Overview of Canine Hypertension
Elevated blood pressure – properly called systemic arterial hypertension – is an increase in the systolic or diastolic arterial blood pressure (ABP). Blood pressure has two values: the systolic pressure, which is the high value that develops as the heart contracts and pumps blood, and the diastolic pressure, the low value that occurs as the heart relaxes and fills. For example, 120/80 means a systolic pressure = 120 mm Hg and diastolic pressure = 80 mm Hg.
A systolic ABP consistently exceeding greater than 170 to 180 mm Hg in the dog is considered high. Diastolic pressure in dogs should not exceed the 100 to 110 mm Hg range, provided it is recorded when the dog is relaxed.
Causes of High Blood Pressure in Dogs
Chronic kidney disease
Diseases of the endocrine system such as Cushing’s disease
Tumors of the adrenal gland, such as pheochromocytoma, which is an adrenocortical tumor causing Cushing’s disease or Conn’s disease
Central nervous system disorders.
Some cases of hypertension are idiopathic or essential, which means that they have no known cause.
A dog predisposed to kidney disease is more likely to develop hypertension.
Hypertension can affect your dog by causing injury to the following “target” organs including: brain, eyes, heart, kidneys and blood vessels. Hypertension can be suspected by symptoms and clinical examination but can only be diagnosed by repeated measurements of the ABP.
What to Watch For
Symptoms of high blood pressure in dogs include:
Symptoms related to underlying diseases such as endocrine disorders
Diagnosis of Hypertension in Dogs
Diagnostic tests are needed to recognize hypertension, to help determine its cause, and exclude other diseases. Tests may include:
Complete medical history and physical examination. Examination should be directed towards the target organs of hypertension. Careful inspection of the eyes, nervous system, heart and kidneys should be completed.
Diagnosis requires measurement of arterial blood pressure. This is generally done using a cuff, similar to that used in children, and a blood pressure device. The stethoscope or auscultatory method used in people cannot be used in dogs; instead, the pressure must be determined with either a Doppler flow device or an oscillometric device. Dogs can have an “artificially” elevated blood pressure if they become excited. Accordingly, the veterinarian should make repeated measurements of blood pressure before making a diagnosis of hypertension. This may require a brief hospitalization in order to allow repeated measurements in a calm patient.
The underlying cause of hypertension must be identified and this may require blood tests of endocrine function, X-rays or ultrasound examination of abdominal organs.
Treatment of Hypertension in Dogs
Treatment for hypertension may include one or more of the following:
Treatment of the underlying cause. This treatment should be individualized for the patient and the associated problems.
Hospital treatment. A hypertensive crisis (very high blood pressure with severe clinical signs) should be treated aggressively. This requires hospital treatment with drugs that lower blood pressure. These may include sodium nitroprusside, diuretics, amlodipine or other vasodilator drugs.
Drug therapy. Chronic treatment of hypertension in dogs may be accomplished with enalapril, benazepril, amlodipine, a beta-blocker or some combination of this therapy.
Reduction in weight and in dietary sodium. However, without drug therapy, these measures will be ineffective in controlling hypertension in dogs.
Home Care and Prevention
Administer all treatments as prescribed. Schedule regular follow-up visits to ensure that treatment is controlling the blood pressure. Monitor your dog’s activity, alertness, appetite and general quality of life on a regular basis.
Hypertension develops in association with diseases that, at this time, are not preventable.
In-depth Information on Hypertension in Dogs
Hypertension can be difficult to diagnose in dogs. The stethoscope (listening) method used to diagnose hypertension in people cannot be used in dogs. A Doppler device is needed to detect blood flow or a special instrument that measures oscillations in the blood vessels must be used. Excitement can artificially raise blood pressure, just as it does in people (white coat effect).
The diagnosis of hypertension requires close attention to the technical aspects of blood pressure measurement such as selection of the appropriate cuff size and assuring uniform compression of the artery.
When there are associative clinical signs or diseases related to hypertension, a high blood pressure measurement is of great significance. In the otherwise healthy dog, diagnosis should be approached cautiously so as not to label a healthy, but perhaps excited, pet as hypertensive.
The underlying cause of hypertension must be addressed. Known causes include: chronic kidney diseases, hyperadrenocorticism (Cushing’s disease), hyperthyroidism, tumors of the adrenal gland (pheochromocytoma/adrenocortical tumor), drugs such as those used to treat urinary incontinence in dogs and central nervous system disorders.
Hypertension can also develop from diseases of the endocrine organs. Diseases of the adrenal gland are particularly common in dogs and have been associated with hypertension. One example is Cushing’s disease, which may be controlled by medication.
Some cases of hypertension are idiopathic or essential, which means they have no known cause.
Hypertension can cause serious injury to target organs including the brain, eyes, heart, kidneys and blood vessels in these and other organs. These changes can include:
Cerebral or brainstem vascular injury can cause swelling (edema) or the bleeding into the brain that is also called a stroke. Clinical symptoms include abnormal behavior, depression, neurological deficits, head tilt, seizures and coma.
Retinal edema (swelling) or hemorrhage and retinal detachments (separation of the layers) can lead to sudden blindness. Sudden blindness may also develop consequent to bleeding into the eye, known as intraocular hemorrhage or hyphema.
Elevated blood pressure increases the work of the heart. Frequently a murmur or extra heart sound, an atrial gallop, will be heard with the stethoscope in dogs with hypertensive heart disease. Left ventricular thickening (hypertrophy) and heart enlargement (cardiomegaly) are indications of chronic hypertension. These changes can be identified by an echocardiogram (most sensitive), electrocardiogram or thoracic radiograph (least sensitive). Coronary arteries also are injured from high arterial pressures. Heart failure stemming from hypertensive heart disease is exceedingly rare. In dogs with chronic valvular heart disease, hypertension increases the risk for development of congestive heart failure.
Kidney disease is one of the most common reasons for high blood pressure. Glomerular disease is especially associated with hypertension. High blood pressure continues to injure the kidneys creating a vicious cycle.
Injury to blood vessels or direct transmission of pressure across the microscopic blood vessels and capillaries is responsible for many of the clinical signs of hypertension.