Changes in the EEG in horses during surgery: the effect of an intravenous infusion of alfentanil.

The research assesses the impact of alfentanil, a powerful painkiller, on the Electroencephalogram (EEG) response of horses undergoing surgical procedures.

Study Design and Methodology

• The study involved 17 yearling Welsh Mountain ponies, which were pre-anesthetized with acepromazine and anesthetized using thiopentone and halothane. Their lungs were ventilated immediately after endotracheal intubation, and Atracurium was administered intravenously to create neuromuscular blockade.
• The ponies were grouped randomly into two groups: nine of them formed the alfentanil group and received the drug intravenously. The remaining eight (control group) didn’t receive Alfentanil.
• The researchers then continuously recorded the EEG of the horses using subcutaneous electrodes.
• Baseline measurements were obtained during a 5-minute period before the commencement of surgery.

Data Collection and Analysis

• The EEG variables (ATOT and F50) recorded during the baseline period and castration were compared, and data was reported as the percentage change from baseline.
• Data was analysed statistically using ANOVA and presented as mean data ± SD (Standard Deviation).

Results

• In the alfentanil group, ATOT and F50 decreased slightly but insignificantly during castration.
• The EEG changes recorded in the control group during castration differed to those previously reported in a past study, showing insignificant changes in ATOT and F50.

Conclusion and Implications

• The study found the effect of atracurium on EEG readings, which has not been previously evaluated. It suggests that atracurium could suppress EEG changes during the surgery.
• The sensory-motor input from the cremaster muscle to the cerebral cortex appears to be substantial and the afferent input to the Central Nervous System (CNS) from its muscle spindles would likely be terminated by neuromuscular blockade. This could explain the minimal EEG changes noted in the control group.
• Consequently, this research model was found unsuitable to assess the effects of alfentanil on the EEG recorded during castration, owing to the interference of atracurium.