Hypertension (high blood pressure) has serious consequences for both people and pets. Unlike with humans who can be diagnosed with primary hypertension, this condition is always secondary to another disease process in dogs and cats. Treatment of the underlying disease may itself control the elevated blood pressure, or additional medications specifically designed to treat hypertension may be needed. Untreated, it may lead to acute blindness and further complicate kidney and heart disease.
Normal blood pressure measurements for dogs and cats can be influenced by the device used for measurement, breed, age, gender, reproductive status and circumstances of the measurement. Just like with people, the stress of visiting the doctor can slightly elevate these numbers. An average normal blood pressure (BP) across breeds of dog is about 133/75 mm Hg (systolic/diastolic) and an average normal BP in cats is about 124/84 mm Hg using the oscillometric (cuff) method. Treatment for hypertension in animals begins when the first number, the systolic pressure, reads consistently over 160. At measurements over 180 mmHG, the smallest vessels in the body begin to rupture. These are the vessels in the eyes and the kidneys.
Diseases that are associated with hypertension include hyperthyroidism in cats, chronic renal failure (CHF), Cushing’s disease, and Diabetes Mellitus. More than half of all pets in chronic renal failure have systemic high blood pressure, and it is almost inevitable in untreated hyperthyroid cats. Elevated blood pressure can accelerate kidney dysfunction, shortening life-expectancy. A sudden blindness caused by retinal bleeding is a serious consequence of undiscovered high blood pressure. All pets known to have these conditions should be routinely screened for hypertension. Pets over the age of seven should be screened during wellness examinations.
Treatment for hypertension always begins with addressing the underlying disease first. The blood pressure may be brought into a normal range by treating the primary illness. This is especially true for hyperthyroid cats. For persistent hypertension, several drugs are used alone and in combination to regulate blood pressure:
- ACE inhibitor – (angiotensin converting enzyme is involved in producing vasoconstriction which elevates blood pressure, these drugs inhibit the process) Enalapril, Benazepril
- Calcium Channel Blocker – (relaxes heart muscle contraction) Amlodipine, Diltiazem
- Diuretic – (reduce edema by removing water from tissue) Furosemide, Hydrochlorathiazide
Moderate sodium (salt) restriction may also be helpful in controlling hypertension. Research goes back and forth on how beneficial this may be, but diets made specifically for heart and kidney failure have other intended purposes as well as reduced sodium.