Monitoring Depth of Anesthesia Flashcards
What is DOA?
Depth of anesthesia
In what situations can pt awareness occur? (3)
Trauma
Cardiac surgery
Cesarean section
New brain wave monitoring can be helpful in reducing the risk of awareness, but what is the caveat?
They need to undergo rigorous scientific review process .
A highly trained anesthesia professional should be involved in your surgery. No technology can replace this. True or false?
True damnit.
At the present time, technologies for monitoring awareness has been perfected. True or false?
False
Stated by the ASA and AANA
What does this symbol represent?
American Society of Anesthesiologists
What does our future logo look like?
Kaduceus is depicted on our our logo. He has wings. He must drink Red Bull.
Who do we swear oath to?
Apollo the physician
Where do people that have crappy anesthesia go to after their traumatic surgery?
Post-traumatic Stress Disorder Clinic
If a person experienced an event that threatens the physical integrity of self or others, what does the response include?
Fear, helplessness, and horror
In children, agitation or disorganized behavior
How is the traumatic event persistently reexperienced? (5)
- Recurrent and intrusive distressing recollections of the event
- Recurrent distressing dreams of the event
- Acting or feeling as if the traumatic event were recurring
- Intense pyschological distress at exposure to cues
- Physiologic reactivity on exposure to internal or external cues
___ of ___ patients with awareness had no postoperative sequelae.
8 of 26
Guedels phsyical signs of ____ anesthesia and involved ocular movements, pupils, and eye reflexes.
What drug introduced in the 1940s changed the emphasis from too-deep to too-light anesthesia?
ether
curare
What are the goals of a satisfactory anesthetic? (3)
Adequate perfusion of all organ systems
Unresponsive to noxious stimuli
No awareness or recall of events during the procedure
Conscious awareness during general anesthesia occurs most commonly in what procedures?
General surgery, NOT obstetric
What is the breakdown of causes of awareness?
Faulty anesthetic technique (70%)
Failure to check equipment (20%)
What are poor indicators of consciousness? (3)
Subcortical phenomenon
Movement (cord reflex)
Hemodynamic responsis (HR, BP)
Brainstem
The depth of anesthesia can be defined by suppression of what responses to noxious stimuli? (4)
Movement
Panting
Increased HR, BP
Sweating
What is an agent that quiets or calms the patient without affecting the clarity of consciousness?
What is an agent that allays excitement and produces a calm state?
tranquilizer
sedative
What autonomic indicators of anesthetic depth may be unreliable, but we use anyway? (6)
HR
BP
Pulse amplitude
Sweating
Tearing
Mydriasis
What tools can monitor anesthetic depth? (5)
- EEG (spectral edge, BIS, entropy)
- BAEP (brainstem auditory evoked potentials)
- Lower esophageal contractility
- Skin conductance measure sweating
- EMG (electromyography)
What responses to stimuli are first to go? (10)
- Verbal
- Implicit memory (previous experiences aid without conscious awareness)
- Explicit memory (intentional recollection)
- Purposeful movement
- Involuntary movement
- Ventilation
- Tearing
- Sweating
- BP
- HR
How much more stimulating is laryngoscopy than skin incision?
10 times more
What knowledge is easily recalled and explained?
explicit
What can we not consciously recall and it influences our behavior?
implicit
How much more alfentanil is needed for tracheal intubation than for skin incision?
about 2 times more
Label
At what concentration of iso will produce no movement during laryngoscopy?
At what concentration of iso will produce no movement during intubation?
- 8%
- 2%
What are methods of assessing anesthetic depth? (6)
- Clinical signs/isolated arm
- Dose of anesthetic
- Lower esophageal contractility
- Frontalis EMG (BIS which is an entropy device)
- Hear rate variability
- EEG
Most anesthesiolgists rely on what to assess anesthetic depth?
Clinical experience and dose of anesthetic
What does the isolated arm method involve?
Isolating the forearm with blood pressure cuff inflated above arterial pressure.
Induction with neuromusclar blockade then induced using opposite arm.
If pt is conscious, he can respond by squeezing the isolated hand and are usually free of pain, have no signs of awareness, and don’t remember being awake.
Developed by obstetric and now controversial.
What defines MAC?
ED50 which is not an inherently useful number.
Doses minimally larger than ED50 typically prevent movement.
Concentration-response relation for inhaled anesthetics is steep. True or false?
True, ie. ED95 differed minimally from ED50
The endpoint for MAC is mediated at subcortical levels. True or false?
True.
Thus, since the cortex is more sensitive the MAC is a higher concentration than is really needed. Removal of the cortex does not change MAC, and the concentration of anesthetic needed to cause unconsciousness is much lower.
What factors decrease MAC?
Hypothermia
Severe hypotension
Advanced age
Opioids
Chronic amphetamine
Anticholinesterases
Pregnancy
Hypoxemia
Anemia
A2 agonists
What factors increase MAC?
Hyperthermia
Hyperthyroidism
Alcoholism
Acute administration of amphetamine
Young
What has no effect on MAC?
Duration of anesthesia
Sex
Metabolic state
Hyper/hypocapnia
HTN
What are ways to improve work practices of anesthetists?
Vigilance
Fatigue management
Seek advice
What can be done in the intraoperative phase to reduce awareness? (7)
Scan equipment often
Avoid using the wrong drugs
Give enough hypnotics
Minimize using muscle relaxant
Respont rapidly to suspected inadequate anesthesia
Modulate OR behavior (don’t act like a fool)
Consider using an EEG-based monitor
What muscle is immune to NMBs?
Lower 3rd of esophagus which is why we can monitor lower esophageal contractility.
Label
Awake
Moderate sedation
General anesthesia
Deep anesthesia
What does BIS stand for?
Bi-Spectral Index, or,
BiSpectral Index System
_____ channel EEG data from electrode sensors are placed over the _____ cortex.
Single
frontal
What measures the potential difference between electrodes 2 and 3?
differential amplifier
Which electrode is ground/reference?
Which electrode reduces noise?
1
4
Label the electrode numbers
What is the the name of the BIS that captures both hemispheres?
What do we use it for?
Bilateral
Carotid surgery for example
What is a graphical representation of EEG frequency differences between the two hemispheres?
Density Spectral Array (DSA)
How long does it take for a normal functioning BIS to produce values?
30 secs
What is the derivation of the BIS?
Uses:
Burst suppression ratio
Relative alpha/beta ratio
Bicoherence of EEG
What is the Bispectrum frequency range?
1 - 2 Hz
Label the 3 graphs:
What ranges from 0 to 100% which is the percentage of good epochs in the last 60 that could be used for calculation of the BIS?
SQI (signal quality index)
What are the ranges for the BIS?
0 - 100 (NOT percent)
0 = unconscious
100 = awake
What is the electrical power of EMG range in Hz?
70 - 110
What is the percentage of epochs in the past 63 seconds in which the EEG is considered suppressed?
SR (supression ratio)
What is SEF?
Spectral Edge Frequency at which 95% of the total power lies below.
What occurs to the BIS when the signal quality goes down?
BIS numerical value is outlined.
Label:
Label
- BIS Index numeric region
- Signal quality region
- Message region
- Graphic display region
What graph period for the BIS is used?
What is on the right axis?
1 hour
Secondary variable, like EMG for example
What display is depicted?
Density Spectral Array
During emergence which will respond faster? BIS or SEF?
Bispectral Index (BIS) responds faster than SEF
What signals tend to increase the BIS artifactually? (3)
- 60 Hz
- ECG
- Pacemaker
What appear identical to deep sedation and decrease the BIS? (2)
Hypothermia
Cerebral ischemia
What anesthetics produce unreliable results on the BIS?
Ketamine
N2O
No data for efficacy of BIS for what factors? (2)
High dose of opioids
Pts with neuro disease
What will high electrode impedance do to the BIS value?
increase it
Prevention of implicit memory at BIS of ____ to ____.
50% of subjects fail to respond to verbal commands with BIS of ___ to ____.
No frank awareness with BIS < ____.
Who reported this data?
84 - 91
67 - 79
50
Aspect Medical
What is the incidence of awareness for electective and emergency surgery?
0.2 - 0.4%
What can the BIS NOT do? (3)
Predict movement
Predict hemodynamic response
Momen consciousness returns
The BIS is designed to measure the effect of _________.
When pts move during surgery with a BIS < 60, additional ______ may suppress movement.
hypnotic anesthetic drugs
analgesia
What was the hypothesis in “movement” trials?
Movement/autonomic responses correlate with analgesia.
EEG changes correlate with hypnosis/consciousness.
Strong correlations were found with BIS and ______.
High correlation with BIS and what 3 factors?
hypnotic drugs
sedation
consciousness
memory
With a BIS < ____, the probability of implicit memory is very low.
50
BIS can be used to make clinical decisions. True of false?
False, it can help guide decisions. It needs to be used in conjunction with traditional monitoring.
What drugs produced the following curves regarding the BIS?
What may cause a sudden BIS decrease? (5)
Drugs bolus
Less noxious stimuli
NMBs
Profound hypotension, hypothermia
Paradoxical emergence
What can cause a sudden BIS increase? (3)
Artifact
Sudden changes to anesthetics, FGF rates
Moving bovie to new pain site
What are BIS alternatives? (2)
Entropy (eEEEG)
Patient State Index (PSI–SEDLine)
What is entropy?
What happens to entropy when pt is awake?
Irregularity and unpredictability of signals
Awake, highly irregular → high entropy
What are the two Entropy parameters?
Response Entropy (fast-reacting)
State Entropy (steady and robust)
What type of entropy would record cortical activity?
State Entropy (SE)
What type of entropy would record muscle activity?
Response Entropy (RE)
What is the range for “clinically meaningful anesthesia with low probability of consciousness”?
40-60
What’s depicted?
SedLine (Patient State Index)
What is the optimal hypnotic state for general anesthesia using the PSI?
25 - 50
What does the AAAA, AANA, and ASA combine to form?
Anesthesia Awareness Campaign, Inc.
What is the spectral edge frequency range in Hz?
0.5 - 30 Hz
