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I&M for Anesthesia - Fall 2013 > BIS > Flashcards

BIS Flashcards

0
Q

Levels of unconsciousness

A

Perception of explicit memory
Perception and no explicit memory
No perception and implicit memory
No perception and no memory

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1
Q

Components of anesthesia

A

Unconsciousness/hypnosis
Analgesia
Muscle relaxant

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2
Q

Explicit memory

A

Refers to intentional or conscious recollection of prior experiences

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3
Q

Implicit memory

A

Information not associated with any conscious recollection

Recall may occur during dreaming, hypnosis, or other psychological methods

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4
Q

Percent of legal claims against anesthesia providers

A

Two

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5
Q

Worst thing they have ever experienced

A

Awareness under anesthesia

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6
Q

How big of a problem is awareness?

A

More common than necessary
One of every thousand patients
Three of every thousand cardiac patients
Up to forty eight with severe trauma

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7
Q

Individual patient response variance to anesthetic

A 
Unique tolerance (some predictable, others not)
Fluctuations in hemodynamics stability
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8
Q

Circumstantial variance in anesthetic requirement

A

Surgical stimulus
User error
Delivery device failure

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9
Q

Measuring depth - clinical signs

A 
Heart rate
Blood pressure
Sweating
Lacrimation
Pupil diameter
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10
Q

Measuring depth - isolated forearm technique

A

Tourniquet applied to one arm prior to MR

Spontaneous movement or movement to command indicates light anesthesia

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11
Q

Measuring depth - skin impedance

A

Quantitative measure of sweat production

Factors that affect sweating (atropine, autonomic neuropathy) reduce accuracy

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12
Q

Measuring depth - surface electromyelogram

A

Only useful in patients that are not receiving full MR

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13
Q

Most widely applied technology for measuring anesthetic depth

A

EEG

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14
Q

Last sense to be suppressed by anesthesia

A

Auditory

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15
Q

Used alone or in combination with EEG

A

Auditory evoked potentials

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16
Q

BIS index range

A 
0 flatline
0-20 burst suppression
20-40 deep hypnotic state
40-60 GA
60-80 moderate sedation
80-100 responds to normal voice
100 awake
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17
Q

Moderate sedation

A

Responds to loud commands or prodding, shaking

18
Q

General anesthesia

A

Low probability of explicit recall

Unresponsive to verbal stimulus

19
Q

BIS is used to

A

Prevent patient awareness
Titrate anesthetic to prevent OD
Facilitate faster wake ups, shorter PACU stays
Cost savings

20
Q

How does BIS work

A

Analyzes analog EEG signal and incorporates facial EMG

Plugged into proprietary algorithm

21
Q

EEG is

A

Recording of electrical activity along scalp

Arises from ion currents across cell membrane of neurons with similar spatial orientation

22
Q

Contribute most to EEG signal

A

Pyramidal neurons of the cortex

23
Q

Beta
Alpha
Theta
Delta

A

Awake
Eyes closed
Light sleep
Deep sleep

24
Q

First order EEG analysis

A

Looks at amplitude mean and variance

Identifies periods of EEG suppression

25
Q

EEG depression is defined as

A

At least a .5 second interval during which the EEG voltage does not exceed plus or minus 5 mV

26
Q

Suppression ratio

A

Ratio of time over the previous 63 seconds that the EEG waveform exhibited suppression

27
Q

Second order EEG analysis

A

Fourier analysis of the EEG waveform parses out the individual frequency components, creating a power spectrum

Displayed as a compressed spectral array (CSA) or density spectral array (DSA)

28
Q

Spectral edge frequency (SEF)

A

Frequency below which certain percentage of the power signal is located
Has been studied as an independent predictor of anesthetic depth
Poor positive predictive values for awareness

29
Q

The cutoff range for SEF

A

14-15 Hz

30
Q

SEF can be higher than 15 Hz during

A

Deep anesthesia or burst suppression

31
Q

EEG third order (bispectral) analysis

A

Measures correlation of phase between different frequency components
Physiological significance unclear
May be helpful for noise reduction

32
Q

Why are normal monitors important when using EEG and BIS?

A

Monitors are not intuitive
Information given is only as good as the info they get
Programmed to identify and disregard common artifact, but are not perfect

33
Q

What do we know about the BIS algorithm?

A

Incorporates suppression ratio, power spectrum analysis, bispectral analysis of frontal EEG as well as facial muscle EMG

EMG is high weighted component

34
Q

The relationship between BIS and SR

A

Linear

SR 50 = BIS 20
SR 100 = BIS 0

35
Q

BIS waveforms - pre MR and post MR

A

Pre - high frequency background fuzziness

Post - cleaner, underlying spindles and delta

36
Q

Sources of noise

A 
Electrocautery
Forced air warmer
Cardiac pacemaker
Hair shaver
Endless others
37
Q

Limitations to BIS

A

Signal processing lag time - can range from 14-155 seconds

Failure to account for certain drugs with known anesthetic effects - ketamine, N2O, xenon, dexmedetomidine?

38
Q

T or F. Sevoflurane and isoflurane exhibit more BIS reduction than halothane

A

True

39
Q

Paradoxical changes

A

Increase in BIS with deepening anesthetic

Decrease in BIS just prior to awakening

40
Q

Pathophysiologic conditions leading to reduction in BIS

A

Hypoglycemia
Decrease in CBF
Focal or global brain pathology
Hypothermia

41
Q

Beta adrenergic agents epinephrine, ephedrine, and isoproterenol have all been shown to

A

Increase BIS

Not seen with phenylephrine (pure alpha adrenergic agonist)

42
Q

B-Aware trial

A

Lower awareness rate in BIS group vs routine
Episodes of awareness occurred when 55-59 and 79-82
Decreases awareness in 82% in high risk adults having GA

I&M for Anesthesia - Fall 2013 (13 decks)

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