The minimum infusion rate (MIR) of propofol for total intravenous anesthesia after premedication with xylazine in horses.

This study conducted research into the rate propofol should be infused for total intravenous anesthesia (TIVA) in horses, after premedication with xylazine. It found that the minimum infusion rate (MIR) and Cp(50) were 0.10 +/- 0.02 mg/kg/min and 5.3 +/- 1.4 microg/ml respectively, and estimated the 95% effective dose (ED(95)) as 0.14 mg/kg/min (1.4MIR).

Determining Propofol Infusion Rate for TIVA in Horses

• The research aimed to discover an appropriate infusion rate for propofol, which is utilized for total intravenous anesthesia (TIVA) in horses. This was done by determining the minimum infusion rate (MIR) that is comparable to the minimum alveolar anesthetic concentration (MAC) of inhalation anesthetic. This was carried out under a constant ventilation state using intermittent positive pressure ventilation (IPPV).
• Furthermore, to understand the effect of this MIR, the concentration of propofol in the arterial blood was measured. This was done to identify the concentration corresponding to the MIR, called a Cp(50), which is the concentration that prevents reaction to a stimulus in 50% of the population.

Evaluating Anesthetic Depth and Effective Dose

• The study took it a step further to estimate the 95% effective dose (ED(95)), conceptualizing it as the infusion rate necessary to achieve a satisfactory anesthetic depth. This was important in maintaining the desired level of anesthesia during the surgical procedure.
• The depth of anesthesia was gauged by analyzing the gross purposeful movement responses of horses to painful stimuli. These results helped to quantify the anesthetic potency and duration of propofol’s anesthetic effect.

Findings and Conclusion

• The study resulted in the MIR and Cp(50) of propofol being 0.10 +/- 0.02 mg/kg/min and 5.3 +/- 1.4 microg/ml respectively. These measurements help to establish an efficient dosing strategy for propofol in horses undergoing TIVA.
• The 95% effective dose (ED(95)) was estimated as 0.14 mg/kg/min, which is 1.4 times the MIR. This suggests that an infusion rate higher than the minimum infusion rate is likely necessary to maintain an adequate depth of anesthesia in 95% of cases.