Efficacy and safety of stored and newly prepared tribromoethanol in ICR mice.
This study, performed in conjunction with an in vitro evaluation of tribromoethanol (TBE), consisted of three trials with three objectives. The first objective was to compare anesthetic efficacy and short-term pathologic findings of TBE, ketamine-xylazine (K-X), and sodium pentobarbital (NaP). The second objective was to evaluate how changes of TBE that occur during the perceived most favorable and least favorable storage conditions (8 weeks at 5 degrees C in the dark [5D] and 25 degrees C with exposure to light [25L], respectively) affect anesthetic efficacy and short-term pathology when compared to newly prepared TBE. The third objective was to perform a 6-week clinical assessment of animals that received newly prepared TBE. All animals that received TBE (400 mg/kg) and 14 of 15 that received K-X (K, 120 mg/kg; X, 16 mg/kg) were anesthetized, as defined by loss of pedal reflex. In comparison, only 8 of 15 animals administered NaP (60 mg/kg) were anesthetized. Anesthetic duration for animals that received K-X was 31.7 min, which was significantly (P = 0.0085) longer than animals that received TBE (18.5 min). Recovery times for TBE and K-X were not significantly different (26.5 and 27.5 min, respectively). Pathologic lesions associated with TBE administration were significantly (P = 0.001) greater than those associated with K-X. NaP was not associated with any pathologic lesions. The pH of newly prepared and 5D TBE was 6.5 to 7.0, whereas that for 25L TBE was 3.0. Anesthetic induction, duration, recovery times, and pathologic lesions were not significantly different, regardless of the pH or storage condition of the solution. It was noted, however, that the average anesthetic duration for animals administered newly prepared TBE in the second trial was longer (37.7 min) than the first trial that used newly prepared TBE. For the third trial (long-term clinical assessment), the average anesthetic duration for TBE was 46.5 min, significantly (P < 0.025) longer when compared to the first trial that used newly prepared TBE. During the third trial, 10 animals were found dead or moribund. All animals that were found moribund were necropsied and found to exhibit a marked ileus. Because of the variability in anesthetic effectiveness, pathology, and morbidity and mortality associated with the use of TBE, we do not recommend the use of this anesthetic agent in ICR mice.