Revisiting tribromoethanol as a safe and effective murine anesthetic for veterinary clinical and biomedical research

Mus musculus, the house mouse, is the most widely used mammalian model in biomedical research. Mice frequently undergo injectable anesthesia for numerous research procedures, with the most common anesthetic protocol being ketamine-xylazine (K/X). 2,2,2-Tribromoethanol (TBE), a non-regulated chemical, is also used, but has been linked to peritonitis. The focus of this study was to directly compare these two anesthetic protocols by evaluating induction rates, recovery times, organ weight data, and immune endpoints. Forty-five CD-1 female (8-10 week-old) mice were divided into three experiments. Two anesthetic events were performed 2 weeks apart. For each experiment, mice received an intraperitoneal (IP) injection of sterile phosphate buffered saline, (PBS; n = 3 mice), an IP injection of K/X (n = 6 mice), or an IP injection of sterile TBE (n = 6 mice). In a separate third anesthetic event (n = 5 mice/treatment), post-treatment peripheral blood and peritoneal lavage samples were collected for a 9-plex cytokine analysis. Mice were euthanized 2 weeks after the last anesthetic event. Induction rates were non-significantly but numerically more rapid with TBE as compared to K/X, at 2.7 ± 0.6 min and 4.0 ± 0.7 min, respectively. TBE mice had significantly more rapid recovery time (∼25 min) compared to K/X (∼50 min), which also had 50 % anesthetic mortalities. Organ weight ratios, immune phenotype, cytology, serum and peritoneal lavage cytokine levels, and histopathology were unremarkable. TBE performed better and more safely as a murine anesthetic for light anesthesia compared to K/X based on recovery times, no mortalities, and an absence of local and systemic inflammation.