Effects of thiopental on the human somatosensory evoked response.

Abstract

SummaryThe effect of Thiopental on the human somatosensory evoked response (E.R.) recorded on the scalp was studied in chronic schizophrenic patients. The E.R. was recorded successively before, during and after the intravenous injection of different dosages of Thiopental until after awakening. The changes in the latencies of the main positive peak and the main negative peak and the changes in the amplitude were analyzed quantitatively, comparing with the mean latency and the mean amplitude before injection.I observed a systematic change in latency, which increased and recovery was delayed proportional to the dosage. Among the peaks constituting the major positive peak, the latency of the later peak increased more, regardless of its polarity. The latency of the main positive peak increased without drug induced sleep. On an average, the increase without sleep is the same as the level to which the latency recovered when awakening occurred (125%).The changes in amplitude were inconsistent. There was a tendency to decrease at the beginning, but the individual changes differed markedly among subjects and dosages. Although it can not be applied in all subjects, analysis revealed two phases during the drug induced sleep. The later phase accompanied by characteristic E.R. pattern with augmented the first positive peak was attributed to the postnarcotic sleep. With larger dosages, synchronization of the EEG in beta frequency to the peripheral stimulation occurred first prior to the appearance of E.R.