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I&M II > I. Anesthetic Depth > Flashcards

I. Anesthetic Depth Flashcards

1
Q

Definition of Anesthesia

A

“a reversible state of drug-induced unconsciousness in which the patient neither perceives nor recalls noxious stimulation.”

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2
Q

Basic elements of anesthesia

A
  1. Diminished motor response [Analgesic]
  2. Reversability [Reversal Agent]
  3. Analgesia [Analgesic]
  4. Unconsciousness [Hypnotic]
  5. Muscle Relaxation [Paralytic]
  6. Amnesia [Ammestic]

HINT: DRAUMA

Sedative/Anxiolysis also considered a “Basic Anesthesia Element”

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3
Q

What anesthetic agent may be considered a “complete anesthetic”?

A

Propofol

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4
Q

sleep-like state, drowsiness, unconsciousness

A

hypnotic

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5
Q

calm state, relieves anxiety, relaxation

A

Sedative/Anxiolytic

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6
Q

Memory loss

A

Amnestic

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7
Q

Direct vs Indirect Memory Loss

A

Direct: Midazolam

Indirect: Unconsciousness

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8
Q

loss of sensation/pain, abolish reflexes

A

Analgesic

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9
Q

T/F: analgesics abolish BOTH somatic and autonomic reflexes.

A

TRUE

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10
Q

produce immobility

A

Muscle relaxants

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11
Q

Hypnotic examples

A
  1. VA
  2. Propofol
  3. Ketamine
  4. Etomidate
  5. STP (Sodium Thiopental)
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12
Q

Anxiolytic examples:

A
  1. Versed (Midazolam)
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13
Q

Amnestic examples

A

Midazolam and other Benzos

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14
Q

Analgesic examples

A
  1. Opioids (Fentanyl, Morphine, etc.)
  2. LA
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15
Q

Hypnotics come in what two varieties?

A
  1. Inhaled
  2. IV (Direct Hypnosis)
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16
Q

MAC: Minimum alveolar concentration required to prevent ____% of subjects from ____ in response to skin incision.

A
  1. 50%
  2. “gross purposeful movement”
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17
Q

What metric do we utilize to measure a patient’s level of MAC (i.e. on-board)?

A

End Tidal Concentration

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18
Q

With regard to MAC, movement is said to be ____.

A

All or none

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19
Q

MAC is considered to be both a ____ and ____ concept.

A
  1. unifying
  2. additive
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20
Q

MAC-awake

A

1/3 - 1/4 MAC

most patients will wake when stimulated

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21
Q

MAC-95

A

1.2 - 1.3 MAC

95% of patients will not move

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22
Q

MAC-BAR

A

> 1.5 MAC

100% of patients will not move

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23
Q

Hypnosis (and unconsciousness) is mediated in the ____.

A

cortex

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24
Q

Immobility is mediated in the ____.

A

spinal cord

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25
Q

T/F: IV hypnotics cause both varying degrees of hypnosis and immobility

A

FALSE!

Inhaled Hypnotics cause both hypnosis and some degree of immobility

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26
Q

T/F: inhaled hypnotics cause some degree of analgesia.

A

FALSE!

the IV hypnotic/induction agent KETAMINE causes analgesia.

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27
Q

Inhaled hypnotics synergistic with what other anesthestic adjuncts?

A
  1. Opioids
  2. Benzos
  3. N2O

HINT: “Sin-ha-BON”

Synergistic-Inhaled

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28
Q

T/F: IV and Inhaled Hypnotics are synergistic

A

FALSE

(confirm)

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29
Q

Although there are no uniform clinical signs to assess depth of anesthesia whilst using inhaled hypnotics, what metrics can provide some insight into depth?

A
  1. ↑HR
  2. ↑BP
  3. Sweating
  4. ↑RR (confirm)
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30
Q

When IV hypnotics are used for induction, what occurs after the initial bolus?

A

redistribution

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31
Q

What are the two major components of a TIVA?

A
  1. Propofol
  2. Analgesic (i.e. Remifentanyl)
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32
Q

T/F: Ketamine’s analgesic properties is typically sufficient to blunt responses to laryngoscopy and incision.

A

FALSE

Ketamine may not blunt responses to major noxious stimuli

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33
Q

IV hypnotics are synergistic with ____.

A

opioids

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34
Q

what techniques can be used to assess depth of anesthesia whilst using IV hypnotics?

A
  1. Verbal responsiveness
  2. Loss of eyelash reflex
  3. loss of corneal reflex

HINT: think during a MAC case

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35
Q

Opioids are not true ____.

A

anesthetics

…due to weak hypnotic effect

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36
Q

Analgesics decrease MAC by ____, but still possess a “ceiling effect”

A

60-70%

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37
Q

Opioid-only anesthesia may be considered for what patients?

A

Patients with no circulatory reserve
valve disease, IHD, Trauma

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38
Q

T/F: opioid-only anesthesia rarely leads to incidences of awareness.

A

FALSE

it has a high incidence of awareness due to lack of hypnosis

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39
Q

5 goals of anesthesia

A
  1. Patient Safety
  2. Insufficient/Excessive anesthetic
  3. Unresponsive to noxious stimuli
  4. No awareness/recall
  5. Facilitate adequate operating conditions

HINT: SONAR

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40
Q

Question to ask oneself prior to surgical incision:

A

“Is my patient optimally narcotized, anesthetized, & paralyzed?

HINT: NAP

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41
Q

T/F: there is no reliable stimulus or response measurement to assess depth.

A

TRUE

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42
Q

Different methods we can estimate depth?

A
  1. Physical assessment (HR,BP, Movement)
  2. MAC (Et Inhalational Agent)
  3. EEG and Processed EEG (BIS)
  4. EMG
  5. BAEP (Brainstem Auditory Evoked Potentials)
  6. LES Contractility (LES tone/pressure, Spontaneous & Evoked Potentials)

HINT: BLEEP Mac

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43
Q

Depth Monitoring Pic

A
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44
Q

MOST reliable physical signs of anesthetic depth

A
  • Gross purposeful movement
  • Reflexive movement to stimulus
  • Immediate hemodynamic stimulus response
  • Immediate respiratory stimulus response
  • Response to soft stimulation (shaving, surgical prep, positioning, etc.)
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45
Q

Less reliable physical signs of anesthetic depth

A
  • Heart rate
  • Respiratory rate
  • Blood Pressure
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46
Q

How does NMBD limit physical assessment of anesthetic depth

A

Inhibits:
- movement
- eye opening
- breathing/tachypnea

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47
Q

How do Beta Blockers, Ca Channel blockers, Vagalytics, Epi, etc. limit physical assessment of anesthetic depth?

A
  • Attenuates autonomic responses to noxious stimulus
  • can mask HR/BP increase
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48
Q

With regard to pupils, which drug causes mydriasis?

A

Scopolamine

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49
Q

which drug/s can cause miosis?

A

narcotics

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50
Q

how can patient positioning affect anesthetic depth assessment?

A

prone position can hide lacrimation

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51
Q

Michigan Awareness Classificaition Instrument

A

0: No awareness
1: Isolated auditory perceptions
2: Tactile perceptions (intubation)
3: Pain
4: Paralysis (feeling one cannot move, speak, or breathe)
5: Paralysis and pain

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52
Q

What does the designation “D” represent on the Michigan Awareness Classification Instrument

A

Distress (reports of fear, anxiety, suffocation, sense of doom, sense of impending death…)

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53
Q

Why does awareness generally occur?

A

imbalance

[HIGH] Demand/Tolerance (Pain) vs [LOW] Supply (meds, sedation)

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54
Q

Risk factors for “High Demand/Tolerance vs Low Supply” cases

A
  • Drug addiction (cocaine, alcohol)
  • Chronic Pain (long term opiate)
  • Long-term use Anti-Convulsants (Kepra®) & Benzos
  • Genetics (Red hair)
  • Female
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55
Q

Risk factors for “Low Demand & Very Low Supply” cases

A
  • Low perfusion states (EF <40%, Trauma, youth)
  • ASA Class 4 or 5
  • End Stage Lung disease
  • Marginal Exercise tolerance
  • Pulmonary HTN

First 2 are a result of safety risk if given too much anesthesia, therefore less than ideal is often given

HINT:P²ALE

56
Q

Other General risk factors for Awareness

A
  • Any situation where depth of anesthesia may have to be weighed against the hemodynamic instability of the patient
  • Hx of awareness
  • N20/Narcotic technique with little VA
  • Provider Inexperience
  • Hx of difficult intubation or anticipated DI
  • Equipment malfunction
  • < 0.7 MAC (age-adjusted)
  • Use of NMB (no movement if distressed)
57
Q

Overall Anesthesia Awareness Incidence Rate

A

0.1-0.2% in non-OB & non cardiac surgery

  • 20k to 40k in USA annually
  • 3/2000 patients
58
Q

obstetric awareness rate

A

0.4%

59
Q

Cardiac surgery awareness rate

A

1.1-1.5%

60
Q

Major trauma awareness rate

A

11-43%

hemodynamically instability overrides demand for adequate sedation

61
Q

Average number of law suits annually regarding closed claims of awareness

A

10

62
Q

All anesthetic depth monitors are based on what measured concept?

A

Electroencephalography (EEG)

63
Q

EEG reads ____ caused by action potentials (low-voltage currect) in brain activity and uses special adhesive electrodes

A

electrical current

64
Q

T/F: EEG pads must be placed in areas without hair.

A

TRUE

65
Q

EEG waves are measured in what unit?

A

Hertz (Hz)

Waves/sec

66
Q

T/F: EEG technology directly measures consciousness

A

FALSE

likely to be conscious at certain level

67
Q

EEG Beta waves:

A

13-30 Hz

Awake

68
Q

EEG Alpha waves:

A

8-13 Hz

Moderate Sedation

hint: mAc cases

69
Q

EEG Theta waves:

A

3.5-8 Hz

General Anesthesia

70
Q

EEG Delta Waves:

A

0-3.5 Hz

Deep Anesthesia

71
Q
A

Beta Wave (Awake)

72
Q
A

Alpha Wave (moderate sedation)

73
Q
A

Theta Wave (General Anesthesia)

74
Q
A

Delta Wave (Deep Anesthesia)

75
Q

For EEG waveforms, as anesthetic effect increases, EEF frequency ____, and waveform amplitude ____.

A
  • decreases (transmission slows)
  • increases
76
Q

Wave Progression (Awake to deep anesthesia)

A

Beta, Alpha, Theta, Delta

Bold Anesthesia Tames Druggies

77
Q

____ utilizes EEG and a proprietary algorithm to provide a value that correlates with increased risk of intraoperative awareness

A

Bispectral Index (BIS)

78
Q

what BIS values are believed to indicate decreased incidence of intraoperative awareness?

A

40-60

79
Q

The BIS has ____ electrodes that are placed where?

A

4

over the frontal cortex

80
Q

Job of BIS Electrode 1

A

Ground

81
Q

what BIS electrodes use a differential amplifier to measure potential difference?

A

Electrodes 2 and 3

82
Q

job of BIS electrode 4

A

remove noise

83
Q

What must be done before BIS application?

A
  • clean forehead with alcohol, then wipe dry
  • wait until patient is asleep to apply (abrasive)
  • place folded gauze (b/w BIS and skin) between electrode 1 and connection port; this prevents BIS from twisting and potentially scraping/cutting forehead
84
Q

why is the BIS bispectral?

A

it analyzes signals from the frontal lobe at various frequencies (B, A, T, D)

85
Q

BIS algorithm collects data over ____ seconds

A

15-30

86
Q

BIS value: likely to follow commands

A

≥80

87
Q

BIS value: gray zone (50% of patients fail to follow commands)

A

70-79

88
Q

BIS value:
- memory impaired
- decreased probability of explicit recall

A

<70

89
Q

BIS value: high sensitivity to reflect unconsciousness

A

<60

90
Q

BIS value:
- balanced anesthetic
- adequate hypnosis
- improved recovery
- decreased incidence of intra-operative awareness

A

40-60

91
Q

BIS value:
- significantly deep anesthetic
- assoc with negative outcomes

A

<40

92
Q

What BIS level is associated with cerebral ischemia

A

<20

93
Q

What BIS value is associated with:
- ↑ stroke, MI, Mortality risk

A

<40 for > 5 min

94
Q

T/F: BIS value of <20 is associated with decreased POCD.

A

FALSE

<40

95
Q

Burst Supression occurs at what BIS value?

A

20

96
Q

The BIS value reflects the reduced ____ produced by most anesthetics

A

cerebral metabolic rate

97
Q

CMR increases/decreases as BIS value falls

A

decreases

98
Q

“Lack of EEG activity”

A

Burst Suppression

99
Q

T/F: The BIS tells us the probability of that a patient will respond to a command AND the probability that the patient will remember the command.

A

FALSE

Will not tell us the probability of whether the patient will remember the command, BUT does correlate to impaired memory function

100
Q

T/F: Burst Suppression is never intentionally utilized.

A

FALSE

some neurosurgeries require it, but a neuro tech will use a different monitor to track brain activity

101
Q

BIS metric that indicates confidence/trustworthiness of BIS value

A

Signal Quality Index (SQI)

102
Q

How is SQI calculated?

A

based on impedance data and artifacts

103
Q

Desirable SQI value

A

> 90

Closest to 100 as possible

104
Q

Poor SQI value

A

<50

105
Q

BIS value: % average of EEG activity over time that falls below preset limit.

A

Suppression Ratio (SR)

106
Q

This BIS value is derived from the electrical power of muscle movement (muscle tone).

A

Electromyelography (EMG)

107
Q

Range of frequencies used by EMG

A

70-110 Hz

108
Q

The larger EEG waveform graph covers what span of time?

A

One Hour Trend Window

1 hour

109
Q

The smaller EEG waveform graph is called what and covers what span of time?

A

Raw EEG Window

20 seconds

110
Q

BIS Monitoring Screen labeled

A
111
Q

Under what circumstances is the EMG function rendered useless?

A

If the patient is under NMB (duh, there’s no muscle tone to measure)

112
Q

What responds faster: BIS value vs EMG value

A

EMG

113
Q

what measurement unit does the EMG use?

A

25mm/sec

114
Q

Factors that can influence BIS values:

A
  1. EMG artifact & NMB Agents
  2. Medical Devices
  3. Medications & Anesthetics
  4. Clinical Conditions
115
Q

Examples of EMG Artifact/NMB agent BIS interference:

A
  1. Excessive muscle tone in forehead = ↑ BIS value
  2. NMB agents = ↓ EMG & MAY ↓ BIS value
116
Q

Under stable anesthesia, without EMG artifact, NMB have what effect on BIS values?

A

little or no effect

117
Q

Examples of medical devices that that can influence BIS values?

A
  1. Pacemakers
  2. Forced Air Warmers (applied over head)
  3. Electrocautery
  4. Endoscopic Shaving Devices
118
Q

Medications that INCREASE BIS value:

A
  1. Ketamine: transient ↑ BIS & ↑ EMG
  2. Etomidate: transient ↑ BIS
119
Q

Why can Etomidate ↑ BIS value?

A

causes myoclonus (muscle contraction)

120
Q

What drugs DECREASE BIS values?

A
  1. Opioids
  2. Benzodiazepines

Due to synergism with hypnotics

121
Q

Clinical conditions that influence BIS values:

A
  1. Cardiac Arrest
  2. Hypovolemia/Hypotension
  3. Cerebral Ischemia/Hypoperfusion
  4. Hypoglycemia
  5. Hypothermia
  6. Disorders (Dementia, Alzheimers, Postictal Suppression following ECT, Genetic low-voltage EEG)
122
Q

BIS - Light - Clinical Application Flowchart

A
123
Q

BIS - Adequate - Clinical Application Flowchart

A
124
Q

BIS - Deep - Clinical Application Flowchart

A
125
Q

Differences in BIS and Masimo Sedline - Patient State Analyzer:

A

Sedline:
- more channels (4)
- measures Left AND Right sides of brain
- “Processed EEG” value (instead of BIS value)
- 0-100 range (same as BIS)
- 25-50 optimal range for hypnotic state for surgical anesthesia
- Less interference
- Cerebral Oximeter function
- Very Expensive

126
Q

Utility Trial (1997)

A
  • Propofol only
  • 13-23% ↓ in propofol use
  • 35-40% faster time to wakeup/extubation
  • 16% faster PACU discharge
  • Better assessments
  • No difference in intra-op events
127
Q

B-Aware Trial (2004)

A
  • High-risk of awareness patients
  • 82% reduction in incidence of awareness with recall
128
Q

Cochrane Review (2007)

A
  • Meta-Analysis (20 studies)
  • **Reduced propofol use by 1.3 mg/kg/hr
  • Reduced MAC by 0.17**
  • Reduced times to Eye-opening, response to command, PACU discharge
  • Shortened PACU Stay
  • Reduced incidence of intra-op recall with high-risk patients
129
Q

Avidan Study (2008)

A
  • Demonstrated that both utilization of the BIS and adhering to 0.7-1.3 MAC ETAG were effective at reducing incidences of recall and awareness with high-risk patients
  • first trial, both methods performed equally
  • trial repeated in 2011, ETAG outperformed BIS alone (2 vs 7 incidences of awareness)
130
Q

BIS cost effective?

A

Pads: $20-40

Considering financial costs resulting from the 3/2000 cases of awareness, there is an estimated savings of $10k-$25k

also save drug costs

some manufacturers will cover legal fees if BIS <60 during case

131
Q

What may be done for a patient if you believe they may have experienced awareness during surgery?

A

administer benzos (amnesia)

132
Q

BIS is best used in conjunction with what two other adjuncts?

A
  1. traditional vital sign monitoring (BP)
  2. EtAG (End tidal anesthetic agent)
133
Q

One of the best uses of the BIS is to reduce volatile agent; what are the patient benefits of doing so?

A
  1. better hemodynamic stability
  2. faster emergence
  3. less PONV
  4. faster recovery
134
Q

Are TIVA cases good cases for the BIS?

A

YES

these cases generally utilize 0.5 MAC + Propofol, making it very difficult to assess anesthetic depth

135
Q

Types of cases the qualify as good cases for BIS use:

A
  1. Trauma
  2. Cardiac (any case with hemodynamic instability - will be using ↓VA)
  3. OB with GA
  4. TIVA (anything with lower MAC req.)
  5. Carotid Surgery
  6. Spines

I&M II (7 decks)

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