Neuromonitoring in the operating room and intensive care unit: an update.

Several pathophysiological processes cause reversible functional abnormalities before the appearance of any structural, irreversible damage, in which case the observation of these abnormalities can constitute an invaluable warning signal to prevent the occurrence of irreversible neurological sequelae. Several processes occurring in the operating room (OR) and intensive care unit (lCU) belong to this last category and justify the usefulness of clinical neurophysiology as a neuromonitoring tool during surgery and in coma. Recent technological advances offer new concepts in monitoring of brain signals. In ICU and OR, modern computer technology has recently provided a large number of sophisticated neuromonitoring systems. The dimensions of the helmet vary because it is adjustable. Therefore, the helmet takes into consideration the individual head size and shape. Electrodes for electroencephalography (EEG), stimulus-induced brain oscillations, early somatosensory EPs (SEPs), and brainstem auditory EPs (BAEPs) are generally placed according to the International 10–20 System. Improvement in EEG assessment may be obtained with optimal electrode montages and objective spectral parameters. The montages currently in use are symmetrical and favor central and occipital electrodes. Monitoring of carotid endarterectomy (CEA) is necessary when selective shunting is performed. Monitoring techniques differ in many respects, such as the physiological mechanism studied, the invasiveness of the technique, and subjective versus objective assessment.