinary therapeutic food developed dan, furosemide, an ACE inhibitor and moderate dietary salt