Pets can have high blood pressure Print E-mail
News - Rubrieke
Friday, 20 March 2015 01:41
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Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

An acquaintance of mine has just had her cat diagnosed with high blood pressure and she was amazed that animals had this condition. So, I thought I would write a brief, quite medical summary of the condition in our pets.

In most dogs and cats hypertension, or high blood pressure, is a complication or an underlying disease, whereas humans often suffer from essential hypertension, where there is no underlying cause.

Hypertension is more common in cats than dogs. Although it is routine to test people’s blood pressure, even at the pharmacy, testing blood pressure in dogs and cats is only now becoming more commonplace.

Because of the large variations in size – a 2.5 kg cat to an 80 kg Great Dane – the equipment used in the veterinary field is actually more complex and much more expensive than that used for people and is not available at all clinics.

Animals are generally stressed when they go to the vet, and that is why it is assumed that their blood pressure will be higher. This is called the “white coat effect” and occurs in people as well. Implanted monitors have, however, shown that the blood pressure will decrease to the patient’s normal after five to ten minutes in a quiet, non-stressful environment.

The average blood pressure in our animals is also about 120 – 140 / 80-90 mmHg, which is similar to people’s. Elevations greater than 160 mmHg should be investigated and treated medically to prevent damage of other organs in the body.

High blood pressure is dangerous as it causes damage to the eyes, kidneys, heart and brain. The retinal blood vessels become convoluted to try to dissipate the pressure and finally they burst and cause retinal bleeding and even retinal detachment, which results in blindness that could be permanent if the retina detaches.

This is seen in cats with hypertension. The owner will notice that the pupils are dilated and fixed and haemorrhage may even be visible in the anterior chamber of the eye.

The effect on the brain is more difficult to assess. Animals with very high blood pressure show behavioural changes and mental dullness. They may have seizures. They probably have severe headaches, just like those that humans experience.

The kidneys experience pressure damage to the filtering mechanism, which then leaks proteins when it should retain them. This causes ongoing inflammation. The high blood pressure in the blood vessels of the filtration region causes scarring and loss of functionality. Eventually kidney failure will result.

The effect on the heart is logical: because the blood pressure in the blood vessels is high, the heart has to pump harder to move the blood into circulation. This results in thickening of the heart muscle.

Underlying disease conditions commonly associated with high blood pressure are kidney disease and hyperthyroidism in cats, both common diseases of older cats. It thus makes sense to check blood pressure as part of a geriatric monitoring programme as the condition may be “silent” until organ damage occurs.

In dogs, diseases of the adrenal gland cause increased blood pressure. Adrenal gland tumours cause periodic hypertensive crises due to adrenalin release. Adrenal enlargement due to Cushing’s disease also results in secondary hypertension.

Our pets are more and more just like us – prone to the same diseases and often requiring chronic medical management. Early diagnosis prevents ongoing damage to organs such as the eyes and kidneys, and early intervention will prolong life and improve quality of life.

So, the next time you are at your veterinarian, ask for a routine blood pressure evaluation for your older pets. If they do not have the equipment they can refer you to a place that does. It may just be that “a stitch in time saves nine”.

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