Detomidine and the combination of detomidine and MK-467, a peripheral alpha-2 adrenoceptor antagonist, as premedication in horses anaesthetized with isoflurane.

The research investigates the effects of the drug MK-467 in combination with detomidine as a premedication for horses undergoing anaesthesia with isoflurane. Findings suggest that MK-467 enhances cardiac function and tissue oxygen delivery during anaesthesia, potentially improving patient safety, although the precise dosage requires further exploration.

Objective of the Experiment

• The key objective of the experiment was to explore the potential benefits of using MK-467 combined with detomidine as pre-anaesthetic medication for horses that were to be anaesthetized with isoflurane.

Methods

• Seven healthy horses were involved in this experimental, crossover study.
• Horses received either detomidine and butorphanol alone or with MK-467, with a two-week wash-out period in between treatments.
• Anaesthesia was induced with ketamine and midazolam, and maintained with isoflurane.
• Several health-indicators in the subjects were monitored – heart rate, mean arterial pressure, end-tidal isoflurane concentration, blood gas composition, central venous pressure, inspired oxygen fraction and cardiac output.
• Blood samples were taken for further analysis, and various other data were calculated, including cardiac index, systemic vascular resistance, ratio of arterial oxygen tension to inspired oxygen, and tissue oxygen delivery.

Results

• The results suggest that induction times were shorter when MK-467 was used, and more dobutamine was administered. Additionally, both heart rate and cardiac index were higher, while systemic vascular resistance was higher in horses pre-administered with just detomidine.
• Arterial oxygen tension and tissue oxygen delivery showed increases 40 and 60 minutes after induction with DET + MK compared to DET alone. Furthermore, plasma concentrations of detomidine were found to be reduced in the group given MK-467.
• The research suggests that MK-467 serves to enhance cardiac function and tissue oxygen delivery in horses sedated with detomidine before isoflurane anaesthesia.

Conclusion

• The research concludes that the use of MK-467 in combination with detomidine as a premedication before isoflurane anaesthesia results in improved cardiac function and tissue oxygen delivery.
• This has potential implications for improving patient safety during the perioperative period.
• However, the researchers note that further study is needed to determine the optimal dose of MK-467 to ensure its effect on mean arterial pressure is minimised.