This page features pictures of our equipment used to monitor blood pressure in cats. Because the feline blood vessel is so small, a doppler transducer is used rather than a stethoscope to magnify the sound of the pulse. Otherwise, the technique is the same as in a human. A little bitty kitty cuff is placed on the extremity, and the transducer is placed over the vessel. A front or back leg or the tail can be used; sometimes a small amount of fur must be shaved to be able to hear the blood flow. Once the blood flow is audible, the sphygmomanometer is used to inflate the cuff. While the cuff is inflated, the pulse cannot be heard because the vessel is occluded. As the pressure is released, the blood flow resumes. The value at which the pulse is first heard is called the systolic pressure value (the top number of a BP reading, as in 120 for a BP reading of 120/85). A diastolic value (the bottom number) frequently cannot be obtained in cats.
This is a picture of the speaker used to hear the pulse detected by the doppler crystal sensor (a 9.4 MHz focused transducer). The sensor is the little brown rectangular structure attached by the cord. Ultrasound gel is applied to the sensor to amplify the sound. The speaker volume can be increased to aid in hearing. Head phones may also be used.
The cuff is removable and is attached to the pressure pump and gauge (sphygmomanometer). The cuff size is chosen based on the diameter of the extremity and is positioned based on the vessel location. After ultrasound transmission gel is applied, the sensor is applied to the vessel on the side of the cuff furthest from the body. The cuff is fully inflated then readings are determined as the cuff is slowly deflated.
The sphygmomanometer reads from 0 to 300 mmHg (millimeters of mercury, the units used to designate pressure). In cats, only a systolic (top) number is generally obtained. Normal should be around 120-130. Because nearly every cat in the veterinary hospital is nervous, we give a "white coat syndrome" allowance and adjust our high normal cutoff to 170. If it is above 170 and the patient does not appear any more nervous than the average patient, then the blood pressure is considered elevated (also known as hypertension). If the patient has signs of chronic hypertension, such as a heart murmur or changes noted in the eyes, those findings are interpreted in conjunction with the blood pressure readings.
As with people, hypertension is common in older cats. Hypertension in cats is often secondary to another problem such as kidney insufficiency or hyperthyroidism. Most of the time, we cannot determine just by looking at a cat whether or not his/her blood pressure is normal. If the blood pressure is elevated for a long time and causes signs, you may notice sudden blindness (caused by detachment of the retina, the back layer of the eye), increased pupil dilation, increased vocalization and clinginess, or vague non-specific signs. High blood pressure also affects the heart and can eventually cause heart failure, in which you may notice hard or fast breathing, open mouthed breathing, coughing, poor appetite, and/or severe lethargy. Sudden blindness, breathing problems, and severe lethargy are emergencies. If treatment is instituted quickly enough, some of these problems can be reversible. If they persist, damage may be permanent and may cause premature death.
Since hypertension is common and can cause severe signs, it is best to PREVENT these problems by routinely measuring your cat's blood pressure and addressing it at the first signs of elevation. We recommend measuring your cat's blood pressure annually starting at age 7 (when cats are considered young seniors) then every 4-6 months starting around 12 years of age (when cats are considered geriatric). The same timeline goes for routine senior lab work (see also bloodwork page & senior wellness page.) Visit our hypertension & kidney disease page for a case study on a cat with acute blindness secondary to hypertension. We hope to keep your kitty healthy so that he or she may live a very long, happy life!
Feel free to speak to our health care team members if you have any questions about blood pressure monitoring or senior care for cats!