hot off the press, Chelsea’s paper has come out on-line in Lab Animals. this study nicely shows that pre-warming before general anaesthesia in rats is effective at maintaining core body temperature. general anaesthesia reduces the ability of the body to maintain core temperature, and because the normal temperature gradient between the warm core and cooler periphery is lost, this results in hypothermia. therefore, if the normal temperature gradient can be reduced (by pre-warming the periphery), the onset of hypothermia can be delayed, for 40 minutes in this case. pre-warmed rats also recovered approximately 5 times faster from anaesthesia.
additionally, chelsea was able to quantify the relationship between rectal temperature (a common way of monitoring body temperature during anaesthesia) and core body temperature (measured with telemetry), showing that while rectal temperature measuerements are less accurate, they maintain a fairly constant, predictable, relationship with core temperature.
always nice to get one of the three good emails:
Dear Dr. Pang:
It is a pleasure to accept your manuscript LA-16-193.R2, entitled “Forced-air pre-warming prevents peri-anaesthetic hypothermia and shortens recovery in adult rats”, for publication in Laboratory Animals. Thank you for your fine contribution.
this is for Chelsea‘s summer project work improving temperature management in rats around the time of general anaesthesia, an even that is associated with reduced capacity for normal body temperature control, leading frequently to hypothermia. the consequences of hypothermia in veterinary species are not well understood as they have received little attention; however, the negative consequences in people are well documented, even with relatively small drops in temperature as little as 1 degree Celsius.
Chelsea showed that pre-warming rats with a glorified hot air dryer was very effective at protecting them from the onset of hypothermia during aproximately 40 minutes of anaesthesia. In contrast, rats that were not warmed at all, showed a dramatic, linear decrease in temperature, well below that which would be considered acceptable in human anaesthesia. subsequently, these rats took over 4 times longer to recover than the pre-warmed rats.
well done to Marika on completing and publishing a simple, but hopefully very useful study evaluating the performance of a sedation scale for dogs. sedation is commonly used in dogs to allow a range of minor procedures to be done, such as x-rays, scans, examining injuries. it is very common for research studies to assess sedation and we noticed that very few studies use the same scale to make this assessment. this makes it difficult, if not impossible, to compare results between studies.
an unexpected, and surprising result, was that a number of dogs were more deeply sedated than expected. this highlights the importance of closely monitoring our patients and reversing the effects of any drugs that can be reversed once a procedure is complete.
in the spirit of openness, data for this study were deposited in a repository.
this study was a nice collaborative project with a radiologist, lab animal veterinarian, and pathologist. rabbits have a reputation of being difficult to intubate (placing a breathing tube in their windpipes), as it takes practice to master the technique. as a result, a new device, the v-gel has been developed to make the process of providing oxygen and anesthetic agent faster and simpler. in a fairly simple study we compared the v-gel to traditional airway management (endotracheal intubation). the v-gel was faster to place than the endotracheal tube and, importantly, placing it was consistently quick, minimizing any period of decreased ventilation.
where the v-gel did not perform as well as expected was in the size of airway provided: it showed a tendency for the tip of the device to migrate towards the larynx and reduce the airway diameter. though this reduction in diameter was unfortunate, it was not smaller than with an endotracheal tube.
the paper is available open access through the Frontiers group (with access to the rather snazzy video pictured below):
an old friend, Cholowat Pacharinsak, was kind enough to ask me to write a chapter on anaesthesia equipment for a book he was co-editing. the page proofs have been approved and this should be published later this year (ISBN 9781466585676).
after a wonderfully swift (and painless) review and publication process, our paper focusing on appetite as an outcome of enhanced recovery after surgery in cats has been published in the journal of feline medicine and surgery.
a small change in anaesthesia technique, substituting alfaxalone for ketamine, resulted in 20% more cats beginning to feed within an hour after surgery. importantly, pain relief was equivalent between treatment groups. this paper was the result of a summer project by Tatum and Marika, carried out with the support of a local spay-neuter clinic.
a while ago, we compared intraperitoneal pentobarbital as a euthanasia technique with carbon dioxide overdose in rats. we expected, naively, that this would serve as an appropriate gold standard but were disappointed to find considerable variety in its effects, including a fairly high misinjection rate. the misinjection rate has been documented before, in rats and mice e.g. Corey-Avila et al. 2007 Lab Anim 36:25-30.
we wondered if the variability in effect could be improved, if not the misinjection rate. so we compared a fairly standard dose of pentobarbital with a high dose and a larger volume of the standard dose. time to loss of consciousness was shorter with both high dose and high volume approaches and similar with each technique; however, the time to death was substantially faster in the high dose group (5 times faster than the standard dose and 3 times faster than the high volume group). thus, the higher dose shortens the time to death, limiting any period of suffering that might exist. additionally, because of the reduced variability, we were able to suggest guidelines for when a misinjection has occurred i.e. if loss of consciousness does not occur within 2.5 minutes of injection. these findings should improve both the speed and predictability of euthanasia in rats when using an intraperitoneal pentobarbital injection technique.
this project was the work of katie zatroch, who is now an anesthesiology resident. the resultant paper has been published in BMC Vet Research (DOI: 10.1186/s12917-017-0982-y).