A comparison of the ability of the EEGo and BIS monitors to assess emergence following neurosurgery.

PURPOSE: Deep anesthesia during microvascular decompression (MVD) for trigeminal neuralgia and cerebral aneurysm clipping may delay emergence. A new electroencephalographic (EEG) monitor, the EEGo, processes a raw EEG signal using time-delay analysis to display a reproducible signal transition from deep anesthesia through the excitement state to the awake state. We hypothesized that the EEGo monitor would be superior to the bispectral (BIS) monitor, not only in aiding emergence but also in detecting sudden changes in levels of hypnosis.

METHODS

Twenty-one patients undergoing neurosurgery were studied (16 MVD, 5 cerebral aneurysm clipping). Each patient had both EEGo and BIS monitoring with only one monitor available for viewing by the anesthesiologist. The anesthetic was titrated based on the available monitor, and the time to emergence was measured. Intraoperative detection of arousal and the timing of burst suppression during propofol administration were also examined.

RESULTS

In the MVD patients, there was no statistical difference in wake-up times between the EEGo and BIS groups. Additionally, there were no episodes of intraoperative awareness and no differences in patient satisfaction. Compared to EEGo waveform output, a decrease in BIS output was delayed in four patients receiving propofol for burst suppression during cerebral aneurysm clipping, indicating enhanced hypnosis. One case of intraoperative arousal, which occurred at a BIS reading of 43 arbitrary BIS units, was detected earlier with the EEGo.

CONCLUSIONS

While the EEGo was faster than the BIS at indicating planned changes in levels of hypnosis throughout propofol administration prior to temporary clipping during aneurysm surgery, the EEGo was not superior to the BIS monitor in facilitating a more rapid emergence following neurosurgery.