Mary Allen
Feline hypertension/hypertension is a common problem. In practice, despite easy-to-learn methods, blood pressure in cats is unfortunately measured too seldom, often with fatal consequences.
Despite major educational campaigns in the media, many cat owners are unaware that their cats can suffer from high blood pressure just like us humans. And just like in humans, this disease is insidious, since for a very long time there are no warning signs. The symptoms are insidious and initially very unspecific, but if recognized too late, this can result in serious health damage for our house tiger, which is then usually irreversible.
Initially, affected cats show no or only slight changes, such as frequent meowing, poorer eating, from time to time staring in front of themselves, sometimes apathy, or a quickly passing, unnoticed unsteady walk, i.e. changes that are not perceived as unusual at all.
However, if high blood pressure remains undetected, there is a risk of dangerous damage to the kidneys, heart, eyes, and nervous system with symptoms that can no longer be overlooked, such as e.g. B. sudden loss of vision, bleeding in the eye, cramps, paralysis of the legs … Unfortunately, most cats are only presented at this stage, much too late – the high blood pressure has now quietly and unnoticed caused serious damage to the vital organs that remain irreversible. This is why high blood pressure is often referred to as the “silent killer”. Sadly, such damage could have been avoided by simply taking regular blood pressure measurements.
When do we speak of high blood pressure?
It is well known that blood pressure is not a fixed quantity, it varies from cat to cat and – depending on the current stress level – even within the same animal. Therefore, not only the recording of standard values in the healthy condition of the individual cat is important, but in particular the entire handling in practice.
In general, we speak of high blood pressure as a measurement of over 140-150 mmHg, but it is therapeutically required if it is regularly higher than 160 mmHg. If the blood pressure rises above 180 mmHg, severe hypertension is present, which has serious consequences for vital organs.
Classification of hypertension in cats
A distinction is made between primary (idiopathic) and secondary hypertension :
- Idiopathic: No other disease can be identified as the cause of hypertension.
- secondary: an underlying disease or medication used is assumed to be the cause of hypertension.
Idiopathic hypertension is relatively rare, accounting for 13-20% of all cases, and little research has been done on what causes it.
In about 80% of cases, hypertension is secondary, which means it is the result of another underlying disease. The most common diseases associated with high blood pressure are, in descending order:
- chronic renal failure,
- hyperthyroidism,
- diabetes mellitus,
- age-related diseases such as osteoarthritis when treated with blood pressure-increasing drugs such as cortisone or NSAIDs, or simply
- Pain – regardless of the cause (e.g. tumors).
In veterinary medicine, the so-called white coat syndrome (white coat hypertension, white coat effect) is also taken into account, which is triggered by the excitement in the unfamiliar surroundings of the practice and by the handling by the staff. These stress factors can lead to a physiological increase in blood pressure to over 200 mmHg in cats.
At this point, the TFA is the most important support for the correct diagnosis, only if cat-friendly handling is mastered can the blood pressure measurements be meaningful.
Pathological consequences of hypertension
Blood pressure is built up by the heart’s action of contraction (systole) and relaxation (diastole) and the tension in the vessels. A healthy blood pressure is responsible for the smooth functioning of all organs – only with correct blood pressure are they flushed through, supplied with oxygen and nutrients, and receive work orders via messenger substances that are washed in and out, wholly securing life and survival (dangerous situations). If we bear this in mind, it seems almost incomprehensible to us today that checking blood pressure has not always been part of general preventive care.
If the blood pressure changes permanently, the organs can no longer fulfill their important functions and depending on where the damage first manifests itself, corresponding failure symptoms occur. The organs most sensitive to changes in blood pressure are the kidneys, heart, eyes, and brain.
kidney
The most common cause of high blood pressure is chronic kidney disease (CRF). The kidneys play a special role in this interaction, as they share the control of blood pressure with the heart. It is partly responsible for ensuring that the volume of blood circulating through the body is sufficient to supply the organs. If the blood pressure rises disproportionately over a longer period, the fine regulatory structures such as the kidney glomeruli are damaged and no longer fulfill their filtration task – we then speak of renal insufficiency. At the same time, the destruction of these fine working units of the kidney in turn leads to a failure of the kidneys’ general task of keeping blood pressure constant.
That is, high blood pressure leads to chronic kidney disease (CKD), and CKD in turn leads to high blood pressure.
heart
Over 70% of cats with hypertension suffer from secondary changes in the heart. With constant high blood pressure, the heart has to work against increased vascular resistance, so that in many cats the left heart muscle thickens (concentric left ventricular hypertrophy), which reduces the ventricular volume, meaning less blood fits into the ventricle. However, since the heart has to provide sufficient blood for the circulatory system, it tries to increase its performance. It beats faster and faster (tachycardia) and gets out of rhythm with increasing frequency (arrhythmia). In the long run, this leads to an ever weaker heart output, up to and including sudden heart failure.
hyperthyroidism
Over 20% of cats with an overactive thyroid suffer from high blood pressure. Thyroid hormones (mainly T3) influence the contractile force and increase the heart rate (positive inotropic and chronotropic, in hyperthyroid cats we often find a heart rate > 200 mmHg). In addition, they influence the tension of the vessels and the viscosity of the blood, so that the blood pressure rises as a result.
diabetes mellitus
According to current studies, every second cat with blood sugar also suffers from high blood pressure, although this increase is usually moderate. This is different from humans, where diabetes is a recognized risk factor. Because diabetic cats also commonly have CKD, it is very difficult to establish a direct link here, but cats with diabetes and high blood pressure are more likely to have eye damage than those without hypertension.
Symptoms of high blood pressure
The most common symptom that cats with high blood pressure present in the practice are sudden blindness. The eye is most sensitive to high blood pressure. A pressure of 160 mmHg or more can damage the eye. We observe bleeding, dilation of the pupils (mydriasis), or different pupil sizes anisocoria). In the back of the eye,e we find strained vessels, retinal edema, and even retinal detachment. Fortunately, not all damage is irreversible; the eye can recover with the immediate initiation of antihypertensive therapy.
Every second cat shows damage to the central nervous system (encephalopathy) due to high blood pressure. If the blood pressure is high for a long time, this can lead to cerebral edema or cerebral hemorrhage with corresponding symptoms such as unsteady gait (ataxia), tremors, seizures (epilepsy), vomiting, personality changes (withdrawing, aggressiveness), pain (head clenching) up to sudden lead to death.
In an emergency, the cat is admitted to the hospital, the blood pressure is measured every four hours and the therapy is adjusted in such a way that the blood pressure drops sufficiently.
Blood pressure measurement
A blood pressure measurement should be integrated into the normal annual check-up. Advantageously, the blood pressure measurement can be carried out very easily and quickly by the TFA with a little practice.
The measurement of systolic blood pressure using Doppler (Doppler flowmeter) or oscillometry (HDO = High Definition Oscillometry) is reliable and practical. Both techniques are performed with a probe that can be placed on the tail or the forelimb, with the forelimb tending to be better suited for the Doppler method and the base of the tail for HDO measurement.
HDO
The HDO measurement appears to be the simpler method for beginners since only a cuff has to be put on and the device records the blood pressure at the push of a button using a complicated technique the values and curves then appear on the PC.
doppler
With a little practice, the Doppler method is just as easy. The measurement is not carried out using the device alone, but directly by the examiner with a probe and headphones. We use the Doppler method in our practice and are very satisfied with it.
Positioning of the cat and the cuff
As we are used to in a cat-friendly practice, when it comes to measuring blood pressure, we follow the cat’s wishes, because any excitement can raise blood pressure (> 200 mmHg).
Blood pressure should be measured at heart level, just like in humans. This is always the case with the cat lying on its side, regardless of whether we put the cuff on the front limb or the tail. Not all cats love to lie on their side, but we can measure the blood pressure of a sitting or standing cat to the same extent.
The location at the base of the tail is preferable for more anxious cats since we do not manipulate as close to the head, but experienced cats also like to reach out with the front leg and take the measurement very calmly. I must manipulate the legs very carefully, as older cats in particular often suffer from joint pain. The inflatable cuff is securely fastened over the artery with a Velcro fastener, but must not constrict the blood flow under any circumstances.
With the Doppler system, the blood flow = pulse is now detected with the probe and the headphones. This requires good contact between the skin and the probe. Since cats react sensitively to alcohol, we completely avoid it and only apply a lot of contact gel – so it is usually not necessary to shave the measuring point, which is always very unpopular with cat owners.
The guidelines of the IFSM (International Society of Feline Medicine) expressly recommend headphones so that the cats are not disturbed by the noise of the measuring device. Experience has shown that pulsatile blood flow is found very quickly with a little practice. It is important to place the probe on the vessel without pressure, otherwise, the blood flow is suppressed and can no longer be heard. To begin with, it is advisable to practice taking blood pressure measurements on cats that are under anesthesia following surgery.
Avoiding the White Coat Effect – The Feline-Friendly Practice
We assume that cat owners know, through education during previous visits, how to put a cat in the appropriate transport basket at home without stress and how to make transport in the car as comfortable as possible: with a pheromone-based device sprayed blanket to snuggle up in the basket (no cat likes to travel on bare ground) and a blanket to cover the basket to give a sense of security. And we also assume that the practice is cat-friendly equipped and organized. Nevertheless, the visit to the practice remains an adventure for our velvet paws and so we have to make an extreme effort in the treatment situation not to let stress arise. For example, the presence of the owner can be very calming for some cats, and the experienced, trained TFA ensures that the cat cooperates with us with her level-headed, gentle demeanor.
The cats should also be given sufficient time to familiarize themselves with the surroundings and those present – some like to inspect the space, and others first observe the situation from the safety of the basket before deciding to come out and contact us.
If the cat is brought in the cat-friendly transport box with a removable upper part, it is also welcome to sit in the bottom part and the blood pressure measurement is carried out safely on the tail.
It is crucial to fix the cat as little as possible. If it does become restless, we interrupt the measurement process until the cat has calmed down again. It’s always amazing how well our cats respond positively to gentle coaxing and stroking. We never work with coercive measures! If the cat is relaxed and trustingly gives us its paw, the measurements are quick and meaningful.
Before the actual measurement, the cuff should be inflated and deflated a few times so that the cat gets used to the feeling of pressure. The first measurement is usually discarded, then ideally 5-7 measurements are taken and recorded. These readings should have a range of less than 20%. The mean value, which is the binding value for blood pressure, is calculated from these measured values. Each subsequent check-up must be carried out under the same conditions. Therefore, the documentation of the measurement location (paw or tail) is also very important, as it has been proven that different pressures are measured depending on the location of the measurement.
Routine treatment of hypertension
As stated at the beginning, feline hypertension is usually secondary and the underlying disease (CKD, hyperthyroidism) must always be identified and treated.
In addition, however, the treatment of high blood pressure is always necessary to prevent further organ damage and to improve the health of the cat. The aim is to achieve at least a blood pressure below 160 mmHg in first-time hypertensive patients. Studies have shown that with blood pressure below 150 mmHg, the least subsequent organ damage is to be expected. Therapy should therefore be geared towards achieving and maintaining this value in the long term. The value in a healthy cat is between 120 and max. 140 mmHg.
The drug of choice for the treatment of hypertension is currently the calcium channel blocker amlodipine (besylate which is approved for cats. With this agent, a reduction of 30-70 mmHg is achieved and in 60-100% of cats it is sufficient as monotherapy. There are no complications if blood pressure is monitored continuously.
If treatment with amlodipine alone cannot lower the blood pressure sufficiently, then other medications – depending on the concomitant or underlying disease – must be used (e.g. ACE inhibitors, beta-blockers, spironolactone). These active ingredients are usually used in combination with amlodipine in a titrating manner until the onset of action.
Notice!
When the blood pressure is low, the body reacts very quickly. A simple example is the noticeable lack of performance and tiredness or the collapse. If the blood pressure is too high, the body reacts very slowly, i. H. accordingly, it is only recognized when the damage can no longer be overlooked.
- Blood pressure measurement is part of the annual check-up.
- Blood pressure measurement is simple and can easily be performed by the veterinary nurse.
- Hypertension is preventable and easily treatable.
- The hypertensive cat should be monitored closely, even if the blood pressure has returned to the normal range after drug therapy.
Blood pressure measurement – when and how often?
- Experts recommend checking blood pressure in cats every twelve months from the age of 3-6 years. This makes it possible to record the individual normal values and represents good training for the future.
- Annual check-ups may be sufficient for healthy older cats aged 7-10 years.
- In geriatric cats older than ten years, however, measurements every six months are more reliable. Similar to humans, it has been researched that blood pressure increases by 2 mmHg per year with increasing age. That is why the blood pressure in older cats is always in the higher normal range.
- Since animals physically age much faster than we do in shorter time dimensions, the recommended shorter intervals of six months between controls are also understandable.
- The most important argument for closely monitoring older cats is that they very often suffer from diseases that cause high blood pressure (such as secondary hypertension due to chronic renal failure). Cats with these risk factors may need to be checked every three months to limit further organ damage.
Frequently Asked Question
What to do if the cat has high blood pressure?
The drug of choice for lowering chronic high blood pressure is amlodipine besylate, a calcium channel blocker that causes peripheral artery dilation. The starting dose should be 0.125 mg/kg.
Can you measure blood pressure in cats?
Doppler measurement is the most accurate and effective method of measuring blood pressure in cats. Elevated blood pressure in cats can be caused by various diseases. The most common triggers are hyperthyroidism, hypertrophic cardiomyopathy (HCM), and kidney disease.
How much does it cost to take a cat’s blood pressure?
How much does a blood pressure measurement cost? The costs for the pure blood pressure measurement are <20€.
What happens if a cat eats a blood pressure pill?
If the cat accidentally swallows a pill, this will result in a massive disruption of the hormonal balance. Symptoms such as vomiting and diarrhea also occur. This leads to circulatory collapse, liver failure, and damage to the gastrointestinal tract.
How do I know if my cat has diabetes?
The most common symptoms in cats with diabetes are: increased thirst (polydipsia) increased urination (polyuria) increased food consumption (polyphagia).
How much should a cat drink a day?
An adult cat needs between 50 ml and 70 ml of liquid per kilogram of body weight every day. For example, if your cat weighs 4 kg, it should drink 200 ml to 280 ml of fluids per day. Your cat does not drink the amount all at once but in many small individual portions.
How often should a cat urinate per day?
Most adult cats urinate two to four times a day. If your cat urinates much less often or more often, this can indicate a urinary tract disease. In this case, you should consult your veterinarian.
How does thyroid disease in cats become noticeable?
In cats, the hypofunction of the thyroid gland is rarely detected. The symptoms often develop insidiously and are very variable. Striking is increasing tiredness and reluctance to exercise up to lethargy and mental retardation.