Role of electrolyte concentrations and renin-angiotensin-aldosterone activation in the staging of canine heart disease.

Hypochloremia is a useful marker for stage D HD in dogs. Poor furosemide dosage correlation to serum concentration may indicate variable and poor absorption, especially at higher dosages, advanced disease, or both. A small number of stage D dogs met proposed criteria for diuretic resistance. Greater RAAS inhibition in stage D versus stage C indicates effectiveness of RAAS-suppressive treatments in this group of dogs with refractory CHF.