[The effects of ketamine on the electroencephalogram--typical patterns and spectral representations]

In 40 female patients aged between 17 and 79 years, the pre- and intraoperative EEG was recorded and processed by personal computer. For induction of general anesthesia patients received between 2 and 3 mg/kg ketamine i.v. within 30 s. In the phase of diminished ketamine effects enflurane was given in addition. Activity in the theta band was observed in all patients during general anesthesia, and in 30% there were complexes. These complexes differ in their spectral content of burst suppression patterns. Under effect of ketamine nearly all patients showed fast beta waves in the EEG. It is proposed that the spectral domain of EEG evaluations be enhanced to an upper limit of 45 Hz.