Little research has been done in the past in order to enable meaningful inclusions of EEG recording in the standardized neurological examination procedure in horses. Since there is still a lack of basic information concerning the reliability of EEG recordings in horses, this examination method is still very infrequently used in equine medical practice. One reason therefore is that a good EEG ¿ examination in an awake and standing horse is very difficult to achieve because of accumulating movement ¿ artefacts. So the horses should be sedated to reduce these artefacts to an acceptable limit to get reasonable results.
In this study 10 healthy horses were sedated with 4 different variants of sedatives and were examined with EEG to investigate the changes induced by the sedations. The recorded EEG ¿ data was subjected to a Fast-Fourier-Transformation to quantify background-activity. Furthermore a visual screening was carried out to identify and describe paroxysmal changes and artefacts in EEG ¿ recordings.
All sedation procedures achieved a clear reduction of the movement-artefacts that override normal EEG activity. Sedation caused an increase of slow delta activity from average 49% (without sedation) to 57 to 73%. Effects were depending on the drug/drug combinations and the time after application. By sedation the repeatability of the measurement was improved.
Visual screening showed that sedation influenced EEG by the cumulative occurrence of sleep-spindles. Based on the results of this study Xylazine and Detomidine are considered as useful for EEG ¿ examination whereas Acepromazine and Detomidine combined with Butorphanol are less qualified.
In this study changes in the EEG produced by sedation could be clearly detected and quantified. To optimize the recording protocol further studies are necessary.