Effects of isoflurane and sevoflurane alone and in combination with butorphanol or medetomidine on the bispectral index in chickens

Abstract Background The bispectral index (BIS) is an anaesthesia monitoring technique able to assess the level of central nervous system depression in humans and various animal species. In birds, it has been validated chickens undergoing isoflurane anaesthesia. aim this study was evaluate avian species influence sevoflurane on BIS, each at different minimum anaesthetic concentrations (MAC) multiples, alone or combined with butorphanol medetomidine. Ten (5 males 5 females) underwent general alone, either intramuscular administration (1 mg/kg) medetomidine (0.1 mg/kg), a prospective cross-over (i.e., 6 treatments per animal). BIS measurements were compared heart rate (HR), non-invasive blood pressure (NIBP) visual analogue scale (VAS) depth. Results HR significantly increased, both NIBP VAS reduced, higher gas concentrations. (but not VAS) additionally affected by type gas, being lower sevoflurane. Butorphanol had no additional effect, but led differences HR, NIBP, particular reduction VAS. With respect deeper hypnosis absence difference between gases, correlated all other measures (except where significant relationship found) before (BISpre) after stimulation (BISpost) did remain constant, increased increasing MAC indicating that BISpost suppressed proportionately suppression BISpre values due concentration. Furthermore, neither nor BIS. Conclusions degree monitored neuromuscular reflexes VAS, indicate records depth from one deducted alone. provided complementary information such as spinal without deepening hypnotic state. As consequence, concluded improves assessment chickens, improving quality