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Anesthesia Equipment Exam 2 > Depth of Anesthesia Monitoring > Flashcards

Depth of Anesthesia Monitoring Flashcards

1
Q

History of Anesthesia

A

Morton held a ether-dipped handkerchief over the mouth of the pt in the Ether Dome (considered the first successful anesthetic)

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2
Q

N2O at Mass General

A

Attempted in 1845 but the pt moved and cried out w incision but had no recall. When they used ether the pt had no mvmt but pt was aware and had no pain

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3
Q

Development of Nursing Anesthesia

A
  • Civil War 1864-1865: Union Army Nurse Catherine Lawerence recorded practicing anesthesia in her autobiography
  • many other nurses used chloroform
  • Franco-Prussian War 1870-1871: Male and Female nurse taught to induce anesthesia and used as anesthetists
  • reports more common in 1880s
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4
Q

Key Figures in Nursing Anesthesia

A

Sister Mary Bernard: entered St. Vincents in PN 1887 and took over anesthesia duties in 1888

Franciscan Sisters of St. Johns: in IL prepared sisters to serve as nurse anesthetists and sent them to other MW hospitals

Sister Mary Erhard: 1886 administered anesthesia on Maui for 42 years

Sisters of St. Francis in Rochester, MN: 1889 St Mary’s Mayo Clinic built and opened. Etith and Dinah Graham directed and supervised nursing and administered anesthesia

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5
Q

The Mother of Nursing Anesthesia

A
  • trained by Dr. William Mayo
  • Dinah Graham administered for awhile
  • Edith administered until she married Mayo
  • Alice Magaw (MoA) her friend and successor took over
  • Florence Hendersen introduced to anesthesia dept
  • the NAs became integral to success of St. Mary’s hospital and the Mayo brothers became known for their surgery and excellence in anesthesia
  • known for making anesthesia safer
  • Henderson developed methods of ether administration and assessment criteria
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6
Q

Evolution of NA

A

1908: Agatha Hodgins at Lakeside Hospital in Cleveland, OH chosen by Dr. Crile as anesthetist.
- Lakeside konwns for its success in surgery and anesthesia
1915: Lakeside School of Anesthesia was founded as fist NA program in Cleveland and led to other NA programs

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7
Q

Who founded the AANA?

A

Agatha Hodgins of the Lakeside Hospital and School of Anesthesia

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8
Q

WWI

A

Prior to WWI, few physicians specialized in anesthesia. In 1911 Francias McMechan felt it should be a profession only for physicians

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9
Q

Lakeside Challenge

A

1916: letter sent to Dr. Crile by Ohio BOM telling him to cease the training of NAs, or lose the nursing school’s accreditation
1917: at a hearing Dr. Crile persuaded the board to lift the order by citing how many other facilities were successfully using nurse anesthetists

• Crile and supporting physicians successfully advocated for the Ohio legislature to legalize the practice of anesthesia by nurses

1919: bill approved that legalized practice of nursing anesthesia under supervision of a physician

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10
Q

Kentucky (Frank v South)

A

1916: Louisville society of anesthesiologists passed a resolution that only a physician should administer anesthesia, attorney general concurred

– Louis Frank and his nurse anesthetist Margaret Hatfield joined with that state board of health to file a suit against the Kentucky state medical association

• Lost the initial suit, but won in the appeals – Nurse anesthesia is not the practice of medicine

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11
Q

California (Chalmers-Francais v Nelson)

A

– Dragmar Nelson a nurse anesthetist charged with practice of medicine

– At every level of the California civil court system it was decided in favor of Dragmar Nelson – established legality of nurse anesthesia practice

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12
Q

Breakthroughs in Technology

A
  • pulse ox (standard of care in 1987)
  • anesthesia gas analysis
  • improved monitoring technology and devices
  • fiberoptic imaging
  • US guided techniques
  • BIS/Entropy monitoring
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13
Q

Why Monitor Depth of Anesthesia?

A
  • to prevent awareness
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14
Q

Awareness

A
  • the unexpected and explicit recall by pts of events that occur during anesthesia
  • estimated at 0.0068 to 1%
  • may be higher in children
  • most pts don’t have pain but have vague auditory recall, a sense of dreaming generally not disturbing
  • some experience total pain and recall (traumatic)
  • concern for PTSD and other psychological sequelae
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15
Q

Issue of Awareness More Prominent - 2003/2004

A
  • FDA allowed Aspect Medical (makers of BIS) to declare BIS monitors reduce incidence of awareness
  • sentinal alert from TJC 2004 on awareness developed Task Force on IntraOp Awareness
  • also a hypothesis that DoA monitors help providers titrate meds and reduce oversedation, morbidity, and mortality
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16
Q

Court of Public Opinion

A

the movie “Awake” in 2007 brought the issue to the publics eye

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17
Q

Major DoA Monitors

A

- BIS (Aspect Medical)

- Entropy (GE)

  • Narcotrend
  • Cerebral State Monitor
  • SEDLine
  • SNAP II

AEP

18
Q

Goals of DoA Monitors

A
  • Ability to detect level DoA and risk of awareness
  • Determine if patient is unnecessarily too deep and at risk of prolonged recovery and increased M and M
  • No matter what, the monitor it should work similarly across all patient pops
  • Should work the same regardless of meds and anesthetic technique employed
19
Q

Baseline Principles of EEG Analysis

A
  • 1937: Gibbs et al, discussed the relationship between brain wave patterns (EEG) and neuronal activity changes associated with drug administration *
  • Information is collected by frontal electrodes and the signals are processed to yield an “index value” to determine the depth of anesthesia
20
Q

EEG Activity and DoA

A
  • Cells in cortex provide synaptic activity and results in changes of voltage that can be detected by electrodes placed on the forehead/scalp
  • Multiple waveforms with varying frequency ranges correspond to specific neurophysiological processes
  • grouped into frequency bands in order of freq:

delta, theta, alpha, beta

21
Q

Table Explanation of Waves

A
22
Q

Delta

A

<3 Hz

  • very low freq, depressed functions (coma, deep GA, hypoxia, ischemia, infarction, poor metabolism), may result from thalamic depression
23
Q

Theta

A

4-7 Hz

  • low freq, seen under GA. Inhibition of thalamic pacemaker cells
24
Q

Alpha

A

8-12 Hz

  • med freq, higher amplitude, awake but eyes closed (EEG seen in occipital lobes)
  • prominently seen in awake pts
  • thought to reflect cyclical activity of thalamic pacemaker cells
25
Q

Beta

A

13-24 Hz

  • high freq, low amplitudes, awake state
  • present in prefrontal regions of brain
  • reflect thalamocortical pathways
26
Q

EEG Waveforms Under Anesthesia

A
27
Q

2 EEG Processing Techniques

A
  1. Time Domain
  2. Frequency Domain
28
Q

Time Domain

A
  • voltage changes plotted against time
  • burst suppression is identified in this domain
  • complex signals cannot be fully analyzed by using time domai methods alone
29
Q

Frequency Domain

A
  • advancemnt of microprocessing enabled fast calculations (Fourier transformation) = analysis of freq domain
  • freqs present in EEG compared w degree to which these freqs are present
30
Q

BIS

A
  • bispectrol technology
  • proprietary algorithm developed by Aspect Medical and approved in 1996
  • frontal EEG recordings converted to a number (BIS Index)

- range 0 (isoelectric) to 100 (awake)

- 40 to 60 good goal

  • most widely used DoA monitor in US
31
Q

Evolution of BIS Graphic (single side EEG to bilateral monitoring)

A
32
Q

Principle of BIS

A

• 2 dimensional spectral analysis (Bispectral)

– Refers to the statistical process

  • Quantifying quadratic nonlinearities of the system
  • “Represents the degree of phase coupling of two fundamental frequencies and a modulation frequency represented by the sum of the two frequencies”
  • CLEAR AS MUD!!!!

– Basic premise is the changes in clinical state are represented by changes in phase coupling

- key point: another tool in the toolbox! Rarely should you make decisions on ONE thing alone, use different tools to make clinical decisions

33
Q

To BIS or not to BIS?

A
  • should be reliable across all pt pops and all types of anesthetics, but a cantelope on a BIS is a 28
  • most beneficial in TIVAs or in the ASC
  • GA has a MAC level that corresponds to “depth” and literature shows MAC = little recall
34
Q

Pros/Cons of BIS

A

PROs:

  • large trials have assessed that it decreases awareness
  • BIS algorithm designed for use w Propofol, Versed, and ISO (beneficial for TIVA)

CONs:

  • some studies funded by Aspect Medical (makers of BIS)
  • BIS index doesn’t accurately reflect all drugs (no change in BIS w N2O, increases w ketamine)
  • Artifact from Bovi, Bair Hugger, etc.
35
Q

BIS Spectrum

A
  • 0 to 100 (higher = more awake)
  • low probability of recall w BIS <60
  • target range 40-60
  • lower isn’t always better, too low = too deep, overly anesthetized
36
Q

BIS and Awareness Related Outcomes

A

Studies:

  • Ekman (2004): 4945 pts monitored w BIS between 40-60, awareness 0.04% vs 0.18% in control group
  • Myles (2004) “B-Aware Study”, 2643 pts at high risk of awareness. Only 2 out of 1225 in BIS group had recall vs 11 in control group
  • Avidan (2008) “B-Unaware Study”
37
Q

Cocrane Data on BIS

A
  • BIS reduces awareness in high risk pts but not in routine cases, therefore BIS is not a standard of care
38
Q

Too Low of a BIS

A
  • improved outcomes via reducing anesthetic needs 20-25% w reduced recovery time, reduced postop N/V, reduction in long term outcomes…

BUT “prolonged, deep anesthesia” (BIS <45) = significant independent risk factor for 1 year post op mortality

39
Q

Triple Low

A
  1. low BIS
  2. hypotension
  3. low end tidal anesthetic concentration

= triple mortality at 30 days

40
Q

What to do if awareness happens in your patient?

A
  • follow up, listen, acknowledge facts
  • pts less likely to sue of provider is open and upfront about situation
41
Q
A

Anesthesia Equipment Exam 2 (6 decks)

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