Monitoring Depth of Anesthesia Flashcards by Anna Logan

What is DOA?

Depth of anesthesia

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In what situations can pt awareness occur? (3)

Trauma
Cardiac surgery
Cesarean section

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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 .

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A highly trained anesthesia professional should be involved in your surgery. No technology can replace this. True or false?

True damnit.

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At the present time, technologies for monitoring awareness has been perfected. True or false?

False

Stated by the ASA and AANA

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What does this symbol represent?

American Society of Anesthesiologists

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What does our future logo look like?

Kaduceus is depicted on our our logo. He has wings. He must drink Red Bull.

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Who do we swear oath to?

Apollo the physician

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Where do people that have crappy anesthesia go to after their traumatic surgery?

Post-traumatic Stress Disorder Clinic

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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

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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

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___ of ___ patients with awareness had no postoperative sequelae.

8 of 26

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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

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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

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Conscious awareness during general anesthesia occurs most commonly in what procedures?

General surgery, NOT obstetric

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What is the breakdown of causes of awareness?

Faulty anesthetic technique (70%)

Failure to check equipment (20%)

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What are poor indicators of consciousness? (3)

Subcortical phenomenon

Movement (cord reflex)

Hemodynamic responsis (HR, BP)

Brainstem

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The depth of anesthesia can be defined by suppression of what responses to noxious stimuli? (4)

Movement
Panting
Increased HR, BP
Sweating

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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

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What autonomic indicators of anesthetic depth may be unreliable, but we use anyway? (6)

HR
BP
Pulse amplitude
Sweating
Tearing
Mydriasis

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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)

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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

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How much more stimulating is laryngoscopy than skin incision?

10 times more

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What knowledge is easily recalled and explained?

explicit

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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?

1. 8% 1. 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. ## Footnote 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

1. BIS Index numeric region 2. Signal quality region 3. Message region 4. 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.

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