What is blood pressure?
Blood pressure refers to the pressure against the walls of arteries during the time the heart contracts and empties itself of blood, and during the time the heart relaxes and fills with blood.
When the heart contracts, this is known as systole, and the systolic pressure is the maximum pressure against the walls of the arteries.
When the heart relaxes, it is known as diastole, and diastolic pressure is the minimum pressure against the walls of the arteries.
How is blood pressure measured?
Measuring blood pressure in your dog is like measuring your own blood pressure.
- Your dog will be taken to a quiet room and gently laid on their side, giving them time to calm down.
- If your veterinarian is using a Doppler method of measurement, they will usually shave a small patch of fur on the underside of your dog’s wrist (metacarpal) or ankle (metatarsal) and tape a small probe on the skin.
- An appropriately sized cuff will then be placed above this area, inflated, then slowly deflated.
- As the cuff deflates, your veterinarian will listen for the pulsing sound of the blood, at which point the systolic blood pressure will be recorded. Unfortunately, determining diastolic blood pressure in pets with this technique is difficult and unreliable.
- Multiple readings should be done to allow your dog to get used to the machine, helping to prevent stress-related readings.
These measurements will be taken over a period of a few minutes, with the results being averaged out.
What is systemic hypertension?
Systemic hypertension describes high blood pressure throughout the body: a sustained elevation in systolic pressure of 140mmHg or greater, in diastolic pressure of 90mmHg or greater, or both. The American College of Veterinary Internal Medicine recommends that treatment be initiated when systolic pressure remains over 160 mmHg persistently.
Dogs can experience temporary elevations in blood pressure due to stress, including being in a veterinary hospital. It is important to take several readings and to create as quiet an environment as possible. Most often, having the dog’s owner present helps relieve some of the stress involved. Hypertension in dogs is often due to an underlying disease and is called secondary hypertension. If no underlying disease is present or can be identified, then it is called primary hypertension.
Hypertension is more common in older dogs, consistent with the development of an underlying disease such as chronic kidney disease, or excessive levels of steroids produced by the adrenal glands in dogs with Cushing's syndrome. Younger dogs may develop hypertension if they have kidney disease due to infection (such as leptospirosis) or a developmental kidney abnormality.
What are the signs of hypertension?
The signs of hypertension include:
- Sudden blindness, bleeding inside the globe of the eye, and persistently dilated pupils
- Detached retina, causing blindness
- Nervous system signs like depression, head tilt, seizures, disorientation, wobbly or uncoordinated movements (called ataxia), circling, weakness or partial paralysis, or short, rapid, back-and-forth movements of the eyes (called nystagmus)
- Increased drinking and urinating with the progression of chronic kidney disease
- Blood in the urine (called hematuria)
- Bleeding in the nose and nasal passages (known as epistaxis or nosebleed)
- Heart murmurs or abnormal heart rhythms
What causes hypertension?
The cause of primary hypertension is unknown. Secondary hypertension accounts for a majority of hypertension in dogs, and can be attributed to kidney disease, adrenal gland disease (Cushing’s syndrome), diabetes mellitus (less common), pheochromocytoma (adrenal gland tumor and very uncommon), or central nervous system disease (rare).
How is hypertension treated?
Treatment of hypertension depends upon the underlying cause, if any. If the dog develops a serious complication related to hypertension, like acute kidney failure or bleeding into the eye, they may need to be hospitalized. In general, once any underlying condition is appropriately managed, medication and nutrition are important to normalizing blood pressure.
Medications that are commonly used to manage hypertension in dogs include angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists (ARBs), beta blockers, diuretics, and calcium-channel blockers. Additional medications may be required, depending on the response to initial therapy. Therapeutic nutrition is generally accepted as an important part of long-term management.
What kind of monitoring will be required?
The treatment goal for a dog with hypertension is a systolic pressure of 160mmHg or less. Periodic laboratory testing will be required to monitor for medication side effects and progression of disease. Regular blood pressure measurements will also need to be taken to ensure treatment continues to be successful.
Potential complications of hypertension in the dog include:
- Congestive heart failure
- Chronic kidney disease
- Retinal degeneration and subsequent blindness
- Retinal hemorrhage and possible detachment, causing blindness
- Bleeding into the eye
- Stroke (cerebral vascular accident)
What is the prognosis for hypertension?
The course of hypertension in dogs depends on the underlying cause. When blood pressure is well managed, the risk of potential complications is minimized. Medication for hypertension is generally a lifetime undertaking and may be adjusted over time, as needed.
