GE HEALTHCARE B20, User'S Reference Manual

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B40/B20 Patient Monitor
18-4
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 range guidelines
NOTE: Individual patients may show different values. These are only guidelines.
Entropy in typical general anesthesia
(1) Awake: RE > SE
(2) Induction: RE = SE
(3) Intubation response: RE increases rapidly
(4) Maintenance: RE = SE
(5) Wake-up: RE increases prior to SE
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