Effects of alfentanil on the equine electroencephalogram during anaesthesia with halothane in oxygen.

This research investigated the effects of the opioid alfentanil on the brain activity of horses during anaesthesia. The study found that alfentanil altered the electroencephalogram (EEG) readings in horses but did not change the auditory evoked potential, suggesting that any excitement behaviors observed in horses following alfentanil administration are not caused by changes in cortex activity.

Introduction

• The study aim was to determine how alfentanil, an opioid, impacts the brain activity in horses during anaesthesia via an inhalant known as halothane.
• Previous research has shown that opioids have differing effects on the minimum alveolar concentration of inhaled anaesthetics in horses.

Methods

• The researchers used electroencephalogram (EEG) to monitor the horse’s brain activity.
• They also recorded the auditory evoked potential, a measurement of the brain’s response to sound stimuli.
• This was carried out in 8 ponies over the course of an hour, whilst under anaesthesia and being infused with alfentanil.

Results

• Following the alfentanil infusion, there were noticeable changes in the EEG readings, with both the spectral edge and median frequencies decreasing by 26% and 36% respectively.
• However, there were no changes to the auditory evoked potential suggesting that the alfentanil had no effect on this.

Conclusion

• The changes in the EEG readings mimic what has been observed in other species when given alfentanil.
• This suggests that any excitement behaviours noted in horses following the administration of alfentanil does not originate from the cortex, the area monitored by the EEG.
• As such, the research adds further understanding to how alfentanil interacts with equine biological systems during anaesthesia.