Background context. Electroencephalography (EEG) is one of the oldest and most commonly utilized modalities for intraoperative neuromonitoring. Historically, interest in the EEG patterns associated with anesthesia is as old as the discovery of the EEG itself. The evolution of its intraoperative use was also expanded to include monitoring for assessing cortical perfusion and oxygenation during a variety of vascular, cardiac, and neurosurgical procedures. Furthermore, a number of quantitative or computer-processed algorithms have also been developed to aid in its visual representation and interpretation. The primary clinical outcomes for which modern EEG technology has made significant intraoperative contributions include: (1) recognizing and/or preventing perioperative ischemic insults, and (2) monitoring of brain function for anesthetic drug administration in order to determine depth of anesthesia (and level of consciousness), including the tailoring of drug levels to achieve a predefined neural effect (e. g., burst suppression). While the accelerated development of microprocessor technologies has fostered an extraordinarily rapid growth in the use of intraoperative EEG, there is still no universal adoption of a monitoring technique(s) or of criteria for its neural end-point(s) by anesthesiologists, surgeons, neurologists, and neurophysiologists. One of the most important limitations to routine intraoperative use of EEG may be the lack of standardization of methods, alarm criteria, and recommendations related to its application. Lastly, refinements in technology and signal processing can be expected to advance the usefulness of the intraoperative EEG for both anesthetic and surgical management of patients. Objective. This paper is the position statement of the American Society of Neurophysiological Monitoring. It is the practice guidelines for the intraoperative use of raw (analog and digital) and quantitative EEG. Methods. The following recommendations are based on trends in the current scientific and clinical literature and meetings, guidelines published by other organizations, expert opinion, and public review by the members of the American Society of Neurophysiological Monitoring. This document may not include all possible methodologies and interpretative criteria, nor do the authors and their sponsor intentionally exclude any new alternatives. Results. The use of the techniques reviewed in these guidelines may reduce perioperative neurological morbidity and mortality. Conclusions. This position paper summarizes commonly used protocols for recording and interpreting the intraoperative use of EEG. Furthermore, the American Society of Neurophysiological Monitoring recognizes this as primarily an educational service.
