N1033787
5.4 Interpretation of premedication affecting body temperature In the current study, only premedication combinations of opioids, alpha-2-agonists and acepromazine were analysed, as the n number of the other drug combinations was too small. The study found that when comparing body temperature decreases and premedication, there was no statistically significant difference, and so it was determined that there was no relationship between the two. This was surprising, as it is well-documented that drugs used for anaesthesia and sedation are known to contribute to peri-anaesthetic hypothermia. Studies such as Rufiange et al( 2021) found that following administration of a premedication with ketamine, midazolam and hydromorphone, the body temperature of unwarmed rats did slightly reduce, and Rose, Kwong and Pang( 2016) found there was a modest decrease in temperature associated with premedication and assumed this occurred due to the decreased activity and muscle relaxation that premedication causes. It is thought that the sedation, and concurrent reduction in activity, is what is associates premedication with a decrease in body temperature. In the study by Clark-Price et al( 2021), it was found that dogs administered an α2-adrenergic receptor agonist such as dexmedetomidine had a greater decrease in rectal temperature than those that did not. They highlight that in dogs, α2-adrenergic receptor agonists cause an initial vasoconstriction( Talke et al, 1997), centralising blood flow Granholm et al, 2007), which may result in the peripheral tissues cooling and the temperature in the mucosal tissue in the rectum reducing, potentially causing a lower reading on a rectal thermometer. The same study also found that the type of opioid used as part of the anaesthetic protocol influenced the changes in anaesthetised dog’ s rectal temperatures. Butorphanol( a κ-opioid receptor agonist and μ-opioid receptor antagonist) or buprenorphine( a partial μ-opioid receptor agonist) reduced rectal temperatures significantly less than a full μ-opioid receptor agonist such as methadone. They suggest that the development of hypothermia following the administration of opioid drugs may be due to the drugs causing a decreased ability to peripherally vasoconstrict( Kurz et al, 1995) and a lowering of the thermoregulatory set point in the central nervous system( Spencer, Hruby, and Burks 1990). This contradicts the findings of Khenissi et al( 2017), who found that all dogs in their study did have a statistically significant reduction in rectal temperature, however dogs that received dexmedetomidine as part of their premedication had a higher rectal temperature that those that did not.
ANIM32126 – EBVN Project 29