hypertension

CANINE HYPERTENSION

SYSTEMIC HYPERTENSION

(High Blood Pressure)

Doctor, Dolly's eye is red!
Frequently, a concerned client will present a cat or, less frequently, a dog to their regular veterinarian with the complaint that one or both eyes was or currently is red inside. Most of the time the veterinarian will examine the eye and diagnose inflammation (uveitis) or injury as the cause of the redness. In some cases, this diagnosis is correct. Unfortunately, in some cases this diagnosis is incorrect. A significant condition which isn't often diagnosed until the patient is blind or has a stroke is called "systemic hypertension" or high blood pressure.

What is systemic hypertension?
In humans and pets, two types of high blood pressure are recognized--essential (due to unknown cause) and secondary (due to some underlying disease). In humans, essential hypertension is the most common type. Secondary hypertension is the most common type in veterinary medicine. The most common causes of hypertension in dogs include kidney disease, adrenal disease, hypothyroidism (underactive), diabetes and pituitary tumor. In cats, kidney disease, hyperthyroidism (overactive) and heart muscle disease are the most common causes. In humans, systemic hypertension is called the 'silent killer' because there are no characteristic feelings or outward symptoms or signs of high blood pressure until a stroke occurs. If people cannot tell they have high blood pressure, how can our pets be expected to "tell us"?

What is normal blood pressure?
In humans, our blood pressure is often reported as being normal at 120/80 millimeters of mercury (mm Hg). The first number (120 mm Hg) is the systolic pressure or how much force the heart exerts to push out the blood. The second number (80 mm Hg) is the diastolic pressure or the resting tension of the arteries (blood vessels which carry blood from the heart to the body organs). In veterinary medicine, we cannot always get a diastolic reading because of patient anxiety or noise in the environment. Normal blood pressure in the dog and cat is less than 160-170 mm Hg systolic.

How is a blood pressure reading obtained?
A blood pressure evaluation is performed every time you are seen by your regular physician and we are familiar with the technique. In veterinary medicine, we cannot get the blood pressure exactly as it is done in humans, but it is most frequently done in a similar manner. At research institutions, blood pressure is measured via the 'direct' method. In this technique, a needle is threaded directly into an artery and the blood pressure is measured through a complicated piece of equipment known as a pressure transducer. This technique can be extremely accurate but is difficult to perform and your pet does experience slight discomfort. The second, and most commonly performed method, is the 'indirect' method. It requires an amplifier and a pressure sensor instead of a stethoscope. A small 'cuff' is applied around the patient's leg and the pressure sensor is placed on an area of skin where the fur is clipped at the 'wrist' or 'ankle'. After this preparation, the technique is then almost exactly the same as with humans. Because of the expense of the equipment, I would estimate that less than 10% of veterinary hospitals have indirect blood pressure equipment.

What are some of the signs of high blood pressure?
The typical patient seen in our referral ophthalmology practice is a dog or cat who is over 10-years old and seems healthy to the client. The cat could have had redness to one or both eyes which came and then resolved once or maybe twice before. Alternatively, the client may have noticed that the cat's pupils were becoming more and more dilated and now the cat appears blind. When taken to the regular veterinarian, blood work, a physical examination and perhaps x-rays were done and medication prescribed which didn't help. Dogs and cats may have nose bleed, weight loss, increased thirst, increased drinking and weight loss or abnormal "neurologic" signs. During the examination at our hospital, blood may be found in the front of the eye (hyphema) or behind the lens inside the eye (intravitreal hemorrhage) OR one or both retinas are found to be detached (retinal detachment) with no signs of inflammation. Occasionally, the findings will be that of small hemorrhages (bleeding) within or beneath the retina or we will find extremely dilated blood vessels in the retina. These hemorrhages are not visible without a complete eye examination. We will then perform the 'indirect' blood pressure test and usually find that the patient¹s blood pressure is over 200 mm Hg and sometimes the blood pressure will be greater than 300 mm Hg! Many times, clients aren't even aware of a problem due to hypertension in their dogs.

What are the causes of and treatment for hypertension?
In both dogs and cats, kidney disease is the most common cause of systemic hypertension. Because kidney disease can cause hypertension and hypertension can cause kidney disease, many different parameters and blood tests must be evaluated. The above systemic conditions should be ruled out and medication needs to be staarted. Medication is usually a tablet given by mouth once or twice daily. For cats who are difficult to give tablets to, the medication can be prepared in a fish or chicken flavored base and given as a liquid. Once medication is begun and once the blood pressure is stabilized in the normal range, the blood tests must be repeated to assess what happens to the kidneys and other body organs when the blood pressure is lowered. As in people, blood pressure medication must be continued for the life of the pet.

Is blood pressure evaluation necessary?
Blood pressure evaluation is very necessary in older dogs and cats. Early detection and treatment can help prevent blinding and fatal complications such as stroke. I would recommend that a blood pressure reading be performed on an annual basis for every pet over 10 years of age or any pet displaying chronic kidney disease or any nose bleed or redness (blood) inside the eye.

reprinted with kind permission from Dennis Hacker, D.V.M., DIPLOMATE, A.C.V.O. (Veterinary Ophthalmologist)
10324 San Pablo Ave. El Cerrito, CA 94530 510-559-1755 510-559-1757
e-mail:drhacker@animal-eye-specialists.com web site: http://www.animal-eye-specialists.com

*****************

The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.