ABSTRACT OF THE WEEK

Journal of feline medicine and surgery
Volume 17 | Issue 12 (December 2015)

Comparison of axillary, tympanic membrane and rectal temperature measurement in cats.

J Feline Med Surg. December 2015;17(12):1028 - 1034.

Victoria A Smith¹, Valerie Lamb², Alix R McBrearty³

¹ Small Animal Hospital, School of Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK v.smith.1@research.gla.ac.uk.; ² Southern Counties Veterinary Specialists, Hangersley, UK.; ³ Small Animal Hospital, School of Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.

© ISFM and AAFP 2015.

Abstract

OBJECTIVES:Rectal temperature (RT) is routinely used to assess body temperature in cats but has limitations and can be poorly tolerated. Axillary temperature (AT) and tympanic membrane temperature (TMT) are reported alternatives. This study aimed to determine the differences between RT and AT, and between RT and TMT in cats. Additional aims were to examine the effect of environmental and patient factors on these differences and to assess patient tolerance to each technique.

METHODS:AT, TMT and RT were measured in immediate succession. Measurement order was randomised, as was the choice of left or right axilla and tympanic membrane. A digital thermometer and a veterinary infrared ear thermometer were used. The subjective tolerance of each procedure was recorded.

RESULTS:One hundred and fifty cats were included. Significantly more conscious cats were tolerant of AT (90.6%) than TMT (81.2%) and RT (53.0%). The rectal-axillary temperature difference ranged from -1.2°C to 1.4°C (median 0.1°C) and was within ± 0.5°C in 78.0% of cats. On multivariable analysis the difference was larger in overweight cats, neutered cats, cats in which the right axilla was used and as the RT increased. The rectal-tympanic membrane temperature difference ranged from -1.6°C to 3°C (median -0.3°C) and was within ± 0.5°C in 51.3% of cats, significantly fewer than for AT (P <0.001). The rectal-tympanic membrane temperature difference increased as the RT increased.

CONCLUSIONS AND RELEVANCE:TMT and AT should not be used interchangeably with RT in cats. When RT measurement is not possible, AT is recommended over TMT as it is better tolerated and significantly fewer cats had clinically unacceptable differences (>0.5°C). AT may more closely reflect RT in normal or underweight cats than it does in overweight cats.

Companion Notes

Prospective report comparing axillary, tympanic membrane and rectal temperature measurement in 150 cats

Introduction on body temperature assessment

- gold standards for core body temperature are invasive contact devices

(used in anesthetized or critical care cases)

- esophageal thermistors

- pulmonary artery thermistors

- in canine medicine:

- rectal temperatures shown to have good agreement with core temperature

- in feline medicine:

- rectal temperature (RT) can be difficult to perform

- particularly in fractious cats or those with rectal or perianal disease

- can be stressful for the cat especially with serial measurements

- possibly it may cause cross-contamination or rectal injury

- accuracy affected by the following:

- depth of measurement

- feces

- conditions affecting local blood flow

- in cases of aortic thromboembolism RT may be inaccurate

- axillary temperature (AT)

- in pediatric medicine, the technique is convenient (RT can be frightening)

- skin and subcutaneous tissues in thinner in younger infants

- assessed in 1 study of 31 cats

- statistics suggested it's not interchangeable with RT

- tympanic membrane temperature (TMT)

- pyroelectric sensors that measure infrared radiation from tympanum

- tympanic membrane is well vascularized by internal carotid arteries

- these also perfuse the hypothalamus

- advantages include the following:

- reading obtained within 1 second

- better tolerance than with RT

- reported disadvantages include the following:

- greater variability between measurements than with RT

- resentment of probe placement

- assessed in several studies in cats with contradictory conclusions

Study design

- study population: 150 cats seen at a veterinary teaching hospital

- convenience sample of cats needing a RT measurement

- 117 were conscious for measurements

- procedure: assistant gently restrained cats; observer obtained temperatures

- the following were measured in immediate succession:

(random method order and choice of left or right axilla and tympanum)

- AT (Kruuse Digital Thermometer; Jørgen Kruuse)

- tip placed as proximally as possible in axilla in close contact with skin

- midway from cranial and caudal margins

- foreleg gently held against chest wall

- TMT (Pet-Temp Model PT 300; Advanced Monitors)

- RT (Kruuse Digital Thermometer; Jørgen Kruuse)

- placed in a disposable cover and coated in lubricant

- tip inserted a minimum of 1.5 cm into rectum

- gently placed in close contact with mucosa

- hypothermia: <37.8°C; hyperthermia: >39.2°C

- subjective tolerance of each recorded

Results

- significantly more conscious cats were tolerant of AT than TMT and RT

- AT, 90.6% were tolerant

- TMT, 81.2% were tolerant

- RT, 53.0% were tolerant

- median rectal-axillary temperature difference: 0.1°C; range of -1.2°C to 1.4°C

(RATD = rectal-axillary temperature difference)

- within ± 0.5°C in 78.0% of cats

- in multivariable analysis the difference was larger in subgroups

- overweight cats

- associated with a 0.34°C increase in RATD over cats with BCS of 1-5

(within ± 0.5°C of RT was considered clinically acceptable)

- neutered cats

- RATD of intact cats 0.38°C lower than that of neutered cats

- cats in which right axilla was used

- as the RT increased

- median rectal-tympanum temperature difference: -0.3°C; range -1.6°C to 3°C

- within ± 0.5°C in 51.3% of cats (significantly fewer than for AT)

- difference increased as RT increased

- 33.3% cats were hypothermic and 9.3% were hyperthermic

"TMT should not be used interchangeably with RT in cats as a wide range of RTMTD [rectal-tympanic membrane temperature difference] was found, and 48.7% of cats had clinically unacceptable differences between TMT and RT. Clinically unacceptable differences between AT and RT were found in 22% of cats and therefore these methods should also not be used interchangeably."

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