The Narcotrend monitor and the electroencephalogram in propofol-induced sedation.
BACKGROUND
The Narcotrend (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 delta 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.
Doenicke
Alfred W
AW
Institute for Anesthesiology, Ludwig Maximilians University, Munich, Germany. doenickeaw@aol.com
Kugler
Johann
J
Kochs
Eberhard
E
Rau
Jeus
J
Mückter
Haraed
H
Hoernecke
Rainer
R
Conzen
Peter
P
Bromber
Harry
H
Schneider
Gerhard
G
D000293:Adolescent; D000328:Adult; D016292:Procedural Sedation; D004569:Electroencephalography / Q000295:instrumentation; D005072:Evoked Potentials, Auditory; D006801:Humans; D006993:Hypnotics and Sedatives; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation; D015742:Propofol
D006993:Hypnotics and Sedatives; D015742:Propofol