Hypertension (high blood pressure) is very common in CKD cats, and can have some very serious
consequences, including a stroke or blindness.
It may contribute to
the development of
proteinuria.
It may further damage the kidneys.
Therefore if at all possible, you must ensure your cat's blood pressure is
checked regularly.
Your cat has hypertension that needs treating if the blood pressure measurement is
consistently over 160 mmHg.
If your cat's blood pressure is over 180mmHg and your cat has serious
symptoms such as sudden onset blindness or seizures, it is a medical
emergency and your cat needs immediate treatment.
In most cases hypertension can be easily controlled using medication.
The best medication is usually amlodipine (common
trade names are Norvasc
or Istin). It is effective, reasonably priced, is unlikely to make blood pressure fall too
low, and in some cases may even reverse blindness caused by hypertension.
What is Hypertension?
The heart pumps blood through the body via
large blood vessels known as the arteries. Hypertension means the pressure (or tension)
in the arteries is elevated. T
his creates
more work for the heart, and can eventually cause damage to the blood
vessels, which may cause problems elsewhere in the body.
One of the kidneys' functions is to help to control blood pressure.
Damaged kidneys often cannot do this properly, so hypertension is common
in CKD cats, though it is also possible to have hypertension without CKD
being present.
Mar Vista Vet
has an overview of high blood
pressure in cats.
Hypertension in the dog and cat (2020)
Elliott J, Syme HM & Jepson RE (Eds.) Springer is a new book about
hypertension, though it is probably too technical for most laypeople.
From a practical
perspective, you do not need to know too much about these. What is
important is to monitor your cat for systemic hypertension and to treat it if
present. How to do both is discussed below.
Systemic Blood Pressure
and
the Renin-Angiotensin-Aldosterone System (RAAS)
The renin-angiotensin-aldosterone-system has a
number of roles within the body, including the regulation of:
the volume of fluid in the body
blood pressure
electrolytes such as potassium
If blood flow to the kidneys is reduced for whatever
reason, the kidneys are stimulated to
produce hormones called renin and angiotensin. The adrenal gland is
stimulated to produce another hormone called aldosterone. This is known as
the renin-angiotensin-aldosterone system
(RAAS).
If the RAAS is activated repeatedly in this way, these hormones make the blood vessels in the body constrict, which
in turn leads to hypertension.
It is known that the RAAS may be activated by CKD in
humans and this may also be a factor in cats.
Feline hypertension: Part 1
(2012),
Atkins C states "several studies
have indicated that the renin-angiotensin-aldosterone system (RAAS) is
probably abnormally activated in many or, perhaps, most cats with systemic
hypertension, particularly with concurrent renal disease."
Modifying the RAAS has been shown to be of
benefit in human
CKD patients, but
Feline CKD: New horizons - where do we go from here?
(2013) Taylor S & Sparkes AH Journal of
Feline Medicine and Surgery15 Suppl 1 pp45-52
states "blockade in humans with
proteinuric CKD have been demonstrated in multiple studies. However,
current evidence in cats does not demonstrate the same findings, despite
proteinuria being a negative
prognostic indicator. More research is needed, although differences
between the species in the type of renal disease encountered might
help to explain the disparity."
It is not practicable to measure intraglomerular
blood pressure (blood pressure within the kidneys in particular) in cats but it is usually higher than systemic blood
pressure, and it may be elevated even if systemic blood pressure is not.
If intraglomerular blood pressure is too high, it
may cause loss of function and scarring in the kidneys. On the other hand, reducing blood pressure within the kidneys can lead to a reduction in the
amount of blood flowing through the kidneys, which in turn may reduce the
glomerular
filtration rate, a measure of kidney function. This may have a
negative effect on kidney function in some cats, which may be seen in the
form of elevated BUN and creatinine levels.
Whilst it is true that
hypertension is more common in cats with these conditions, it is gradually
becoming clear that primary hypertension (sometimes referred to as
idiopathic, meaning no obvious cause can be
found) does exist in cats, and may in
fact contribute to the development of CKD.
If the blood vessels within the kidneys are damaged because of
hypertension, eventually CKD can result. The
National institute of Diabetes and Digestive and
Kidney Diseases explains more about this in humans.
Feline hypertension: Part 1
(2012) Atkins C says
"adding to the confusion in
understanding the pathogenesis of hypertensive renal disease, renal
disease begets hypertension and hypertension begets renal disease."
(There is a third kind of hypertension, situational hypertension. This was
previously called "white coat syndrome," because it refers to apparently
elevated blood pressure that is actually caused by stress e.g. vet visits.
This type of hypertension does not require treatment).
Systemic hypertension is
problematic only because chronically sustained increases in BP cause
injury to tissues; the rationale for treatment of hypertension is
prevention of this injury."
(2015) Grauer GF Clinician's Brief May
2015 pp65-69 states "Tighter control of hyperphosphatemia, renal
proteinuria, and systolic hypertension may improve treatment outcome."
Unfortunately hypertension is not usually
visible. There can be certain symptoms as described
below, but
these are not always present and even if they
are,
most laypeople would not realise they can be warning signs of
hypertension. In order to obtain an accurate diagnosis, blood
pressure needs to be measured, but unfortunately
many vets do not routinely check CKD cats for hypertension, even though
CKD patients are at increased risk of hypertension.
How Common is Hypertension?
Prevalence
of systolic hypertension in cats with chronic renal failure at
initial evaluation (2002) Syme HM,
Barber PJ, Markwell PJ & Elliott JJournal of the American
Veterinary Medical Association 220 pp1799-1804, found an
incidence rate of high blood pressure of only 20% in cats at initial diagnosis
of CKD. However, since the risk of high blood pressure developing increases as
the CKD worsens, it appears that at least one third of CKD cats have high
blood pressure. In fact, as mentioned in
Changes in systolic blood pressure over time in
healthy cats and cats with chronic kidney disease
(2015)
Bijsmans ES, Jepson RE, Chang YM, Syme HM, Elliott J Journal of
Veterinary Internal Medicine29(3) pp855-6, other studies
indicate that the incidence of high blood pressure
in CKD cats is as high as 65%.
The Bijsmans study found that
increasing age is a significant factor in developing hypertension, but
healthy cats were less at risk. Elevated kidney values were an independent
risk factor for the development of hypertension. Therefore if you have a
CKD cat, you should monitor blood pressure whatever the cat's age.
(1990) Kobayashi DL, Peterson ME, Graves TK, Lesser M &
Nichols CE Journal of Veterinary Internal Medicine4(2)
pp58-62 found that 87% of the cats in the study with hyperthyroidism also
had hypertension. Therefore you need to be particularly careful if your cat has both hyperthyroidism and CKD.
Using
corticosteroids
may also lead to hypertension, so cats taking them should be monitored.
Symptoms of Hypertension
There are a surprising number of possible symptoms of hypertension in cats.
A cat with untreated
or uncontrolled hypertension may have a stroke. A stroke means that the
blood supply to part of the brain is cut off. Symptoms of stroke include
an
inability to move (see below),
weakness on one side of the body,
the head tilting to one side, circling and
blindness.
A stroke is a medical emergency and you need to go to the vet immediately.
I
f your cat
has a stroke because of
high blood pressure, there is a chance of recovery
if
treatment is started quickly enough. See
below for more
on this.
Davies Veterinary Specialists
have some information about strokes in cats and dogs and state "strokes
in dogs and cats are often not as debilitating as they are in people. With
appropriate care, your pet may recover very well."
Up to 46% of cats with hypertension have neurological problems. Neurological problems are
more common if blood pressure is very high, or if it has suddenly
worsened.
Manifestations of hypertensive encephalopathy in
cats (2023) Moretto L,
Beckmann K,
Günther C,
Herzig R,
Rampazzo A,
Suter A,
Steffen F & Glaus T Journal of Feline Medicine and Surgery25(2) looked
at 56 cats with hypertension and found that 31 of them had neurological
symptoms only (the others had additional symptoms, such as ocular (eye)
problems).
Seizures
These may
be a symptom of hypertension.
Seizures may take a number of different forms. There
may be the classic jerking and loss of consciousness, but being "spaced
out" or mentally absent may also be a type of seizure.
Pet Place
has some helpful information about seizures.
Other possible causes of seizures include epilepsy
or
a brain tumour.
In some cases vets tell people the most likely cause of their cat's
seizures is a brain tumour and
the only thing to do is perform an expensive MRI scan or let the cat die.
Whilst it is true that some older cats may have a brain tumour (which
fortunately is often treatable),
the causes mentioned above are far more likely in a CKD cat and should
therefore be considered first.
I would always ask to check blood pressure and treat if it is high before
fearing the worst regarding brain tumours or having an MRI scan performed.
(2016) Lowrie M, Bessant C, Harvey RJ, Sparkes A &
Garosi L Journal of Feline Medicine & Surgery18(4)
pp328-336 reports on
a particular kind of epilepsy called feline audiogenic reflex seizures
(FARS) which was recently identified in cats. This is most often found in
elderly (over 15) or Birman cats, and is triggered by high-pitched noises,
such as crinkling a paper bag or touching keyboard keys.
International Cat Care
explains more about this condition. Although phenobarbital
is usually used for epilepsy in cats,
Levetiracetam in the management of feline audiogenic
reflex seizures: a randomised, controlled, open-label study (2017) Lowrie M, Thomson S,
Bessant C, Sparkes A, Harvey RJ & Garosi L Journal of Feline
Medicine and Surgery19(2) pp200-206 found that a different
medication called levetiracetam (Keppra) seems to work better for this
condition.
Sometimes cats can appear blind after seizures and you will get a negative
menace response, but this should not last for long, and in fact cats who
appear to be blind after a seizure are not
normally blind — my
Harpsie had
a negative menace response after his seizures and several vets were
convinced he was blind, but he could still see well enough to play with Cat Dancer.
However, blindness can be a symptom of hypertension in its own right (see
below).
I am really surprised how many vets do not
seem to realise that seizures may be caused by hypertension.
I have lost count of the number of cats I've heard about who have simply
been put on phenobarbital (an epilepsy medication) rather than having
their blood pressure measured. In every single one of these cases apart
from one, once the cat was given appropriate blood pressure medication, it
was possible to stop the phenobarbital (which should always be done
gradually) and the seizures never returned.
Having said that,
occasionally cats who have had a
stroke will start to have
seizures, and in such cases anti-convulsant medication may be required.
Do not panic if your cat has seizures caused by hypertension.
Manifestations of hypertensive encephalopathy in
cats (2023) Moretto L,
Beckmann K,
Günther C,
Herzig R,
Rampazzo A,
Suter A,
Steffen F & Glaus T Journal of Feline Medicine and Surgery25(2) states
"clinical neurological signs were reversible or
partly reversible in 92% of cases, including cats with severe seizures and
stupor."
Howling, Especially at Night
In some ways,
this is the classic symptom of feline hypertension for me. I have lost
count of the number of people who have told me their cat was doing this
with no other likely cause as described below, I
suggested the cat should be tested for hypertension, and the cat was
indeed found to have hypertension.
Although many vets do not seem to be
aware of this possible symptom,
Increased vocalisation in elderly cats
(2015) Gunn-Moore DA European Journal of Companion Animal Practice 25(3)
pp20-29 states "Chronic kidney disease can result in increased vocalisation when
associated systemic hypertension
causes cerebral vascular compromise (as in CDS). It can also occur when
polyuria without adequate access to water cause cerebral dehydration,
when polydipsia/polyuria predisposes to a secondary UTI (see UTI), or
when severe uraemia results in uraemic encephalopathy."
Manifestations of hypertensive encephalopathy in
cats (2023) Moretto L,
Beckmann K,
Günther C,
Herzig R,
Rampazzo A,
Suter A,
Steffen F & Glaus T Journal of Feline Medicine and Surgery25(2) also
mentions howling as a possible symptom of hypertension.
Sometimes howling is not cause for concern, e.g. my perfectly healthy
ten
year old howls when she is taking her sticks for a walk around the house.
However, if your cat starts howling, or in different situations to those
where s/he howled previously, I would have it checked out.
Inability or Reluctance to Walk
These may be neurological symptoms of hypertension.
If the
hypertension causes a stroke, the cat may find it hard to walk, and may
want to stay in one place, or may seem to have weakness in the legs.
Humans with high blood pressure often report having a very bad headache.
There is no way to know if our cats have a headache, but I have heard of a
couple of cats pressing their heads against walls, which might be
indicative of a headache. Such behaviour is sometimes also seen in cats
with brain tumours.
Lethargy
Cats with hypertensive encephalopathy may be lethargic. You may also see
lethargy in cats with
heart problems caused by
hypertension.
Unfortunately this is a relatively common occurrence in cats with
untreated hypertension. The hypertension causes the retinas to detach, so
the cat becomes blind.
I sometimes hear from people whose cats have become
blind and the vet just ascribes it to old age and says the cat will learn
to live with it but
Feline Retinopathies
(2016) Myrna K VeterianKey says that ocular changes are seen
in 40-60% of cats with hypertension and require treatment.
You may notice a
change in your cat's eyes, such as dilated pupils or uneven pupils (uneven
pupils are known as anisocoria). You
can
also try checking for a menace response: stand behind your cat if possible,
cover one of his/her eyes, then move your hand towards your cat's face and see if s/he reacts (a
positive menace response) or not (a negative menace response). Switch eyes
and do it again, because your cat might only be blind in one eye. Another
option is to get your cat's attention, then drop a cotton wool ball and
see if the cat follows the ball with his/her eyes.
Sometimes
cats can appear blind after
seizures and you will get a
negative menace response, but this should not last for long, and in fact
they are not normally blind — my Harpsiehad
a negative menace response after his seizures and several vets were
convinced he was blind, but he could still see and play with Cat Dancer.
Blindness may also manifest
itself in a less obvious manner. e.g. your cat may no longer jump and
climb, which you might ascribe to weakness, when in fact it is caused by
an inability to see where s/he is jumping. Your cat may also walk
differently, perhaps keeping to the side of rooms, or walking through food
(because s/he cannot see it).
Even if your cat's retinas detach because of
high blood pressure, if
treatment is started quickly enough, there is a chance of the retinas
re-attaching and your cat regaining some sight. See
below for more
on this.
One other possible cause of blindness in cats is the use of an antibiotic
called
enrofloxacin (Baytril), though this is extremely rare if dosage guidelines are
adhered to
.
Hypertension in cats and dogs
(2002) Stepien RL Presentation to the
Waltham/OSU Symposium: Small Animal Cardiology 2002
has a photo of a cat with detached retinas.
Pet Place
has an article about detached retinas, including information on other
possible causes.
VCA Hospitals have some information on
anisocoria (uneven pupils).
Bleeding Within the Eyes (Retinal Haemorrhage)
Bleeding within the eyes may also
be a sign of hypertension. The bleeding happens in the back chamber of the
eye, so it is often not visible. Cats
with retinal haemorrhage are not usually blind.
Ocular hemorrhage
(2021) Clode A Clinician's BriefOct 2021 pp12-15 has
a diagnostic and treatment chart.
Pet Place
also has some information about
hyphema, a type of bleeding within the eye
(intraocular), so it may be visible.
Iris aneurysm in feline hypertensive oculopathy
(2020) Linek J Veterinary
Ophthalmology23pp436– 441 found
that 30% of the cats with hypertension in the study had hyphema.
Heart Problems
Hypertension can damage the heart because the increased
pressure places a strain on the heart, which has to pump blood
around the body.
The most common finding is left ventricular
hypertrophy, which means the left ventricular chamber of the heart is
enlarged. Obviously you would not be able to see this, but here are some
possible heart-related signs of hypertension.
Heart Murmurs and Galloping Heart Rhythm
These are
possible signs of heart problems caused by hypertension, though they may
also indicate heart problems with other causes. In some cases a heart
murmur is not a cause for concern, especially if it is not of recent
origin (see
Heart
Problems), but
Blood
pressure in small animals Part 2: hypertension target organ damage heart
and kidney
(2009) Carr
AP & Egner BE European Journal of
Companion Animal Practice19(1) pp1-5 states
that "
A new murmur or gallop rhythm should
always lead to a blood pressure measurement."
Lethargy
Cats with heart problems caused by hypertension may be lethargic. You may
also see lethargy in cats with
neurological problems caused by
hypertension.
I am often asked when to seek veterinary help for these symptoms. I know it
can be expensive going to the ER or out of hours vet, especially if funds are
tight. I personally would seek veterinary help as follows:
If you think your cat has had a stroke, I would go to the vet
immediately.
A stroke is a medical emergency, so if necessary you will have to go to the ER or out of hours vet. The sooner treatment begins, the
better the chances for survival, and without permanent disability.
According to
Veterinary Partner, starting treatment within six hours of the
stroke "appears to be protective to neurologic tissues."
If you think your cat has gone blind, the sooner you start the
medication, the more likely that s/he will regain the lost vision, so I would
seek a same day appointment if the vet is open. I would be prepared to wait
overnight but if it were any longer than that, perhaps because of a holiday
weekend,
I would go to the ER or out of hours vet. How quickly you notice the
blindness is also a factor: if you realise very quickly, you have more room
for manoeuvre than if it suddenly dawns on you and you realise that actually,
your cat has probably been blind for several days or a week.
If you think your cat has heart problems caused by hypertension, I
would check the
Heart Diseases page to see if other urgent symptoms are present. If my cat
appeared to have other urgent symptoms, I would go to the vet, ER or out of hours
vet immediately. If my cat only had milder symptoms, such as nosebleeds, I would seek a same or next
day appointment, as long as my cat did not appear to be in distress. If
it was the weekend or a holiday, I would keep my cat quiet and get in to see
my vet as soon as possible after they opened. Keep a close eye on your cat and
be prepared to go to the ER or out of hours vet if your cat seems to be
worsening.
if you think your cat has had a seizure caused by hypertension, or if
you are seeing other possible signs of neurological problems caused by
hypertension, I would seek a same day appointment, as long as the
cat did not appear to be in distress (cats often seem fine after a seizure) and
as long as there was only one seizure lasting around 1-2 minutes. If it was the weekend or a holiday, I
mighy wait until my vet opened again, but if my cat had further seizures, I would go to the ER or out of
hours vet. If you cannot afford
to do that, it may well be safe to wait, but keep a close eye on your cat. If
your cat starts to have one seizure after the other (which fortunately is
unlikely), or has a longlasting seizure (over five minutes), it is a medical emergency and you need to go to the vet, ER or out
of hours vet as soon as possible.
In all cases, if you are able to measure your cat's blood pressure at home
and it is over 180 mmHg, I would seek urgent veterinary assistance. See
Emergency Treatment
for more information.
Other Symptoms of
Hypertension
Worsening Kidney Values
Since hypertension can adversely affect the kidneys, one possible symptom is a
worsening of kidney values in bloodwork, particularly if it appears to occur
quite suddenly. I recommend always having blood pressure checked in any cat
whose bloodwork worsens unexpectedly.
Other Symptoms
These symptoms still indicate a need to test for and treat hypertension if it
is present, but you do not need to rush to the
vet or ER. On the other
hand, I would not accept an appointment a week or two into the future either.
If you see these symptoms, try to be seen within a maximum of three days, but
ideally faster, of course.
Although
nosebleeds in themselves may not appear too serious, in a cat with
hypertension they may be a sign of damage caused by the
hypertension.
Clinical approach to patients with epistaxis
(2004) Gieger T & Northrup N Emergency Medicine26(1)
pp30-44
says "Increased capillary fragility with subsequent rupture can result
from hypertension."
Dental abscesses or a
low
blood platelet count may also cause nosebleeds.
Epistaxis (2018) Hillsman S & Tolbert MK
Clinician's BriefAug 18 p51 lists other possible causes.
A number of
people have reported this symptom over the years. In all cases, the cat
has turned out to have hypertension, often with a systolic reading over
200 mm Hg. Alternatively, red ears are sometimes seen in cats with food
allergies.
Blood in Urine
This can be
a sign of hypertension. It may also indicate the
presence of a urinary tract infection, or
There is a condition called "benign renal
haematuria" which means there is bleeding from the kidney but the cause is
not known; however, this is rare in cats.
Severe or
ongoing haematuria may cause or worsen anaemia, so you should always take
your cat to the vet if you see this symptom.
Cats who do
not eat are at risk of developing a potentially life-threatening condition
known as hepatic lipidosis;
Mar Vista Vet
has more information about this.
Therefore, it is important to try to find the cause and treat it as
quickly as possible.
How to
Diagnose Hypertension
Hypertension is often known as the silent killer because it is not usually
apparent and can be hard to detect until there is a crisis and the urgent
symptoms discussed above appear. There are a few subtle signs you or
your vet might be able to detect (see
below) but there is no
guarantee you will see these and even if you do, you won't know how severe the
hypertension is.
The ideal
preventative measure is for your vet to monitor your cat's blood pressure
regularly with proper equipment.
Unfortunately, not every vet has the equipment with which to check blood pressure. If your vet does not have the
necessary equipment, encourage him or her to purchase it. An alternative is to
call around other vets in your area — some are happy to do a one off blood
pressure check for non-clients for US$25 or so. My vet charges about
£16 to check blood pressure. Vets who do
home visits may be able to help, and it can be better for your cat to measure
blood pressure at home. You can also look into monitoring your cat's blood
pressure at home using your own equipment.
Your vet will use the equipment with which s/he is most comfortable.
Cross-sectional survey of non-invasive indirect
blood pressure measurement practices in cats by veterinarians
(2022)
Navarro I, Summers S, Rishniw M & Quimby J Journal of Feline Medicine and Surgery24(12) pp1195-1202 concludes "Though most veterinarians in this
survey had oscillometric devices in their practice, this survey identifies
a preference among veterinarians for the use of Doppler ultrasonic flow
detectors to yield more trustworthy blood pressure measurements in cats."
With
a doppler monitor, only the systolic pressure is recorded because diastolic
readings tend to be unreliable.
How to
Measure Blood Pressure
Preparation
Cats can suffer
from "white coat syndrome", also known as situational
hypertension, where their blood pressure rises from the
stress of the vet or hospital visit. This causes artificially inflated
readings that are not accurate, so it is best to make sure your cat
is as relaxed as possible before any tests are run:
you should
always try to be present when blood pressure is taken.
blood pressure
should be tested before any
other testing or handling is done.
blood pressure
should be measured in a quiet room. If possible, try to give your
cat 5-10 minutes to get used to the room before the blood pressure is
measured.
if your cat gets stressed at the vet's, it can sometimes help to cover the cat's
head with a towel or blanket. This would probably make humans more
stressed, but it does help some cats: we used to do this for Harpsie
whenever he had blood taken and it definitely made him calmer.
the person taking the measurements should be experienced in taking blood pressure in
cats.
Blood pressure
is often measured by wrapping the cuff around the cat's tail or a front paw.
Many cats seem to prefer having measurements taken on the tail, but some
studies have found that using the tail may result in higher readings.
ISFM Consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen BA
Journal of Feline Medicine and Surgery19 pp288–303 say "The
site for BP measurement will depend partly on what is tolerated best by
the cat, but the forelimb may be better for Doppler measurements while the
tail is better for HDO [high-definition
oscillometric]."
recommend discarding the first
measurement, then measuring blood pressure 5-7 times., but notes "In
some patients, measured BP trends downward as the process continues. In
these animals, measurements should continue until the decrease plateaus
and then 5-7 consecutive consistent values should be recorded."
The average of these readings is the cat's
blood pressure measurement. Do not rush taking the readings.
Some vets apparently ask people to leave their cat for several hours so the
readings can be taken over a longer timeframe and the cat may have calmed
down. Knowing my cats, their stress would only increase the longer they
were there, especially if I were not with them. I would also worry that my
cats might not eat while at the vet's. Personally, I would rather get
blood pressure checked several times during a single appointment with me
present, which is what I've always done.
You will
normally be told your cat has a blood pressure of x, with x being a
number, e.g. 160. See
below for
information on what the number means.
Sparkes AH, Blundell C, Cannon M, Gaut N, Harvey A, Jacmenikova Z,
Taylor S, Turner A-L & Zoltowska A International Society for Feline
Medicine shows how to measure blood pressure.
Measuring Blood Pressure at Home
Measuring blood pressure at home is the best choice for most cats because
they are far less stressed
Comparison of home blood pressure and office blood
pressure measurement in dogs and cats
(2022) Koo ST & Carr AP Canadian Journal of Veterinary Research86(3) pp203–208 unsurprisingly found that blood pressure
measurements taken at home were lower than in the vet's office, differing
by up to 27.75 mmHg. The study found that 41% of the cats exhibited
situational hypertension (also known as white coat syndrome,
where a cat's blood pressure appears to be higher than it is because of
the stress of being at the vet's). It concludes "Home blood
pressure (HBP) measurement is a practical method for measuring blood
pressure and should be encouraged to reduce the likelihood of unwarranted
diagnosis of hypertension and unnecessary medical interventions in the
form of prescriptions for medications or diagnostics to lower blood
pressure."
Unfortunately the upfront cost of most blood pressure monitors is too high
for many people. In such cases, a possible compromise would be to find a
vet or veterinary nurse/technician who is prepared to come to your home to
measure your cat's blood pressure. This might cost more than taking your
cat to the vet, but your cat will be less stressed and the blood pressure
readings should be more accurate. Alternatively, your vet might be
prepared to loan you one of the practice's blood pressure monitors for a day or two (perhaps over a weekend so
you can obtain several readings) for a fee.
Still, some people with CKD cats have purchased blood pressure
monitoring equipment for home use, and been trained in its use by their
vet. This is more convenient and it avoids the problem of "white coat
syndrome."
If possible, try to test the model you are thinking of purchasing before
going ahead; I bought an expensive model but never really mastered using it.
My cat was
small and dainty, and even my vet struggled to measure her blood
pressure. After my cat died, I eventually sold the monitor on eBay and the
person who bought it had no problems using it on his larger, sturdier cat.
Reasonably Priced Home Blood Pressure Monitoring Equipment
In the last few years, a more reasonably priced blood pressure monitor has
become available for home use.
is a
Chinese oscillometric veterinary blood pressure monitor available
to order in many parts of the world.
It stores up to 100 readings for future reference, and alerts you if your
cat is wriggling too much to get an accurate reading. It can run off
batteries or the mains.
Whilst
naturally not as good as the veterinary quality equipment (it
has an instruction manual written in Chinglish, and it also takes a long
time to register the readings), it is ridiculously good value,
costing around US$50-75 (including shipping from China), depending upon
where you live,
and therefore very affordable for most people.
A number of Tanya's CKD Support Group members have purchased this model
over the last few years and the vast majority like it.
Some of them
have taken the Contec into their vet's office and checked their readings
against those taken with their vets' expensive equipment. They usually
find that overall the monitor is reasonably accurate, and certainly
sufficient for monitoring trends.
You may also need a neonatal cuff to fit your
cat (it comes with a size 2 or 3, but your cat may need a different size). If
the size you use is too small or tight, it can make the reading look
higher than it actually is. If the size you use is too big or loose, it can make the reading
look lower than it actually is.
Model no. 811-B is a popular Doppler machine that has been used by a number
of people dealing with CKD over the years. You do need a vet's
prescription to buy one. It costs from US$785 but essential accessories (cuffs etc.) cost extra,
so your total cost will be in the region of US$1200.
Another brand which
several people with CKD cats have purchased. With all
the extras, it costs about US$1000. This link also has a video from Dr
Gary Norsworthy showing how to measure blood pressure. I used to have this
model, but I could never get it to work, and my vet found it challenging
too (my cat was small and dainty, which might have been a factor).
Sells the Vet BP Doppler kit for £759. You may need to ask your vet
to order it on your behalf.
Factors Affecting Blood Pressure Measurements
A number of factors can affect blood pressure.
Blood pressure measurements in 780 apparently
healthy cats (2017) Payne JT,
Brodbelt DC & Luis Fuentes V Journal of Veterinary Internal Medicine31(1) pp15-21 found that the mean blood pressure in healthy cats
was 120.6 but it was higher in cats who were older, male, neutered,
nervous or with a history of being a stray.
Effects of Stress on Blood Pressure Measurements
Some vets refuse to measure or treat blood pressure in stressed or nervous
cats, claiming that the results will be inaccurate. This stress response
is often known as the "white coat effect." More recently, it has
been given the name of situational hypertension.
Whilst stress may indeed affect the results, it will only do so by 20 or
so points.
On the other
hand,
Evaluation of Doppler ultrasonic and oscillometric
methods of indirect blood pressure measurement in cats
(2004) Habermann CE, Morgan JD, Kang CW & Brown SA International
Journal of Applied Research in Veterinary Medicine2(4) pp279-289
found that
the usual method of measuring blood pressure in cats (Doppler) tends to
understate the result by around 11-24 points
in conscious cats. So although
stress may be affecting your cat's results, if you are using Doppler equipment,
it may be underestimating your cat's blood pressure measurement (though
this study is now quite old and the equipment could well have improved
since then).
Comparison of home blood pressure and office blood
pressure measurement in dogs and cats
(2022) Koo ST & Carr AP Canadian Journal of Veterinary Research86(3) pp203–208 unsurprisingly found that blood pressure
measurements taken at home were lower than in the vet's office, differing
by up to 27.75 mmHg. The study found that 41% of the cats exhibited
situational hypertension (also known as white coat syndrome,
where a cat's blood pressure appears to be higher than it is because of
the stress of being at the vet's).
If you follow the tips
above on how to measure blood pressure, you will minimise the risks of
inaccurate results. If you see urgent symptoms as described
above, such as
a stroke or blindness, I would ask your vet to consider treating anyway.
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822
says "The presence of TOD (eg, retinopathy and
CKD) justifies initiating treatment after a single measurement session,
but in most cases, results should be confirmed by measurements repeated on
multiple (>2) occasions."
If your cat's blood pressure readings are over 160 mmHg on two or more
occasions, I would want to treat it, even if the readings were taken at
the vet's.
"Spiking" Blood
Pressure
It is normal for a cat's blood pressure to vary throughout the day.
Diurnal variations of blood pressure in cats
(2006)
Mishina M, Watanabe N, Watanabe T Journal of Veterinary Medical Science68(3) pp243-8 found that blood pressure in healthy cats
peaked at 8 a.m. and 7 p.m.
Diagnosing hypertension in primary care: a
retrospective cohort study to investigate the importance of night-time
blood pressure assessment
(2023) Armitage LC, Davidson S, Mahdi A, Harford M, McManus R, Farmer A,
Watkinson P & Tarassenko L British Journal of General Practice73(726)
e16-e23 found that 10.8% of the human patients in the study had blood
pressure that was higher at night than during the day. It is not known if
this applies to cats, but if you have a blood pressure monitor for home
use, it might be worth checking your cat's blood pressure late at night.
Unfortunately sometimes a cat's blood pressure will "spike" (increase dramatically, then
reduce to normal levels) at intervals, which means you may notice symptoms
of hypertension in your cat but tests at the vet appear normal.
More worryingly, you may see no symptoms but your cat's blood pressure
could be spiking and causing harm without you realising it. I feel quite
strongly about this because I lost one of my cats to the effects of
spiking blood pressure. She did not have CKD, indeed her only health
problem was hypertension. She therefore had been on amlodipine for several
years and her blood pressure was always fine during vet checks (which were
usually performed every three months), but she
suddenly collapsed (briefly) at home one evening and a veterinary cardiologist discovered
the next day that her heart
had been damaged by hypertension. He was hopeful that bringing her blood
pressure under proper control would improve her heart function and added
another medication to her regimen for this purpose, but she collapsed and
died at the vet's during a check up ten days later.
If you suspect that your cat has spiking blood pressure, I would
discuss with your vet how to test for this. One possible method would be
for your cat to be kept at the hospital and to have blood pressure checked
every hour. A better solution would be if you could borrow (or buy) a
blood pressure monitor and check your cat's blood pressure frequently at
home yourself after being shown how to do this.
If you suspect your cat has spiking blood pressure, I would also consider
asking for a referral to a veterinary cardiologist.
What to Do if Blood Pressure Measuring
Equipment is Not Available
The following
tests are no substitute for the proper measurement of blood pressure
using dedicated equipment, but if you live in the middle of nowhere with
no blood pressure testing equipment available, at the very least ask
your vet to perform them. But if your cat has signs of damage caused by
hypertension, you should treat regardless, see
below.
You could also consider buying the cheaper monitor for home use which
only costs about US$50 (see
above).
Retinal
Examination
Firstly, you and your vet should regularly examine the retina (a fundic
exam) — often there are retinal changes caused by hypertension prior to
retinal detachment occurring, though
unfortunately these are not always visible, even to a vet.
An older cat's pupils may not dilate and contract the same
as in a younger cat so you should try to ascertain how your cat's pupils
respond to light i.e. what is normal for your cat.
Jorgensen Laboratories sells an indirect
viewing lens for US$52, though you would probably need your vet's help in
understanding how to use it.
Femoral
and/or Jugular Pulse
You can also try to become familiar with the way your cat's femoral pulse
feels (this is the pulse in the femur, the thigh bone). If your cat has
hypertension, the pulse will usually feel stronger than the norm for your cat.
Your vet can teach you how to assess this.
You can also watch for jugular pulsing: slightly elevate your cat's chin and
watch in the jugular area (in the neck) — you shouldn't see any pulsing.
PetCoach has instructions on how to take the
femoral pulse.
Enlarged Aorta
The aorta is the large artery running from
the heart.
A chest x-ray may show that it is enlarged — in
Feline cardiology: back to the basics Bright
JM Delaware Valley Academy of Veterinary Medicine states
"This change is often noted as a normal aging change in cats; however, an
enlarged aortic root may also indicate systemic hypertension." This
was what alerted my cardiologist to the fact that my cat's hypertension
was actually not under control.
Blood Pressure: Important Numbers
A normal blood pressure is when systolic
pressure is below 140 mmHg.
Treatment is usually started when systolic pressure is over 160 mmHg.
If your cat's blood pressure is over 180mmHg and your cat has serious
symptoms such as sudden onset blindness or seizures, it is a medical
emergency and your cat needs immediate treatment.
The goal is ideally systolic blood pressure below 150 mmHg, though you
may have to settle for below 160 mmHg.
Systolic blood pressure should not fall below 120 mmHg (hypotension)
in a CKD cat.
mmHg is pronounced millimetres of mercury.
When to Start Treatment
The recommendations differ depending upon whether your cat has target
organ damage or not.
What is meant by target organ damage? Cats are considered to have target organ damage
if they:
are showing the severe symptoms of hypertension
described above; and/or
have kidney bloodwork which has worsened;
and/or
have
proteinuria.
Proteinuria (2013)
Syme H Presentation to the 38th World Small Animal Veterinary
Association World Congressmentions that hypertension may promote proteinuria.
The chances of your cat developing target organ damage
depend upon how long your cat has had hypertension (whether you knew about it
or not); how severe it is; whether it has been treated up to now; and whether
your cat has any other conditions that increase the risk of hypertension,
such as CKD or
hyperthyroidism.
The chances of target organ damage occurring in the future
increase once blood pressure is consistently over 160 mmHg. Ocular (eye)
problems have occurred with blood pressure as low as 168 mmHg, according to
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822. The risk of
ocular and neurological problems (seizures, stroke etc.) is much higher
once blood pressure is over 180 mmHg.
One member of Tanya's CKD Support Group's cat went blind even though her
cat's blood pressure had never been high when measured by her vet,
veterinary cardiologist and veterinary ophthalmologist. Since her cat
clearly had target organ damage (blindness), the cat was treated and
successfully regained her sight. In this case, it is possible that the
cat's blood pressure was spiking.
Average Systolic Blood Pressure Measurement (mmHg)
Risk of Damage
to Organs
BP Substage
Treatment Plan
Under 140
Minimal
Normotension
No treatment necessary
140-159
Low
Prehypertension
Treatment is not normally necessary. However, it may be
appropriate to begin or increase blood pressure medications if ocular or
neurological signs are present
160 - 179
Moderate
Hypertension
Begin or increase blood pressure medications
Over 180
Severe
Severe
hypertension
Begin or increase blood pressure medications
IRIS staging of CKD
(2019) International Renal Interest Society
follows the ACVIM guidelines:
Systemic hypertension in cats
(2022) Sparkes A Clinician's BriefMar 22 pp20-21 gives an overview of when and how to treat
hypertension.
≥ 150 mmHg on a single occasion, and there is clear evidence of ocular or
neurological TOD; or
≥
160 mmHg on at least two separate occasions, and there is evidence of TOD
including ocular, neurological, cardiac or kidney damage.
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society states
"
The general consensus is to institute therapy in a patient
with evidence of TOD, if reliable measurements of BP indicate that
systolic BP exceeds 160 mm Hg (that is, for hypertensive and severely
hypertensive patients...)
and in a patient with persistent hypertension. Animals with CKD are
presumed to have TOD, even though it may not be clinically apparent." Thus, if your cat has
CKD and hypertension, you should treat the hypertension as if TOD were
present. Please see the
table above.
See below
for when emergency treatment is required.
Emergency Treatment for Cats With Target Organ Damage (TOD)
Some cats with hypertension require emergency treatment.
Evaluation
of presentation, treatment and outcome in hypertensive emergency in dogs
and cats: 15 cases (2003-2019) (2022) Beeston D, Jepson R &
Cortellini S Journal of Small Animal Practice63(10)
pp784-791 states that in humans, it is considered a hypertensive crisis
when systolic blood pressure is over 180mmHg. This is then sub-divided
into hypertensive urgency if there is no target organ damage, but
hypertensive emergency if there is target organ damage. (In this study,
75% of the cats were found to have
acute kidney
injury, and half of those had acute on chonic kidney disease (aCKD)).
The same approach is also being taken in veterinary medicine.
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822 states
"Regardless of knowledge of
predisposing disease conditions, diagnosis of SBP ≥ 180 mm Hg (high TOD
risk category) in a patient with signs of intracranial TOD (eg, focal
facial seizures) necessitates immediate emergency treatment. The need for
aggressive treatment in such cases typically requires 24-hour care
capability, and referral to such a facility is warranted when 24-hour care
is not available."
ISFM Consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen BA
Journal of Feline Medicine and Surgery19 pp288–303 say
"Cats with evidence of TOD at the time of diagnosis and/or cats with SBP
>2OO mmHg should have their SBP and clinical signs monitored closely
during the first 24-72h. For some cats (eg, those with overt hypertensive
encephalopathy or severe cardiac complications) hospitalisation may be
required to allow close monitoring and control of the SBP In other cases,
initial daily re-evaluation may be sufficient. " They provide
suggestions for how to deal with urgent cases (see the Emergency
Treatment panel on page 299).
Treatment is not
normally necessary. Check in 3-6 months.
Blood pressure between 160
mmHg and 179 mmHg
Check blood pressure twice within the next eight weeks, and recheck for
target organ damage. If the blood pressure upon recheck is below 160 mmHg,
recheck in 3-6 months. If blood pressure is over 160 mmHg, check for
underlying conditions, and begin treatment with blood pressure medication
Blood pressure over 180 mmHg
Check blood pressure twice within the next two weeks, and recheck for
target organ damage. If the blood pressure upon recheck is below 160 mmHg,
recheck in 3-6 months. If blood pressure is over 160 mmHg,
check for underlying conditions, and begin treatment with blood pressure
medication.
If you are giving an
erythropoiesis stimulating agent such as Epogen, Procrit, Eprex or
Aranesp for anaemia, I
would check blood pressure each time you check the anaemia.
Indirect SBP is > 170 mmHg
on at least two separate occasions, and the clinician does not consider
‘white coat hypertension’ is likely to be the cause."
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society states
"The general consensus is to institute therapy in a patient
with evidence of TOD, if reliable measurements of BP indicate that
systolic BP exceeds 160 mm Hg (that is, for hypertensive and severely
hypertensive patients...)
and in a patient with persistent hypertension. Animals with CKD are
presumed to have TOD, even though it may not be clinically apparent."
Thus, if your cat has CKD and hypertension, you should treat the
hypertension as if TOD were present.
I have always treated my cats for hypertension if their blood
pressure was over 160 mmHg on two separate occasions 1-2 weeks apart (I
usually check after a week, not two), even
if they did not show any symptoms. I would not feel comfortable checking
over a period of eight weeks.
If
Your Vet Refuses to Test or Treat Your Cat for Hypertension
I sometimes hear about vets who refuse to test a CKD cat for hypertension,
saying things like "oh, your cat is only Stage 2, he's fine."
This is a mistake.
I also hear about vets who refuse to treat hypertension, perhaps because they believe
treatment will do more harm than good.
Let me spell this out loud and clear: if your cat has untreated
hypertension, it could kill him or her. So if you have not been able
to check your cat's blood pressure, find a way to do so. If you have checked your cat's
blood pressure and it is at a level where it needs to be controlled (see
above), insist upon
treatment. If your vet refuses, find another vet.
If you have not been able to check your cat's blood pressure or only have
one measurement, but there are signs of target organ damage, it is safer to treat
anyway.
Treatment recommendations for CKD in cats
(2023) International Renal Interest Society state that, for cats exhibiting target organ damage, treatment
should begin immediately without the need to prove persistent
hypertension.
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822
says "The presence of TOD (eg, retinopathy and
CKD) justifies initiating treatment after a single measurement session."
Systemic hypertension in cats
(2022) Sparkes A Clinician's BriefMar 22 pp20-21 gives an overview of when and how to treat
hypertension.
Therefore, if you suspect your cat has hypertension because
of signs of target
organ damage such as blindness, I would want to
try amlodipine and see if your cat improves. If your vet is nervous about
treating for hypertension on this basis,
Veterinary Partner mentions that amlodipine is a
pretty safe drug and is unlikely to cause the opposite problem of
hypotension (low blood pressure), even in a cat whose blood pressure is not
overly elevated.
Blood
Pressure Target
Your target varies depending upon whether your cat has CKD or not.
Blood Pressure Levels and
Targets in
Healthy Cats
Diurnal variations of blood pressure in cats
(2006)
Mishina M, Watanabe N, Watanabe T Journal of Veterinary Medical Science68(3) pp243-8
found that the average blood pressure over a 24 hour period in healthy
cats was 118.4 mmHg (with a range of 107.4 - 129.4 mmHg).
Blood pressure measurements in 780 apparently
healthy cats (2017) Payne JT,
Brodbelt DC & Luis Fuentes V Journal of Veterinary Internal Medicine31(1) pp15-21 found that the mean blood pressure in healthy cats
was 120.6 but it was higher in cats who were older, male, neutered or with
a history of being a stray.
Thus, a level of around 120 is a good target for healthy cats.
Blood Pressure Levels and
Targets in
CKD Cats
You are unlikely to reach a level of 120 mmHg, but then
a CKD cat
is no longer a healthy cat.
state that the goal for CKD cats is to reduce blood pressure to under 160 mmHg and to
reduce the risk of target organ damage.
ISFM Consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen BA
Journal of Feline Medicine and Surgery19 pp288–303 say "an
initial target SBP of <160 mmHg.
Given that the IRIS group suggests the risk of TOS is minimal if SBP is
<150 mmHg, and that some cats with TOD have pressures below 160 mmHg, a
target of <150 mmHg may be an appropriate long-term goal."
state
"regardless of the initial magnitude of BP, the goal of treatment should
be to maximally decrease the risk of TOD (SBP [systolic blood pressure] <
140 mm Hg) and that antihypertensive treatment should be adjusted on
re-evaluation if SBP is ≥160 mm Hg, with a minimal goal of treatment being
to achieve a decrease in SBP to ≤160 mm Hg."
The guidelines add
"A gradual, persistent decrease in BP is the therapeutic goal. Acute
marked decrease in BP should be avoided."
Reassessment of "normal" values in dogs and cats
with chronic kidney disease
(2019) Grauer GF International Renal Interest Society says
"All these findings support the view that blood pressure below the
currently classified hypertensive cut off (160 mm Hg; i.e. 140-159 mm
Hg) may contribute to kidney injury in some animals. For example,
treatment targets in hypertensive people that are also
proteinuric tend to
be lower."
Therefore your goal should be a blood pressure measurement between 120
and 159 mmHg, but ideally
between 120 and 149 mmHg (or even 140 mmHg) if possible. In practice you will
probably find you are at the top end of the scale.
Although healthy cats may have blood pressure below 120 mmHG, the minimum
level for a CKD cat tends to be a little higher because of the tendency for CKD cats to
have high blood pressure, and the
need to avoid falls in blood pressure that can adversely affect the kidneys
(see
above).
Treatment recommendations for CKD in cats
(2023)
International Renal Interest Society
state "Systolic
blood pressure <120 mm Hg and/or clinical signs such as weakness or
tachycardia indicate hypotension, which is to be avoided."
Hypertension is usually easily controlled, which should help your cat feel
better.
Treatment recommendations for CKD in cats
(2023)
International Renal Interest Society
does mention that
"reducing
blood
pressure
may
lead
to small
and
persistent
increases
in creatinine
concentration
(<45
μmol/l
or 0.5
mg/dl
increase)or
SDMA concentration (<2.0
μg/dl)." In my experience, this is
relatively rare; in fact, since hypertension can itself damage the
kidneys, getting it under control may actually lead to improved kidney
values in some cats.
Hypertension has
been associated with proteinuria and histological renal injury...Proteinuria,
in turn, has been associated with more rapid progression of renal disease
and increased all-cause mortality in numerous clinical settings, including
CKD and hypertension. Antihypertensive treatment generally decreases the
severity of proteinuria, at least if the hypertension is severe."
If your cat has a condition that is contributing to the hypertension, such
as
hyperthyroidism,
it is important to treat that condition. Doing so may even mean the
hypertension resolves without the need for additional treatment.
Sodium Restriction
Your vet may ask you to restrict your cat's sodium intake.
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
states "it is likely that those with kidney disease, especially those with
nephrotic syndrome, are salt sensitive. Furthermore, salt restriction
enhances the antihypertensive efficacy of some antihypertensive drugs,
particularly those that interfere with the renin-angiotensin-aldosterone
system (RAAS). This evidence from laboratory studies of dogs and cats
serves as the basis for the recommendation to feed a diet with reduced
sodium chloride content to dogs and cats with CKD, regardless of IRIS
stage."
However,
Treatment recommendations for CKD in cats
(2023)International Renal Interest Societystate that there is no evidence this is helpful for
cats, and that if it is done, it should be done gradually and in addition
to, rather than instead of, medication.
High-sodium diets do not appear to promote HT in
cats with reduced renal function" but then adding "high salt intake may
produce adverse consequences in some settings, including animals with CKD.
The panel therefore recommends avoiding high dietary sodium chloride
intake. However, the selection of appropriate diet should include other
patient-specific factors, such as underlying or concurrent diseases and
palatability."
The ACVIM consensus statement does also mention that restricting sodium
intake can activate the
RAAS.
The
food data tables provide information about the sodium content of many
cat foods available in the USA. Please see
Nutritional Requirements for more information about sodium and whether to
reduce your cat's intake.
If you do decide to try to restrict sodium intake at your vet's request, you should do it gradually.
Medications
There are several types of medication used to
control blood pressure in cats, and many of these are heart medications. You may be offered amlodipine (a calcium
channel blocker), telmisartan (an ARB), benazepril (an ACE inhibitor) or,
less commonly, atenolol (a beta blocker).
If you are in the USA, you may well be offered
telmisartan, because, as
the
US Food and Drug Administration reports,
telmisartan, under the trade name of Semintra, was approved in the USA in
2018 for the treatment of hypertension in cats. However, most experts
agree that amlodipine is the drug of choice, though for severe hypertension you may need to
use another
medication in addition to the amlodipine.
The preferred treatment is a drug called
amlodipine,
which is a heart medication in the calcium channel blocker family.
Changes in retinal vascular diameters in senior
and geriatric csts in association with variation in systemic blood
pressure
(2021) Enache A-E, Dietrich UM, Drury O, Trucco E, MacGillivray T, Syme
H, Elliott J & Chang Y-M Journal of Feline Medicine and Surgery
23(12) pp1129-1139 states "as a calcium channel blocker, the
amlodipine relaxes the tone of arterioles and causes a reduction in the
arterial BP with a dilating effect on cardiac and vascular smooth muscle
cells, thereby improving vascular resistance."
Amlodipine is widely available and not normally too expensive.
You may be
offered generic amlodipine or you may be given a branded version — I have
used both with no problems. Brand names include
Norvasc
in the USA and Canada and
Istin in Europe and Australasia.
it works for most cats.
ISFM Consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen BA
Journal of Feline Medicine and Surgery19 pp288–303
refer to "60–100% of cats responding to amlodipine as a monotherapy,
albeit with dose adjustment being needed in some."
The study also mentions that amlodipine may reduce blood pressure by 30 t0
70 mmHg.
most importantly, it may help cats who have suffered a stroke, and may reverse blindness in cats who have
suffered retinal detachment caused by the hypertension.
it takes effect quickly
(usually within a week).
it is reasonably priced. In the USA, it is often available in pharmacies'
$4 specials range or similar.
Amlodipine and Strokes
A stroke is a medical emergency and you need to get your vet to the
hospital for in-patient treatment as quickly as possible. According to
Veterinary Partner, starting treatment
with amlodipine within six hours of the
stroke "appears to be protective to neurologic tissues."
Even if you do not manage to get help within six hours, you should still
ensure your cat is treated as soon as possible because improvements may
still be seen.
Your cat may be
quite inactive after a stroke, so make sure s/he is kept hydrated and
takes in food. You may have to carry your cat to the litter tray for a few
days, or use puppy pads.
Don't give up
hope:
Vet Info states that "on average, most
feline patients recover and return to normal in two to three weeks after
the stroke."
Seizures are a relatively
common symptom of hypertension in cats (they may have other causes too).
Occasionally cats who have had a
stroke will start to have seizures, and in such cases anti-convulsant
medication may be required.
If your cat has high blood pressure (especially if it is over 180 mmHg) and has suddenly lost his/her
vision, s/he may need to be hospitalised.
See Emergency
Treatment for more information.
If your cat is blind because of hypertension, there is an approximately
50:50 chance of the retinas re-attaching and your cat regaining some sight
if treatment with amlodipine is started quickly enough (usually within
three days of detachment).
Cornell University College of Veterinary Medicine
says "We can treat a cat’s high blood pressure with a drug called
amlodipine, which may allow a retina to reattach itself, and the cat can
get some of its vision back." Plumb's Veterinary Drug Handbook
says "some vision may be restored in about 50% of cases of blindness
secondary to hypertension."
Even if you do not start amlodipine immediately, there is still hope: I
know of several CKD cat who went blind but regained their sight, even
though treatment was not begun for some time, in a couple of cases not for
2-4 weeks. The longest I know of was a cat who showed some improvement
(I saw the photos) even though treatment was not begun for twelve weeks.
Feline comorbidities: the intermingled relationship between chronic kidney
disease and hypertension (2021)
Lawson JS & Jepson RE Journal of Feline Medicine and Surgery23(9) pp812-822 says "the feline retina may potentially regain
function even with prolonged detachhment."
Visual outcome in cats with hypertensive
chorioretinopathy (2019) Young WM,
Zheng C, Davidson MG & Westermeye HD Veterinary Ophthalmology 22(2)
pp161-167 states "With treatment, the prognosis for long-term vision in
cats with hypertensive chorioretinopathy, even following complete retinal
detachment, is good." The study found that 57% of the cats in the study
regained some vision. For some bizarre reason, male cats were more likely
to regain their sight.
If your cat is blind and you can see
a veterinary ophthalmologist, s/he may be able to suggest other measures in
addition to the use of amlodipine to reduce inflammation and increase the chances of the retinas
reattaching; but many people just use amlodipine with the help of their
general vet and see an improvement in their cat's vision.
How long it takes to see improvement varies. Many people think they can
detect small improvements after around a week, but it can take a month or
longer to see the full effect, so don't give up hope too early on.
What have you got to lose by trying amlodipine? Your cat may well regain
at least some vision, and even in s/he does not, s/he will be safe from
the other risks of untreated hypertension.
If your cat's retinas do not re-attach, or if your
cat's vision improves, then later worsens again (as occasionally happens),
do not despair. Cats cope far better with blindness than humans do because they are less
reliant on sight for navigation than humans are, and I would not
consider blindness in itself to be grounds for euthanasia.
The usual
starting dose for cats is 0.625 mg per day, given once daily.
However,
some cats need double this dose (1.25 mg), either because of their size
or the severity of their hypertension.
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
says
"If an antihypertensive agent of choice is only partially effective, the
usual approach is to increase the dosage before adding another drug."
In some cases, even lighter cats may need higher doses, either because
their hypertension is severe or if their hypertension does not respond
to the lower dose.
Factors influencing the relationship between the
dose of amlodipine required for blood pressure control and change in
blood pressure in hypertensive cats
(2016) Bijsmans ES, Doig M, Jepson RE, Syme HM, Elliott J &
Pelligand L Journal of Veterinary Internal Medicine30(5)
pp1630-1636 states "As the goal of antihypertensive treatment is to
reduce blood pressure to normal levels as quickly as possible in order
to prevent TOD, the authors suggest that cats with SBP > 200 mm Hg
should have an initial starting dose of amlodipine of 1.25 mg PO q 24
hours."
ISFM
consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen
BA Journal of Feline Medicine and Surgery19 pp288–303 say
"For cats with SBP ≥ 200 mmHg, consideration should be given to
commencing therapy at 1.25 mg/cat (0.25 mg/kg) q24h PO."
In very rare cases, a cat may need up to 2.5 mg per
day, but
ISFM
consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen
BA Journal of Feline Medicine and Surgery19 pp288–303
say only few cats need such a dose and you should check to make sure
your cat is definitely taking the medication (and not spitting it out
when you are not looking). In practice, many vets would prefer to give a
lower dose of amlodipine and add another blood pressure medication.
It can take up to a week for amlodipine to work, though you may see
results more quickly. Your vet should check blood pressure 7-10 days after
starting amlodipine, though personally I prefer to check it after a week.
If blood pressure remains severely elevated with a dosage of 0.625 mg, the dosage may be increased
to 1.25 mg per day. Any changes (especially reductions) in dosage should be made gradually, to
give the cat's body time to get used to the lower dose.
Once a cat is taking blood pressure medication, it will normally need to
be given for life.
How to Cut Amlodipine into Cat-Sized Doses
The usual dose is 0.625 mg
per day, but since the tablets dispensed are often 5 mg, this means you need
to break the tablet into eight, a tricky thing to do. One method of doing
this is to use flat-edged tweezers:
Snap the
pill in half with your fingers.
Take the
half-pill and grip it firmly in the tweezers so that the edge of the
tweezers are gripping the piece right in the middle. Then just grasp the
other half of the piece with your other hand, and snap it off.
Repeat step
2 until you have eight pieces.
This method
also works for the 2.5 mg tablets (which you would usually divide into four
rather than eight).
Generic amlodipine
is also available, but these pills tend to be even
smaller than brand name Norvasc, so you may find that overall there is no
advantage because you waste more of the lower priced pills.
Other Methods of Administration
UK and Europe
In the UK it is
much easier to find cat-sized doses of amlodipine. The downside is that
these medications are far more expensive than generic amlodipine. The upside is that you know your cat is
getting a more exact dose each day.
I used a
cat-sized version (0.625 mg) stocked by my vet and made by
Summit Veterinary Pharmaceuticals Limited for my own cats, with no
problems. It was much easier simply being able to give a single pill rather
than having to break it into tiny pieces. These can only be ordered by
vets.
In March 2015 a 1.25 mg chewable tablet form of amlodipine called
Vivelin, marketed by Orion Corporation, was approved in Ireland,
but it does not ever seem to have been released. In
November 2015 a chewable form of amlodipine made by Ceva called
Amodip was launched in Europe. Amodip comes
in 1.25 mg chewable tablets and is designed to be easy to break into halves
if your cat is on the more usual dose of 0.625 mg. As far as I can tell,
these products are in fact one and the same.
Drugstore News
reports that amlodipine is actually free at
Publix pharmacies, though I suspect this
won't apply to feline prescriptions.
Thriving Pets
sells 100 0.625 mg tablets for US$70.
If you enter the word "tanya" (without the ") in the
promotional code box, you will receive a 10% discount on orders over US$100.
Shipping is free for orders over US$80 after the discount.
In the USA it is possible to have medications compounded (made specially for your cat in
cat-sized doses,
sometimes in flavoured form) by a
compounding
pharmacy. Capsules or liquid suspensions (a liquid form of medication)
are available, but if you opt for this, make sure
you use a reliable compounding pharmacy. If you use a compounded amlodipine suspension,
you should keep it in the fridge and discard it after 14-28 days.
Wedgewood Pharmacy
offers a suspension product containing amlodipine (2.5mg/ml) and
famotidine (20mg/ml).
Some people
in the USA have amlodipine made into a
transdermal medication,
but I would not recommend this, because it is hard
to know how much of the medication is being absorbed when it is given in this
way. In fact, a couple of
Tanya's
Feline CKD Support Group
members
have found that the transdermal amlodipine they have used has not
successfully controlled their cat's blood pressure, whereas the more usual
commercially available form has done so. Since amlodipine is such an important
medication, if at all possible, I would use the other forms. If you do
need to use transdermal amlodipine for some reason, be aware that
Treatment of feline hypertension with transdermal
amlodipine: a pilot study (2007) Helms SR Journal of the
American Animal Hospital Association43(3) pp149-56 found that in
cats given this form, blood pressure was 20 mmHg higher than in cats given
standard amlodipine.
Amlodipine: Possible
Downsides
Activation of
the RAAS
One potential downside of amlodipine is that it may activate the RAAS (see
above for an
explanation of what this means).
Plumb's
Veterinary Drug Handbook
states "There is concern that using
amlodipine alone for treating hypertension in cats with renal disease may
expose glomeruli to higher pressures secondary to efferent arteriolar
constriction. This is caused by localized increases in RAAS axis activity
thereby allowing progressive damage to glomeruli.'
However, it is usually more important to get the hypertension under
control and avoid or minimise target organ damage, and for most cats
amlodipine is the best choice for this.
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822 states "Despite
the potential role of either the systemic or intrarenal RAAS axis in the
pathogenesis or maintenance of hypertension, CCB, specifically amlodipine
besylate, have been the first choice for antihypertensive treatment because of
established efficacy."
One possible compromise is to use other blood pressure medications in addition
to amlodipine when appropriate, see below
for more information.
Amlodipine and Hypotension (Low Blood Pressure)
Amlodipine appears to be a safe medication for the vast majority of cats, and
does not seem to lower blood pressure too far, as may happen with some other
types of
blood pressure medication. Indeed,
Blood
pressure in small animals Part 2: hypertension target organ damage heart and
kidney
(2009) Carr
AP & Egner BE states "Adverse side
effects from a rapid drop in blood pressure (weakness, syncope, organ
failure) are rarely reported."
Possible signs of low blood pressure include
lethargy, fainting, drinking more, nausea, pale gums, and fast and shallow
breathing.
If you are at all concerned about any of the symptoms you see, contact your
vet who can check to see if your cat's blood pressure has fallen too low
(below 120 mmHg for a CKD cat).
Amlodipine Possible Side Effects
The worst side effect of using amlodipine generally appears to be that some cats may become a bit lethargic when first
starting it, but this should wear off as their bodies get used to
the medication. In fact, most cats eventually seem brighter once their blood pressure
is under control.
Other possible side effects include constipation, upset stomach,
loss of appetite and, rarely, swelling of the limbs or an increased heart rate.
You should contact your vet if you notice an increased heart rate.
Chronic kidney disease (2007)
Polzin D
Delaware Valley Academy of Veterinary Medicine says "amlodipine
may promote hypokalemia in cats with chronic renal insufficiency/failure."
Therefore
you should ensure your cat's potassium levels are monitored and
potassium supplementation begun if
necessary.
Amlodipine should be used with caution in cats with liver disease.
If your cat does not seem to do well on amlodipine, it may be worth trying
another brand — some members of Tanya's Support Group have found this makes a
difference.
If, in addition to
lethargy, you see any of the symptoms linked to low blood pressure mentioned
above, contact your vet.
The European Medicines Agency says
(clause 4.8 on page 9) that "Cerenia should not be used concomitantly
with Ca-channel antagonists as maropitant has affinity to Ca-channels."
The University of Zürich Institute for Veterinary
Pharmacology and Toxicology also
mentions this (in German). In principle this means that amlodipine
should not be used with
maropitant (Cerenia),
a treatment commonly given to CKD cats to help with nausea and vomiting. 'Concomitantly' has a rather
vague medical meaning in that it means during the same time period, but in
this context I don't know exactly what time period the EMA is referring
to, i.e. do they mean at the same time or on the same day? Both of these
medications tend to be given once daily, so they have a relatively long
effect. Maybe giving them both on the same day but 12 hours apart
(i.e. one in the morning and one in the evening) would probably be
acceptable, but check with your vet or pharmacist.
Fosrenol
is a lanthanum carbonate-based phosphorus binder used for some CKD cats. In 2011 the US Food
and Drug Administration issued a
Safety Labeling Change which states "There have been reports of serious cases of
gastrointestinal obstruction, ileus, and fecal impaction reported in
association with lanthanum, some requiring surgery or
hospitalization. Risk factors for gastrointestinal obstruction identified
from post-marketing reports include alteration in gastrointestinal anatomy
(e.g., history of gastrointestinal surgery, colon cancer) hypomotility
disorders (e.g., constipation, ileus, diabetes) and concomitant
medications (e.g., calcium channel blockers). Some cases were reported in
patients with no history of gastrointestinal disease." Since
amlodipine is a calcium channel blocker, I would check with your vet before
using both fosrenol and amlodipine.
Cimetidine
(Tagamet) (used to
control gastric hyperacidity) may increase the effects of amlodipine (thereby possibly
reducing blood pressure too far), so it would probably be safer to use
another histamine H2 antagonist such as famotidine (Pepcid AC) instead.
Plumb's Veterinary Drug Handbook mentions that
cyproheptadine, an appetite
stimulant commonly used in CKD cats, may also have calcium channel
blocking effects and cause low blood pressure. In theory this means there is a risk that
cyproheptadine
in combination with amlodipine could reduce blood pressure too far.
It is probably safer not to use these two drugs together, but in practice
many people seem to use both medications without any problems. Be guided
by your vet.
Early research indicated that glucosamine (used to treat
arthritis) might cause elevated blood sugar
and elevated blood pressure in humans.
Glucosamine sulfate (2016) US National
Library of Medicine discusses glucosamine sulfate. It says (with regard to
humans) "Glucosamine appears to be safe for most people with
diabetes, but blood sugar should be monitored closely. Early research
suggests that glucosamine sulfate can increase insulin levels. This might
cause blood pressure to increase. However, more reliable research suggests
that glucosamine sulfate does not increase blood pressure. To be cautious,
if you take glucosamine sulfate and have high blood pressure, monitor your
blood pressure closely."
Veterinary Links Recommending
Amlodipine
Some vets may recommend other treatments for
hypertension. In the UK in particular, you may be offered benazepril (e.g.
Fortekor) and be told this is sufficient to control your cat's high blood
pressure. Although benazepril is sometimes used in addition to
amlodipine (see below),
it is rarely a good first or only choice. Here are some links to show to your vet
if necessary.
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
says
"the initial therapeutic choice should be a CCB,
specifically amlodipine, when SBP is ≥180 mm Hg or TOD is present.".
Latest tips for management of feline hypertension
(2018) Barrs RV Presentation to the
World Small Animal Veterinary Association Congress states "Amlodipine
besylate, a second-generation dihydropyridine that blocks L-type
calcium channels in vascular smooth muscle, is the first-choice
antihypertensive agent in cats."
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822 states "Despite
the potential role of either the systemic or intrarenal RAAS axis in the
pathogenesis or maintenance of hypertension, CCB, specifically amlodipine
besylate, have been the first choice for antihypertensive treatment
because of established efficacy."
ISFM Consensus guidelines on the diagnosis and management of hypertension
in cats
(2017) Taylor SS, Sparkes AH,
Briscoe K, Carter J, Cervantes Sala S, Jepson RE, Reynolds BS & Scansen BA
Journal of Feline Medicine and Surgery19 pp288–303
state "based on current data, the dihydro-pyridine calcium
channel blocker amlodipine besylate is the drug of choice for the
management of hypertension in cats."
Chronic kidney disease (CKD) in dogs and cats — staging and management
strategies (2015) Chew D
Presentation to the Virginia Veterinary Medical Association 2015 Virginia
Veterinary Conference says "Calcium channel blockers do not offer
direct renoprotection, but do control systemic blood pressure much better
than ACE-inhibitors."
How I treat hypertension
(2012) Atkins CE Veterinary Focus22(1) pp17-23 states "the literature and clinical
experience leads one to conclude that amlodipine is the single best agent
for managing feline systemic
hypertension", although he does also mention that in some cases he uses it
in conjunction with other medications (see
below).
11 guidelines for conservatively treating chronic
kidney disease
(2007) Polzin D
Veterinary MedicineDec 2007 says "Amlodipine
is the first-choice drug for managing elevated blood pressure in cats with
chronic kidney disease (evidence grade 2). It is typically highly
effective in reducing blood pressure in cats, often by as much as 20 to 50
mm Hg."
Feline hypertension: risks, diagnosis and management
(2007) Atkins CE Presentation to
theWorld Small Animal Veterinary Association World Congress states that "the literature and clinical
experience would, nevertheless, lead one to appropriately conclude that
amlodipine is the single best agent for the management of feline systemic
hypertension."
Chronic renal failure in the cat (2006)
Sparkes AH Presentation to the World Small Animal Veterinary
Association World Congress states "in
cats monotherapy with amlodipine (a calcium channel blocker) is generally
regarded as the treatment of choice for systemic hypertension."
Angiotensin II Receptor Blockers (ARBs) e.g. Telmisartan (Semintra)
Telmisartan
(Semintra or Micardis) is an angiotensin II receptor blocker. Like ACE inhibitors
(discussed below), this medication has
previously been used more for
its other effects (as opposed to its effects on blood pressure), and was approved in Europe in 2012 for the treatment of
proteinuria
in CKD cats under the trade name of Semintra.
If you are in the USA, you may now be offered
telmisartan to treat your cat's hypertension, because, as the
US Food and Drug Administration reports,
telmisartan, under the trade name of Semintra, was approved in the USA in
2018 for the treatment of hypertension in cats. However, telmisartan
should not be used as the sole hypertensive therapy in cats with blood pressure over 200 mmHg.
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
says "the initial therapeutic choice should be a CCB, specifically
amlodipine, when SBP is ≥180 mm Hg or TOD is present. An alternative first
choice agent, particularly in proteinuric cats, is telmisartan where
recent clinical trials have demonstrated this ARB reduces SBP in
hypertensive cats with similar efficacy to amlodipine."
Efficacy of long-term oral telmisartan treatment in
cats with hypertension: results of a prospective European clinical trial
(2019) Glaus TM, Elliott J, Herberich E, Zimmering T & Albrecht B
Journal of Veterinary Internal Medicine33(2) pp413-422
found that telmisartan "was effective in reducing SABP [systolic arterial
blood pressure] in hypertensive cats with SABP ≥160 mmHg and ≤200 mmH." In
this study telmisartan was not tested in cats with blood pressure over 200 mmHg.
It reduced blood pressure by 20 mmHg, which is a much smaller reduction
than amlodipine can provide, though this lower reduction may be acceptable
for some cats.
If my cat had a blood pressure reading over 200 mmHg, I
would not be too happy with the average reduction provided by telmisartan.
Indeed,
Inhibition of the renin-angiotensin-aldosterone
system in cats and dogs: the emerging role of angiotensin II receptor
blockers (2022) Coleman A & Elliott J International Renal Interest
Society explains the benefits of telmisartan for the treatment of
hypertension but adds "These data
support the efficacy of telmisartan for the treatment of feline systemic
hypertension, although the utility of this drug in cats with SBP >200
mmHg, evidence of severe target organ damage, severe azotemia, or a
combination of these, remains untested."
Inhibition of the renin-anglotensin-aldosterone
system in cats and dogs: the emerging role of angiotensin II receptor
blockers (2022) Coleman A & Elliott J International Renal Interest
Society says
"ARBs may also have advantages when
compared to other antihypertensive agents. For
example, differences between the effects on the renal microvasculature of
these drugs as compared to the dihydropyridine calcium channel blocker,
amlodipine, may translate to differences in these drugs' renoprotective
effects. Amlodipine causes preferential dilation of the afferent renal
arteriole, which may exacerbate glomerular hypertension and promote
progressive renal injury, especially if systemic arterial blood pressure
is not effectively decreased during its administration. In contrast,
through preferential dilation of the efferent renal arteriole,
RAAS-blocking agents (both ACE-i and ARB) reduce intraglomerular pressure,
mitigating glomerular hypertension and proteinuria, if present. However,
the clinical significance imparted by these theoretical differences is not
known."
Unlike amlodipine, telmisartan does not seem able to reverse blindness caused by
hypertension, nor to help with strokes.
Therefore,
if your cat has had a stroke or gone blind, your priority should be to use
amlodipine (though in some circumstances it may be appropriate to use both
amlodipine and telmisartan).
Telmisartan Dosage
When marketed for the treatment of proteinuria in the UK, Canada and the
EU,
Semintra comes in liquid form in a 30ml (blue)
bottle, with a 4mg/ml strength, i.e. each ml contains 4 mg of telmisartan.
It is also available in some countries in a 10mg/ml strength (red bottle).
Unlike amlodipine, telmisartan is usually given twice a day
to start with.
The FDA says that "Initially Semintra is given twice a day for the first
14 days at 1.5 mg/kg and then decreased to once a day at 2.0 mg/kg" but
adds that the dose needs to be adjusted by your vet as appropriate.
Treatment recommendations for CKD in cats
(2023) International Renal Interest Society suggests
"Calcium
channel
blocker
(CCB),
such
as amlodipine(0.125
to 0.25
mg/kg
oncedaily)
or angiotensin receptor blocker (ARB),
telmisartan (2 mg/kg once
daily)."
Assessing hypertensive cats
(2019) Caney S Improve Veterinary Practice In Focus states
that the usual dosage of telmisartan when used as the only treatment for
hypertension is 2-3mg/kg once a day.
Telmisartan Used in
Conjunction with Amlodipine
If I had to choose a single treatment for hypertension, I would use
amlodipine rather than telmisartan. However, telmisartan can be a good
additional choice if amlodipine alone is not sufficient to control your
cat's blood pressure. It is also safe, according to
the manufacturer of Semintra, which
states "During concomitant therapy with amlodipine at the recommended dose
no clinical evidence of hypotension was observed."
Assessing hypertensive cats
(2019) Caney S Improve Veterinary Practice In Focus states
that, when combined with amlodipine, the dosage of telmisartan is 1mg/kg
per day (plus the usual dose of amlodipine).
Treatment recommendations for CKD in cats
(2023) International Renal Interest Society states
"Combine
amlodipine and telmisartan if either drug
alone
does not lead to
adequate control of blood
pressure."
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
says "animals classed as severely hypertensive with evidence of severe or
progressing neural or ocular TOD. This generally constitutes an emergency,
where combination therapy with a CCB plus a RAAS inhibitor is an
appropriate first step in dogs, and a CCB [amlodipine] will often be used
alone in cats."
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
also says "Whether
telmisartan can be used safely in combination with amlodipine to achieve
lower target SBPs in cats, and if using it in this manner leads to
enhanced renoprotection, remains to be determined." However, several
members of Tanya's CKD Support Group have found it effective when used in
this manner.
Telmisartan is used to treat proteinuria, so there is more information about
it on the
Proteinuria page, including cautions, interactions and side effects.
ACE Inhibitors: Benazepril etc.
Some vets may offer heart medications known as
ACE inhibitors,
which include benazepril (Fortekor/Lotensin) and enalapril (Enacard), to
treat high blood pressure.
How ACE Inhibitors Work
ACE inhibitors (ACEI) work by preventing the conversion of a hormone called angiotensin I into
another hormone called angiotensin II, the role of which is to constrict
blood vessels. ACE inhibitors relax the blood vessels, which helps to
reduce both systemic and
intraglomerular blood pressure (some blood
pressure medications have no or only a limited effect on intraglomerular
blood pressure).
ACE inhibitors are also used to control
proteinuria in CKD
cats.
Why ACE Inhibitors Alone Are Not the Best
Choice to Treat Hypertension
they are also less likely to control blood pressure consistently, and this
may become more of an issue, the longer the cat has been on the
medication..
Renal Disease
(2006)
Polzin DJ
Delaware Valley Academy of Veterinary Medicine
says "ACEI
have not been found to be consistently effective in lowering blood
pressure in cats with CKD."
Blood
pressure in small animals Part 2: hypertension target organ damage heart
and kidney
(2009) Carr
AP & Egner BE European Journal of Companion Animal Practice
19(1) pp1-5 states "Blood pressure
reduction achieved with an ACEi is usually relatively minor. ACEi as sole
agents resulted in initial control of hypertension in only 6 of 16
hypertensives, after 6 months only 2 of 16 were still controlled."
they may cause increases in creatinine levels when first begun — see the
next section.
unlike amlodipine, they do not seem able to reverse blindness caused by
hypertension.
Therefore,
if your goal is to control systemic hypertension, particularly in a cat who
has gone blind, you normally start by using amlodipine only.
ACE Inhibitors: Possible
Downsides
In principle it sounds good that ACE inhibitors may
reduce blood pressure within the kidneys. However, it is a delicate
balancing act because doing this can lead to a reduction in the
amount of blood flowing through the kidneys, which in turn may reduce the
glomerular
filtration rate, a measure of kidney function. This may have a
negative effect on kidney function in some cats, which may be seen in the
form of elevated BUN and creatinine levels. One study,
Effects of benazepril in cats with experimentally
induced or sopantaneously occurring chronic renal failure
(2007) Watanabe T & Mishina M
Journal of Veterinary Medical Science69(10) pp1015-1023,
found that benazepril appeared to improve creatinine levels as well as
proteinuria in cats with naturally occurring CKD, but other studies have
found the opposite.
How much of a problem this can be is debatable.
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822 states
that in cats who do not also have heart
disease "the administration of ACEI commonly produces only very modest
increases in serum creatinine concentration (0.5 mg/dL; 50mmol/L), which
is generally well tolerated."
In most cats this increase is temporary, which should be
tolerable in cats in the early stages of CKD. However, since benazepril is
often prescribed by vets at any stage of the disease, in principle it is possible that
a rise in creatinine levels in a cat in IRIS Stage 4 might be enough to
push a cat over the CKD precipice. Indeed,
Proteinuria
(2013) Syme H Presentation to the 38th World Small Animal Veterinary
Association World Congress states "Treating cats that are severely azotaemic or that
have prerenal azotaemia with ACE-inhibitors may actually speed their
demise."
Using ACE Inhibitors in
Addition to Amlodipine
It is sometimes necessary to use other medications in addition to amlodipine. I had to do this for my non-CKD cat with hypertension
because after three years, amlodipine alone was not sufficient to control
her blood pressure.
Some vets like to use ACE inhibitors in addition to amlodipine because
calcium channel blockers (such as amlodipine) may activate the
RAAS.
In contrast, since ACE inhibitors work by preventing the conversion of
angiotensin I into angiotensin II, they not only do not activate the RAAS,
they may reduce the risk of activation.
Plumb's Veterinary Drug Handbook
states
"There is
concern that using amlodipine alone for treating hypertension in
cats with renal disease may expose glomeruli to higher pressures secondary
to efferent arteriolar constriction. This is caused by localized
increases
in RAAS axis activity thereby allowing progressive damage to glomeruli. It
is postulated that using an ACE inhibitor with amlodipine may help prevent
this occurrence."
Chronic kidney disease (CKD) in dogs and cats — staging and management
strategies (2015) Chew D
Presentation to the Virginia Veterinary Medical Association 2015 Virginia
Veterinary Conference says ""Balanced" antihypertensive protocols
use BOTH ACE-inhibitors and calcium channel blockers to best control
intraglomerular and systemic hypertension."
Feline hypertension: clinical features and
therapeutic strategies (2004)
Bright JM Presentation to the World Small Animal Veterinary Association
World Congress 2004 discusses using amlodipine in conjunction with ACE
inhibitors in
cats who do not respond to amlodipine alone.
Generally speaking, it is safer to start ACE inhibitors at a lower dose and
increase only as necessary. The usual doses for benazepril when given
to treat proteinuria are
here,
but be guided by your vet as to the best dose when combining with
amlodipine.
Monitoring Cats on Both Amlodipine and
ACE Inhibitors
Treatment recommendations for CKD in cats
(2023) International Renal Interest Society
recommends using an ACE inhibitor in addition to amlodipine if
amlodipine alone is not sufficient to control blood pressure, but warns
"Take care not to introduce CCB/RAAS inhibitor treatment to unstable dehydrated cats
as glomerular
filtration rate [a measure of kidney function] may drop precipitously if
these drugs
are introduced before the patient is adequately hydrated."
If you do add an ACE inhibitor to your cat's treatment plan, be sure to
get blood values checked 7-10 days after starting the ACE inhibitor.
Blood
pressure in small animals Part 2: hypertension target organ damage heart
and kidney
(2009) Carr
AP & Egner BE European Journal of Companion Animal Practice
19(1) pp1-5 states "When using ACEi, it is
important to monitor for azotemia as this can occur secondary to the
vasodilator effect."
Feline
hypertension: diagnosis and management (2002) Elliott J
Presentation to the 27th World Small Animal Veterinary Association
Congress also discusses
the use of ACE inhibitors in addition to amlodipine in cats who do not
respond to amlodipine alone, and recommends checking bloodwork if ACE
inhibitors are added, since these drugs may cause an increase in
creatinine levels.
Beta Blockers e.g. Atenolol
Sometimes vets offer other heart medications for hypertension, such as
atenolol, which is a
beta blocker.
Beta blockers are not usually used alone to control hypertension —
ISFM consensus guidelines on the diagnosis and
management of feline chronic kidney disease (2016) Sparkes AH,
Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I, Langston C, Lefebvre H,
White J & Quimby J Journal of Feline Medicine & Surgery18
pp219-239 state that "monotherapy with... atenolol is not effective in most
hypertensive cats."
However, atenolol may occasionally be used in addition to other medications
such as amlodipine where the amlodipine is not sufficient to control the cat's
blood pressure.
Atenolol can be effective to control a fast heart rate (tachycardia):
Feline hypertension: Part 1
(2012) Atkins C says "Tachycardia not only contributes to hypertension
but is also harmful to the cardiovascular system; persistent tachycardia
should be managed with atenolol."
If Your Cat Does Not Respond To
Treatment
If you are using amlodipine as the only medication, you may need to either increase the dose, or add
in another medication such as telmisartan.
If you are using telmisartan. you may need to switch to amlodipine or use
amlodipine as well as telmisartan, although
Systemic hypertension
(2022) Brown SA & Roura X International Renal Interest Society
says "animals classed as severely hypertensive with evidence of severe or
progressing neural or ocular TOD. This generally constitutes an emergency,
where combination therapy with a CCB plus a RAAS inhibitor is an
appropriate first step in dogs, and a CCB [amlodipine] will often be used
alone in cats."
If you are using an ACE inhibitor (e.g. benazepril), this is often not enough alone to control hypertension. You may well have to switch to
amlodipine or use amlodipine as well as the ACE inhibitor.
In rare cases, cats may have hypertension that does not respond to
treatment because of a condition known as
hyperaldosteronism.
Prognosis
Survival after diagnosis of hypertension in cats attending primary care
practice in the United Kingdom
(2018) Conroy M, Chang Y-M, Brodbelt D & Elliott J Journal of
Veterinary Internal Medicine32(6) pp1846-1855 found
that only 1.34% of the cats in the study were checked for the presence of
hypertension. This is quite worrying because 19.5% of the cats who were checked were found to have
hypertension. Cats diagnosed with hypertension because of another illness
(such as CKD) had a better chance of survival, as did cats who did not
progress to TOD.
Most feline members of Tanya's CKD Support Group whose hypertension is
detected and kept under control seem to do well.
TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE
EXTREMELY DANGEROUS.
I have
tried very hard to ensure that the information provided in this website is
accurate, but I am NOT a vet, just an ordinary person who has lived
through CKD with three cats. This website is for educational purposes
only, and is not intended to be used to diagnose or treat any cat. Before
trying any of the treatments described herein, you MUST consult a
qualified veterinarian and obtain professional advice on the correct
regimen for your cat and his or her particular requirements; and you
should only use any treatments described here with the full knowledge and
approval of your vet. No responsibility can be accepted.
If your cat
appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
This site was
created using Microsoft software, and therefore it is best viewed in
Internet Explorer. I know it doesn't always display too well in other
browsers, but I'm not an IT expert so I'm afraid I don't know how to
change that. I would love it to display perfectly everywhere, but my focus
is on making the information available. When I get time, I'll try to
improve how it displays in other browsers.
This site is a labour of love, from which I do not make
a penny. Please do not steal from me by taking credit for my work.
If you wish to
link to this site, please feel free to do so. Please make it clear that
this is a link and not your own work. I would appreciate being informed of
your link.
