I. Anesthetic Depth Flashcards
(135 cards)
1
Q
Definition of Anesthesia
A
“a reversible state of drug-induced unconsciousness in which the patient neither perceives nor recalls noxious stimulation.”
2
Q
Basic elements of anesthesia
A
- Diminished motor response [Analgesic]
- Reversability [Reversal Agent]
- Analgesia [Analgesic]
- Unconsciousness [Hypnotic]
- Muscle Relaxation [Paralytic]
- Amnesia [Ammestic]
HINT: DRAUMA
Sedative/Anxiolysis also considered a “Basic Anesthesia Element”
3
Q
What anesthetic agent may be considered a “complete anesthetic”?
A
Propofol
4
Q
sleep-like state, drowsiness, unconsciousness
A
hypnotic
5
Q
calm state, relieves anxiety, relaxation
A
Sedative/Anxiolytic
6
Q
Memory loss
A
Amnestic
7
Q
Direct vs Indirect Memory Loss
A
Direct: Midazolam
Indirect: Unconsciousness
8
Q
loss of sensation/pain, abolish reflexes
A
Analgesic
9
Q
T/F: analgesics abolish BOTH somatic and autonomic reflexes.
A
TRUE
10
Q
produce immobility
A
Muscle relaxants
11
Q
Hypnotic examples
A
- VA
- Propofol
- Ketamine
- Etomidate
- STP (Sodium Thiopental)
12
Q
Anxiolytic examples:
A
- Versed (Midazolam)
13
Q
Amnestic examples
A
Midazolam and other Benzos
14
Q
Analgesic examples
A
- Opioids (Fentanyl, Morphine, etc.)
- LA
15
Q
Hypnotics come in what two varieties?
A
- Inhaled
- IV (Direct Hypnosis)
16
Q
MAC: Minimum alveolar concentration required to prevent ____% of subjects from ____ in response to skin incision.
A
- 50%
- “gross purposeful movement”
17
Q
What metric do we utilize to measure a patient’s level of MAC (i.e. on-board)?
A
End Tidal Concentration
18
Q
With regard to MAC, movement is said to be ____.
A
All or none
19
Q
MAC is considered to be both a ____ and ____ concept.
A
- unifying
- additive
20
Q
MAC-awake
A
1/3 - 1/4 MAC
most patients will wake when stimulated
21
Q
MAC-95
A
1.2 - 1.3 MAC
95% of patients will not move
22
Q
MAC-BAR
A
> 1.5 MAC
100% of patients will not move
23
Q
Hypnosis (and unconsciousness) is mediated in the ____.
A
cortex
24
Q
Immobility is mediated in the ____.
A
spinal cord
25
**T/F**: IV hypnotics cause both varying degrees of hypnosis and immobility
FALSE!
**Inhaled Hypnotics** cause both hypnosis and some degree of immobility
26
**T/F**: inhaled hypnotics cause some degree of analgesia.
FALSE!
the IV hypnotic/induction agent **KETAMINE** causes analgesia.
27
Inhaled hypnotics synergistic with what other anesthestic adjuncts?
1. **O**pioids
2. **B**enzos
3. **N**2O
HINT: "Sin-ha-BON"
**Syn**ergistic-In**ha**led
28
**T/F**: IV and Inhaled Hypnotics are synergistic
FALSE
(confirm)
29
Although there are no uniform clinical signs to assess depth of anesthesia whilst using inhaled hypnotics, what metrics can provide some insight into depth?
1. ↑HR
2. ↑BP
3. Sweating
4. ↑RR (confirm)
30
When IV hypnotics are used for induction, what occurs after the initial bolus?
redistribution
31
What are the two major components of a TIVA?
1. Propofol
2. Analgesic (i.e. Remifentanyl)
32
**T/F**: Ketamine's analgesic properties is typically sufficient to blunt responses to laryngoscopy and incision.
FALSE
Ketamine may not blunt responses to major noxious stimuli
33
IV hypnotics are synergistic with ____.
opioids
34
what techniques can be used to assess depth of anesthesia whilst using IV hypnotics?
1. Verbal responsiveness
2. Loss of eyelash reflex
3. loss of corneal reflex
HINT: think during a MAC case
35
Opioids are not true ____.
anesthetics
...due to weak hypnotic effect
36
Analgesics decrease MAC by ____, but still possess a "ceiling effect"
60-70%
37
Opioid-only anesthesia may be considered for what patients?
Patients with no circulatory reserve
*valve disease, IHD, Trauma*
38
**T/F**: opioid-only anesthesia rarely leads to incidences of awareness.
FALSE
it has a high incidence of awareness due to lack of hypnosis
39
5 goals of anesthesia
1. Patient **S**afety
2. Insufficient/Excessive **a**nesthetic
3. Unresponsive to **n**oxious stimuli
4. No awareness/**r**ecall
5. Facilitate adequate **o**perating conditions
HINT: SONAR
40
Question to ask oneself prior to surgical incision:
"Is my patient **optimally** *narcotized, anesthetized, & paralyzed*?
HINT: NAP
41
**T/F**: there is no reliable stimulus or response measurement to assess depth.
TRUE
42
Different methods we can estimate depth?
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
43
Depth Monitoring Pic
44
MOST reliable physical signs of anesthetic depth
* Gross purposeful movement
* Reflexive movement to stimulus
* Immediate hemodynamic stimulus response
* Immediate respiratory stimulus response
* Response to soft stimulation (shaving, surgical prep, positioning, etc.)
45
Less reliable physical signs of anesthetic depth
* Heart rate
* Respiratory rate
* Blood Pressure
46
How does NMBD limit physical assessment of anesthetic depth
Inhibits:
- movement
- eye opening
- breathing/tachypnea
47
How do Beta Blockers, Ca Channel blockers, Vagalytics, Epi, etc. limit physical assessment of anesthetic depth?
- Attenuates autonomic responses to noxious stimulus
- can mask HR/BP increase
48
With regard to pupils, which drug causes mydriasis?
Scopolamine
49
which drug/s can cause miosis?
narcotics
50
how can patient positioning affect anesthetic depth assessment?
prone position can hide lacrimation
51
Michigan Awareness Classificaition Instrument
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
52
What does the designation "D" represent on the Michigan Awareness Classification Instrument
Distress (reports of fear, anxiety, suffocation, sense of doom, sense of impending death...)
53
Why does awareness generally occur?
imbalance
[HIGH] Demand/Tolerance (Pain) vs [LOW] Supply (meds, sedation)
54
Risk factors for "High Demand/Tolerance vs Low Supply" cases
- Drug addiction (cocaine, alcohol)
- Chronic Pain (long term opiate)
- Long-term use Anti-Convulsants (Kepra®) & Benzos
- Genetics (Red hair)
- Female
55
Risk factors for "Low Demand & Very Low Supply" cases
- Low **p**erfusion states (EF <40%, Trauma, youth)
- **A**SA Class 4 or 5
- End Stage **L**ung disease
- Marginal **E**xercise tolerance
- **P**ulmonary HTN
*First 2 are a result of safety risk if given too much anesthesia, therefore less than ideal is often given*
HINT:P²ALE
56
Other General risk factors for Awareness
- *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
Overall Anesthesia Awareness Incidence Rate
0.1-0.2% in non-OB & non cardiac surgery
- 20k to 40k in USA annually
- 3/2000 patients
58
obstetric awareness rate
0.4%
59
Cardiac surgery awareness rate
1.1-1.5%
60
Major trauma awareness rate
11-43%
*hemodynamically instability overrides demand for adequate sedation*
61
Average number of law suits annually regarding closed claims of awareness
10
62
All anesthetic depth monitors are based on what measured concept?
Electroencephalography (EEG)
63
EEG reads ____ caused by action potentials (low-voltage currect) in brain activity and uses special adhesive electrodes
electrical current
64
T/F: EEG pads must be placed in areas without hair.
TRUE
65
EEG waves are measured in what unit?
Hertz (Hz)
*Waves/sec*
66
T/F: EEG technology directly measures consciousness
FALSE
*likely to be conscious at certain level*
67
EEG Beta waves:
13-30 Hz
*Awake*
68
EEG Alpha waves:
8-13 Hz
*Moderate Sedation*
hint: m**A**c cases
69
EEG Theta waves:
3.5-8 Hz
*General Anesthesia*
70
EEG Delta Waves:
0-3.5 Hz
*Deep Anesthesia*
71
Beta Wave (Awake)
72
Alpha Wave (moderate sedation)
73
Theta Wave (General Anesthesia)
74
Delta Wave (Deep Anesthesia)
75
For EEG waveforms, as anesthetic effect increases, EEF frequency ____, and waveform amplitude ____.
- decreases *(transmission slows)*
- increases
76
Wave Progression (Awake to deep anesthesia)
Beta, Alpha, Theta, Delta
*Bold Anesthesia Tames Druggies*
77
____ utilizes EEG and a proprietary algorithm to provide a value that correlates with *increased risk of intraoperative awareness*
Bispectral Index (BIS)
78
what BIS values are believed to indicate decreased incidence of intraoperative awareness?
40-60
79
The BIS has ____ electrodes that are placed where?
4
over the frontal cortex
80
Job of BIS Electrode 1
Ground
81
what BIS electrodes use a differential amplifier to measure potential difference?
Electrodes 2 and 3
82
job of BIS electrode 4
remove noise
83
What must be done before BIS application?
- 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
why is the BIS bispectral?
it analyzes signals from the frontal lobe at various frequencies (B, A, T, D)
85
BIS algorithm collects data over ____ seconds
15-30
86
BIS value: likely to follow commands
≥80
87
BIS value: gray zone (50% of patients fail to follow commands)
70-79
88
BIS value:
- memory impaired
- decreased probability of explicit recall
<70
89
BIS value: high sensitivity to reflect unconsciousness
<60
90
BIS value:
- balanced anesthetic
- adequate hypnosis
- improved recovery
- decreased incidence of intra-operative awareness
40-60
91
BIS value:
- significantly deep anesthetic
- assoc with **negative outcomes**
<40
92
What BIS level is associated with cerebral ischemia
<20
93
What BIS value is associated with:
- ↑ stroke, MI, Mortality risk
<40 **for > 5 min**
94
T/F: BIS value of <20 is associated with decreased POCD.
FALSE
<40
95
Burst Supression occurs at what BIS value?
20
96
The BIS value reflects the reduced ____ produced by most anesthetics
cerebral metabolic rate
97
CMR increases/decreases as BIS value falls
decreases
98
"Lack of EEG activity"
Burst Suppression
99
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.
FALSE
*Will not tell us the probability of whether the patient will remember the command, **BUT** does correlate to impaired memory function*
100
T/F: Burst Suppression is never intentionally utilized.
FALSE
*some neurosurgeries require it, but a neuro tech will use a different monitor to track brain activity*
101
BIS metric that indicates confidence/trustworthiness of BIS value
Signal Quality Index (SQI)
102
How is SQI calculated?
based on impedance data and artifacts
103
Desirable SQI value
>90
*Closest to 100 as possible*
104
Poor SQI value
<50
105
BIS value: % average of EEG activity over time that falls below preset limit.
Suppression Ratio (SR)
106
This BIS value is derived from the electrical power of muscle movement (muscle tone).
Electromyelography (EMG)
107
Range of frequencies used by EMG
70-110 Hz
108
The larger EEG waveform graph covers what span of time?
*One Hour Trend Window*
1 hour
109
The smaller EEG waveform graph is called what and covers what span of time?
*Raw EEG Window*
20 seconds
110
BIS Monitoring Screen labeled
111
Under what circumstances is the EMG function rendered useless?
If the patient is under NMB (duh, there's no muscle tone to measure)
112
What responds faster: BIS value vs EMG value
EMG
113
what measurement unit does the EMG use?
25mm/sec
114
Factors that can influence BIS values:
1. EMG artifact & NMB Agents
2. Medical Devices
3. Medications & Anesthetics
4. Clinical Conditions
115
Examples of EMG Artifact/NMB agent BIS interference:
1. Excessive muscle tone in forehead = ↑ BIS value
2. NMB agents = ↓ EMG & *MAY* ↓ BIS value
116
Under stable anesthesia, without EMG artifact, NMB have what effect on BIS values?
little or no effect
117
Examples of medical devices that that can influence BIS values?
1. Pacemakers
2. Forced Air Warmers (applied over head)
3. Electrocautery
4. Endoscopic Shaving Devices
118
Medications that INCREASE BIS value:
1. Ketamine: transient ↑ BIS & ↑ EMG
2. Etomidate: transient ↑ BIS
119
Why can Etomidate ↑ BIS value?
causes myoclonus (muscle contraction)
120
What drugs DECREASE BIS values?
1. Opioids
2. Benzodiazepines
*Due to synergism with hypnotics*
121
Clinical conditions that influence BIS values:
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
BIS - Light - Clinical Application Flowchart
123
BIS - Adequate - Clinical Application Flowchart
124
BIS - Deep - Clinical Application Flowchart
125
Differences in BIS and Masimo Sedline - Patient State Analyzer:
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
Utility Trial (1997)
- 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
B-Aware Trial (2004)
- High-risk of awareness patients
- 82% reduction in incidence of awareness with recall
128
Cochrane Review (2007)
- 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
Avidan Study (2008)
- 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
BIS cost effective?
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
What may be done for a patient if you believe they may have experienced awareness during surgery?
administer benzos (amnesia)
132
BIS is best used in conjunction with what two other adjuncts?
1. traditional vital sign monitoring (BP)
2. EtAG (End tidal anesthetic agent)
133
One of the best uses of the BIS is to reduce volatile agent; what are the patient benefits of doing so?
1. better hemodynamic stability
2. faster emergence
3. less PONV
4. faster recovery
134
Are TIVA cases good cases for the BIS?
YES
*these cases generally utilize 0.5 MAC + Propofol, making it very difficult to assess anesthetic depth*
135
Types of cases the qualify as good cases for BIS use:
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
