Comparison of the influence of two different constant-rate infusions (dexmedetomidine versus morphine) on anaesthetic requirements, cardiopulmonary function and recovery quality in isoflurane anaesthetized horses.

This article studies the effects of two different anaesthetic drugs, dexmedetomidine versus morphine, on the medical procedure of horses. The researchers discovered that applying dexmedetomidine under a constant rate infusion method produced better results, such as reduced requirements for isoflurane and better recovery for the horses, compared to using morphine for anaesthetic purposes.

Study Design and Methodology

• The study involved 20 healthy adult horses undergoing elective surgery. They were part of a prospective, blinded, clinical study meaning that the experiment was planned beforehand and the horses were randomly assigned to receive either a constant rate infusion (CRI) of morphine or dexmedetomidine.
• This involved maintaining anesthesia during surgery using isoflurane in conjunction with oxygen/air, whilst also applying mechanical ventilation. The aim was to maintain a light surgical plane of anesthesia, with the level of isoflurane (FÉISO) initially set at 0.9% and then later adjusted by the anaesthetist per an objective flow-chart.

Findings

• The researchers found minimal variations in cardiopulmonary function between the two groups, meaning both the morphine and dexmedetomidine groups maintained almost similar heart and lung functions. This indicated that both anesthetic agents were suitable for use in horses.
• However, it was noted that horses in the group receiving dexmedetomidine required less ketamine, another sedative, and had lower isoflurane concentration after one hour. Also, they needed fewer adjustments in their anaesthetic depth, suggesting that dexmedetomidine offered a more stable, steady state of anesthesia.
• This group also showed better recoveries, with fewer complications during the post-operative stage compared to the horses in the group receiving morphine.

Problems and Complications

• However, certain post-operative complications were seen in the group receiving morphine, with one horse suffering from post-operative colic and pulmonary oedema and two others showing box-walking behaviour.
• These complications, though isolated, highlighted potential issues with using morphine as an anesthetic.

Conclusion

• The study concluded that dexmedetomidine, administered under a constant rate infusion, was more advantageous as an anaesthetic in horses, producing a more stable anaesthetic depth, reducing the need for isoflurane and leading to better post-operative recoveries.
• On the other hand, use of morphine in a similar setting was associated with post-operative complications in some cases.