GE CARESCAPE, User Manual

Page: 357 / 548

Entropy
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Graphical display:
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Entropy values: Low Entropy values
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EEG: Regular EEG
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Patient Status: Suppressed EEG
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Graphical display:
Entropy range guidelines
NOTE
Individual patients may show different values. These are only
guidelines.
RE SE
Description
100 90
Awake
60–40 60–40
Low probability of recall, clinically adequate level for
most surgical operations
<40 <40
Deep anesthesia
0 0
Suppressed EEG
Burst suppression ratio (BSR)
BSR is defined as the percentage of time of suppressed (isoelectric, flatline) EEG
periods during the last minute of observation. Emergence of burst suppression pattern
may indicate very deep anesthesia, hypothermia or ischemia.
Typically, during general anesthesia, in the absence of requirements for profound
levels of anesthesia, BSR is 0%. Higher levels of burst suppression indicate very deep
hypnosis/unconsciousness level. Burst suppression generally emerges with Entropy
values below 40, but may not appear even with very low Entropy values.
Entropy practicalities
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It is very important to ensure good contact between the sensor electrodes and skin.
With careful skin preparation, correct sensor placement and use of correct cable,
the skull and sinuses between the electrodes and the brain interfere minimally
with the signal acquisition. See the sensor instructions for use for more detailed
information.
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A high quality EEG signal is the prerequisite for successful Entropy calculation.
Displaying the raw EEG within the Entropy EEG waveform adjacent to the Entropy
values may help the user to confirm the signal quality. Raw EEG on the screen may
also enable the clinician to view the EEG for recognizable and clinically relevant
patterns of EEG activity.
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Do not use other sensors than Entropy sensors by GE.
2062971-001 CARESCAPE Modular Monitors 357