Monitoring of anaesthesia in neurophysiological experiments

CORTICAL activity can be substantially changed by the type of anaesthetic u sed, and by its dose level. For easy monitoring of depth of anaesthesia we describe the changes in electroencephalogram and electrocardiogram accompan ying changes in depth of anaesthesia in the cat. Anaesthesia was induced by the volatile anaesthetic isoflurane. The high-frequency components (around 30 Hz) in the electroencephalogram disappear in deep anaesthesia. The elec trocardiogram also shows substantial changes in contamination due to muscle fasciculations with anaesthesia level. Fasciculations appear as noise in t he electrocardiogram. The amplitude of the electrical muscle activity conta minating the ECG can be easily used for the maintainance of a constant leve l of anaesthesia during a neurophysiological experiment. NeuroReport 10:781 -787 (C) 1999 Lippincott Williams & Wilkins.