The use of EEG spectral analysis after thiopental bolus in the prognostic evaluation of comatose patients with brain injuries.

The value of EEG data and evoked potentials (EP), combined with the patient's clinical status, are important parameters used to document decerebration, but their reliability is at its best when the decerebration is nearly complete. Based on spectral analysis of the EEG we compiled criteria for the cerebral function with application of agents known to alter the normal EEG. We found very distinct and different pattern responses in spectral analysis of the EEG after the bolus injection of 100-500 mg Thiopental, correlating well with the patient's prognosis. In a study with 40 patients, those who showed a significant increase of power in all frequencies, especially a short lasting increase in beta (3-7 min) survived in 84%. On the other hand, all the patients who had a decrease of absolute power in all frequency band died, even when brainstem reflexes and various pain reactions were still present. Spectral analysis after Thiopental bolus injection also permits a very immediate assessment of slight improvements or deteriorations in the clinical course.