Comparison of rectal, tympanic membrane and axillary temperature measurement methods in dogs

A non-invasive method to determine core temperature for cats and dogs using surface temperatures based on machine learning

BACKGROUND

Rectal temperature (RT) is an important index of core temperature, which has guiding significance for the diagnosis and treatment of pet diseases.

OBJECTIVES

Development and evaluation of an alternative method based on machine learning to determine the core temperatures of cats and dogs using surface temperatures.

ANIMALS

200 cats and 200 dogs treated between March 2022 and May 2022.

METHODS

A group of cats and dogs were included in this study. The core temperatures and surface body temperatures were measured. Multiple machine learning methods were trained using a cross-validation approach and evaluated in one retrospective testing set and one prospective testing set.

RESULTS

The machine learning models could achieve promising performance in predicting the core temperatures of cats and dogs using surface temperatures. The root mean square errors (RMSE) were 0.25 and 0.15 for cats and dogs in the retrospective testing set, and 0.15 and 0.14 in the prospective testing set.

CONCLUSION

The machine learning model could accurately predict core temperatures for companion animals of cats and dogs using easily obtained body surface temperatures.

Variation of rectal temperature in dogs undergoing 3T-MRI in general anesthesia

OBJECTIVES

Managing body temperature during MRI scanning under general anesthesia poses challenges for both human and veterinary patients, as many temperature monitoring devices and patient warming systems are unsuitable for the use inside an MRI scanner. MRI has the potential to cause tissue and body warming, but this effect may be counteracted by the hypothermia induced by general anesthesia and the low ambient temperature usually encountered in scanner rooms. This study aimed to observe temperature variations in dogs undergoing MRI under general anesthesia.

MATERIALS AND METHODS

In this prospective observational study, client-owned dogs scheduled for 3-Tesla MRI under anesthesia between February and October 2020 at a veterinary teaching hospital were eligible for enrollment. Recorded data included breed, body mass, body condition score, age, fur quality, pre- and post-MRI rectal temperatures, time in the MRI room, scan area and coil used, application of contrast medium, choice of anesthetic agents, use of blankets, and infusion therapy. Group comparisons were conducted using the Mann-Whitney U-test or Kruskal-Wallis test, with p < 0.05 considered significant.

RESULTS

In total 171 dogs met the inclusion criteria. The median body temperature at admission was 38.4°C (IQR 38.1-38.7°C). The median body temperature before MRI was 38.2°C (IQR 37.8-38.6°C), and the median temperature after the MRI scan was 37.7°C (IQR 37.238.2°C) resulting in a median temperature difference (∆T) before and after MRI of - 0.6°C (IQR -0.8--0.1°C). The median duration of MRI scans was 49 min (IQR 38-63 min). A temperature loss of more than 0.1°C was observed in 121 (70.8%) dogs, 29 (16.9%) dogs maintained their temperature within 0.1°C, and 21 (12.3%) dogs experienced a temperature increase of more than 0.1°C. Factors associated with a higher post-MRI temperature included greater body mass, medium or long fur, and the application of α2- receptor-agonists.

CONCLUSION

Dogs undergoing MRI under general anesthesia are likely to experience temperature loss in the given circumstances. However, in larger dogs and those with much fur, an increase in body temperature is possible and more common than generally anticipated, although clinically insignificant in most cases.

Comparison of Axillary versus Rectal Temperature Timing in Canine and Feline Patients

Research on alternatives to rectal thermometry in canine and feline patients has focused on equipment and measurement location but not procedure duration. In a crossover clinical scenario, we evaluated the time prior to (Pre-TempT) and after (Post-TempT) rectal and axillary thermometry in a diverse demographic of canine (n = 114) and feline (n = 72) patients. Equipment duration was controlled to determine a presumptive total time (TTime) associated with each thermometry method. Pre-TempT and TTime were significantly shorter in axillary thermometry trials for both canine and feline pets (p < 0.001). There was no difference in Post-TempT between thermometry methods in canine patients (p = 0.887); however, the Post-TempT was longer in felines after axillary thermometry (p = 0.004). Reductions in Pre-TempT and TTime were not significant in Scottish Fold breed cats. Within the feline rectal trials, the TTime of domestic-long-haired breeds was significantly longer than that of domestic-short-haired breeds (p = 0.019). No other tested parameter (i.e., size, body shape, age, weight, breed, coat type, or procedure order) played a significant role in these results. Axillary thermometry was faster than rectal thermometry in both canine and feline pets, primarily due to the time associated with animal approach and restraint (Pre-TempT). These results have implications for optimizing clinic workflow, appointment durations, and patient handling time.

Body temperature measurement in anesthetized dogs - comparison of nasal, axillary, rectal and esophageal temperature

OBJECTIVE

To evaluate different methods of monitoring body temperature in anesthetized dogs with comparison to core temperature obtained via esophageal probe.

METHODS

Client-owned dogs undergoing general anesthesia for various procedures were included in this observational study. The temperature was taken sequentially every 10 minutes from the rectum, axilla, and nasal cavity with a digital thermistor thermometer, and compared to esophageal core temperature via paired t-tests. Differences from the gold standard esophageal temperature were assessed via Bland-Altman plots and further evaluated for factors like time under anesthesia and presence of Hypo-/Normo- or Hyperthermia. In addition, it was analyzed whether a correction factor for peripheral measurement sites (nasal cavity and axilla) would be applicable in a reliable representation of the body temperature. The level of significance in all tests was set at p<0.05.

RESULTS

In this study, 95 simultaneous temperature measurements at the 4 different sites were obtained from 30 dogs. Mean difference and limits of agreement from esophageal temperature for the different measurement methods were 0.0±0.72°C for rectal temperature, -1.2±1.42°C for axillary and -1.0±2.02°C for nasal temperature. Axillary and nasal temperatures were not significantly different (p=0.5721 and p=0.9287, respectively) from esophageal temperature with a +1.2°C and +1°C correction factor, respectively.

CONCLUSION AND CLINICAL RELEVANCE

During perioperative temperature measurement in anesthetized patients, rectal and esophageal measurements can be used interchangeable. However, if these are not available, the use of axillary or nasal sites is only reliable after applying a correction factor.

Comparison of axillary and inguinal temperature with rectal temperature in dogs at a veterinary teaching hospital

OBJECTIVES

The objective of the study was to determine the agreement between rectal, axillary and inguinal temperatures and to estimate the accuracy of these measurements in detecting hyperthermia and hypothermia in dogs presented at a veterinary teaching hospital in the tropical Guinea Savannah zone.

MATERIALS AND METHODS

Prospectively, body temperature was measured in 610 dogs, using digital thermometry in the axillary, inguinal and rectal regions.

RESULTS

Overall, axillary and inguinal temperatures significantly underestimated rectal temperature, with a mean difference of -0.39 ± 0.02°C (95% confidence interval: -0.43 to -0.35; limit of agreement: -1.27 to 0.49) and - 0.34 ± 0.02°C (95% confidence interval, -0.37 to -0.30; limit of agreement: -1.15 to 0.47), respectively. The limits of agreement of axillary and inguinal temperatures were wide and above the pre-determined maximal acceptable difference of ±0.50°C recommended for clinical significance of rectal temperature in dogs. Bland-Altman plots showed that the confidence intervals of the mean differences of axillary and inguinal temperatures did not include the value zero, thereby indicating that the tested methods lack agreement with rectal temperature. Sensitivity and specificity for the detection of hyperthermia with axillary temperature were 72.1% and 30.5%, respectively. In contrast, sensitivity and specificity for the detection of hyperthermia with inguinal temperature were 77.9% and 26.2%, respectively. The magnitude of disagreement between axillary, inguinal and rectal temperatures was affected by age, breed and sex being slightly lower in mature, non-native breed and female dogs.

CLINICAL SIGNIFICANCE

Axillary and inguinal temperature measurements in dogs significantly underestimated rectal temperature measurements by -0.39 ± 0.02°C and -0.34 ± 0.02°C, respectively. The results indicate that axillary and inguinal temperatures should not be used as a replacement for rectal temperature due to the wide limits of agreement. In addition, axillary and inguinal temperatures may not be suitable in detecting hyperthermia because the sensitivity were lower than the required set-point of 90.0% for clinical identification of hyperthermia.

The Effect of Two Acute Bouts of Exercise on Oxidative Stress, Hematological, and Biochemical Parameters, and Rectal Temperature in Trained Canicross Dogs

Canicross is a sport discipline that connects human and canine athletes in running. Changes in physiological, hematological, and biochemical parameters, and exercise-induced oxidative stress have not been thoroughly characterized in canicross dogs. The aim of our study was the assessment of the health status of trained canicross dogs that were subjected to two acute bouts of exercise with their owners during the training season. Health status was assessed by measuring the rectal temperature, hematological and biochemical parameters, as well as blood oxidative stress parameters (plasma malondialdehyde, lipid peroxidation marker; whole blood glutathione peroxidase and erythrocyte superoxide dismutase1, antioxidant enzymes) before and during a two-day canicross training session and after a 24-h rest period. Seven trained canicross dogs (three females/four males) aged 12–120 months were included in the study. Blood samples were collected before and immediately after the first acute bout of exercise (day 1), after the second acute bout of exercise (day 2), and after 24 h of rest (day 3). Rectal temperature was measured at the same time as blood sample collection. The majority of hematological and biochemical parameters remained within reference ranges at all sampling times. Rectal temperature was significantly higher after training on days 1 and 2 compared to resting temperature on day 3. Hematological parameters did not change significantly; however, there were significant differences in urea, creatinine, creatine kinase, and triglycerides between specific sampling times. Despite significant changes, these biochemical parameters remained within reference ranges. Significant changes in biochemical parameters seem to reflect the dogs' physiological response to each acute bout of exercise, considering all biochemical parameters and rectal temperature returned to pre-exercise values after a 24-h rest period (day 3). No significant differences in oxidative stress parameters were found between any sampling times. Relatively high erythrocyte superoxide dismutase1 activity at all sampling times may indicate that the canicross dogs are adapted to training by an increased expression of antioxidant enzymes. Based on our results, we can conclude that the trained canicross dogs included in our study were healthy, in good physical condition, and fit for the two acute bouts of field exercise.

The agreement of rectal temperature with gingival, ocular and metacarpal pad temperatures in clinically healthy dogs

AIMS

To compare alternative methods of recording body temperature (BT) with rectal temperature (RT) in clinically healthy dogs.

METHODS

This prospective study included 97 healthy mixed-breed dogs (43 females and 54 males). The gingival temperature (GT) was collected by using a human non-contact, infrared forehead thermometer, while ocular temperature (OT) and metacarpal pad temperature (MPT) were obtained with an infrared thermal camera. The degree of agreement was determined using the Bland-Altman method, with RT considered as the reference temperature.

RESULTS

A total of 382 readings were obtained from four different anatomical regions. The mean difference and their 95% limits of agreement for the differences between RT-GT, RT-OT, and RT-MPT were 0.18°C (-0.95 to 1.32°C), 0.79°C (-0.45 to 2.04°C), and 0.50°C (-0.63 to 1.62°C), respectively. The GT, OT, and MPT values were within ±0.5°C of RT for 65.9, 19.5, and 52.5% of dogs, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Although GT, OT, and MPT were a quick way to estimate BT in dogs, these measurements were not comparable with RT. The GT measurement achieved the best agreement with RT measurement (lowest bias and the highest proportion of measurements within ±0.5°C). The GT could be considered an option for monitoring changes to body temperature in clinically healthy dogs where RT measurement is not possible.

Predicting military working dog core temperature during exertional heat strain: Validation of a Canine Thermal Model

Military working dogs (MWDs) operate under a wide range of conditions, including hot environments. Predicting how long a MWD can safely work without overheating is important for both health and performance. A Canine Thermal Model (CTM) was developed to predict core temperature (Tc) of MWDs. The CTM calculates heat storage from the balance of heat production from metabolism and heat exchange with the environment. Inputs to the CTM are: meteorological conditions (ambient temperature, relative humidity, solar radiation and wind speed), physical characteristics of the dog (mass, length), and metabolic activity (MET level, estimated from accelerometer data). The CTM was validated against Tc measured in 23 MWDs during training sessions (11.6 ± 5.0 min (mean ± standard deviation), range 4-26 min) in October (24 °C, 52% RH), March (14 °C, 74% RH), or August (28 °C, 64% RH), and 24 kennel MWDs during a standard exercise walk (11.4 ± 3.3 min, range 5.6-18 min) in July (26 °C, 77% RH). The CTM was considered acceptable if predicted Tc was within ±0.5 °C of measured Tc at the end of exercise. Compared to Tc at the end of training sessions (39.8 ± 0.6 °C, range 38.4-41.1 °C) and exercise walks (40.0 ± 0.7 °C, range 38.9-41.4 °C), the CTM-predicted Tc was within ±0.5 °C for 71 of 84 cases (85%) and 19 of 24 cases (79%), respectively. The mean difference between CTM-predicted and measured final Tc during training was -0.04 ± 0.43 °C, with 80 of 84 cases (95%) within the range of ±2 SD (Bland Altman comparison). During exercise walks the mean difference was -0.15 °C ± 0.57, with 23 of 24 cases (96%) within ±2 SD. These results support the use of the CTM to predict Tc of MWDs for the types of physical activities described above.

Comparison between rectal and body surface temperature in dogs by the calibrated infrared thermometer

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Dogs poorly tolerate rectal temperature measurements with a contact thermometer.

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Existing alternative approaches used uncalibrated infrared thermometers.

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Gum and inguinal temperature are correlated moderately to rectal temperature.

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Hyperthermia was detected with sensitivity and specificity up to 90.0% and 78.6%.

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Future studies should include a calibrated thermometer and control external factors.

Because dogs tolerate conventional rectal temperature measurements poorly, a calibrated infrared thermometer was tested for assessing canine body surface temperature. Body surface temperature of 204 dogs was estimated on various sites (digit, snout, axilla, eye, gum, inguinal region, and anal verge). Having rectal temperature as the gold standard, temperature difference, Spearman's correlation coefficient, hyperthermia and hypothermia detection sensitivity and specificity, and stress response score was calculated for each measurement site. Although the canine body surface temperature was considerably lower than the rectal temperature, there was a moderate correlation between both temperatures. Spearman's coefficients were 0.60 (p < 0.001) for the inguinal region with a single operator and 0.50 (p < 0.001) for the gum with multiple operators. Measurement site on the gum additionally guaranteed hyperthermia detection sensitivity and specificity up to 90.0% (95% CI: [66.7 100]) and 78.6% (95% CI: [71.6 85.2]), respectively. Measurements with the infrared thermometer provoked a statistically significant lower stress response (mean stress scores between 1.89 and 2.48/5) compared to the contact rectal measurements (stress score of 3.06/5). To conclude, the correct body surface temperature measurement should include a calibrated thermometer, reliable sampling, and the control of external factors such as ambient temperature influence. The transformation of body surface temperature to the recognized rectal temperature interval allows more straightforward data interpretation. The gum temperature exhibited the best clinical potential since the differences to rectal temperatures were below 1°C, and hyperthermia was detected with the sensitivity of up to 90%.

Assessment of Non-Contact Infrared Thermometer Measurement Sites in Birds

The standard method of obtaining body temperature in a bird can be a stressful event, making routine evaluations challenging. Twenty-eight privately owned birds in good health were enrolled in the study to compare digital and infrared (IR) temperature readings. Digital thermometer readings in the cloaca were compared with two different IR thermometers, Ototemp (OT) and VetTemp (VT), used at the skin of the cloaca, breast, axillary area and tympanic membrane. The majority of the IR temperature readings were not significantly different from the cloacal digital reading. Additionally, the different IR thermometers read close to each other at individual reading sites. The IR measurements at the axilla (OT, mean = 40.35°C, SD = 1.24°C; VT, mean = 40.20°C, SD = 1.38°C) were most similar to the standard cloacal measurement (mean = 40.83°C, SD = 0.88°C). For veterinarians who currently avoid measuring cloacal body temperatures to prevent unnecessary stress on avian patients utilizing IR thermometers in the axillary region provide a less invasive and reasonable measurement of core body temperature in birds to allow for a more comprehensive assessment of health status.

Investigating factors affecting the body temperature of dogs competing in cross country (canicross) races in the UK

Increasing numbers of people are running with their dogs, particularly in harness through the sport canicross. Whilst canicross races are typically held in the winter months, some human centred events are encouraging running with dogs in summer months, potentially putting dogs at risk of heat related injuries, including heatstroke. The aim of this project was to investigate the effects of ambient conditions and running speed on post-race temperature of canicross dogs in the UK, and investigate the potential risk of heatstroke to canicross racing dogs. The effects of canine characteristics (e.g. gender, coat colour) were explored in order to identify factors that could increase the risk of exercise-induced hyperthermia (defined as body temperature exceeding the upper normal limit of 38.8°C).108 dogs were recruited from 10 race days, where ambient conditions ranged from - 5 to 11°C measured as universal thermal comfort index (UTCI). 281 post race tympanic membrane temperatures were recorded, ranging from 37.0-42.5°C. There was a weak correlation between speed and post-race temperature (r = 0.269, P < 0.001). Whilst no correlation between any single environmental factor or UTCI and post-race temperature was found, the proportion of dogs developing exercise-induced hyperthermia during the race increased with UTCI (r = 0.688, P = 0.028). Male dogs (χ(1) = 18.286, P < 0.001), and dark coated dogs (χ(2) = 8.234, P = 0.014), were significantly more likely to finish the race with a temperature exceeding 40.6°C. Prolonged elevati°n of body temperature above this temperature is likely to cause heatstroke. At every race dogs exceeded this critical temperature, with 10.7% (n = 30) of the overall study population exceeding this temperature throughout the study period. The results suggest male dogs, dark coloured dogs, and increased speed of running all increase the risk of heatstroke in racing canicross dogs. Further research is required to investigate the impact of environmental conditions on post-race cooling, to better understand safe running conditions for dogs.

Agreement of Axillary and Auricular Temperature with Rectal Temperature in Systemically Healthy Dogs Undergoing Surgery

Obtaining a patient's temperature is an important part of a patient's physical examination. As human medicine transitions to noninvasive temperature measurements, so does veterinary medicine. Historically, temperature measurement has been obtained from rectal readings; however, alternative methods, such as axillary and auricular temperatures, are increasing in popularity. The purpose of the study was to compare these alternative techniques to the gold standard of rectal temperature. Temperatures were obtained three ways for each patient: rectal, axillary, and auricular. Results indicated a positive linear relationship between rectal and axillary temperatures (bivariate correlation coefficient [r] = 0.65, P < .001) and axillary and auricular temperatures (r = 0.55, P < .001). Agreement was strongest between rectal and auricular temperatures (r = 0.80, P < .001). The average discrepancy between axillary and rectal temperature was 1.2°C [2.1°F] with the highest difference being 4.0°C [7.3°F]. The average discrepancy between auricular and rectal temperature was 0.6°C [1.2°F] with the highest difference being 2.2°C [4.1°F]. Despite auricular temperatures having stronger agreement, Bland-Altman Limits of Agreement testing revealed that it was a poor predictor of rectal temperature. Based on these results, axillary and auricular temperatures should not be substituted for rectal temperature.

Comparison of rectal and tympanic membrane temperature in healthy exercising dogs

The ability to monitor body temperature in athletes at risk of hyperthermia is essential in all species. Currently, the only commonly accepted temperature monitoring site in dogs is the rectum. This is impractical in field situations as it takes time, requires additional handlers to restrain the dog and is not tolerated by all animals. Tympanic membrane temperature (TMT) monitoring may provide a rapid measure of body temperature to facilitate identification of heat stress and heat stroke in canine athletes. In human studies, TMT diverges from rectal temperature (RT) as body temperature increases during exercise induced hyperthermia so is not recommended for monitoring human athletes. If the same divergence occurs in dogs, TMT may not be suitable for use when monitoring the temperature of canine athletes. The aim of the study was to determine if TMT diverged from RT following exercise in healthy dogs. 24 healthy dogs were recruited to the study. Body temperature was measured using a veterinary auricular infrared thermometer to record TMT and an electric predictive rectal thermometer. Temperatures were recorded pre- and post-exercise in a non-clinical setting, familiar to the dogs. The mixed model approach showed that exercise had no effect on the difference between RT and TMT (F(1,201)=0.026, P=0.872). The overall mean difference of RT minus TMT was 0.39 °C (n=116). 68.4% of readings fell within the accepted 0.5 °C difference in temperature recording method. In line with previously reported TMT to RT comparison studies in dogs, this study found that TMT measured consistently lower than RT. Using a correction factor of 0.4 °C minimised the difference. The hypothesis that dogs would show greater differences between TMT and RT following exercise was not supported, suggesting that TMT could be used to monitor body temperature in exercising dogs where RT is not possible.

Eye and Ear Temperature Using Infrared Thermography Are Related to Rectal Temperature in Dogs at Rest or With Exercise

Rectal body temperature (BT) has been documented in exercising dogs to monitor thermoregulation, heat stress risk, and performance during physical activity. Eye (BTeye) and ear (BTear) temperature measured with infrared thermography (IRT) were compared to rectal (BTrec) temperature as the reference method and assess alternative sites to track hyperthermia, possibly to establish BTeye IRT as a passive and non-contact method. BT measures were recorded at 09:00, 11:30, 12:30, and 02:30 from Labrador Retrievers (N = 16) and Beagles (N = 16) while sedentary and with 30-min play-exercise (pre- and 0, 15, 30-min post-exercise). Total exercise locomotor activity counts were recorded to compare relative intensity of play-exercise between breeds. BTrec, BTeye, and BTear were measured within 5 min of the target time. Each BT method was analyzed by analysis of variance for main effects of breed and time. Method differences were compared using Bland-Altman plots and linear regression. Sedentary BT differed by breed for BTrec (p < 0.0001), BTear (p < 0.0001), and BTeye (p = 0.06) with Labs having on average 0.3-0.8°C higher BT compared to Beagles. Readings also declined over time for BTeye (p < 0.0001) and BTear (p < 0.0001), but not for BTrec (p = 0.63) for both breeds. Total exercise (30-min) activity counts did not differ (p = 0.53) between breeds. Time and breed interaction was significant in response to exercise for both BTrec and BTear (p = 0.035 and p = 0.005, respectively), with a marginal interaction (p = 0.09) for BTeye. All the three methods detected hyperthermia with Labs having a higher increase compared to Beagles. Both BTear and BTeye were significantly (p < 0.0001) related to BTrec in all dogs with sedentary or exercise activity. The relationship between BTeye and BTrec improved when monitoring exercise hyperthermia (r = 0.674) versus measures at rest (r = 0.381), whereas BTear was significantly related to BTrec regardless of activity (r = 0.615-0.735). Although BT readings were significantly related, method bias (p < 0.02) was observed for BTeye to slightly underestimate BTrec, whereas no bias was observed between BTear and BTrec. This study demonstrates that IRT technology effectively measures both ear and eye temperature and enables effective monitoring of BT changes at rest, with exercise, and between breeds. However, ear, and not eye, temperature is a better reflection of rectal temperature.

Axillary temperature measurement: a less stressful alternative for hospitalised cats?

Rectal temperature measurement (RTM) can promote stress and defensive behaviour in hospitalised cats. The aim of this study was to assess if axillary temperature measurement (ATM) could be a reliable and less stressful alternative for these animals. In this prospective study, paired rectal and axillary temperatures were measured in 42 cats, either by a veterinarian or a student. To assess the impact of these procedures on the cat's stress state, their heart rate was checked and a cat stress score (CSS) was defined and graded from 1 (relaxed) to 5 (terrified). A moderate correlation was found between RTM and ATM (r=0.52; P<0.0001). RTM was on average 0.9 °C (1.6 °F) higher than ATM (P<0.0001), although a wide variation was found in the difference between these two measurements (-2.1 °C to 3.6 °C (-3.8 °F to 6.5 °F)). ATM failed to identify hypothermia in 25 per cent of the cases and hyperthermia in 19 per cent of the cases but may be considered less stressful than RTM. Indeed, RTM induced a mildly greater increase in heart rate (+6 bpm; P=0.01) and in CSS (+0.2; P=0.001) than ATM. The results were not affected by operator type. In conclusion, RTM should remain the standard method to obtain accurate temperatures in cats.

Body temperature measurements in pigs during general anaesthesia

The aim was to compare rectal, pharyngeal and oesophageal temperature measurements in anaesthetized pigs. Data were compared using the Bland-Altman method, and correlation coefficients and error measures were calculated. Sixty-six sets of data were collected from 16 pigs weighing 16.2 ± 4.2 kg. The bias (and 95% limit of agreement) for rectal and pharyngeal compared with oesophageal temperature were 0.69 (-1.18 to 2.57) ℃ and 0.22 (-0.84 to 1.28) ℃, respectively. The correlation coefficients for rectal and pharyngeal compared with oesophageal temperature were 0.47 and 0.87, respectively. The absolute error for rectal and pharyngeal compared with oesophageal temperature was 0.7 ± 0.9℃ and 0.2 ± 0.5℃, respectively. Pharyngeal temperature measurement may be more suitable than rectal temperature measurement for estimation of oesophageal temperature during general anaesthesia of pigs.

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

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.