This study was conducted in 6 healthy goats (1-3-years-old) and anaesthesia was induced using isoflurane delivered via a mask. ~1 h after induction to anaesthesia, and with the end-tidal isoflurane concentration held constant for at least 20 min. Following baseline isoflurane minimum alveolar concentration (MAC) determination, tiletamine and zolazepam (TZ) (0.55, 1.1, 2.2, 4.4 or 8.8 mg/kg) or saline were administered i.v. in an unmasked, 6*6 Latin square design. Goats received each of the 6 treatments, in a random order, with a 7-day washout period between treatments. Response to treatment was defined as the percentage difference between baseline and post-treatment isoflurane MAC. The group values (mean SEM) for isoflurane MAC before and after treatment. The mean baseline MAC of the 6 treatment groups was 1.310.03%. Saline administration did not significantly (P>0.05) affect MAC. Neither was there an effect of time, or treatment group, on the baseline MAC. TZ, at all dose rates, significantly (P<0.0001) decreased the isoflurane MAC from baseline. The percentage decrease in MAC varied from 29% for the low dose (0.55 mg/kg) to 77% for the high dose (8.8 mg/kg). The differences in MAC reduction between the two lowest doses and the two highest doses were not statistically significant. The percentage difference in MAC was not affected by order of treatment and the time taken to re-determine MAC did not differ significantly among the treatment groups. Recovery from anaesthesia was uneventful in all cases. The magnitude of MAC reduction with TZ was dose related. It is concluded that isoflurane MAC is decreased in a dose-dependent manner, following i.v. administration of TZ. The result indicates that the use of TZ as a premedication or induction agent in goats, at doses studied, will allow a significant decrease in the concentration of isoflurane required to maintain general anaesthesia.
- anaesthesia benzodiazepines inhaled anaesthetics injectable anaesthetics isoflurane pharmacology goats anesthesia inhaled anesthetics injectable anesthetics tiletamine zolazepam Capra Bovidae ruminants Artiodactyla mammals vertebrates Chordata animals ungulates eukaryotes
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