High Blood Pressure in Your Dogs or Cat

Hypertension

Ron Hines DVM PhD 1/16/08

Until recently, veterinarians rarely measured your pet’s blood pressure. This is because the standard arm cuffs used on humans just didn't’t work well on dogs or cats. But with easier access to specialized equipment, blood pressure examination has become much more common.
High blood pressure in all creatures is a stealth disease. That is, there are few or no signs of the problem until after damage has occurred. Any area of the body that is rich in small blood vessels can be damaged by hypertension. These tiny arteries are only meant to hold a specific pressure. When the pressure becomes too high, they may burst or leak causing damage to the tissue that surrounds them. Pets do not seem to suffer the strokes we do that are brought on by high blood pressure. Instead, their kidneys and eyes (retinas) are more likely to be damaged. Occasionally, other conditions that limit blood flow to the kidneys actually cause the hypertension. In any case, the majority of dogs and cats with kidney problems also have some degree of elevated blood pressure.
Most vision loss in older pets is due to age-related clouding of the lenses of the eye (cataracts). But occasionally, high blood pressure will cause blindness by destroying cells of the retina.
When you pet’s blood tests show an elevated blood urea nitrogen (BUN) or creatinine both possible signs of kidney damage – a check of it’s blood pressure is also good idea.
High blood pressure can also occur with other diseases of pets besides kidney disease. Pets with over active thyroid glands often have high blood pressure. This is particularly a problem in older cats. Dogs with over active adrenal glands are also subject to high blood pressure as are pets with diabetes.
If a routine health examination of your pet detects high blood pressure (not due to excitement), there is probably an underlying health problem causing it. In contrast, humans most commonly have elevated blood pressure with no apparent underlying health problem.
Many veterinarians now screen older (7yr+) pets for high blood pressure during their yearly health examinations. Other than age, another reason to check pet blood pressure is when abnormalities are detected in the retinas of your pet’s eye. So any time your pet appears to be unable to see clearly, have the deep portions of its eyes examined.
Damage to the body due to high blood pressure is undoubtedly not limited to the kidneys and eyes. It is unhealthy for all body organs and can be a contributing factor in many common disease of dogs and cats.

How We Detect High Blood Pressure in Pets
We use the same principle to examine your pet’s blood pressure as we do in humans. A flexible cuff , designed especially for pets, is placed around the lower front leg or tail and the cuff is inflated until blood supply has been cut off. Then, as pressure is slowly released, we listen for the point at which the first squishing sounds are heard (the systolic pressure or first number). In people, this is done with a stethoscope. In animals, we need an amplifier called a Doppler to hear this point clearly. In humans the point at which sounds are no longer heard is called the diastolic pressure. In pets, only the systolic pressure can be determined accurately with the Doppler method. There are more sophisticated machines that can measure both systolic and diastolic pressure in pets. These numbers are quite variable in pets and what is normal is in debate. But most veterinarians agree that systolic pressure should not be over about 170 mm of mercury (Hg). And diastolic pressure, when it is known, should not exceed 110mm. Some more conservative veterinarians use 150/83 as the normal range in dogs and 160 over 100 as the normal range for cats.
Some pets become so nervous at the vet’s office that their blood pressure increases. So the temperament of the animal must be taken into account when interpreting this data.

Treatment for High Blood Pressure
If changes have been found in your pet’s retinas, the best course of action is to have your veterinarian schedule your pet an appointment with a veterinarian who specializes in the treatment of eyes. These veterinary ophthalmologists are available in most urban areas. The American Veterinary Medical AssociationAmerican Veterinary Medical Association can provide you with names of these specialists in your area.
When high blood pressure is found, a complete blood work-up is usually performed to try to determine an underlying cause.
One of the most common drugs used to treat hypertension in people is also often effective in animals. It is enalapril maleate (Vasotec & generics). This drug belongs to a class of drugs known collectively as ACE-inhibitors http://en.wikipedia.org/wiki/ACE_inhibitor Your veterinarian my suggest another drug in this class. If these drugs are not effective, a group of drugs called calcium channel blockers may be used (Amlodipine).

A low salt diet may also be recommended by your veterinarian. Once the blood pressure has been controlled, have it rechecked several times a year.

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