The Minimum Infusion Rate (MIR) of Propofol for Total Intravenous Anesthesia after Premedication with Xylazine in Horses

Abstract

To investigate an adequate infusion rate of propofol for total intravenous anesthesia (TIVA) in horses, the minimum infusion rate (MIR) comparable to the minimum alveolar anesthetic concentration (MAC) of inhalation anesthetic was determined under constant ventilation condition by intermittent positive pressure ventilation (IPPV). In addition, arterial propofol concentration was measured to determine the concentration corresponding to the MIR (concentration preventing reaction to stimulus in 50% of population, Cp₅₀). Further, 95% effective dose (ED₉₅) was estimated as infusion rate for acquiring adequate anesthetic depth. Anesthetic depth was judged by the gross purposeful movement response to painful stimulus. MIR and Cp₅₀ were 0.10 ± 0.02 mg/kg/min and 5.3 ± 1.4 μg/ml, respectively. ED₉₅ was estimated as 0.14 mg/kg/min (1.4MIR).