What is Blood Pressure?
The term "blood pressure" describes the exerted pressure on the artery walls both when the heart contracts and expels blood and when it relaxes and fills with blood. Systole, the heart's contraction, causes the greatest amount of pressure to build up against the artery walls. The minimal pressure exerted on the walls of the arteries occurs during diastole, which is when the heart relaxes.
A pulse of blood is pumped through the arteries when the heart contracts. The systolic blood pressure is produced by this pulse. The blood pressure in the arteries decreases between heartbeats; this is known as the diastolic blood pressure. In animals, the mostly gauged is the systolic blood pressure. Systolic pressure fluctuates during the day. In order to direct blood flow to the organs that are most active at the time, arteries are constantly narrowed or enlarged. Because the diameter of a dilated artery is greater, blood may flow through it more easily. Blood pressure is lower if arteries are dilated because less pressure is required to pump blood through the dilated artery. With aging, blood pressure also has a tendency to slightly rise.
What is high blood pressure (hypertension)?
Pets are increasingly being diagnosed with hypertension, or high blood pressure, which has long been known to be a concern in humans. In older persons, hypertension is highly common and frequently linked to smoking or a stressful lifestyle. Animals' hypertension almost always results from an underlying illness. However, dogs are relatively resistant to hypertension.
What is systemic hypertension?
The term "systemic hypertension" refers to elevated blood pressure throughout the body. This refers to a persistent increase in systolic pressure of at least 140 mmHg, diastolic pressure of at least 90 mmHg, or both. Like people, dogs can experience brief increases in blood pressure because of stressors, such as visiting a vet clinic. It's therefore useful to review multiple readings and to make the surroundings as calm as possible, then take an average of the readings. In dogs, hypertension is frequently brought on by an underlying illness, and is referred to as secondary hypertension. When the condition exists without a known or existing underlying condition, it is referred to as primary hypertension.
What causes hypertension in dogs?
Dogs can experience hypertension, or high blood pressure, just like humans do. It frequently occurs in conjunction with underlying medical diseases. The cause of primary hypertension is unknown. Secondary hypertension accounts for a majority of hypertension in dogs, and can be attributed to kidney disease, heart disease, endocrine disorders e.g., adrenal gland disease, diabetes mellitus (less common), pheochromocytoma (adrenal gland tumor and very uncommon), or central nervous system disease (very rare).
Older dogs are more likely to acquire hypertension, which is consistent with the onset of underlying diseases like chronic kidney disease or high amounts of corticosteroids produced by the adrenal glands in Cushing's syndrome-affected dogs. Younger dogs who have renal illness because of an infection (such leptospirosis) or a developmental defect of the kidneys may develop hypertension too.
How does hypertension cause problems?
In hypertension, the blood vessel walls are damaged by the elevated blood pressure, which results in bleeding and the production of blood clots. If the blood arteries in the eye, kidney, heart, or brain are affected, this can lead to extremely serious issues. Additionally, a high blood pressure requires the heart to pump harder against more resistance, which puts more strain on the heart muscle.
How is Hypertension detected in dogs?
Detecting and treating hypertension in dogs typically involves a combination of diagnostic tests and management strategies.
1. Physical Examination:
During routine veterinary check-ups, a veterinarian may detect hypertension through physical examination findings such as an increased heart rate, abnormal heart sounds, or evidence of organ damage.
2. Blood Pressure Measurement:
Blood pressure measurement is the most reliable method for diagnosing hypertension in dogs. It is typically measured using an inflatable cuff placed around a dog's limb or tail, similar to the procedure in humans.
What is the range of a dog's normal blood pressure?
Systolic blood pressure in most healthy canines ranges between 120 to 180 mmHg. Although senior animals do have a tendency to have slightly higher blood pressure than young canines, a dog is considered hypertensive if their blood pressure is continuously over 180-190 mmHg. Overweight dogs and sight-hounds like Greyhounds typically have higher blood pressure.
What are the clinical signs of hypertension?
In the early stages of disease there are few, if any, signs of hypertension itself, but because hypertension is commonly associated with an underlying disease, signs of that disease may be noticed in the pet. Appetite may be decreased in kidney failure, or may be increased in diabetes, and both conditions can cause weight loss, excessive drinking and occasionally vomiting.
Signs related to secondary damage to blood vessels will depend upon the organ affected. Damage to the blood vessels in the eye may cause sudden onset blindness, and this is often the first recognizable indication of hypertension in cats. Damage to blood vessels in the brain can cause strokes and other neurological disorders, and increased blood pressure in the blood vessels that supply the kidney can cause further deterioration in kidney function.
Other signs of hypertension include:
1. Eyes:-
Bleeding inside the globe of the eye,
Persistently dilated pupils
Detached retinas
2. Nervous system signs:-
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)
3. Kidneys: -
Increased drinking and urinating with the progression of chronic kidney disease
Blood in the urine (called hematuria)
4. Nose: -
Bleeding in the nose and nasal passages (known as epistaxis or nosebleed)
5. Heart
How is Hypertension Treated?
1. Identifying Underlying Causes:
Treating the underlying cause of hypertension is crucial. If an underlying condition is present, such as kidney disease or Cushing's disease, addressing that condition may help manage the hypertension.
2. Medications:
In cases where hypertension is severe or persistent, medication may be prescribed to lower blood pressure. Commonly used medications include angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists (ARBs), beta blockers, diuretics, and calcium channel blockers. These medications are only used under veterinary supervision as the dosage and choice of medication may vary based on the dog's specific condition.
3. Dietary Management:
A specific diet may be recommended that is low in sodium to help manage hypertension. Reducing sodium intake can be beneficial for dogs with high blood pressure and certain underlying conditions. The importance of therapeutic diet in long-term management is universally acknowledged.
4. Lifestyle Changes:
In some cases, lifestyle modifications may be recommended, such as weight management, regular exercise, stress reduction, and minimizing exposure to stressful situations.
What kind of monitoring is recommended for a hypertensive dog?
A dog with hypertension should have a systolic pressure of no more than 140 mmHg and a diastolic pressure of no more than 90 mmHg. To monitor the progression of the condition and the adverse effects of medicine, periodic laboratory tests are necessary. Dogs with hypertension may experience the following complications:
Chronic kidney disease
Bleeding into the eyes
Stroke (cerebral vascular accident)
What is the expectation for the future of a hypertensive dog?
The underlying cause determines how hypertension in dogs progresses. The chances for potential ramifications are reduced when blood pressure is properly controlled. Medication for hypertension is commonly a lifelong commitment that may require adjustments over time, therefore, regular monitoring and follow-up visits with a veterinarian are essential to evaluate the dog's response to treatment and make any necessary adjustments and to ensure proper management and care.
References
Brown S et al (2007) Guidelines for the Identification, Evaluation, and Management of Systemic Hypertension in Dogs and Cats. J Vet Intern Med 21 (3), 542-558 PubMed.
Acierno M J & Labato M A (2005) Hypertension in renal disease: diagnosis and treatment. Clin Tech Small Anim Pract 20 (1), 23-30 PubMed.
Henik R A (1997) Systemic hypertension and its management. Vet Clin North Am Small Anim Pract​ 27 (6), 1355-1372 PubMed.
Michell A R (1993) Hypertension in companion animals. Vet Annual 33, 11-23 VetMedResource.
Brown S A (2004)Canine hypertension: risk and management.Proceedings of the North American Veterinary Conference.