2a. EPs Monitoring Flashcards

1
Q

What is the purpose of evoked potential monitoring?

A

detects injury to the spinal cord and measures neuronal function

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2
Q

what 4 things may affect EP monitoring?

A

hypotension
anesthetic drugs i.e. volatile agents
hypothermia
spinal cord retraction

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3
Q

latency

A

time of administration of stimulus to peak response (time necessary for the evoked response to be measured in the brain)

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4
Q

amplitude

A

magnitude of the peak response/intensity of the evoked response

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5
Q

how do VAs and N2O affect latency and amplitude of EPs?

A

↓ amplitude and ↑ latency

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6
Q

which is more sensitive to depressant effects of anesthetics between motor (MEP) and somatosensory (SSEP) EPs?

A

MEPs

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7
Q

what MAC may be used without altering signal quality of EPs?

A

MAC ≤ 0.5

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8
Q

effect of propofol on EP monitoring?

A

dampening of evoked potential response

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9
Q

effect of opioids and benozos on EP monitoring?

A

no interference

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10
Q

what type of injury can occur from transcranial stimulation and how is this prevented?

A

facial muscle activation causes pt to bite down with significant force and cause injury to tongue, lips, cheeks, teeth etc. Therefore a soft bite block should be inserted to avoid injury.

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11
Q

What is the purpose of the Hunt-Hess Scale

A

determines severity of a patient’s subarachnoid hemorrhage (a high grade corresponds to a higher severity)

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12
Q

what hunt-hess scale score corresponds to an asymptomatic patient?

A

1

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13
Q

A patient with SAH will require intubation if his Hunt-Hess score is (Select 2)

A

4 and 5

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14
Q

NIRS

A

Near Infrared Spectroscopy used to assess cerebral O2 Sat
* Used when cerebral perfusion could be compromised

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15
Q

NIRS goal parameter

A

maintain the NIRS value at a minimum of 75% of the baseline reading

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16
Q

Normal ICP

A

5 to 15 mm Hg in adults

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17
Q

intracranial hypertension values

A

20 to 25 mm H

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18
Q

gold standard for ICP monitoring

A

intraventricular catheter (it allows for drainage of CSF to lower ICP)

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19
Q

what is the most frequent complication of ICP monitoring

A

Infection

20
Q

ICP should be monitored in patients with a normal CT scan with two or more of the following criteria…

A
  • age older than 40
  • unilateral or bilateral motor posturing
  • systolic blood pressure (SBP) less than 90 mm Hg
21
Q

Cushing’s triad

A
  • systemic hypertension
  • bradycardia
  • irregular respiratory pattern
22
Q

who else should undergo ICP monitoring?

A
  • patients with severe traumatic brain injury (TBI)
  • a Glasgow coma scale (GCS) sum score below 9
  • an abnormal CT scan
23
Q

What change in EPs is suggestive of the possibility of cerebral ischemia?

A

A 50% decrease in amplitude or a 10% increase in latency

24
Q

effect of ketamine and etomidate on EP monitoring?

A

increases amplitude
no effect on latency

25
Q

motor or sensory: descending (efferent) tracts

A

motor

26
Q

motor or sensory: ascending (afferent) tracts

A

sensory

27
Q

main voluntary motor tract

A

lateral corticospinal tract (2nd: ventral corticospinal)

28
Q

sensory functions of the dorsal column

A

deep touch
vibration
proprioception

29
Q

sensory functions of the lateral spinothalamic tract

A

pain and temperature

30
Q

sensory functions of the ventral spinothalamic tract

A

light touch

31
Q

SOMATOSENOSORY-EVOKED POTENTIALS (SSEPs)

A

MONITOR INTEGRITY OF PERIPHERAL & CENTRAL SOMATOSENSORY NERVE PATHWAYS OF BRAIN & SPINAL CORD

(DORSAL COLUMN & LATERAL SENSORY TRACT OF THE SPINAL COLUMN)

32
Q

upper extremity monitoring

A

placing the stimulus at the median nerve

(located between the tendons of the flexor carpi radialis and the palmaris longus)

33
Q

lower extremity monitoring

A

POSTERIOR TIBIAL NERVE

(Located between the Achilles tendon & medial malleolus of the ankle)

34
Q

ALMOST ALL ANESTHETICS INCREASE LATENCY & DECREASE AMPLITUDE EXCEPT

A

KETAMINE, ETOMIDATE & OPIATES

35
Q

anesthetic management during SSEPs monitoring

A

NARCOTIC BASED, TIVA, <0.5 MAC VAA

36
Q

DOES ADMINISTRATION OF PARALYTIC AFFECT SSEP MONITORING?

A

NO
HOWEVER, MUST AVOID IF MOTOR RESPONSE BEING MONITORED

37
Q

GOLD STANDARD FOR MONITORING FOR EP MONITORING

A

MOTOR-EVOKED POTENTIALS

(USUALLY COMBINED WITH SSEPs)

38
Q

USED TO ASSESS FUNCTIONAL INTEGRITY OF MOTOR TRACTS:

A

CORTICOSPINAL TRACT

39
Q

how do MEPs differ from SSEPs, VEPs, and BAEPs?

A

MEPs evaluate descending motor pathways from the cerebral cortex past the neuromuscular junction to peripheral muscle groups

(the others provide information about ascending sensory neural pathways from the periphery to the cerebral cortex)

40
Q

BAEPs monitor basic brainstem function by monitoring which tracts?

A

ENTIRE AUDITORY PATHWAY FROM DISTAL AUDITORY NERVE TO MIDBRAIN

41
Q

what cranial nerve is stimulated by BAEPs?

A

8
Vestibulocochlear

42
Q

what can commonly effect on BAEPs during anesthesia and surgery?

A

hypothermia AKA patient temperature less than 35°C
(increased latency & prolonged interpeak intervals)

43
Q

VISUAL-EVOKED POTENTIALS (VEPs) monitor the FUNCTION OF VISUAL PATHWAY along what tracts?

A

Retina to the occipital cortex and everything in between, including the optic nerve and the optic chiasm

44
Q

WHY DO VEPS HAVE QUESTIONABLE USEFULNESS IN ANESTHETIZED PATIENTS?

A

VEPs are the most sensitive neuromonitoring modality with regards to anesthesia

45
Q

WHAT IS ONE ANESTHETIC TECHNIQUE FOR VEPS MONITORING?

A

opioid-based TIVA with muscle relaxants & BIS monitoring

46
Q
A