Plus-Hex CLINICAL butorphanol or buprenorphine. The mechanisms proposed include impaired vasoconstriction [ 27 ] and a lowered thermoregulatory set point [ 28 ]. Contrastingly, Khenissi et al. [ 1 ] observed higher temperatures in dogs administered dexmedetomidine, highlighting the variability across studies.
The lack of association in the present study most likely reflects confounding factors including unevenly distributed sample sizes, and variable dosing, routes and timings of administration. Nevertheless, both current and previous findings suggest that premedication contributes to perianaesthetic hypothermia, particularly when intervals between premedication and induction are prolonged [ 3 ].
Effect of the length of the MRI procedure on body temperature
The most consistent finding of this study was that MRI procedures were associated with significant decreases in body temperature, in agreement with earlier reports [ 1, 5, 6, 18, 29, 30 ]. Duration within the MRI suite was directly correlated with temperature decrease; the longer patients remained in the scanner room, the greater the decrease observed.
This effect is likely to be multifactorial. MRI suites are maintained at low ambient temperatures to prevent the magnet overheating, with an average of 20 ° C recorded in the present study. Human studies show that operating theatre temperatures below 23 ° C significantly increase the risk of hypothermia in anaesthetised patients [ 31, 32 ], suggesting that the inherently cool MRI environment contributes directly to thermal loss in veterinary patients.
Anaesthesia itself is also a contributing factor. Patients in this study were anaesthetised before being transferred to the MRI suite, with an interval of approximately 20 minutes between induction and scanning. Hypothermia typically develops in three phases, with a 1 – 1.5 ° C decline in core temperature during the first hour of anaesthesia, due to redistribution of heat from the core to the periphery [ 33 ]. Thus, movement to the scanner during this critical period likely compounded the temperature loss. The mean decrease observed( 1.3 ° C) was consistent with this redistribution phase. Further investigation is required to clarify the interaction between time under anaesthesia and time in the MRI facility.
A further consideration is the restriction on active warming strategies. Owing to the magnetic field, common warming devices such as forced warm-air blankets and heat mats cannot be used in MRI suites, despite being proven to be effective in limiting heat loss in anaesthetised dogs [ 18 ]. The absence of these methods is likely to have contributed to the pronounced cooling observed in this setting.
Impact on the practice and veterinary team
The results of this study highlight that dogs anaesthetised for MRI investigations often undergo temperature changes during the procedure, with temperature most likely decreasing. Veterinary nurses( VNs) monitoring the anaesthetics of future patients can therefore assume that, in most cases, their patient ' s body temperature will decrease, and can implement steps to minimise this decrease.
Limitations
There were several limitations to the current study. The sample size was considered low, and the dogs enrolled were a heterogeneous population, which was not investigated and could have influenced the results. MRI scan sequences differed among patients and were not recorded, which again could have influenced the body temperature of the patients. Altogether, the study lacked a controlled environment.
One major limitation was the collection of the BCS data. The anaesthetic monitoring forms included a box for the VN to write the BCS of the patient whose anaesthesia they would be maintaining and monitoring. The data for this study could have been collected in a much shorter period if this information had been filled in for all patients; however, it had been missed on many forms, so those patients could not be enrolled in the study.
The BCS of the dogs enrolled in the study was assigned by one of five VNs. This is another limitation of the study, as assigning a BCS is subjective and involves the opinions of the observer [ 9 ], so the VNs could have differed in their opinions of each dog ' s BCS, which could have influenced the results of the study.
The final limitation of the study was that different brands of digital thermometers were used to measure the rectal temperatures of the dogs, and there was no record of whether a thermometer cover was used. This could have caused discrepancies and differences in the results, as different thermometers and whether or not a thermometer cover is used could influence temperature readings.
Conclusions
This study investigated changes in the body temperature of anaesthetised dogs undergoing MRI investigations and the factors that may influence these changes. The results showed that BCS and the length of time in the MRI facility had a statistically significant correlation with the decrease in a dog ' s body temperature while under anaesthesia. The type of recumbency during the scan, patient age and type of premedication were found not to have a statistically significant correlation with the body temperature decrease.
Volume 40( 6) • December 2025
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