Rectal temperature (RT) is the most common method to determine the body temperature of cats during a physical examination. This technique may be poorly tolerated in some patients, especially those with a fractious nature or cats with rectal or perianal disease. The procedure of taking a rectal temperature can be stressful for many cats while in a less familiar environment, such as a veterinary hospital.
Two other methods of measuring temperature are available as alternatives, axillary temperature (AT) and tympanic membrane temperature (TMT). With this study, the authors’ main objective was to compare the differences between RT and AT, and RT and TMT in cats. In addition, they wished to monitor the effect of environmental and patient factors on these differences and assess patient tolerance to each technique. Each temperature measuring technique – AT, TMT, RT – were measured in immediate succession with the measurement order randomized (pertaining to right or left axilla and tympanic membrane). The instruments used were a digital thermometer and a veterinary infrared ear thermometer. The amount of tolerance for each procedure was measured subjectively.
One hundred and fifty cats were included in this study. The results showed that AT (axillary temperature, 96.6%) was significantly better tolerated than TMT (81.2%) and RT (53.0%). A previous recommendation suggests that any variation greater than ± 0.5° C from the RT measurement is unacceptable. 22% of cats had ATs that differed by more than this value, therefore it is recommended not to use the techniques interchangeably. 48.7% of TMTs were not within ± 0.5° C so this technique is also not recommended to be interchangeable with RT. On multivariate analysis, the difference between techniques was larger in overweight cats, neutered cats, cats in which the right axilla was used and as the RT increased (particularly between RT and TMT in this instance).
In conclusion, AT and TMT should not be used interchangeably with RT when a RT technique can be used in a cat patient. In situation where RT cannot be used or it would be inaccurate (such as in cases of aortic thromboembolism), AT would be preferred over TMT because it is better tolerated and there were significantly fewer cats with clinically unacceptable differences between AT and RT. In cases where the cats are normal or underweight, AT more closely resembles RT measurements. (VLT)