Brain wave and electromyography responses to butorphanol during ketamine-and halothane-induced anaesthesia in horses

Abstract

According to clinical experience the use of butorphanol is suitable for the deepening of sedation and analgosedation and is also used in premedication for general anaesthesia. Our presumption was that the depth of anaesthesia in horses that we earlier defined by the parameter SEF90, is the same as in humans. We proved this hypothesis by using a pEEG monitor. We also proved that the monitor we used is an important instrument for the depth and safety control in equine anaesthesia. In this study using 10 horses we established the influence butorphanol administered with detomidine has on EEG and EMG on the left temporal muscle. Both drugs were applied for premedication in ketamine-induced and halothane-induced anaesthesia. The EEG (SEF90) and EMG measurements were performed with a pEEG monitor with a computer-modified programme, while heart rate, blood pressure, SpO2, EtCO2 and respiratory rate were measured by means of an anaesthesia monitor. Based on the brain's electrical activity (EEG) and electrical activity of the left temporal muscle (EMG) it was established that the addition of butorphanol in premedication caused a significant reduction of SEF90 and EMG values during ketamine-induced and halothane-induced anaesthesia. An increase of heart rate, blood pressure and decrease of respiratory rate occurred during anaesthesia with ketamine while halothane anaesthesia also caused an increase in SpO2. No correlations were found between SEF90, EMG and other measured parameters.