A narrative review in this issue brings us up to date on our current understanding and usage of processed electroencephalography monitors during anesthesia. Ten commercially available products exist that convert cortical, electrical signals into a dimensionless index as a gauge of anesthetic depth. Limitations of these monitors include (1) exclusively proprietary algorithms specific to each device, rendering comparisons between devices inherently difficult, (2) confinement to frontal lobe activity and lack of penetration into deeper, subcortical structures, and (3) sensitivity to a variety of sources of interference during monitoring. An American Society of Anesthesiologists practice advisory recommends against the routine use of these monitors, instead favoring their utilization for patients that may benefit from reduced anesthetic doses (eg, geriatric patients at risk for postoperative cognitive dysfunction).
1. Fahy BG, Chau DF. The technology of processed electroencephalogram monitoring devices for assessment of depth of anesthesia. Anesth Analg. 2018;126:111–117.