Comparison of five preanesthetic medicaments in thiopental-anesthetized cats: antagonism by selected compounds.

Effects of IM injections of saline solution (groups 1, 2, 3, and 4), xylazine (2.2 mg/kg of body weight, groups 5 and 6), acepromazine (0.11 mg/kg, groups 7 and 8), ketamine (11 mg/kg, groups 9 and 10), meperidine (4.4 mg/kg, groups 11 and 12), and diazepam (1 mg/kg, groups 13 and 14) were compared in atropinized cats. Treated cats were anesthetized to loss of palpebral reflex with thiopental, IV. Within 2 minutes, the cats were given IV injections of 0.15 mg of 4-aminopyridine (4-AP) with 0.125 mg of yohimbine/kg (groups 2, 6, 8, and 10), 0.04 mg of naloxone/kg (groups 3 and 12), or 5 mg of the benzodiazepine antagonist Ro 15-1788/kg (groups 4 and 14). Groups 1, 5, 7, 9, 11, and 13 were given saline solution instead of the test antagonists. Required doses of thiopental, arousal time, walk time (measured from injection of antagonists), respiratory rate, and heart rate were recorded. Induction phenomena were also recorded. Emergence was graded as smooth, fairly smooth, fairly smooth in some cats to fairly rough in other cats, rough, or very rough. In group 1 cats, mean arousal time (MAT) was 20.1 minutes, mean walk time (MWT) was 50 minutes, and emergence was rough. In groups given saline solution as the antagonist, the MAT, MWT (both expressed in minutes), and emergence, respectively, were: group 5 = 52.5, 65.5, smooth; group 7 = 15.6, 36.2, fairly smooth; group 9 = 22.5, 58.1, rough; group 11 = 31.3, 52.7, fairly smooth to fairly rough; and group 13 = 91.8, 427, very rough.(ABSTRACT TRUNCATED AT 250 WORDS)