Neuromonitoring (FINAL EXAM)

Question 1

Anesthesia for S-EMG & T-EMG

Answer 1

For reliable EMG: Train-of-Four must be 4/4 with minimal/no fade

Question 2

Somatosensory Evoked Potentials (SSEPs)

Answer 2

Monitor somatosensation
Stimulation at peripheral nerve

Recording at scalp (or periphery) and measures a cross section of the spinal cord

Question 3

SSEEPs monitoring and response type

Answer 3

Monitoring points at different stages of pathway
Responses tiny
Multiple trials averaged
Note: causes foot/hand twitching – NOT motors

Question 4

SSEPS alert criteria?

Answer 4

Monitor amplitude and latency of waveforms

Alert criteria:
50% amplitudedecrease
10% latency increase

Question 5

Anesthesia for SSEPs

Answer 5

Max 1.0MAC inhalation agent, though <0.5MAC ideal (or no gas, institution specific)
Steady state important, including BP
Paralytics OK with SSEPs
Anesthesia + IOM goal: decipher surgically relevant changes

Question 6

Transcranial Motor Evoked Potentials (tcMEPs)

Answer 6

Monitor voluntary movement
Stimulation at scalp
Recording at muscles throughout body
Causes whole body twitch/bite – can cause severe tongue laceration
Bilateral soft bite blocks!!

Question 7

Anesthesia for TcMEPs

Answer 7

TOF 4/4, bilateral soft bite blocks, TIVA
Why TIVA:
- Increased reliability & accuracy
- Less stimulation
- ALERTs – not anesthesia’s fault!
- Sometimes responses still obtainable at 0.5MAC, but not ideal

Precedex and MEPs
New literature shows dose dependent effect on MEPs – no loading dose and infusions <0.5mcg/kg/hr

Question 8

EEG

Answer 8

Monitoring electrical activity in brain
Commonly utilized in CEA/TCAR procedures to ensure adequate perfusion during carotid cross clamping.
Anesthesia for EEG – steady state is important. Bolusing propofol can cause burst suppression
What is burst suppression?

Question 9

BAER

Answer 9

Monitoring auditory pathway
Wave I-V and their generators
Commonly utilized in MVDs, Acoustic Neuromas, etc.
Anesthesia for BAERs – least sensitive to anesthesia

Question 10

VEP

Answer 10

Monitoring optic nerve, visual pathway
P100
Highly sensitive to anesthesia and not commonly used modality in OR

Question 11

Communication with neuromonitoring

Answer 11

Neurophysiologist tries to relay pertinent information that will help outcome of case

Regular communication with anesthesia essential to provide best information to surgical team

Relay complete & accurate information/interpretation as opposed to partial information that only confuses

Question 12

Summary of modalities and anesthesia

Answer 12

Question 13

Anesthesia Effects on IOM

Answer 13

Question 14

Anesthesia Gas Causes _____

Answer 14

Dose-dependent decrease in amplitudes

Question 15

Propofol causes ___

Answer 15

Less severe dose-dependent decrease in amplitudes

Question 16

Paralytic causes ____

Answer 16

Unreliable EMG & TcMEPs

Question 17

Decreased BP causes ____

Answer 17

Dampened SSEP &TcMEP amplitudes

Question 18

Ketamine causes ____

Answer 18

Increased signals

Question 19

Opioids cause ____

Answer 19

Mild decrease in amplitudes

Question 20

Precedex causes ____

Answer 20

Dose-dependent decrease in TcMEP amplitudes

Question 21

Requested Anesthesia for SSEPs

Answer 21

0.5MAC, NMB is OK

Question 22

Requested Anesthesia for S/T-EMG

Answer 22

TOF 4/4, gas is OK

Question 23

Requested anesthesia for TcMEPs

Answer 23

TOF 4/4, bilateral bite blocks, TIVA

Question 24

Requested anesthesia for BAERs

Answer 24

none, does not require anything special because anesthesia doesn’t impact it

Question 25

Requested anesthesia for EEG

Answer 25

Steady state, avoid burst suppression & bolusing prop
*Cranis: TIVA, CEAs: gas

Question 26

Requested anesthesia for VEPs

Answer 26

TIVA (but also rarely done in the OR)

Question 27

Which spinal tract is being monitored by somatosensory evoked potentials?

Answer 27

Dorsal Column

Question 28

Which modality is the LEAST sensitive to anesthesia?

Answer 28

BAEP