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. 2021 Apr;85(2):106-111.

Pre-warming following premedication limits hypothermia before and during anesthesia in Sprague-Dawley rats (Rattus norvegicus)

Maxime Rufiange  1 , Vivian S Y Leung  1 , Keith Simpson  1 , Daniel S J Pang  1
Affiliations

Pre-warming following premedication limits hypothermia before and during anesthesia in Sprague-Dawley rats (Rattus norvegicus)

Maxime Rufiange et al. Can J Vet Res. 2021 Apr.

Abstract
in English, French

In humans and other mammals, general anesthesia impairs thermoregulation, leading to warm core blood redistributing to the periphery. This redistribution is an important contributor to hypothermia that can be reduced with pre-warming before anesthesia. Additionally, sedation following premedication has been associated with hypothermia in dogs. In a prospective, randomized, cross-over study, 8 adult male and female rats (weighing 388 to 755 g) were sedated with intramuscular ketamine-midazolam-hydromorphone, then placed in an unwarmed cage or warmed box for 14 minutes, followed by 30 minutes of isoflurane anesthesia with active warming. Core body temperature was monitored throughout. After sedation, warmed rats gained 0.28°C ± 0.13°C and unwarmed rats lost 0.19°C ± 0.43°C, a significant difference between groups (P = 0.004). After anesthesia, warmed rats maintained higher core temperatures (P < 0.0001) with 2/8 and 6/8 of warmed and unwarmed rats becoming hypothermic, respectively. Pre-warming during sedation and active warming during general anesthesia is effective in minimizing hypothermia.

Chez l’humain et les autres mammifères, l’anesthésie générale perturbe la thermorégulation, menant au sang chaud interne se redistribuant vers la périphérie. Cette redistribution est une composante majeure de l’hypothermie et peut être réduite par le réchauffement préemptif. De plus, la sédation suivant la prémédication a été associé à l’hypothermie chez les chiens. Dans cette étude prospective, randomisée et croisée, 8 rats adultes mâles et femelles (388 à 755 g) ont été sédationnés avec ketamine-midazolam-hydromorphone au niveau intramusculaire puis placés dans une cage non-chauffée ou une boîte réchauffée durant 14 minutes, suivi d’une période d’anesthésie générale de 30 minutes sur tapis chauffant. La température interne a été suivi tout au long de l’expérimentation. Après la sédation, les rats réchauffés ont gagné 0,28 °C ± 0,13 °C alors que les rats non-réchauffés ont perdu 0,19 °C ± 0,43 °C, une différence significative entre les groupes (P = 0,004). Après l’anesthésie, les rats réchauffés ont maintenu une température interne supérieure (P < 0,0001) avec 2/8 et 6/8 des rats réchauffés et non-réchauffés hypothermes, respectivement. Le réchauffement préemptif durant la sédation suivi de réchauffement actif durant l’anesthésie générale est efficace pour minimiser l’hypothermie.(Traduit par les auteurs).

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Figures

Figure 1
Figure 1
Mean ± standard error of the mean (SEM) core body temperature following premedication with intramuscular ketamine-midazolamhydromorphone and placement in a warming box or unwarmed cage (n = 8 per treatment group). Rats in the warming box maintained a significantly higher core temperature after premedication injection (P = 0.004).
Figure 2
Figure 2
Mean ± SEM core body temperature of rats during 30 min of general anesthesia with isoflurane and recovery, following initial warming box or unwarmed cage treatment (n = 8 per treatment group). Rats in the warming box group maintained a significantly higher temperature throughout the anesthesia (P < 0.0001). The broken horizontal line represents the hypothermia threshold (36.4°C).
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