Prediction of surgical anesthesia in medetomidine/tiletamine/zolazepam anesthetized dogs using electroencephalography

Changes of electroencephalogram (EEG), mean arterial blood pressure (MAP) and heart rate under surgical anesthesia were investigated in medetomidine (MED) and tiletamine/zolazepam (ZT)-anesthetized dogs. To determine the level of surgical anesthesia, pedal withdrawal reflex was regularly tested after ZT injection. The first time point without pain response was regarded as the beginning of surgical anesthesia (SSA). After SSA, the first time point showing positive pain response was considered the end of surgical anesthesia (ESA). Comparing the control, an additional significant decrease of δ2 and α2 was observed at SSA. Comparing the control, δ2 was significantly decreased at ESA. Significant reductions of MAP were observed at pre-ESA and ESA. Heart rate significantly decreased in all stages. These results suggest that δ2 band power is a valuable parameter for correlating surgical anesthesia in dogs anesthetized with MED and ZT.