THE EFFECT OF NITROUS-OXIDE ON EEG SPECTRAL POWER DURING HALOTHANE AND ISOFLURANE ANESTHESIA

The effect of N2O on EEG during halothane and isoflurane anaesthesia was studied in 24 elective‐surgery patients. The total EEG power and various power bands were analysed with fast Fourier transform power spectra. Anaesthesia was induced by mask. EEG analysis was performed from the data collected before induction and during steady‐state halothane and isoflurane anaesthesia with and without N2O. In both halothane and isoflurane anaesthesia, N2O had a significant effect on EEG. Alpha‐ and beta‐range EEG power and total power decreased during N2O in both groups. Delta‐ and theta‐range power increased during N2O in the halothane group. The study shows that the effect of nitrous oxide should be taken into consideration when EEG is being studied or monitored during anaesthesia. © 1990 Acta Anaesthesiologica Scandinavica Fonden