The influence of butorphanol dose on characteristics of xylazine-butorphanol-propofol anesthesia in horses at altitude.

The study explored how different doses of butorphanol affect the behavior and physiological responses of horses undergoing anesthesia at a high altitude. Despite varying the doses of butorphanol, researchers found that it did not significantly impact the horses’ physiological results, the quality of anesthetic induction and recovery, or recovery time.

Objective and Hypothesis

• Primarily, the researchers wanted to examine how horses respond behaviorally and physiologically to anesthesia, delivered intravenously (IV), at a high altitude. The study took place at an altitude of 2240 m.
• They hypothesized that the dose of butorphanol, a type of pain medication, could alter how horses react to propofol anesthesia when given after xylazine pre-medication.

Methods of the Study

• A group of eight healthy horses was involved in the study. They varied in age and weight but were categorized as mature adults.
• Each horse was anesthetized three times, with a minimum of three weeks between each session to allow for recovery and prevent potential interference with the next anesthesia.
• Xylazine was administered to each horse before they were given varying doses of butorphanol. This was followed by anesthesia induced with propofol.
• During the trial, a range of data was gathered, including heart and respiratory rates, arterial blood pressure, concentration of oxygen and carbon dioxide in the arterial blood (P(a)O(2) and P(a)CO(2)), and arterial pH levels.
• Similarly, the researchers measured the quality of induction and recovery after anesthesia.

Results

• The researchers found that the quantity of butorphanol administered did not significantly affect any of the variables measured.
• After anesthetizing the horse, P(a)O(2) levels dropped and P(a)CO(2) levels rose, but these returned to their normal levels within 15 minutes of recovery from anesthesia.
• Regardless of the dose, butorphanol did not have a noticeable impact on the horses’ physiological response, the quality of anesthetic induction and recovery, or recovery time.

Conclusion

• The study concluded that adjusting the dose of butorphanol does not significantly influence how horses at high altitudes react to anesthesia.
• The researchers cautioned that the low P(a)O(2) levels observed at this high altitude and caused by the general anesthesia suggest a limited toleration for hypoxemia-related complications in anesthetized horses breathing unsupplemented air at high altitude.