Hypertension (high blood pressure) is a common finding in older cats. It often occurs as a result of kidney disease, hyperthyroidism, or other systemic illness; but may also occur without a defined cause. Elevations in blood pressure may result in damage to the retina, kidneys, brain, or other organs. Blood pressure is commonly measured in cats in order to assess the risk of hypertensive events or monitor blood pressure. While several methods exist to assess systolic blood pressure (direct measurement with arterial catheters, or indirect methods with Doppler or oscillometric techniques), Doppler measurements have regularly been shown to be the most reliable in cats.
While several studies have investigated the normal range of blood pressure in cats and the effects of age, sex, and other variables on blood pressure, they have generally been in small numbers of cats. The aim of this paper was to determine the normal range of systolic blood pressure in a large number of cats and to assess the factors that may elevate blood pressure.
Cats for this study were recruited from two rehoming centers in the UK. Cats were 6 months or older and found to be healthy on physical examination. Cats were excluded if they were hypertensive, on any medications affecting blood pressure, had evidence of systemic disease, were pregnant or lactating, were too aggressive to handle, or were hyperthyroid.
Blood pressure was measured using a Parks Doppler in a quiet room by a single observer. Pressures were measured on the right or left front leg following the ACVIM consensus statement guidelines. The first measurements were discarded and the systolic pressure calculated as an average of the next 5 readings. 1007 cats were considered eligible, of which 780 underwent the full screening process.
Statistical analysis was used to look for a correlation between blood pressure and age, sex, neutering status, behaviour score, body condition score, weight, position of cat, and limb used.
Males, previously stray cats, neutered cats, and more anxious cats were found to have a higher blood pressure. Older cats also had higher blood pressure than younger animals. There was a weak trend towards cats with a higher BCS having higher BP, but this was not statistically significant. Up to 29.2% of the variation in systolic blood pressure could be explained by these factors.
Several drawbacks to this study exist. As full bloodwork and urinalysis was not attained in every cat, it is possible that animals with subclinical renal or thyroid disease were included in the analysis. Ages were estimated in many cases and not exact, which may result in errors in analysis. As analysis was performed by manual Doppler analysis and not direct or automated blood pressure measurement, there may have been some inconsistencies in results.
This paper was able to determine the normal range of systolic blood pressures in healthy adult cats of 110.4 to 132.4 with an average of 120.6. It also found that there was an increasing trend in blood pressure with increasing age, as well as a higher pressure in male cats, neutered animals, nervous animals, or cats who were previously strays. (MRK)