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The cerebral state monitor (CSM) (Danmeter A/S, Odense, Denmark) has recently been introduced as a new device to measure the hypnotic component of anaesthetic drugs (Hoymork and others 2007). The CSM's small size and low cost, when compared with the size and cost of other brain monitors, makes it an appealing instrument for use by veterinary professionals during anaesthetic procedures. Previously conducted studies using beagle dogs have shown that higher cerebral state index (CSI) scores were associated with arousal from sedation and a reduction in the depth of hypnosis (Bollen and Saxtorph 2006). Also, the CSI could be used to assess electrical brain activity in dogs during the induction of anaesthesia with propofol (Ribeiro and others 2008). There are many differences in brain anatomy and physiological functions between the rabbit and the dog. Also, the target of general anaesthesia is focused on the central nervous system, therefore, an objective and reliable system to measure anaesthetic depth in the rabbit would be very valuable. To our knowledge, no studies have been published involving the use of CSI monitoring in rabbits during general anaesthesia. Thus, the objective of this study was to analyse the change of CSI during isoflurane or propofol anaesthesia in rabbits, and to study the correlation between CSI, hemodynamic changes and sedation level during general anaesthesia.
Material and methods
Animals and cerebral state index monitoring
All works were accomplished at The Animal Laboratory Center of Shengjing Hospital of China Medical University. After the research committee's approval, 18 New Zealand white rabbits, six months to two-and-a-half-years old, weighing 2.0–3.1 kg, undergoing surgical catheterisation of bilateral carotid and internal jugular vein, were used in this study. During the study, animals were housed indoors in stainless steel cages with free access to food and water, except during the two hours prior to anaesthesia, when they were allowed water only.
CSI, calculated by …