A comparison of the clinical usefulness of three different electroencephalogram monitors: Bispectral Index, processed electroencephalogram, and Alaris auditory evoked potentials.

We compared the usefulness of the Bispectral Index (BIS), Processed electroencephalogram (pEEG), and Alaris auditory evoked potentials (A-AEP). Ninety females scheduled for mastectomy were divided into three groups. Anesthesia was induced with propofol and fentanyl to insert a laryngeal mask airway (LMA) and was maintained by adding nitrous oxide. EEG was monitored by either BIS, spectral edge frequency by pEEG, or A-AEP index by A-AEP. We recorded the number of patients with impedance low enough to extract good EEG signals at the first electrodes application (success rate), the number with an index outside of the range considered appropriate for general anesthesia (inappropriateness rate), changes of the index by LMA insertion or surgical incision (responsiveness), and time to return to good EEG signals after signal disturbance by electric cautery (recovery time). The success rate was larger in BIS > or = A-AEP > pEEG. The inappropriateness rate was smaller in A-AEP < or = BIS , or = pEEG. The A-AEP group showed the largest responsiveness. The recovery time was shorter in pEEG < A-AEP < BIS. In summary, the BIS had the largest success rate, the A-AEP had the least inappropriateness rate and the largest responsiveness, and the pEEG had the fastest recovery time.

Conclusions: We compared the usefulness of three electroencephalogram monitors. The Bispectral Index was the easiest for obtaining low impedance, the auditory evoked potential index had the least inappropriateness rate for general anesthesia and had the largest responsiveness, and the spectral edge frequency was the fastest in stabilizing measurement after electric cautery.