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I&M for Anesthesia - Fall 2013 > Neuro Monitoring > Flashcards

Neuro Monitoring Flashcards

0
Q

MEP - Appropriate Measurement

A

Motor strip surgeries

Spine surgery

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1
Q

Motor Evoked Potentials (MEP) - Pathway

A

True MEP are stimulated on the cortical motor strip and recorded by sensors on peripheral muscle
Transcranial MEP (TceMEP) are stimulations by scalp electrodes placed over motor strip
Direct spinal cord MEP stimulation via epidural electrodes

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2
Q

MEP - Limitations of Measurement

A

Interference of anesthetics
Difficulty in establishing baseline due to electrocautery, NMB, and positioning
Does pt have diagnosed disease such as multiple sclerosis

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3
Q

MEP - Compatibility/Interference

A

Volatile/N2O - increase latency, decrease amplitude
Propofol/benzos/dexmetetomidine - increase latency, decrease amplitude
Etomidate - decreases latency, increases amplitude
Ketamine - no effect latency, increase amplitude
Opiates - no effect
NMB - eliminates

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4
Q

MEP vs EMG

A

EMG is a measurement, MEP is a measured response

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5
Q

MEP - Best Method

A 
Protect ETT from biting
Avoid additional MR after intubation
Steady infusions, avoid boluses
TIVA
Realize the pt will move
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6
Q

EMG - Appropriate Measurement

A

Pedical screw placement or other hardware placement

Works by stimulating the hardware, if EMG is detected, then hardware is through the nerve

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7
Q

Electromyographic (EMG) - Pathway

A

Is a local measurement of muscle activity

No pathway exists

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8
Q

EMG - Compatibility/Interference

A

Volatile - no effect at 1 MAC
NMB - eliminates response
Other - no effect

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9
Q

EMG - Limitations of Measurement

A

Intrinsic muscle disease or NMJ disease such as myasthenia gravis or polio

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10
Q

EMG - Best Method

A

Protect ETT from biting
Be cautious of needles
No NMB after intubating dose

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11
Q

NIM EMG - Pathway

A

Trigeminal… Glossopharyngeal… Internal branch superior laryngeal… Recurrent laryngeal

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12
Q

NIM EMG - Appropriate Measurement

A 
Neck Dissection
Thyroidectomy
Parathyroidectomy
Brainstem surgery
Carotid surgery
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13
Q

NIM EMG - Limitations of Measurement

A

Avoidance of paralytics may result in requiring an increase in anesthetic doses which may result in suppression of EMG signal
Only tests nerve tract patency, airway compromise may occur with hypocalcemia following parathyroidectomy
Not for long term intubation
Decreased signal can indicate nerve stretching, not true damage
Expense
No pediatric sizes

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14
Q

NIM EMG - Compatibility/Interference

A

NMB - eliminates
Local/topical - decreases

Other - no effect

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15
Q

NIM EMG - Best Placement

A 
Avoid paralytic agents
Do not se gel or lubricant on tube
No topical anesthetic
Visualize placement
Not exact relation to incisors/gum
Note orientation of anterior marking
Save all included wires and connectors
Anticipate 0.5-1 larger tube than expected
Dispose in sharps container
Do not leave in place for long term intubation
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16
Q

Brainstem Auditory Evoked Potentials (BAEP) - Pathway

A

Assesses CN VIII (vestibulocochlear aka acoustic nerve through its tract to the pons)

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17
Q

BAEP - Tract Anatomy

A

Ear stuff

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18
Q

BAEP - Appropriate Measurement

A

Vestibular nerve
Acoustic neurons
Facial nerve
Cochlear nerve

Acoustic neuroma on vestibulocochlear nerve puts pressure on facial nerve

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19
Q

BAEP - Limitations of Measurement

A

Difficult to assess permanent injury vs stretch

Often used in surgery with no other alternative (leave a bit of tumor vs hearing loss)

20
Q

BAEP - Compatibility/Interference

A

No effect

21
Q

BAEP - Best Method

A

Plain ol anesthesia

Decrease of BAEP is fairly reliable indicator of Stage 4

22
Q

Visual Evoked Potentials - Pathway

A

Retina to occipital cortex

23
Q

Visual Evoked Potentials - Tract Anatomy

A

Visual cortices
Optic chiasm
Optic nerve

24
Q

Visual Evoked Potentials - Appropriate Measurement

A

Craniopharyngiomas

Suprasellar masses

25
Q

Visual Evoked Potentials - Limitations of Measurement

A

Very sensitive to any anesthetic technique

Not considered reliable intraoperatively due to high incidence of false positives

26
Q

Visual Evoked Potentials - Compatibility/Interference

A

Volatile/benzo/opiates - increase latency, decrease amplitude
N2O - no effect latency, decrease amplitude
Propofol/dexmedetomidine** - decreases
Etomidate - increases
Ketamine - no effect latency, increase amplitude
NMB - ???

27
Q

Visual Evoked Potentials - Best Method

A

No established recommendations
Seldom utilized
Avoid hypotension
Avoid high conc of single agent

28
Q

Facial Nerve Monitoring - Pathway

A

Facial nerve…

29
Q

Facial Nerve Monitoring - Tract Anatomy

A

7th cranial nerve

Brainstem

30
Q

Facial Nerve Monitoring - Appropriate Measurement

A 
Wide local exclusions of face and ear
Parotid surgery
Maxillary surgery
Mastoid-translabrynthine surgery
Excision of acoustic neuromas
Brainstem surgery (pontine and medullary)
31
Q

Facial Nerve Monitoring - Limitations

A

Exacting needle placement

Can get response from V2 and V3 nerve

32
Q

Facial Nerve Monitoring - Compatibility/Interference

A

NMB - eliminates
Dexmedetomidine - none?
Others - none

33
Q

Facial Nerve Monitoring - Best Method

A

Protect ETT from biting
No scalp block
Watch for needle displacement

34
Q

Cortical Mapping - Tract Anatomy

A

Precentral - Motor cortex “positivity”

Postcentral - Somatosensory cortex “negativity”

35
Q

Cortical Mapping - Appropriate Measurement

A

Exact mapping of sensory and motor areas of cerebral cortex

Measures plasticity

36
Q

Cortical Mapping - Limitations

A

Placement of electrodes can be difficult

Placement can be impossible of craniotomy window is not aligned with frontal cortex strips

37
Q

Cortical Mapping - Compatibility/Interference

A 
Volatile/propofol/opiate/NMB - no effect
Nitrous - interferes
Etomidate/ketamine - enhances
Benzos - decreases
Dexmedetomidine - unknown
38
Q

Cortical Mapping - Best Method

A

Optimize cerebral perfusion

Limit cerebral edema

39
Q

Somatosensory Evoked Potentials (SSEP) - Pathway

A

Stimulus… Peripheral nerve…
Dorsal root ganglion…
1st order fibers ipsilateral posterior columns…
2nd order fibers crossing to opposite side…
Medial lemniscus to thalamus…
3rd order fibers to frontal parietal cortex

40
Q

SSEP - Tract Anatomy

A

Gray matter… White matter…

41
Q

SSEP - Appropriate Measurement

A

Spinal surgery with instrumentation where manipulation can result in disruption of blood supply to anterior spinal cord
Brachial plexus surgery
Surgery involving sensory cortex
Thalamic surgery
Thoroco-abdominal aneurysm repair
Repair of aortic coarctation
Carotid surgery to assess cortex integrity
Aneurysm - especially after anterior cerebral

42
Q

SSEP - Limitations

A

False negatives - 1% for neuro cases, higher for aortic
False positives
Not a true measure of motor tract integrity
Greater loss of CBF needed for SSEP change vs EEG
Electrode placement may not be feasible in aneurysm surgery due to location of surgical field

43
Q

SSEP - Compatibility/Interference

A

Volatile/benzos/opiates - increases latency, decreases amplitude
Nitrous - no effect latency, decreases amp
Propofol/dexmedetomidine**- decreases latency and amp
Etomidate - increases latency and amp
Ketamine - no effect latency, increases amp
NMB - increases signal

44
Q

SSEP - Best Method

A

Anesthesia - TIVA propofol ketamine infusion
Analgesia - opioid or ketamine infusion
Paralysis - any
Infuse agents or pressors instead of administering as a bolus
Inform monitoring staff of changes in anesthetic agents
1/2 MAC is OK for board exams
Normotensive and normothermic patients

45
Q

Change in signal

A 
Alert surgeons
Review recent changes
Assess perfusion
Normalize ABG
Normalize BP
Consider change to technique to enhance
46
Q

Functional Magnetic Resonance Imaging (fMRI) - Advantages

A

Differentiates left brain for right brain function

Capacity to show exact location responsible for certain tasks such as eloquent speech and motor areas

47
Q

fMRI - Disadvantages

A

Neural conduction time is much more rapid than MRI pulse sequence
Cost
Time and training of personnel
Multiple foci may show up
Difficult to approximate in relation to surgical site
Does not show tracts, only shows cortical grey matter
Pt has to be awake during scan and be cooperative

I&M for Anesthesia - Fall 2013 (13 decks)

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