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Considerations
for BIS in the ICU
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- Reliance
on the BIS value alone for sedative management is not recommended:
- Clinical
judgment should always be used
- BIS
readings should be interpreted over time and in response to
stimulation, and in the context of patient status and treatment
plan.
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- Charting
BIS
- When
charting a BIS value during sedation assessment, many institutions
chart a pre-stimulation BIS value and a second BIS value 30-60
seconds post-stimulation and evaluate the delta.
- BIS is
often charted with vital signs recordings.
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- Patient movement,
or EMG, may occur with low BIS values and may indicate inadequate
analgesic level
- Artifacts
and poor signal quality may lead to unreliable BIS values. Potential
artifacts may be caused by poor skin contact, muscle activity
or rigidity, head and body motion, sustained eye movements, improper
sensor placement or skin preparation, and unusual or excessive
interference.
- BIS values
should be interpreted cautiously in patients with known neurological
disorders, in those taking psychoactive medications and in children
less than 1 year old.
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- Natural sleep
cycles may affect the hypnotic levels.
- Deep
sleep may cause the BIS value to decrease to levels equivalent
to a very deep sedation state.
- In the
REM sleep pattern, the low amplitude/high frequency EEG patterns
may be similar to those in the awake state, but with co-existing
hypotonia and eyeball movement artifacts.
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- Patients
with a history of substance abuse may require greater drug dosages
to achieve the desired BIS value and meet sedation goals
- In patients
with impaired renal or hepatic function, accumulation of drugs
may occur, and they may require lower drug dosages to achieve
the desired BIS value.
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