Clinical Electroencephalography for Anesthesiologists

The widely used electroencephalogram-based indices for depth-of-anesthesia monitoring assume that the same index value defines the same level of unconsciousness for all anesthetics. In contrast, we show that different anesthetics act at different molecular targets and neural circuits to produce distinct brain states that are readily visible in the electroencephalogram. We present a two-part review to educate anesthesiologists on use of the unprocessed electroencephalogram and its spectrogram to track the brain states of patients receiving anesthesia care. Here in Part I, we review the biophysics of the electroencephalogram, and the neurophysiology of the electroencephalogram signatures of three intravenous anesthetics: propofol, dexmedetomidine and ketamine; and four inhaled anesthetics: sevoflurane, isoflurane, desflurane and nitrous oxide. Later in Part II, we discuss patient management using these electroencephalogram signatures. Use of Corresponding Authors: Patrick L. Purdon, Ph.D., Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, 55 Fruit Street, GRB-444, Boston, Massachusetts, Tel: 617 726 7487, Fax: 617 726 1880. [email protected]. DEPARTMENT AND INSTITUTION Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts PRIOR PRESENTATION OF WORK Drs. Purdon and Brown have summarized some of this work on the website www.anesthesiaeeg.com and have given several seminars on this topic in multiple venues during the last 2 years. CONFLICTS OF INTERST Masimo has signed an agreement with Massachusetts General Hospital to license the signal processing algorithms developed by Drs. Brown and Purdon for analysis of the electroencephalogram to track the brain states of patients receiving general anesthesia and sedation for incorporation into their brain function monitors. HHS Public Access Author manuscript Anesthesiology. Author manuscript; available in PMC 2015 October 01. Published in final edited form as: Anesthesiology. 2015 October ; 123(4): 937–960. doi:10.1097/ALN.0000000000000841. A uhor M anscript