[EEG-effects of halothane. Studies on 50 patients (author's transl)].

Induction of anaesthesia with 1 vol% halothane N2O/O2 3:1 was electroencephalographically registrated in 50 patients between 20 and 80 years. Blood pressure - and pulse rate - measurements were taken at regular intervals. The clinical course of anaesthesia and changes in EEG corresponded. 4-5 min after the beginning of inhalation the first clinical and encephalographic signs were seen: The base-line-electroencephalogram changed characteristically. Weak rhythms disappeared; fast frequencies of 10-32 Hz developed accompanied by clinical excitation, and at the same time low waves of 2-4 (6) Hz increased and became dominant. Distinguishing EEG-features of deep anaesthesia: 15 min after the beginning of halothane inhalation. Here was flattening with high delta (theta) activity. Anaesthesia was lowered by intubation. EEG showed signs of alpha theta or increasing fast activity. In good correlation the blood pressure and pulse rate increased. Deviations from this general behaviour were recorded in patients in poor condition and with blood pressure levels below the need of cerebral blood flow demands.