High blood pressure in dogs is caused by the narrowing of veins that in turn cause the blood to not flow as easily as it should. Since the narrow parts of the veins keep blood from getting through, yet the amount of blood doesn't change, pressure builds against the narrow points. This is what causes the high blood pressure.
Areas of the body where the smallest blood vessels exist are the most vulnerable. These spots include the vessels in the eye or retina and the kidney, which is why both are susceptible to canine blood pressure problems. High blood pressure can cause damage to multiple organs such as the blood vessels, heart and brain, not to mention the eyes and kidneys referenced earlier. Problems in the kidneys manifest as decreased renal function, renal death or proteinuria (high levels of proteins in the urine).
Diseases in these areas such as kidney failure can cause the high blood pressure for the same reason. The disease itself is restricting the flow of blood.
In dogs almost all cases are caused by some other disease where high blood pressure is a symptom of that disease.
What Causes of High Blood Pressure In Dogs?
There are many causes of high blood pressure in dogs such as:
- Diseases of the endocrine system, such as Cushing's disease, hyperthyroidism, and diabetes mellitus
- Chronic kidney disease
- Central nervous system disorders
- Certain medications
- Red Blood Cell Over Production (Polycythemia)
- Administration of therapeutic agents such as glucocorticoids, mineralocorticoids, erythropoietin, sodium chloride, phenylpropanolamine, and nonsteroidal anti-inflammatory drugs
- Some cases of high blood pressure have no known cause and are referred to as Idiopathic Hypertension
Measurement of Canine Blood Pressure
When you measure blood pressure, you measure two numbers - the systolic pressure and the diastolic pressure. The systolic pressure is the highest number. That is the pressure when the heart contracts and pumps blood. The diastolic pressure is the lower number. It's the pressure when the heart relaxes and fills with blood. For dogs only the systolic pressure (top umber) is measured.
There are two types of devices used to measure BP. The first is similar to devices used on humans and the second uses a Doppler. The Doppler has a transducer on the end that is placed over the artery. A sound is heard as the heart beats. The Doppler is placed under the rear or front paw. A cuff is also placed above the transducer on the leg or arm.
It is recommended that blood pressure be checked regularly in dogs over nine years of age. When you take your dog to the vet for his yearly check-up, ask your vet to check his blood pressure. Pressure is measured using a cuff that is at the level of the right atrium. To avoid a false reading due to anxiety, it should be done in a quiet room about 5 to 10 minutes after the dog is able to acclimate to the environment. Guidelines suggest that the first measurement be discarded, and the average of 3 to 7 consecutive additional readings be used.(3)
Standard Blood Pressure Readings and Implications (1)
Blood pressure values vary to reflect the differences between dogs, techniques and the way dogs are handled when measured. More research is needed on dogs to understand the impact of age and sex. In general known effects of breed, sex and age are small with the exception of higher blood pressure seen in sighthounds. Research does show higher blood pressure in males and lower levels in intact females.(3)
There are also differences between breeds and based on obesity.(4)
Blood Pressure Reading
Minimal risk, no treatment is indicated
150/99 to 159/95
No treatment indicated, mild risk of organ damage.
160/119 to 179/100
Treatment needed to reduce risk to the dog and to protect the organs. Considered a moderate risk.
Treatment required to limit complications. Severe risk to organ damage.
Symptoms of High Blood Pressure in Dogs
Signs of high blood pressure in dogs include:
- Sudden blindness
- Behavioral changes
- Dilated pupils
- Heart murmurs
- Blood in urine
- eye hemorrhage
- Nose bleed
- Shrunken or swollen kidneys
- Detached retina
- Rolling of the eyeballs
In a healthy dog, the systolic pressure should be no higher than 170 - 180. The diastolic pressure should be no higher than 100 - 110. Anything higher than that is considered high.
Canine high blood pressure is diagnosed by measuring the blood pressure with a cuff similar to that used to measure blood pressure on a child. However, a stethoscope cannot be used on dogs the way it is on humans. Instead, a Doppler device is used to determine the pressure. Dogs may have an "artificially" elevated pressure due to the stress and excitement of being at the vet called "white coat syndrome", so the vet may need to do several readings over a period of time.
The vet will also examine the dog to check the "target" organs listed above for signs of damage.
A veterinarian will look for signs of organ damage in dog's with high blood pressure.
Increases in SCr readings or a decrease in GFR levels. Diagnosed with a urine test.
Blindness (sudden), Detached retina, papiledema (blood in the optic disk), Glaucoma, Retinal degeneration. Diagnosed with an opthalmic examination.
Stroke. Diagnosed with a neurological examination.
Heart failure. Diagnosis with tests such as ultrasound or electrocardiogram.
Canine High Blood Pressure Treatment
Treatment for canine high blood pressure involves treating the underlying cause of the condition, if a cause can be identified. The goal is to provide a 1x a day therapy designed to reduce the blood pressure while avoiding sudden increases in pressure. Many dogs require more than one medication to control hypertension.
In addition, dog high blood pressure medications such as amlodipine, benazepril, enalapril, or a beta-blocker may be prescribed.
If eye disease is present, special medicated drops are prescribed.
If a dog is overweight, weight reduction will help to lower the blood pressure. There is some debate as to whether a low sodium diet will help or hurt the patient. Evidence suggests that substantial salt restriction alone does not reduce blood pressure in dogs. Talk to your vet about the best diet for your pet.
Source: American College of Veterinary Internal Medicine Consensus Statements, Louisville, KY - 2006, Guidelines for the Identification, Evaluation, and Management of Systemic Hypertension in Dogs and Cats
Canine High Blood Pressure Natural Remedies
Natural medicine also offers several remedies for canine high blood pressure that are known for their ability to support the heart, circulatory system and blood pressure. When researching this approach a good option to explore and review with your veterinarian is offered by PetAlive. Their product contains a blend of multiple homeopathic ingredients believed to support canine heart health:
- Arnica 3X: pulse feeble and irregular, strained heart in sportsman, consequence of hard physical labor.
- Calc fluor 6C: enlarged veins, weakening of supporting tissue.
- Kali phos 6C: one of the greatest nerve remedies; prostration, weakness, marked disturbance of the sympathetic nervous system.
- Lachesis 30C: palpitations, irregular beats, hot flushes, congestive headaches.
Note that these approaches often do not have the clinical research associated with prescription medicines. Claims listed above are based on the Homeopathic Materia Medica, a system of medicine practiced around the world for over 20 years. There are no federally recognized scientific or clinical studies regarding the efficacy of these products and is not accepted by all medical experts. We do not discourage these types of conversations with a Veterinarian. If your Veterinarian believes it will do no harm, it might be worth trying,
Brochure For Additional Reading
(3) Guidelines for the Identification, Evaluation and Management of Systemic Hypertension in Dogs and Cats, S. Brown, C. Atkins et al; Vet Intern Med 2007; 21:542-558
(4) Joes JA. Obesity in dogs: Effects on renal function, blood pressure, and renal disease. Vet Q 1998:20:117-120.
(5) Do cats and dogs need blood pressure medicine? by George Cuellar, DVM, ABVP C/F.