Minimum end-tidal sevoflurane concentration necessary to prevent movement during a constant rate infusion of morphine, or morphine plus dexmedetomidine in ponies.

This research article investigates the effects of different combinations of anesthetic drugs on the minimum amount of sevoflurane, a type of anesthetic, required to prevent movement in ponies during anaesthesia. Specifically, it compares a combination of the drugs dexmedetomidine and morphine to morphine alone.

Research Methodology

• The experiment was a prospective, randomized, and crossover study that involved five healthy adult gelding ponies.
• Each pony was anesthetized twice with a rest period of three weeks in between procedures to wash out any remaining drugs in their system.
• Anaesthesia was induced with sevoflurane in oxygen via a nasotracheal tube and was maintained with sevoflurane in 55% oxygen.
• Ponies were monitored through pulse oximetry, electrocardiography, and measurement of anesthetic gases, arterial blood pressure, and body temperature.
• The ponies were mechanically ventilated and randomly given one of two IV treatments: morphine alone (treatment M) or a combination of dexmedetomidine and morphine (Treatment DM).
• At the 60-minute mark (T60), a stepwise minimum end-tidal sevoflurane concentration necessary to prevent movement (MACNM) determination was started using electrical stimuli to the skin of the lateral pastern region.
• The process was repeated three times in each pony and an average MACNM value was calculated.

Key Findings

• Results show that when morphine is used alone, the average MACNM value for sevoflurane was found to be about 2.79%.
• However, when dexmedetomidine was added to the morphine, the average MACNM value for sevoflurane decreased significantly to 0.89%, which means less sevoflurane is needed to prevent movement. This represents an average reduction of 67%.

Conclusions

• The study concludes that the co-administration of dexmedetomidine and morphine significantly reduces the amount of sevoflurane needed to achieve the same effect compared to using morphine alone.
• This suggests that this combination of drugs might prove beneficial in achieving the desired effects in veterinary anesthesia, as using less sevoflurane could potentially reduce side effects or costs associated with the use of higher quantities of this anesthetic drug.