[Cerebral blood flow velocity and electroencephalogram for the evaluation of intraoperative brain function during...

It is well known that progressive hyperthermia exerts fatal damage on the human body. However, there have been few reports on the brain function or the means to provide adequate monitoring during hyperthermia. The purpose of this study was to introduce two new devices, the Life Scan electroencephalogram (EEG) Monitor (Neurometrics) and the TC2-64 (EME) transcranial Doppler sonography (TCD), both for monitoring brain function during hyperthermia. The Life Scan uses aperiodic analysis, which maps each waveform in relation to its frequency, amplitude, and time of occurrence rather than averaging a large number of waveforms over a given period. The Life Scan shows 80% of the whole amplitude of each wave as the activity edge (AE). The flow velocity of the middle cerebral artery was measured by TCD during hyperthermia. After the induction of modified neuroleptanesthesia (fentanyl and midazolam), AE was maintained at 11 Hz. With an increase in body temperature, AE gradually showed a trend toward a slow wave, though the slowing of EEG was interrupted when the patient awoke to slight stimulation. Therefore, it is speculated that the slowing of EEG in this case was caused by fentanyl. The mean cerebral blood flow velocity increased slightly from 28 to 32 cm.sec-1 by hyperthermia. It is concluded that the adoption of EEG and TCD was useful in determining the intraoperative cerebral function during hyperthermia.