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AMBULATORY ANESTHESIOLOGY

The Narcotrend^TM Monitor and the Electroencephalogram in Propofol-Induced Sedation

Alfred W. Doenicke^*, Johann Kugler, Eberhard Kochs, Jeus Rau, Haraed Mückter^||, Rainer Hoernecke^*, Peter Conzen^*, Harry Bromber^¶, and Gerhard Schneider^#

From the Institutes of *Anesthesiology, Neurology and Psychiatry, Ludwig Maximilians University; Department of Anesthesiology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany; Department of Anesthesia and Critical Care, Johanniter Hospital, Stendal, Germany; ||Walther Straub Institute, Ludwig Maximilians University, Munich, Germany; ¶Department of Anesthesia and Critical Care, Martin Luther University, Halle, Germany; and #Department of Anesthesiology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.

Address correspondence and reprint requests to Dr. Alfred W. Doenicke, Institute for Anesthesiology, Ludwig Maximilians University, Pettenkoferstr. 8a, D – 80336 Munich, Germany. Address e-mail to doenickeaw{at}aol.com.

Abstract

BACKGROUND: The Narcotrend^TM (NCT) is a one-channel electroencephalogram (EEG) monitor of the level of sedation. It is based on a visual EEG scoring system, which was developed by Loomis and modified by Kugler, to yield a visual expert classification (VEC) scheme for differentiation of six levels of sedation (A–F), which are subdivided into 16 substages. We designed the present study to test whether results of the automated classification of one-channel NCT input reflect those from VEC of five-channel EEG.

METHODS: Twelve healthy male volunteers received propofol using two different infusion regimens in a randomized, crossover design with concomitant NCT monitoring and VEC. Scoring results of NCT were compared with those of VEC.

RESULTS: During the infusion period, score differences of more than three substages were observed in 14 of 24 (= 58%) propofol administrations (4%–7% of total data). Often, the NCT indicated lighter sedation than VEC, which revealed more activity from nonfrontal leads. During recovery, NCT reported deeper sedation than VEC in 6 of 24 (= 25%) propofol administrations. Discordant trends (periods of at least five subsequent epochs with monotonic, but opposite trends for both NCT and VEC) were noted in 9 of 24 propofol administrations (37%). Furthermore, NCT had several periods when no staging information was displayed, varying from a few seconds to 10 min.

CONCLUSIONS: As the algorithm of NCT is proprietary and not accessible to the public, reasons for the observed differences between NCT and VEC cannot be analyzed and explanations must remain speculative.

Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999