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Published on: March 31, 2016
Power spectral analysis of the electroencephalogram during induced total spinal block
M Takahashi1, M Murakami, T Nakaho
1Department of Anesthesiology and Emergency Medicine, Tohoku University Postgraduate Medical School, 1-1 Seiryo, Aoba-ku, Sendai 980-8574, Japan.
Purpose:
To evaluate the effects of total spinal block (TSB) on brain function, TSB-induced changes in cortical electrical activities were analyzed using power spectral analysis of an electroencephalogram (EEG).
Methods:
Six patients suffering from chronic pain who were undergoing TSB therapy were studied. TSB was established with intrathecal 1% lidocaine (0.3 ml.kg(-1)) injected through the C1-2 lateral intervertebral space. Mechanical ventilation was continued via a laryngeal mask until the recovery of respiration. The EEG recording was started before TSB induction and continued until 10 min after extubation. The following processed EEG parameters were monitored: spectral edge frequency-90% (SEF90), spectral median frequency (SMF), and relative power in the frequency bands of delta, theta, alpha, beta, and the delta ratio [(alpha + beta)/delta].
Results:
TSB induced an unconscious state more than 40 min in all patients. During TSB, 12-13 Hz in SEF90 and 6-7 Hz in SMF were observed. These values are consistent with the previously reported prearousal threshold from general anesthesia. The other EEG descriptors did not change during the TSB-induced unconscious state.
Conclusion:
The dissociation of cortical electrical activities and the clinical coma-like condition may be characteristic of the TSB-induced unconscious state.
