By Dr. Becker
Greyhounds are known to have higher blood pressure (BP) readings than other breeds. A normal blood pressure in dogs, as in humans, is 120 over 80.
Since blood pressure is usually measured in a clinical setting, researchers in the Department of Veterinary Clinical Sciences at The Ohio State University College of Veterinary Medicine decided to see if the higher BP readings were at least in part due to 'white-coat effect.'
White-coat effect, also known as white coat hypertension or white coat syndrome, is a situation in which patients experience higher blood pressure when visiting the doctor, or in any medical-type setting, but not in other settings.
According to Guillermo Couto, DVM, professor of veterinary clinical sciences at Ohio State University and senior author of the study:
"Some greyhounds come in here with blood pressure above what an instrument can read.
That is, 300 systolic.
We know this could not really be their blood pressure because these dogs would be dead.
But we also almost never get blood pressure under 150 or 160 for systolic."
It is assumed these higher BP readings are due to the anxiety many patients (humans and pets) feel during a clinic visit.
The OSU Study
The study involved 22 healthy, retired racing greyhounds that were part of a blood donation program at OSU's College of Veterinary Medicine.
Systemic blood pressure and heart rate were measured in three different situations, including:
- In the hospital by the investigator
- In the dog's home by the investigator
- In the dog's home by the owner
There was a significant difference between BP and HR readings at the hospital versus at home, but there was no significant difference in the two readings done in the home.
According to Veterinary Practice News:
"The average systolic arterial pressure of the 22 dogs tested in the study was 30 points higher when recorded in a clinic than when recorded at home."
Despite repeated hospital visits, which did decrease heart rate readings in the greyhounds, blood pressure readings remained high. It seems the presence of the owner is more calming to these dogs than repeated exposure to a clinical setting.
Researchers concluded elevated BP and heart rates in retired racing greyhounds in clinical settings are likely the result of a white-coat effect.
They suggest before diagnosing or ruling out hypertension, there is a need to consider where the BP reading is taken. The researchers also discovered that BP measures taken in hind limbs tended to be higher than when front legs were used.
The study authors also suggest owners of retired racing greyhounds take BP recordings at home if possible to get a more accurate reading.
A Breed We Want to Know More About
It is only since racing greyhounds began being placed in adoptive homes and visiting mainstream veterinarians that we've started to uncover some of the physiologic idiosyncrasies of the breed.
The lead author of the OSU study, Dr. Guillermo Couto, and his colleagues are now trying to sort out whether white-coat associated hypertension in greyhounds causes damage to their kidneys or other organs, as is normally the case with chronic high blood pressure.
Dr. Couto, who happens to be an oncologist, adopted his first retired racing greyhound 20 years ago. Since then he has led many studies on the breed to determine the health effects of racing, as well as potential causes for their high rate of bone cancer.
He describes retired racers this way:
"They're hypertensive and yet they don't have target organ lesions that people with hypertension get. They have strokes, unlike most dogs, but the strokes they have are different from strokes in hypertensive humans. Their kidneys and eyes don't take a beating from the high blood pressure," he said. "So my thinking is that greyhounds are 'Type-A personality' dogs. They are raised in a racing environment, but they are pack animals, so this stresses them out. And then once they retire, they are couch potatoes. We're trying to put all of this together, and it's all aimed at promoting wellness in these dogs."
If you've adopted a greyhound or are familiar with the breed, you're probably aware that their normal bloodwork values are quite different from what is considered normal for other dogs.
|Red Blood Cells (RBC)||7.4 – 9.0||5.5 – 8.5|
|Hemoglobin (Hgb)||19.0 – 21.5||12.0 – 18.0|
|Packed Cell Volume (PCV)||55 – 65||37 - 55|
|White Blood Cells||3.5 – 6.5||6.0 – 17.0|
|Platelets||80,000 – 200,000||150,000 – 400,000|
|Total Protein / Globulin||4.5 – 6.0 / 2.1 – 3.2||5.4 – 7.8 / 2.8 – 4.2|
|Creatinine||0.8 – 1.6||0.0 – 1.0|
|T4 (Thyroid)||0.5 – 3.6||1.52 – 3.6|
To someone unfamiliar with greyhounds, these red blood cell values could receive a diagnosis of polycythemia, an extremely rare condition of pathologic overproduction of red blood cells.
On the flip side, the packed cell volume for greyhounds, if it falls into the normal range for other breeds, means the greyhound is anemic and should also be checked for Ehrlichia, a tick-borne bacterial infection.
With such low white blood cell and platelet counts, it's conceivable to the untrained eye that a greyhound might have cancer or some other disease. To add to the confusion, Ehrlichia, which is common in the breed, often lowers WBC and platelet counts.
It is theorized that the normally low WBCs, platelets and total protein of greyhounds might be a natural adaptation in order to manage the increased red blood cell count.
The higher creatinine level in greyhounds is a result of the amount of large lean muscle mass they carry. So as a single finding, a creatinine level in a greyhound that is higher than the level seen in other dogs is probably normal and not an indicator of kidney failure. As a general rule, if the BUN and urinalysis values are normal, so is the higher creatinine number.
Greyhound thyroid levels are generally about half that of other breeds.
Other Greyhound Health Challenges
- Many greyhounds have mildly enlarged hearts and a slight murmur. If your veterinarian detects a heart murmur, a chest x-ray should be taken. If the entire heart is slightly enlarged, it’s probably a normal condition for the dog. However, if the x-ray shows enlargement in the left chamber only, an ultrasound is recommended.
- Greyhounds are at much higher risk of bone cancer (osteosarcoma) than other breeds. The most common sites are in a front leg near the shoulder or in a back leg near the knee. If a greyhound is exhibiting lameness, an x-ray is in order.
- Greyhounds are predisposed to an eye problem called pannus, an auto-immune disorder that causes chronic inflammation of the cornea. The condition usually starts as a lesion on the outside part of the eye and spreads across the cornea. The lesion often resembles spots that can range in color from light grey to brown or black.
Left untreated, pannus can engulf the entire cornea and cause permanent blindness. Eye drops are the standard treatment, and many greyhounds wear eye goggles ('doggles') when they are outdoors.
- Greyhounds are prone to dental disease. Regular at-home dental care is an absolute must with this breed, as well as professional dental exams and cleanings by your veterinarian.
- Greyhounds, although it is rare, can develop a condition known as malignant hyperthermia – a reaction to exposure to inhalant anesthesia. The response in susceptible greyhounds is to spike a very high fever (106 or greater).
Malignant hyperthermia is genetic and will produce the same response each time the dog is exposed to an anesthesia agent, so if it happens once, it will happen at subsequent exposures. But if your dog has had anesthesia in the past with no reaction, the condition should not be a factor in the future.
- Greyhounds get corns on their feet. These are actually lesions on the pads, and they can be serious enough to cause lameness. Be sure to check foot pads during regular at-home wellness exams, and point out any problems or concerns you have to your veterinarian.
- Greyhounds are often sensitive to temperature. Many don't like to be outside during cold weather, and muscle cramps are common when they get chilled. They can heat up quickly as well in warm climates. It's important to limit your pet's exposure to extremes in temperature. Greyhounds have extremely thin skin which is probably a contributor to temperature sensitivity.
- Greyhounds are also prone to sensitive temperaments. They tend to become very attached to their adoptive families and may refuse to eat in other settings when their humans are absent – particularly clinical settings. This is good information for adoptive owners to have in the event their pet is faced with a hospital stay.
Considering Adopting a Greyhound?
Greyhounds are known to make great family pets, despite starting life as racing dogs or as 'surplus' puppies for the racing industry. They do have their share of health issues, but so does every breed – especially the large and giant boys and girls.
If you're thinking about adopting a greyhound, Grey2K USA has a list of national and state adoption organizations. And don't overlook your local animal shelters, rescues and Petfinder.com as potential resources.
If you'd like to know more about greyhounds as a breed and what to expect if you adopt a retired racing greyhound, you can find lots of information at Adopt a Greyhound, The Greyhound Project, Inc.