title: Using EEG to monitor anesthesia drug effects during surgery.
abstract: The use of processed electroencephalography (EEG) using a simple frontal lead system has been made available for assessing the impact of anesthetic medications during surgery. This review discusses the basic principles behind these devices. The foundations of anesthesia monitoring rest on the observations of Guedel with ether that the depth of anesthesia relates to the cortical, brainstem and spinal effects of the anesthetic agents. Anesthesiologists strive to have a patient who is immobile, is unconscious, is hemodynamically stable and who has no intraoperative awareness or recall. These anesthetic management principles apply today, despite the absence of ether from the available anesthetic medications. The use of the EEG as a supplement to the usual monitoring techniques rests on the observation that anesthetic medications all alter the synaptic function which produces the EEG. Frontal EEG can be viewed as a surrogate for the drug effects on the entire central nervous system (CNS). Using mathematical processing techniques, commercial EEG devices create an index usually between 0 and 100 to characterize this drug effect. Critical aspects of memory formation occur in the frontal lobes making EEG monitoring in this area a possible method to assess risk of recall. Integration of processed EEG monitoring into anesthetic management is evolving and its ability to characterize all of the anesthetic effects on the CNS (in particular awareness and recall) and improve decision making is under study.
authors.affiliation: Anesthesiology, University of Colorado at Denver and Health Sciences Center, 4200 East 9th Ave, Campus Box B113, Denver, CO 80262, USA. Leslie.Jameson@uchsc.edu
authors.forename: Leslie C
authors.initials: LC
authors.lastname: Jameson
authors.forename: Tod B
authors.initials: TB
authors.lastname: Sloan
mesh_terms: D000768:Anesthesia, General / Q000379:methods; D000776:Anesthesiology / Q000379:methods; D000777:Anesthetics / Q000494:pharmacology*; D002490:Central Nervous System / Q000187:drug effects; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D011939:Mental Recall / Q000187:drug effects; D016343:Monitoring, Intraoperative / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D012815:Signal Processing, Computer-Assisted
chemical_list: D000777:Anesthetics