High blood pressure in dogs: symptoms and treatment

Overview

Systolic pressure is the highest arterial pressure during heart contraction. Canine treatment decisions usually use this value. Diastolic pressure is the lowest arterial pressure during relaxation. Persistent systolic pressure of 160–179 mmHg represents moderate organ damage risk.

Anxiety at the practice can temporarily raise pressure. This situational rise is not treated like persistent hypertension. Target organ damage means harm to structures such as the eyes, kidneys, brain or cardiovascular system. Treatment aims to reduce these risks.

Causes

Kidneys and hormonal diseases

Secondary hypertension has an identifiable underlying disease. Impaired kidney function is a common canine cause. High pressure can in turn worsen kidney damage.

In Cushing's disease, excessive adrenal cortical hormone production can be associated with hypertension. An adrenal phaeochromocytoma can also raise pressure. Diabetes is a possible but less common cause. Rarely, central nervous system disease may underlie it.

Unknown cause, medication and anxiety

When no predisposing disease is found, the condition is called idiopathic hypertension. It is much less common in dogs than the secondary form. Certain medicines or toxic substances can also raise pressure.

An anxiety-related rise involves activation of the autonomic nervous system. Pressure may fall as fear decreases or the measurement environment changes. Anxiety can therefore lead to a false hypertension diagnosis.

Risk factors

Hypertension is more common in older dogs, which accumulate predisposing diseases with age. Kidney and adrenal diseases are important reasons to assess pressure. A young dog can also be affected with a developmental kidney abnormality or kidney infection.

Among 14 dogs with adrenal-dependent Cushing's disease, 79% were hypertensive at diagnosis. Medication known to raise pressure is another reason to plan measurements. In kidney disease, urinary protein loss particularly warrants assessment of pressure and its effects. Pressure can rise early in kidney disease while blood creatinine remains normal.

Typical symptoms

High pressure does not always cause early signs visible at home. The first noticed change may be sudden blindness.

• Your dog loses sight or starts bumping into things.
• The pupils remain larger than usual.
• Blood is visible in an eye.
• Your dog seems confused or walks in circles.
• Balance becomes unsteady or the head tilts.
• Your dog has a seizure.
• Blood may appear in urine.

Increased thirst and urination may reflect progressing kidney disease. High pressure itself can also increase urine production. Nosebleeds may be associated with pressure, but hypertension is an uncommon primary cause. Your vet may detect a murmur or arrhythmia.

Complications and consequences

Eyes, brain and kidneys

Hypertension can damage retinal vessels and cause bleeding. Retinal detachment may cause sight loss. Blood pressure treatment can help a detached retina reattach. However, sight returns in only a small proportion of these patients. Hypertension-related eye damage has been identified at systolic pressure as low as 168 mmHg. Bleeding can also occur into the front of the eye. A severe rise may cause brain swelling and neurological signs.

In dogs with kidney disease, hypertension has been associated with greater urinary protein loss. It can accelerate chronic kidney disease progression. The left ventricular muscle wall can thicken. Actual heart failure is a less common complication.

Outlook and the underlying disease

The outlook depends on the underlying cause. Well-controlled pressure reduces complication risk. Medication is usually needed lifelong. Nevertheless, it may need adjustment during follow-up.

During follow-up of adrenal-dependent Cushing's disease, 25% of 8 dogs remained hypertensive at 12 months. Good control of Cushing's symptoms does not necessarily mean pressure has normalised.

Diagnosis at the vet

Calm measurement and a suitable cuff

Blood pressure is usually measured with a cuff around a limb or the tail. Measurement is painless. Your dog has 5–10 minutes to settle in the room. A quiet location away from other animals is preferred. Your presence may reduce anxiety.

Your dog can rest comfortably on the floor, your lap or their own bed. Measurement is ideally performed before other stressful procedures. Sedation is generally not used for routine measurement. Cuff width is usually about 40% of limb circumference. An incorrectly sized cuff can distort the result.

The first reading is generally discarded. Assessment uses the mean of 5–7 consistent readings. Marked variation requires a repeat series. Site, position and cuff size are recorded for later visits.

Practices usually use Doppler or oscillometric devices to estimate pressure non-invasively. Direct measurement requires an arterial catheter, so it is unsuitable for routine screening.

Interpreting and confirming readings

Systolic pressure under 140 mmHg carries minimal target organ damage risk. A value of 140–159 mmHg means mildly raised pressure and low risk. Values of 160–179 mmHg indicate moderate risk. At least 180 mmHg indicates high risk.

Greyhounds and Scottish Deerhounds, for example, may have pressures about 10–20 mmHg higher than crossbreeds. Breed-specific reference ranges are used when available. Persistence is generally confirmed by measurements on separate days. In kidney patients without organ damage, a level of 160–179 mmHg is confirmed over 1–2 or 2–4 weeks. With a severe rise, confirmation takes place within 1–2 weeks. Existing organ damage means treatment is not delayed solely for confirmation visits.

Investigating the cause and organ damage

Your vet examines the back of the eyes, heart and neurological status. Blood samples assess kidney function and possible other disease. Urine tests include specific gravity and protein levels. Kidney ultrasound and hormone tests where needed complete the investigation. Urine specific gravity below 1.030 does not confirm kidney disease because hypertension itself can increase urination. If the cause remains unclear, occult kidney disease is also considered.

Treatment

Treating pressure and underlying disease together

Your vet chooses medication according to pressure, organ damage and other conditions. Concurrent kidney or hormonal disease needs its own treatment. The aim is controlled reduction without a rapid collapse in pressure. Kidney patients generally have a target systolic pressure below 160 mmHg. The lowest organ damage risk corresponds to below 140 mmHg.

ACE inhibitors are among medicines used in dogs. They can also reduce urinary protein loss. Angiotensin receptor blockers are another option acting on this hormonal system. A calcium channel blocker such as amlodipine may be needed for severe or poorly controlled hypertension. If one medicine is insufficient, your vet may plan combination treatment.

Dehydration in a kidney patient is corrected before certain blood pressure medicines are started. Inadequate kidney blood flow can reduce filtration. Diuretics are not usual first-line antihypertensives in dogs. They may be needed if fluid accumulation is also present.

Emergency care and monitoring response

Acute organ damage may require hospitalisation and continuous monitoring. Even then, pressure is reduced gradually rather than normalised all at once. After starting or changing medication, pressure may be checked after 7–10 days if no new organ damage signs occur. With active organ damage, review may be within 1–3 days. A stable kidney patient's pressure monitoring continues at least every 3 months.

Follow-up also assesses urinary protein loss. In canine kidney disease, the goal is at least a 50% reduction in urine protein:creatinine ratio, preferably to below 0.5. Blood tests monitor kidney function and medication adverse effects. A marked creatinine rise during treatment may indicate an adverse drug effect. Pressure below 120 mmHg alongside weakness or fainting can mean an excessive reduction. Medication is adjusted according to readings and your dog's condition.

Diet and long-term care

Diet is tailored particularly to any kidney disease and your dog's food intake. Reducing salt alone generally does not lower pressure sufficiently. Nevertheless, very salty food is avoided. Surgical treatment of an adrenal tumour may reduce medication requirements. Pressure therefore remains monitored after successful hormonal disease treatment.

Prevention

Monitoring focuses on dogs with predisposing disease or suggestive findings. Appropriate kidney and hormonal disease care forms part of pressure control. Dogs aged at least 9 years may have annual screening measurements to detect hidden underlying disease too. With known kidney risk, assessments may occur every 6 months, for example.

Routine screening of all young, apparently healthy dogs is not recommended because it can cause false diagnoses.

Current medication is also reviewed if pressure rises. A calm measurement environment reduces anxiety-related misdiagnosis risk.

Important for dog owners

Keep a medication list and tell your vet about changes. Bring your dog's bed if it helps them settle. Your presence and minimal restraint may make measurement easier.

Record changes in sight, balance, thirst and urination. Keep readings alongside the measurement site and how anxious your dog was. Monitoring is needed even if your dog seems well.

Report new weakness or fainting during medication. Treatment is reassessed if pressure has fallen too far.

Frequently asked questions

Can high blood pressure cause no symptoms?

Your dog may have no symptoms despite markedly raised pressure. The first noticed change can be sudden sight loss. Pressure is therefore also measured in kidney or hormonal disease patients that otherwise appear well.

What pressure is dangerous for a dog?

Systolic pressure of 160–179 mmHg carries moderate organ damage risk. At least 180 mmHg carries high risk. Assessment uses reliable repeated readings and examination findings. Acute eye or brain damage may need immediate treatment.

Can anxiety at the vet raise blood pressure?

Anxiety and excitement can cause a temporary rise. Your dog therefore has 5–10 minutes to settle before measurement. The first reading is discarded. Assessment uses the mean of 5–7 consistent measurements. A temporary anxiety-related rise is not treated with antihypertensive medication.

Is low-salt food enough to treat hypertension?

Reducing dietary salt alone generally does not lower pressure sufficiently. Diet is chosen according to other conditions and food intake. Very salty food is avoided. Confirmed hypertension often requires medication. Repeated measurements monitor its effectiveness.

Can medication stop once my dog seems well?

Antihypertensive medication is usually lifelong. Requirements are assessed using pressure measurements. High pressure can persist without visible symptoms. Medication can sometimes be reduced after adrenal tumour surgery. Monitoring continues then too, so medication matches your dog's current needs.