Hypertension in Dogs
You've probably had a friend, a close relative or you may even have been told you had hypertension. However, you might not realize that dogs can also be diagnosed with hypertension.
Hypertension, often called high blood pressure, is the elevation of blood pressure above a number that's expected for the species. According to a consensus statement by veterinary specialists, dogs with systolic blood pressures exceeding 150 mmHg may experience negative effects of their high blood pressure and require medication or further reevaluation.
It is best if several blood pressure measurements are taken, then the highest and lowest numbers are subtracted away, and the average calculated from the remaining values.
You can't ask a dog how he feels, so instead of symptoms of an illness, a veterinarian would look for any signs the dog might be displaying.
Carrie Goldkamp, VMD, DACVIM at Veterinary Specialty Center of Delaware in New Castle, Delaware says some of the more overt signs of hypertension involve the eyes, heart, central nervous systemic, and kidneys.
"Ophthalmologic changes include intraocular bleeding and retinal detachment, and cardiac signs can include heart murmur and congestive heart failure often with coughing, increased respiratory rate and effort."
As Dr. Goldkamp pointed out, "Neurological signs can result from a stroke. Those signs differ based on the part of the brain affected, but can include acute onset changes in gait and balance, blindness, and altered mental activity.
And, if that weren't enough to worry dog owners, Dr. Goldkamp says, "Renal signs include protein in the urine and progressive signs of renal failure that include increased drinking and urination, poor appetite, vomiting, and lethargy."
Unfortunately, early signs of hypertension can be asymptomatic, which means a dog may not show any signs of being sick. And, early clinical signs may be interpreted as normal changes due to the aging process that can include slowing down and not eating as well.
There are two types of hypertension, primary and secondary hypertension. Primary hypertension refers to hypertension without a known underlying cause, whereas secondary hypertension refers to hypertension secondary to an underlying disease.
"Primary hypertension is common in humans, but rare in our dogs," says Saundra E. Willis, DVM, Small Animal Internist at Phoenix Central Lab in Mukilteo, Washington. "Dogs predominantly suffer from secondary hypertension, thus we need to look for underlying disease and treat that whenever a dog is diagnosed with hypertension."
Here are some of the underlying diseases that can commonly cause hypertension in your dog:
- Chronic Renal disease
- Glomerular disease (a protein losing kidney disease)
- Endocrine disease
- Cushing's disease (hyperadrenocorticism)
- Diabetes mellitus
- Acromegaly (growth hormone overproduction)
- Adrenal tumor (pheochromocytoma)
- Polycythemia (abnormal increase in the amount of red blood cells in the circulatory system)
Certain breeds appear to be more susceptible to hypertension than others. Dachschunds, poodles, and certain terrier breeds have an increased risk of Cushing's disease. Australian terriers, Schnauzers, Bichons Frises and Spitz dogs have an increased risk of diabetes mellitus.
Be aware that sight hounds, and especially deerhounds, normally have a higher blood pressure than other breeds says Dr. Willis.
Sight hounds are hounds that primarily hunt by speed and sight, instead of by scent and endurance as scent hounds do. Blood pressure can also be higher in overweight dogs.
You've been noticing that your dog is a little listless lately and had been looking thinner. You're concerned so you make an appointment with your veterinarian.
"I will often check blood pressure three different times to confirm hypertension and to rule out stress as a cause of elevated blood pressure," says Dr. Goldkamp. "I also prefer to check blood pressure when a dog first arrives and then with Mom or Dad in the room to minimize stress."
Dr Goldkamp says, "Hypertension is diagnosed by persistent systolic blood pressure greater than or equal to 160 mmHg as measured by oscillometric or Doppler ultrasonographic methods."
Hypertension is diagnosed by measuring blood pressure using a similar technique used on humans.
"An inflatable cuff is fit around the dog's foreleg, or tail, and the cuff is inflated to occlude blood flow through an artery, " says Dr. Willis. "The stethoscope is not sensitive enough and so we use an ultrasonic probe to detect blood flow. This ultrasonic probe is taped or held over the artery and the sound of the systolic pressure is converted into an audible signal."
According to Dr. Goldkamp, the incidence of canine hypertension is right around the 10 percent mark, in healthy dogs, therefore, routine screening is not recommended. However, any dog that has a condition associated with hypertension should have a blood pressure measurement performed.
Interestingly, Dr. Willis notes in dogs with renal failure, one study showed that 93 percent had hypertension.
When feeding your dog, read the dog food label. Sodium and potassium have a role in blood pressure control in humans and likely in animals. However, how much salt restriction is still being investigated.
Nutrition does not directly cause any of the conditions that result in hypertension, however, higher fat diets can lead to obesity, which can then cause hypertension.
There are several types of medications that are used in dogs to control blood pressure. The type used varies with doctor preference, degree of hypertension, underlying cause of hypertension, and concurrent diseases.
Some examples of medication include angiotensin-converting enzyme (ACE) inhibitors, such as enalapril or benazepril, calcium channel blockers like amlodipine, and adrenergic blockers that include phenoxybenzamine or prazocin.
Addressing underlying diseases associated with hypertension can prevent hypertension. However, it is uncertain if blood pressure control improves survival in pets as it does in humans, although successful treatment of hypertension prevents or minimizes target organ damage.
Dr. Goldkamp tells the story of a patient named Guiness, a geriatric hound mix that originally saw the doctor in 2009 for evaluation of poorly controlled diabetes mellitus. "She was blind from her diabetes and losing weight. We diagnosed her with concurrent hyperadrenocorticism (Cushing’s disease) and hypertension. By addressing both the Cushing’s disease with medical treatment and the hypertension with enalapril, she is still alive today and doing well!"
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