No abstract

Captopril, furosemide, and a sodium-restricted diet were administered t o 6 normal dogs and 10 dogs with congestive heart failure. Serum electrolyte concentrations and renal function were monitored in both groups. In the normal dogs, no clinically meaningful changes in serum electrolyte, urea nitrogen, or creatinine concentrations developed during therapy with a sodium-restricted diet and 4 weeks each of furosemide alone, captopril alone, or furosemide plus captopril. Three of 6 normal dogs on furosemide and a sodium-restricted diet had at least one serum potassium concentration above the reference range during the 4 weeks of observation. One normal dog on captopril, furosemide. and a sodium-restricted diet developed azotemia, and 2 dogs had serum potassium concentrations above the reference range during the 4 weeks of observation. Ten dogs with congestive heart failure were treated with captopril, furosemide, a sodium-restricted diet, and digoxin.herapy for congestive heart failure (CHF) often in-T cludes the use of diuretics and sodium restriction to reduce preload and venous congestion; cardiac glycosides to increase contractility and control supraventricular arrhythmias; and vasodilators to reduce venous congestion, preload, and afterload. Captopril, an inhibitor of angiotensin converting enzyme (ACE), is a popular vasodilator used to treat dogs with CHF. This drug inhibits the formation of angiotensin I1 and results in vasodilation and decreased circulating plasma aldosterone concentrations.' Aldosterone plays an important role in the maintenance of vascular volume and potassium balance via its effects on the renal cortical collecting tubule cell. It also increase the reabsorption of sodium and chloride and promotes the secretion of potassium. The use of ACE inhibitors in human patients with severe renal insufficiency or in those given potassium supplements may increase the risk for h~perkalemia.~.~ It is not known whether the levels of potassium in popular pet foods or sodium-restricted diets will increase the risk for hyperkalemia in dogs receiving ACE inhibitors such as captopril.Functional renal insufficiency has been documented in up to one third of salt-restricted human patients with severe CHF treated with ACE inhibitors and diuretic^.^ This decline in renal function has been attributed to loss of angiotensin Ii-mediated systemic and intrarenal vasoconstrictor effects that maintain renal perfusion pressure and glomerular filtration rate in low output heart failure. Functional renal insufficiency appeared to be alleviated when efforts were made to replenish total body stores of sodium by reducing the diuretic dose and liberalizing dietary sodium intake.' Renal insufficiency is a complication of captopril therapy in dogs with CHF, but the role of sodium restriction is unknown.6 The purpose of this report is to describe the electrolyte concentrations and renal function in both normal dogs and dogs with CHF receiving captopril, furosemide, and a sodium-restricted diet.Etiopathogenesis of the heart failur...