Blood Pressure Screening for Hypertension in Dogs and Cats
Woody Dudley, DVM
Did you know that high blood pressure is commonly seen in our Senior Dogs and Cats?
Many of our senior patients have systemic hypertension (high blood pressure) and we don’t realize it. As in people, blood pressure increases with age. The American Animal Hospital Association recommends yearly blood pressure screening starting at 7 years of age. Our pets may have no symptoms at all yet have hypertension on a routine blood pressure evaluation. The most common cause for hypertension in dogs and cats is Kidney Disease, not plaque in the arteries as occurs in humans.
Hypertension in dogs and cats is usually secondary to other health conditions. In addition to Kidney Disease, other causes for hypertension include anemia, Adrenal Gland Tumors, and hormonal conditions such as Diabetes Melitus, Hyperthyroidism in cats, and in dogs, Diabetes, Cushing’s Disease and Hypothyroidism. When hypertension is found on a routine blood pressure screening, additional blood and urine testing and an ultrasound should be done to determine the underlying cause.
Recent studies of the American Animal Hospital Association indicated that 74% of cats with high blood pressure have abnormalities found through blood and urine tests that reveal signs of kidney disease and up to 65% of cats with kidney disease have high blood pressure.
Is hypertension dangerous to my pet’s health?
High blood pressure is often referred to as the “silent killer”. Suddenly with no warning, a clot or ruptured blood vessel from hypertension can reduce oxygen to the brain, eyes, and kidneys. This can result in brain damage (stroke), blindness, and kidney damage.
Systolic Blood pressure greater than 160 is considered to be at increased risk for damage to certain organs referred to as the target organs. The target organs (organs worst affected by high blood pressure) in dogs and cats are the eyes, brain, and kidneys. In addition, high blood pressure can also place excessive strain on the heart; the heart wall becomes thicker because it has to pump harder with high blood pressure.
Eye damage and blindness occurs as a result of retinal detachment and hemorrhage inside the eye. For this reason, a good eye exam in a dark room with light and magnification is done to see these changes. Intraocular pressure and ultrasound testing is also helpful for diagnosis.
Brain damage or “stroke” from hypertension results in a “clot” that obstructs blood flow or it can be caused by a ruptured blood vessel that leaks blood. Symptoms include disorientation, seizure, abnormal reflexes, trouble walking, coma, sudden death. A good neurological exam and advanced imaging of the brain are needed for diagnosis.
Kidney damage from high blood pressure can lead to kidney failure and scarring of the kidneys. Symptoms include loss of urine control, blood in the urine, drinking excessive amounts of water. Senior Blood and Urine testing is helpful for diagnosis.
When is treatment recommended?
Blood pressure should be treated if over 160mm systolic. Patients between 160-180 are at moderate risk for damage to brain, eyes, and kidneys. Patients over 180 are at high risk for target organ damage to brain, eyes, and kidneys. An inexpensive medication to control blood pressure can be given orally daily for life to prolong your pet’s life and help prevent emergency visits.
How do you take my pet’s blood pressure?
Taking a dog or cat blood pressure is more involved than taking human blood pressure. First, we prefer that the patient is allowed at least 15 minutes or more to become acclimated to the location in the hospital to reduced anxiety. In some situations having the owner present helps reduce anxiety. Lying immobile in a relaxed position if preferred. Standing is not recommended since we prefer that the blood pressure cuff is located near the level of the aorta where blood exits the heart. 6-7 or more blood pressure readings are preferred. The first blood pressure is discarded and the remaining 5 or more are used to obtain an average blood pressure.
Measuring blood pressure in a dog or cat is a complex process and requires 15 minutes under ideal circumstances and perhaps 45 minutes or more in difficult cases. Blood pressure cannot be rushed.