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. 2019 Jul 24:35:8.
doi: 10.1186/s42826-019-0008-y. eCollection 2019.

Aged mice show an increased mortality after anesthesia with a standard dose of ketamine/xylazine

Sandra Schuetze  1   2 , Anja Manig  1   3 , Sandra Ribes  1 , Roland Nau  1   4
Affiliations

Aged mice show an increased mortality after anesthesia with a standard dose of ketamine/xylazine

Sandra Schuetze et al. Lab Anim Res. .

Abstract

Geriatric animal models are crucial for a better understanding and an improved therapy of age-related diseases. We observed a high mortality of aged mice after anesthesia with a standard dose of ketamine/xylazine, an anesthetic regimen frequently used in laboratory veterinary medicine. C57BL/6-N mice at the age of 2.14 ± 0.23 months (young mice) and 26.31 ± 2.15 months (aged mice) were anesthetized by intraperitoneal injection of 2 mg ketamine and 0.2 mg xylazine. 4 of 26 aged mice (15.4%) but none of 26 young mice died within 15 min after injection of the anesthetics. The weight of aged mice was significantly higher than that of young mice (32.8 ± 5.4 g versus 23.2 ± 3.4 g, p < 0.0001). Thus, aged mice received lower doses of anesthetics in relation to their body weight which are within the lower range of doses recommended in the literature or even beneath. There were no differences between deceased and surviving aged mice concerning their sex, weight and their motor performance prior to anesthesia. Our data clearly show an age-related increase of mortality upon anesthesia with low standard doses of ketamine/xylazine. Assessment of weight and motor performance did not help to predict vulnerability of aged mice to the anesthetics. Caution is necessary when this common anesthetic regimen is applied in aged mice: lower doses or the use of alternative anesthetics should be considered to avoid unexpected mortality. The present data from our geriatric mouse model strongly corroborate an age-adjusted reduction of anesthetic doses to reduce anesthesia-related mortality in aged individuals.

Keywords: Aging; Anesthetics; C57BL/6; Geriatric mouse model; Mortality.

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Conflict of interest statement

Competing interestsThe authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Mortality of young and aged mice after anesthesia with ketamine/xylazine. Kaplan-Meier curves of young mice (2 months) and aged mice (26 months) after intraperitoneal injection of 2 mg ketamine and 0.2 mg xylazine. 15.4% of the aged mice but none of the young mice died after anesthesia (log-rank test: p = 0.039)
Fig. 2
Fig. 2
Weight and motor performance. a: Weight of aged mice was significantly higher than that of young mice (32.8 ± 5.4 g versus 23.2 ± 3.4 g; p < 0.0001). Weight of surviving and deceased aged mice did not differ (33.3 ± 5.0 g versus 30.2 ± 7.5 g; p = 0.30). Data are presented as individual values and means and were compared using Student’s t-test (***p < 0.0001; ns = not significant). b: Tight rope test scores [medians (25th percentile/75th percentile)] of aged mice were significantly higher than those of young mice [16(9.75/18.25) versus 1(1/2); p < 0.0001]. Tight rope test scores of surviving and deceased aged mice did not differ [16(10/18.25) versus 11(2.5/19.5); p = 0.83]. Data are presented as individual values and medians and were compared using the Mann-Whitney U-test (***p < 0.0001; ns = not significant)
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