Alfaxalone for total intravenous anaesthesia in horses.

The research paper discusses a study conducted to assess the effectiveness and viability of using alfaxalone, a drug used to induce and maintain anesthesia, in horses. It evaluates the drug’s infusion rates, cardiovascular effects, pharmacokinetics and the quality of the recovery period post anesthesia.

Study Design and Methodology

• The study involved eight Standardbred horses and was conducted in a prospective and experimental setting.
• The horses were premedicated with Intravenous (IV) acepromazine and xylazine, then anesthesia was initiated using guaifenesin and alfaxalone.
• Anesthesia was maintained for three hours using an IV infusion of alfaxanine.
• The infusion rate was determined by the horse’s response to a painful electrical stimulus.
• Venous blood samples were collected regularly for pharmacokinetic analysis and to establish the plasma concentrations of alfaxalone.
• Various cardiopulmonary variables were tracked and the quality of anaesthetic recovery period was scored.

Results

• The medium alfaxalone infusion rate was found to be at 3.1 mg per kg per hour.
• The mean plasma elimination half-life, plasma clearance and volume of distribution for alfaxalone were 41 minutes, 25 mL per minute per kg, and 1.6 L per kg respectively.
• During the anesthesia, the mean arterial blood pressure remained above 70 mmHg in all the horses. Cardiac index reached it’s lowest right after the anaesthesia was induced but was maintained between 74% and 90% of the baseline values after that.
• Six of the eight horses experienced muscle tremors and paddling after the alfaxalone infusion was stopped.
• All the horses were able to stand on their first or second attempt and had a median recovery score of 4.5, suggesting a good to excellent recovery.

Conclusions

• The study concluded that anaesthesia in horses can be effectively maintained using an alfaxalone infusion of approximately 3 mg per kg per hour.
• The rates of infusion used resulted in insignificant haemodynamic changes and a good to high-quality recovery.
• The plasma concentration of alfaxalone stayed stable over the course of the infusion period, and the clearance rates were similar to those in previously published single-dose alfaxalone studies in horses.