VIBRATION STIMULUS-INDUCED EEG BURSTS IN ISOFLURANE ANESTHESIA

The EEG and heart rate reactions to vibration stimulus were studied in 14 patients during moderately deep surgical isoflurane anaesthesia, a t a level when EEG showed a burst suppression pattern. Vibration appli ed to the palm of the hand induced bursts in EEG in 12 patients, usual ly with a latency of about 0.5 sec from the onset, or from the end of the 3 sec stimulus. Increases in heart rate were seen at bursts relate d to both vibration onset and offset, as well as at spontaneous bursts . With spontaneous bursts, an initial positive wave was frequently see n. In 6 patients the vibration induced bursts were different in shape from the spontaneous bursts; no initial positive wave was seen before the negative DC shift in C(z)-F(z) recording. We conclude that EEG bur sts can be evoked by a non-noxious stimulus such as vibration in patie nts during isoflurane anaesthesia.