Determination of minimum infusion rate of propofol in combination with electroacupuncture in goats

Abstract

Total intravenous anesthesia (TIVA) is frequently used anesthetic protocol in animals when inhalation anesthesia is not available. To date, it has not yet been known whether electroacupuncture (EA) can affect propofol-based TIVA in goats. Therefore, the present paper aims to determine the minimum infusion rate (MIR) of propofol, in combination with EA, required to preclude purposeful movement of the extremities in response to standardized noxious stimulation in goats. Twelve clinically healthy goats weighing 17.45 ± 2.15 kg were randomly allocated into two groups with six goats each. Propofol alone (P group) and propofol combined with EA (EA-P group). In the EA-P, propofol was given 30 min after EA stimulation. For induction of anesthesia, a bolus of propofol was administered at 4 mg/kg IV, and an infusion dose of 0.4 mg/kg/min was initially set for maintenance. The MIR of propofol in both groups was determined by testing for responses to stimulation (clamping on a digit with Vulsellum forceps) at 10-min intervals after inducing anesthesia until the end period of the experiment. Cardiorespiratory variables and nociceptive threshold were measured throughout anesthesia. The median propofol MIR was significantly lower in the EA-P group than the P group [0.520 (0.467–0.572) and 0.650 (0.600–0.677)], respectively; p = 0.0013). In the P group, goats anesthetized with MIR showed a significant increase in heart rate and cardiac index (p = 0.0010 and p < 0.0001, respectively), and a decrease in respiratory rate (p = 0.0001). Additionally, the EA-P showed a significant decrease in hemoglobin oxygen saturation following the initial infusion rate at 2 min (p = 0.0023) and 10 min (p = 0.0007) as compared to the P group. A significant increase in nociceptive threshold was recorded in the EA-P threshold than that of the P group (p < 0.005). EA combined with propofol provides antinociception, decreases the MIR of propofol-based TIVA, and subsequently lessens the negative cardiorespiratory consequences related to propofol anesthesia in goats.