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37 Cards in this Set

  • Front
  • Back
What does an EEG monitor?
A measure of unstimulated corticol activity and function (Notes)- The GOLD standard for assessing intraop cerebral ischemia

Summation of the excitatory and inhibitory postsynaptic postentials produced in the pyramidal layer of the cerebral cortex.(Barash)
What information does an EEG give the anesthesia provider?
Info concerning state of arousal, and depth of anesthesia.(notes)

Provides info about overall electrical functioning of the cerebral cortex but not much about the subcorticol brain(brainstem), spinal cord, and peripheral nerves.(Barash)
True or False- Deep levels of anesthesia and cerebral ischemia produce similar EEG changes
True
What are the four EEG frequency bands?
Delta (<4 Hz)
Theta (4-8 Hz)
Alpha (8 - 12 Hz)
Beta (> 12 Hz)
What is burst suppression?
Increasing depth of anesthesia results in EEG slowing with increases in amplitude, leading to periods of electrical silence interspersed with brief episodes of activity. Caused by high concentrations of isoflurane or desflurane, and barbituates.
What is BIS monitoring?
The bispectral Index is a variable derived from the EEG that is a measure of the hypnotic effect of anesthetic effects.
BIS can reliably predict the level of sedation, loss of consciousness, and the probability of recall. True or false
True
BIS can reliably predict movement in response to a noxious stimulation. True or false
False- motor responses to painful stimuli may be mediated by subcorticol structures which are not measured by BIS.
What are the three sensory pathways available for intraoperative monitoring?
Brainstem Auditory Evoked Response (BAER)
Visual Evoked Potentials (VEP)
Somatosensory Evoked Potentials (SSEP)
What means of intraoperative monitoring provides info on descending motor pathways during neurosurgical, orthopedic, or vascular procedures?
Motor Evoked Potentials (MEP)
Which Sensory monitor is the least affected by anesthetics
The BAER's are relatively resistent to anesthetics, it monitors brainstem activities
What procedures are BAER monitoring used for?
Assesses brainstem function in comatose pts and procedures of the CPA (cerebellopontine angle), floor of the 4th Vent., or involving the V, VII, & VIII CN.
What procedures are the VEP's used for?
Records over the occipital cortex--Assesses the visual pathway; Pituitary tumors, craniopharyngiomas, or near the optic tracts.
What is the alarm criteria for EEG monitoring?
Changes in both Frequency and Amplitude as the cerebral cortex becomes increasingly ischemic
What can affect changes in bothe frequency and amplitude in EEG's during intraoperative monitoring?
Hgb & Hct changes(bleeding), hypoxia, Changes in CO2, BP changes (HOTN)
What amount of blood flow is assoc with significant alterations in EEG ?
a drop to approx < 18ml/100g/min...(also can see changes with large Increases in blood flow from unclogged Carotids.
What are the five type of Evoke potentials used intraoperatively to monitor neuro status?
1. Somatosensory (SSEP)
2. Auditory (BSER)
3. Visual (VEP)
4. Dermatomal
5. Motor (MEP)
Where are the recordings set at when peripheral stimuation occurs with Evoke Potentials?
from both central (scalp) and periphery (cervical spine) and brachial plexus.

(multiple recording sites allow for coverage along the entire axis from peripheral stimulation to the primary somatosensory cortex- helps to determine where the injury occurs )
What is the most sensitive measure of cerebral ischemia using intraop SSEP's?
Amplitude changes
Monitoring SSEP's and the amplitude drops 50%, what is the predicted blood flow to the brain?
CBF is @ approx 16ml/100g/min (normal is 50ml)
Monitoring SSEP's at what point is the waveform diminsished?
CBF @ 12ml/100g/min
Where is the first synapse with an ascending volly after a peripheral nerve is stimulated?
stimulus travels up the ipsilateral side of the dorsal columns via the fasiculus gracilus (first order axon) to synapse at the dorsla column nuclei.
Where is the second synapse of the ascending sensory pathway?
The impulse croses over at the medulla and travels along the medial lemmiscal tract (2nd order axon) to synaps in the thalamus
What is the 3rd synapse of the ascending sensory pathway?
The impulse travels from the thalamus to the Primary somatosensory cortex to the third synapse.
Examples of when SSEP monitoring is used?
Lesions such as acoustic schwannomas
Prevention of ischemia during CEA, CABG, Circulatory arrests
C-Spine procedures
What monitoring device is used to monitor brainstem activity?
Auditory BSEP's (Brainstem evoke potentials)
what neuro monitoring is the least affected by anesthesia?
BSEP's
Why is the auditory BSEP's considered far-field response tests?
Because the stimlus is generated in the ear and recorded in the scalp.
What intraoperative uses for the BAEP's?
Acoustic neuromma, brainstem lesions, posterior fossa masses
What neuro monitoring device is rarely used in the OR and is the most sensitive to anesthesia?
VEP's (Visual evoke potentials)
What are the dermatomal evoked potentials?
The stimulation of a single dermatome which results in the depolarization of a single nerve root and the ascending conduction.
Examples of procedures that would use VEP's?
Supra and InfrSellar tumors
Optic nerve tumors and decompression
Occipital cortical masses
Examples of procedures that would use Dermatome Evoke potentials?
Lesions of a specific nerve root
Spina-bifida/tethered cord procedure
brachial plexus explorations
What do MEP's monitor?
Motor Evoke Potentials monitor the descending Spinal cord pathways from teh motor cortex to the ipsilateral thalamus to the lower motor neurons (cross over at the brainstem)
Do Motor evoke potentials detect ischemia or injury?
They detect injury-- usually by the time it is detected it is too late to prevent it.
What do EMG's monitor?
Real time info R/T integrity of the nerves themselves int eh case of creanial nerves- teh underlying brainstem nuclei.
What changes during NM monitoring points to a surgical cause?
1. change is unilateral
2. typically an abrupt change
3. occur in teh absence of anesthesia, hemodynamic or temperature changes
4. not necessarily correlate to the surgical manwuvers.