The quest for anesthetic depth: Albert Faulconer, electroencephalography and the servo-controlled anesthesia machine.

Introduction In October 1996 the Food and Drug Administration approved the use of a new monitoring device of anesthetic effect that integrates various electroencephalogram (EEG) descriptors into a single dimensionless, empirically calibrated number, the Bispectral Index (BIS, Aspect Medical Systems, Natick, MA).1 The BIS monitor is the latest innovation in the quest for a reliable monitoring device of anesthetic depth, the “holy grail” of monitoring for anesthesiologists.2 This new monitor is gaining acceptance in the anesthesia community, but the basic concept of this idea goes back to the early 1950’s. At that time Albert Faulconer and Reginald Bickford from the Mayo Clinic first systematically investigated EEG changes induced by various anesthetic agents.3-5 In a pioneering project, they went a step further and attempted to create the first closed-loop anesthesia delivering device, the servocontrolled anesthesia machine, aimed at automatic control of anesthetic depth via EEG guided delivery of anesthetic agents.6 The following is an illustration of some of the problems associated with this groundbreaking idea.