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The BIG Test > Neuro > Flashcards

Neuro Flashcards

1
Q

What are the 2 tracts included in the Dorsal-Lemniscal System?
Are these sensory or motor tracts?

A
  1. Cuneatus
  2. Gracilis
    *Sensory - touch, pressure, and vibration
    Located in the posterior/dorsal cord (SAD)
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2
Q

SSEP monitoring evaluates what tracts?

A

The Dorsal-Lemniscal System

  1. Cuneatus
  2. Gracilis
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3
Q

Explain the pathway for the the Dorsal-Lemniscal Sensory System including the Cuneatus and Gracilis Tracts of Touch, Pressure, and Vibration?

A

Sensation of touch, pressure, or vibration
Ascend on the IPSILATERAL side of the spinal cord
Cross over in the brainstem
Contralateral thalamus
Primary sensory cortex
*3 neurons

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4
Q

What is the most “direct route” to the sensory cortex for touch, pressure, and vibration?

A

The Dorsal-Lemniscal System

  1. Cuneatus
  2. Gracilis
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5
Q

The _________ serves as an “indirect route” by which sensory info reaches the cerebral cortex.

A

The Reticular Activating System

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6
Q

What is the function of the Reticular Activating System?

A

Maintain the alert/awake state

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7
Q

General anesthetics produce sedation and hypnosis by depressing the _____________.

A

Reticular Activating System

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8
Q

Complete loss of RAS activity =

A

Coma

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9
Q

Name 4 nerves that may be stimulated to elicit SSEPs.

Where are SSEPs recorded from?

A
  1. Tibial
  2. Median
  3. Ulnar
  4. Radial
    SSEPs are recorded from the scalp
    Stimulating electrode is placed peripherally
    Detecting electrode is placed centrally
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10
Q

SSEPs are recorded from the scalp.
The homunculus is used to determine where to place the critical electrode.
Where is the critical electrode for the tibial nerve?
Median and ulnar nerve?

A

Tibial - midline of scalp (longitudinal fissure/sulcus)

Median and Ulnar - lateral to the midline

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11
Q

Components of Typical SSEPs
What does the early component/early peak represent?
What does the late component/late peak represent?

A

Early peak = “direct route” - Cuneatus and Gracilis Tracts

Late peak = “indirect route” - Reticular Activating System (larger in magnitude, longer in duration) * This can be recorded from electrodes placed anywhere over the scalp

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12
Q

What 2 characteristics are monitored by SSEPs?

A
  1. Latency - time it takes to arrive at the cerebral cortex

2. Amplitude - magnitude or size of the potential

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13
Q

With SSEP monitoring, what 2 things would indicate damage is occurring in the neural pathway being monitored?

A
  1. Increase in latency

2. Decrease in amplitude

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14
Q

What is used to monitor for ischemia in the anterior/ventral spinal cord?

A

Motor evoked potentials
Stimulating electrode is placed centrally - motor cortex or cervical spine
Detecting electrode is placed peripherally - popliteal nerve (or could be the involved muscle or spinal cord)
(SSEPs monitor the posterior/dorsal spinal cord only!)

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15
Q

What 5 things are you going to check if the SSEP monitoring tech says there has been a decrease in amplitude and an increase in latency?

A

First of all, suspect spinal cord and/or cerebral ischemia!

  1. Temp - high or low
  2. BP - low, below cerebral auto-regulation levels
  3. PaCO2 - low d/t its affect on CBF
    * Hyperventilation - vasoconstriction of vessels —Decrease ICP (good) BUT decrease BF (bad)
  4. PaO2 - low
  5. Fluid balance - isovolemic hemodilution, Hct < 15%

Altered temp affects SEPs the most!
Hemodilution affects SEPs the least

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16
Q

Brainstem auditory evoked potentials (BAEP) monitor the integrity of CN ________.

A

VIII - 8 - Vestibulocochlear

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17
Q

Visual evoked potentials (VEP) monitor the integrity of CN _________.

A

II - 2 - Optic

* Useful for pituitary resections, transsphenoidal

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18
Q

List the 3 types of evoked potentials in order from very sensitive to least sensitive.

A
  1. VEP - very
  2. SSEP - somewhat
  3. BAEP - barely
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19
Q

EEG Waveforms

List the 4 waveform types along with their frequencies.

A
  1. Delta: 0-4 Hz *Lowest frequency, greatest amplitude
  2. Theta: 4-8 Hz
  3. Alpha: 8-12 Hz
  4. Beta: >12 Hz *Highest frequency, lowest amplitude
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20
Q

EEG Waveforms

Describe the typical brain activities associated with the 4 types of waveforms.

A
  1. Delta - deep sleep
  2. Theta - THE lighter side
  3. Alpha - awake, but resting
  4. Beta - BE awake!
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21
Q

What MAC correlates with an isoelectric EEG pattern?

A

1.5-2 MAC

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22
Q

If you are trying to protect the brain during an ischemic insult do you titrate you level of anesthesia in order to achieve an isoelectric EEG pattern or burst suppression?

A

Burst suppression

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23
Q

All anesthetic agents except ________ depress SSEPs to a varying degree.

A

Muscle relaxants

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24
Q

Which volatile agent causes the least depression in SSEPs?

Which volatile agent causes the most depression in SSEPs?

A

Least depression of SSEPs - Halothane

Most depression of SSEPs - Enflurane

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25
Q

How does nitrous oxide affect SSEP?

A

Causes a decrease in amplitude WITHOUT an increase in latency

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26
Q

Flow through what spinal arterial vessels is monitored by SSEPs?

A

Posterior spinal arteries

*Arterial blood flow to spinal cord - 1 anterior, 2 posterior, segmental/radicular arteries

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27
Q

Why is the “wake-up” test performed?

A

To check spinal motor pathways - anterior/ventral spinal cord integrity (anterior spinal artery perfusion)

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28
Q

What agents will NOT alter BIS?

A

Opioids or analgesics
Nitrous oxide (alone)
Ketamine (may slightly increase BIS)

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29
Q

What 2 fibers conduct pain and temp?

A
  1. A-delta

2. dC

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30
Q

Characteristics of A-delta Fibers

A 
Myelinated 
Larger diameter
"First" or "fast" pain 
Discriminative
Sharp, stinging, pricking 
Duration of pain coincides with duration of stimulus
Somatic
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31
Q

Characteristics of dC Fibers

A 
Unmyelinated 
Smaller diameter
"Second" or "slow" pain
Diffuse, persistent 
Throbbing, burning, aching 
Duration of pain > than duration of stimulus 
Visceral
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32
Q

Where are the cell bodies of A-delta and dC fiber afferents found?

A

Dorsal root ganglion

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33
Q

Explain the pathway for fast-sharp pain.

A

Free nerve endings of A-delta are stimulated
Enter the dorsal cord
Ascend or descend 1-3 segments in the tract of Lissauer
Enter the dorsal horn
Terminate in Rexed’s lamina I & V
2nd neuron crosses to the CONTRALATERAL lateral spinothalamic tract
Ascend to brain

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34
Q

Explain the pathway for slow-chronic pain.

A

Free nerve ending of dC are stimulated
Enter the dorsal cord
Ascend or descend 1-3 segments in the tract of Lissauer
Enter the dorsal horn
Terminate in Rexed’s lamina II & III
Interneurons transmit impulses to lamina V
2rd neuron crosses to the CONTRALATERAL lateral spinothalamic tract
Ascend to the brain

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35
Q

What is the ascending sensory spinal cord tract carrying pain and temp?

A

Lateral spinothalamic tract
(component of the anterolateral sensory system)
3-neuron pathway
1. Peripheral to Rexed’s laminae
2. Cross and then ascend to thalamus
3. Thalamus to somatosensory cortex (postcentral gyrus)

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36
Q

Substantia Gelatinosa = which Rexed’s lamina?

A

II

Or III ?

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37
Q

What is the major NT released from A-delta fibers?

What receptor does this NT bind to on the postsynaptic membrane?

A

Glutamate

AMPA & NMDA

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38
Q

What is the major NT released from dC fibers?

What receptor does this NT bind to on the postsynaptic membrane?

A

Substance P

Neurokinin-1

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39
Q

The Anterolateral System contains what 2 tracts?

Are these tracts sensory or motor?

A
  1. Lateral spinothalamic tract - ascending sensory tract
  2. Ventral spinothalamic tract
    These are sensory tracts!
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40
Q

What is the Dorsolateral Fasciculus/Funiculus/Tract?

A

A descending tract that modulates pain

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41
Q

What sensations are blocked in the lateral columns by epidural or spinal anesthesia?

A

Lateral columns - lateral spinothalamic tract - pain and temp

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42
Q 
Dermatome Landmarks 
Clavicle
Nipples
Xiphoid
Umbilicus
Tibia
Perineum
A 
Clavicle - C4 
Nipples - T4 
Xiphoid - T6 
Umbilicus - T10
Tibia - L4-5
Perineum - S2-S5
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43
Q

Which spinal nerve has no sensory component…it is purely motor?

A

C1

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44
Q

What is the site where pain impulses are attenuated?

A

Substantia gelatinosa (RL II, III)

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45
Q

What NT may be considered the “gate” in the gate control theory of pain?
Explain this.

A

Enkephalin
Enkephalin-releasing interneurons synapse on the substance P-releasing nerve terminal
This decreases the release of substance P = perception of pain is decreased

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46
Q

Describe spinal analgesia as a result of opioid administration in the intrathecal or epidural space.

A

Opioid is injected into the intrathecal or epidural space
Diffuses to the substantia gelatinosa (RL II, III)
Unites with opioid receptors on the primary pain afferent - dC
*Same receptors that are stimulated by endorphins and enkephalins
Release of substance P is reduced

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47
Q

Spinal Analgesia
Describe.
What receptors?
Dominant receptor?
Results from the action of opioids in the _________ after intrathecal or epidural administration.
Results from the action of opioids in the _________ after IV administration.

A

Alters the patient’s perception of pain
Mu-1, Mu-2, kappa, delta
Dominant - Mu-2

Substantia gelatinosa
Periventricular/periaquaductal gray

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48
Q

Morphine is hydrophilic - water loving!

What is the significance of this in regards to intrathecal and epidural placement?

A

Crosses lipid membranes slowly
Onset of analgesia is slow
Duration of analgesia is prolonged
NO early (2 hrs) depression of ventilation
* May occur with epidural placement (d/t greater systemic uptake)
YES late (6-12 hrs) depression of ventilation (d/t rostral spread in CSF)

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49
Q

Fentanyl, Alfentanil, Sufentanil are lipophilic - lipid loving!
(Fentanyl loves Fat!)
What is the significance of this in regards to intrathecal and epidural placement?

A

Crosses lipid membranes quickly
Onset of analgesia is quick
Duration of analgesia is short
YES early (2 hrs) depression of ventilation (d/t significant systemic uptake)
NO late (6-12 hrs) depression of ventilation (minimal rostral spread)

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50
Q

Ventilatory depression is most pronounced after intrathecal or epidural placement of opioid?

A

Epidural

Early depression of ventilation - consider the cause either intrathecal or epidural fentanyl OR epidural morphine

Late depression of ventilation - consider the cause intrathecal or epidural morphine

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51
Q 
Supraspinal Analgesia
Describe. 
What receptors? 
Dominant receptor? 
Results from the action of opioids in the \_\_\_\_\_\_\_\_\_ after IV administration.
A

Alters the patient’s response to pain - “I don’t care”
Mu-1, kappa, delta
Dominant - Mu-1

Limbic system, hypothalamus, thalamus

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52
Q

Describe spinal analgesia as a result of brain control of the substantia gelatinosa.

A

Descending neurons originating in the periventricular and periaqueductal gray matter of the brainstem are transmitted through the nucleus raphe magnus
Terminate on enkephalin-releasing interneurons in the substantia gelatinosa (RL II, III)
Enkephalin attaches to receptors on the dC fiber
Substance P release is inhibited
Reduces the # of pain impulses ascending in the lateral spinothalamic tract
* This is the Dorsolateral Funiculus

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53
Q

Opioids produce analgesia in 3 ways…

A
  1. Initiate action potentials in the Dorsolateral Funiculus
  2. Spinal analgesia - decrease # of pain impulses passing through the substantia gelatinosa
  3. Supraspinal analgesia - action in the limbic system, hypothalamus, thalamus
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54
Q

Where is the somatosensory cortex?

A

Postcentral gyrus

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55
Q

Responses to Opioid Receptor Stimulation

Mu-1, Mu-2, Kappa, and Delta share what in common?

A

All produce spinal analgesia

*Primary receptor for spinal analgesia - Mu-2

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56
Q

Responses to Opioid Receptor Stimulation

All receptors EXCEPT ______ produce supraspinal analgesia.

A

Mu-2

*Primary receptor for supraspinal analgesia - Mu-1

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57
Q

Responses to Opioid Receptor Stimulation

What 2 receptors produce respiratory depression?

A
  1. Mu-2 - mainly
  2. Delta
    * These 2 receptors also both have a high abuse/physical dependence risk
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58
Q

Responses to Opioid Receptor Stimulation

What receptor causes bradycardia?

A

Mu

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59
Q

Responses to Opioid Receptor Stimulation

What receptor causes euphoria? Dysphoria?

A

Euphoria - Mu-1

Dysphoria - Kappa

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60
Q

Responses to Opioid Receptor Stimulation

What 2 receptors have high abuse/physical dependence risk?

A
  1. Mu-2
  2. Delta
    * These 2 receptors also both cause respiratory depression
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61
Q

Responses to Opioid Receptor Stimulation

What receptor causes urinary retention? Diuresis?

A

Urinary retention - Mu-1

Diuresis - Kappa

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62
Q

Responses to Opioid Receptor Stimulation

What receptor causes constipation?

A

Mu-2

minimal Delta

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63
Q

Responses to Opioid Receptor Stimulation

What receptor causes pruritus?

A

Mu-1

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64
Q

Describe how opioid agonist-antagonist (Nalbuphine) work.

A

Antagonist or partial agonist - Mu
Agonist - Kappa (mainly) and Delta
*Analgesia withOUT severe respiratory depression
Can be used to reverse opioid-induced respiratory depression

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65
Q

The spinothalamic tract is severed at C2 on the right. What will happen?

A

Loss of pain and temp transmission on the left at all sensory dermatomes below C2

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66
Q

What are 2 types of nociceptive pain?

A
  1. Somatic

2. Visceral

67
Q

Define neuropathic pain.

A

Abnormal processing of painful stimuli
Initiated by a primary lesion or dysfunction in the nervous system
“Pathophysiological” pain

68
Q

Which nerve fibers appear to be affected by epidural steroids?

A

Unmyelinated C fibers

69
Q

Since s/s of complex regional pain syndrome type I and type II are identical, what differentiates CRPS type I from type II?

A

There is a documented nerve injury preceding CRPS type II

70
Q

Epidural steroid injections

A

Tx for acute radiculopathy
Most effective w/in 2 weeks of onset of pain
Do not last beyond 3 months
Usually steroid + local anesthetic mixture

71
Q

What is the major inhibitory NT of the CNS?

72
Q

GABA opens channels to what ion?

A

Chloride

*Causes hyperpolarization of neurons

73
Q

How does a patient with acidosis change the properties of thiopental?

A

Barbiturates are weak acids
Acid + acid = unionized — More unionized/active drug
- Faster onset of action d/t BBB cross
- Shorter duration of action d/t redistribution
- Slower elimination d/t increased VD

74
Q

Why will thiopental have a pronounced effect in a patient with liver disease and hypoalbuminemia?

A

72-86% of thiopental is bound to albumin

Larger portion of free/unbound/effective drug

75
Q

How are the actions of general IV anesthetics terminated?

A

Redistribution

76
Q

Things to know about barbiturates.

Methohexital
Thiopental
Thiamylal

A

Barbiturates bind to receptors nearby the GABA receptor and prolong the attachment of GABA to the receptor
Depress conduction through the RAS

Weak acids

Intra-arterial injection is BAD - give alpha antagonist: Phenoxybenzamine

pH of solution is > 9, alkaline - do NOT mix with acidic solution like LR — precipitate will form (non-ionized form)

2-7 days of barbiturates leads to enzyme induction

Antianalgesia/promote hyperalgesia

Contraindicated - status asthmaticus (histamine release), porphyria

77
Q

Where dose Ketamine work?

A

NMDA-type glutamate receptors

78
Q

Rank opioids from MOST to LEAST lipid soluble.

A 
Sufentanil
Fentanyl 
Alfentanil
Meperidine
Remifentanil
Morphine
79
Q

The grey matter of the spinal cords is divided into…

A

10 lamina
Known as Rexed’s laminae
Opioids work at lamina II (substantia gelationosa)

80
Q

What opioid has a significant negative inotropic effect and a positive chronotropic effect?

A

Meperidine

81
Q

How do opioids produce bradycardia?

A

Opioids stimulate the vagal nucleus in the medulla

Increases vagal impulses to the heart

82
Q

Do opioids increase or decrease the release of ADH?

83
Q

Your patient is complaining of angina pectoris. Disregarding a cardiac etiology, what else should you consider?
What is the treatment?

A

Opioid-induced spasm of the sphincter of Oddi

Naloxone, nitroglycerine, glucagon

84
Q

What 3 things increase the possibility of skeletal muscle rigidity with opioids?
What receptors are at fault?

A
  1. Large dose
  2. Raid infusion
  3. Concomitant use of nitrous oxide

Mu receptors

85
Q

Which opioid has the smallest VD?

What does this mean?

A

Alfentanil
Small VD means fast elimination

*Only remifentanil is eliminated faster d/t metabolism by nonspecific esterases in the bloodstream
Besides remifentanil, opioids are eliminated by hepatic metabolism

86
Q

What 2 opioids release histamine?

A
  1. Morphine

2. Meperidine

87
Q

What is the most common side effect of intrathecal opioids?

A

Pruritus

Then urinary retention, N/V, and respiratory depression

88
Q

Rank opioids from SHORTEST to LONGEST elimination half-life with continuous administration.

A 
Remifentanil
Alfentanil
Morphine
Sufentanil
Meperidine
Fentanyl 
*Fentanyl loves FAT! Meaning it is lipid soluble - large VD
89
Q

Which has a shorter duration of action: morphine or fentanyl?

A

Fentanyl

*Fentanyl has a longer elimination half-life than morphine d/t its large VD with a continuos infusion

90
Q

Name an opioid competitive antagonist.

A

Naloxone

Low dose reverses pruritus, urinary retention, and nausea
High dose reverses profound sedation and respiratory depression - caution: HTN, dysrhythmias (Vfib), pulmonary edema
It works on all receptors - mu (mainly), kappa, delta

91
Q

What is the duration of action of Naloxone?

92
Q

Rank opioids from MOST to LEAST potent.

A 
Sufentanil 
Remifentanil
Fentanyl 
Alfentanil 
Morphine
Meperidine
93
Q

Name 2 phenylpiperidine derivatives.

A
  1. Meperidine

2. Fentanyl

94
Q

What drug class should be avoided in a patient with heroin addiction taking methadone?

A

Opioid agonist-antagonist

95
Q

During posterior fossa surgery, bradycardia and HTN suddenly occur. What nerve is being stimulated?

A

CN V - 5 - Trigeminal

Pressure on the brainstem

96
Q

During posterior fossa surgery, bradycardia and hypotension suddenly occur. What nerve is being stimulated?

A

CN IX - 9 - Glossopharyngeal

OR CN X - 10 - Vagus

97
Q

What is a concern with tumors or surgery around the glossopharyngeal or vagus nerve?

A

Impaired gag reflex

Increased risk of aspiration

98
Q

Name a common post-op complication following a transsphenoidal or transcranial procedure for tumor removal.

A

Diabetes insipidus

99
Q 
Cerebral Vasospasm 
What is the incidence in subarahnoid hemorrhage patients? 
What are the 3 s/s? 
What is HHH therapy? 
What drug lessens brain ischemia?
A

30% of patients 4-12 days after subarachnoid hemorrhage

3 s/s

  1. Worsening headache
  2. HTN
  3. Confusion

Triple H Therapy
Hypertensive (SBP 160-200), Hypervolemic (CVP > 10), Hemodilution (Hct 33%)

CCB - Nimodipine lessens brain ischemia

100
Q

Name 3 anesthetic goals for intracranial aneurysm surgery.

A
  1. Avoid rupture with abrupt increases in BP
  2. Maintain CPP
  3. Provide “slack” brain (mannitol, lasix, hyperventilate)
101
Q

What is transmural pressure?

What is the significance in regards to a cerebral aneurysm?

A

Transmural pressure = MAP - ICP

An increase in MAP or a decrease in ICP will increase transmural pressure…could lead to rupture of the aneurysm

102
Q

What IV fluids should be avoided in neuro cases?

A

Dextrose-containing fluids
Initially decreases ICP by exerting an osmotic force and pulling water into the vasculature, BUT there will be a rebound increase in ICP as glucose is metabolized in brain cells

103
Q

Cerebral blood flow remains constant/auto-regulated between what pressures?

A

50-150 mmHg

Changing perfusion pressure does NOT normally alter CBF

104
Q

What is the goal PaCO2 during a craniotomy - provide max intracranial decompression with minimal risk of cerebral ischemia?

A

25-30 mmHg

105
Q

Why is controlled hypotension (MAP 50-70 mmHg) extremely useful for aneurysm surgery? Name 2 reasons.

A
  1. Decreasing MAP reduces transmural pressure - rupture less likely
  2. Decreases blood loss and improves visualization
106
Q

What is the only volatile anesthetic recommended for production of deliberate hypotension?

A

Isoflurane

107
Q

Describe intracerebral steal syndrome (aka luxury perfusion).

A

Blood pressure decreases/vasodilator given/hypoventilation/hypercarbia
Normal arteries dilate to increase blood flow
Arteries in the ischemic regions are already maximally dilated
Blood is shunted away from the ischemic region
(vasodilators - nitro, nipride, hydralazine)

Inverse/Reverse Steal (aka Robin Hood)
Hyperventilation/hypocarbia
Normal arteries constrict
Blood is diverted to ischemic regions

108
Q

The spinal nerve root is connected to the paravertebral sympathetic ganglia by…

A

White and gray rami communicans

White rami carry myelinated preganglionic sympathetic neurons
Gray rami carry unmyelinated postganglionic sympathetic neurons (type sC fibers)

109
Q

Where is the epidural space located in relation to the ligamentum flavum?

A

The epidural space is anterior to the ligamentum flavum.

110
Q

Name the cranial nerves and their functions.

A

I Olfactory
II Optic
III Oculomotor - aDDuction of eye (medial rectus), pupil size
IV Trochelar
V Trigeminal - sensory to face, mastication
VI Abducens - aBDuction of eye (lateral rectus)
VII Facial - anterior 2/3 of tongue
VIII Acoustic
IX Glossopharyngeal - posterior 1/3 of tongue
X Vagus
XI Accessory
XII Hypoglossal

111
Q

Explain the cerebrospinal fluid route.

A 
Choroid plexus 
Lateral ventricles
Foramina of Munro
Third ventricle
Aqueduct of Sylvius
Fourth ventricle
Foramina of Lushka (2, lateral) OR Magendie (1, medial) 
Subarachnoid space
Brain 
Arachnoid villi
112
Q

Where is CSF formed?

A

Choroid plexuses of lateral, third, and fourth ventricles

113
Q

Where is CSF reabsorbed?

A

Arachnoid villi

114
Q

Name the major vessels supplying the circle of Willis.

A

Right and left internal carotids + Basilar artery (supplied by the right and left vertebral arteries)

115
Q

Define stump pressure.

A

Measures the pressure transmitted through the circle of Willis back to the carotid artery for which endarterectomy is proposed
Good stump pressure (> 60 mmHg) - brain will be perfused adequately during procedure
Stump pressures are as reliable as EEG monitoring (gold standard) in predicting cerebral ischemia during cross-clamp application in CEA - and are more cost-effective
Too many false positives with stump pressures

116
Q

Effects of General Anesthetics on CBF & CMRO2

Volatile Agents

A

Increases CBF - Halothane the most, Isoflurane the least

Decreases CMRO2

117
Q

Effects of General Anesthetics on CBF & CMRO2

Nitrous Oxide

A

Increases CBF

Increases CMRO2

118
Q

Effects of General Anesthetics on CBF & CMRO2

With the exception of Ketamine, IV general anesthetics…

A

Decrease CBF

Decrease CMRO2

119
Q

Effects of General Anesthetics on CBF & CMRO2

Ketamine

A

Increases CBF

Increases CMRO2

120
Q

Blood supply to the spinal cord.

A

One anterior spinal artery - 75%
Two posterior spinal arteries - 25%
Eight segmental/radicular arteries (arise from the intercostal and lumbar arteries) - 1 cervical, 2 thoracic, 1 lumbar - anterior and posterior at each site

121
Q

Artery of Adamkiewicz

aka the great radicular artery (GRA)

A

The largest radicular artery
Enters the vertebral canal from the LEFT side
It is NOT bilateral
Enters in the lower thoracic or upper lumbar region
Joins the anterior spinal artery b/t T8 and T12 (75%)
Joins the anterior spinal artery b/t L1 and L2 (10%)
*It may be the major source of blood to the lower 2/3rds of the spinal cord
Interruption of flow = paraplegia
Becomes an issue with repair of the distal descending thoracic aorta

122
Q

The 2 posterior spinal arteries are formed from the anastomoses of the ________ and __________.

A

Posterior branch of the vertebral artery
Second posterior radicular artery
*Supplies 25% of the blood to the spinal cord

123
Q

Decorticate vs. Decebrate Rigidity

A

Decorticate:
Damage to brain above cerebellum and brainstem (supratentorial)
Upper extremity flexion & lower extremity extension

Decerebrate: 
Damage to or compression on brainstem 
Arms extended, adducted, and pronated
Legs extended with plantar flexion of the fee
Body arched, clenched teeth
Mechanical ventilation required
124
Q

What is normal ICP?
What is Cushing’s triad?
At what ICP does focal ischemia occur? Global ischemia?

A

< 15 mmHg
S/S of Cushing’s triad are seen with SLIGHT elevations in ICP

Cushing’s triad: HTN, bradycardia, irregular respirations - late sign of increased ICP

Focal ischemia: 25-55 mmHg
Global ischemia: > 55 mmHg

125
Q

Where is the pituitary gland located?

A

Housed in the sella turcica

Found in the sphenoid bone

126
Q

You are concerned about the risk of venous air embolism with a craniotomy in the sitting position.
Describe the proper positioning of a single-orifice catheter and a multi-orifice catheter for optimal air entrapment.

A

Single-orifice: 3 cm ABOVE the SVC-atrial junction

Multi-orifice: 2 cm BELOW the SVC-atrial junction

127
Q 
Time from birth until fontanelles close. 
Anterior
Posterior
Anteolateral
Posterolateral
A

Anterior: 18 mo
Posterior: 2 mo
Anteolateral: 2 mo
Posterolateral: 2 years

128
Q

Which cranial nerve controls motor activity of the larynx and pharynx?

A

CN X - 10 - Vagus

129
Q

What is cerebral blood flow in mL/min?

As a % of CO?

A

750 mL/min
15% of CO
Ischemia when CBF falls to about 50% of normal

130
Q

What is the formula for cerebral blood flow?

A

CBF = CPP/CVR

131
Q

What is the formula for cerebral perfusion pressure?

A

CPP = MAP - ICP (or RAP if it is higher than ICP)

132
Q

Name 3 things that alter cerebral vascular resistance.

A
  1. PaCO2 (CBF will increase 1 mL/100g/min for each 1 mmHg increase in PaCO2)
  2. PaO2 (when it falls below 50 mmHg)
  3. Temp (7% decrease in CBF & CMR for each 1 deg C decrease)
133
Q

What is the single most important determinant of cerebral blood flow? In other words, the most potent vasodilator of the cerebral vascular system?

A

PaCO2

CBF is proportional to PaCO2 when PaCO2 varies b/t 20 and 80 mmHg

134
Q

What is the only IV anesthetic that dilates the cerebral vasculature and increases CBF by 50%?

135
Q

Does metabolic acidosis or alkalosis alter CBF?

A

NO - ions do NOT cross the BBB

136
Q

What % of the intracranial volume is occupied by brain, blood, and CSF?

A

Brain: 80%
Blood: 12%
CSF: 8%

137
Q

What is papilledema?

A

Edema of the optic disk as a result of increased ICP

Involves the CN II - 2 - Optic

138
Q

What are the 3 ICP waveforms?

A
  1. A waves aka plateau waves - indicate increased ICP
  2. B waves
  3. C waves
    * B and C waves are of lesser magnitude than A waves
139
Q

Name 3 potent cerebral vasoconstrictors.

A
  1. Thiopental
  2. Etomidate
  3. Propofol
140
Q

Rank the common therapies to reduce increased ICP from FASTEST to SLOWEST.

A
  1. Hyperventilation (immediate)
  2. Mannitol (15 min)
  3. Lasix (30 min)
  4. Dexamethasone
141
Q

How does Mannitol decrease brain swelling?

A

Sugar similar to glucose
Cannot permeate the cerebral capillary
Exerts a high osmotic pressure across the cerebral capillary wall

142
Q

What are some adverse effects of Mannitol?

A

Pulmonary edema if poor LV function
Rebound increase in ICP if BBB disrupted
Electrolyte abnormalities - hyper/hyponatremia
Does NOT alter serum glucose levels

143
Q

What is the specific gravity of CSF?
What is the rate of formation of CSF?
What is the volume of CSF?

A

1.003-1.009
500-700 mL/day
150 mL (subarachnoid space = 25 mL)

144
Q

What is the most common site of obstruction leading to hydrocephalus?

A

Aqueduct of Sylvius

145
Q

Name 3 regions of the brain with NO BBB.

A
  1. Chemoreceptor trigger zone
  2. Capillaries of the choroid plexus
  3. Posterior pituitary
146
Q

Name the 2 tracts that transmit impulses from the motor cortex to the spinal cord.

A
  1. Pyramidal Tract aka corticospinal tract

2. Extrapyramidal Tract (basal ganglia, cerebellum, and brainstem to spinal cord) - posture and involuntary movement

147
Q

In acute spinal shock, what happens to BP, SVR, and HR?

A

Decreased BP & SVR

Decreased HR

148
Q 
Autonomic Hyperreflexia 
When does this occur? 
Why does this occur? 
Associated with lesions located where? 
S/S? 
What anesthetic technique is effective for prevention? 
What is the treatment?
A

Follows the period of spinal shock (1-3 weeks)

Results from reflex stimulation (bladder, bowel, any pain) of the sympathetic preganglionic neurons below the level of a spinal cord lesion

Associated with a lesion at or ABOVE T6

HTN, bradycardia, cutaneous vasoconstriction BELOW the injury, cutaneous vasodilation ABOVE the injury

Spinal anesthesia is effective in prevention

Tx: removal the stimulus, deepen anesthetic, Nipride

149
Q

Excessive brain dopamine is associated with what disease?

Diminished brain dopamine is associate with what disease?

A

Excessive brain dopamine - Schizophrenia

Diminished brain dopamine - Parkinson’s

150
Q

List 4 anesthetic concerns for patients with multiple sclerosis.

A
  1. Anesthesia, esp. spinal, may exacerbate the disease
  2. Avoid elevations in temp
  3. Supplement with steroids
  4. Sux may cause hyperkalemia
151
Q

When the seizure threshold increases, is the patient more or less likely to have a seizure?

A

Seizure threshold increases = less likely to have a seizure

152
Q

Does alkalosis increase or decrease the seizure threshold?

A

Decreases the seizure threshold = more likely to have a seizure

153
Q

Name 2 metabolic factors and 4 electrolyte disorders that decrease the seizure threshold.

A
  1. Hypoglycemia
  2. Hypocapnia/hyperventilation
  3. Hypocalcemia
  4. Hypomagnesemia
  5. Hyponatremia (TURP syndrome)
  6. Hypernatremia
154
Q 
Venous Air Embolism 
When is there a risk? 
S/S
Treatment 
Where should the Doppler be placed for detection?
A

When a negative pressure gradient exists between the RA and the veins at the operative site (sitting, beach chair)

Increased dead-space, end-tidal nitrogen, decrease in end-tidal CO2, increase in PaCO2, decrease in PaO2, hypotension, tachycardia, “millwheel” murmur

Tx: flood the field, turn off N2O, administer 100% O2, aspirate CVC, give fluids, vasopressors, horizontal position
*If laparoscopic surgery, halt insufflation of gas and place in left lateral position with a slight head down tilt (Durant maneuver)

Doppler - over the RA, 3-6th intercostal spaces, to the right of the sternum

155
Q

What would you do if a cerebral aneurysm was to rupture intra-op?

A 
Aggressive fluids/blood 
Controlled hypotension (MAP 40-50 mmHg) - Nipride, labetalol, esmolol
156
Q

What drugs are associated with increased resistance to NDMR?
What condition is associated with increased resistance to NDMR?

A

Antiepileptic drugs

Burns

157
Q

What 4 drugs should be avoided in the patient with Parkinson’s disease on L-DOPA?

A
  1. Droperidol
  2. Metoclopramide
  3. Prochlorperazine
  4. Alfentanil - possibly
  • These patients may also be on a MAO-B inhibitor, selegiline
  • Sux may cause hyperkalemia
158
Q

What can be given to treat the droperidol-induced extrapyramidal reactions?

A

Diphenhydramine

159
Q

What 4 drugs are prohibited in the patient taking an MAO-I?

Isocarboxazid, Phenelzine, Pargyline, Tranylcypromine

A
  1. TCA (imipramine)
  2. Meperidine
  3. Ephedrine
  4. Fluoxetine

*Reversal of depression is produced by inhibition of MAO-A

160
Q

List concerns with tricyclic antidepressants.

A

Anticholinergics (atropine, scopolamine) could increase the risk of central anticholinergic syndrome
Anticipate exaggerated pressor responses
Incidence of dysrhythmias with inhaled agents may be increased
Respiratory depression with opioids may be exaggerated

161
Q

Why are sodium levels important in a patient taking lithium?

A

LOW sodium will decrease renal excretion of lithium…leading to toxicity

*Concurrent treatment with lithium and a diuretic can cause lithium toxicity

162
Q

All eye muscles are innervated by Oculomotor CN 3 EXCEPT which 2 muscles?

A
  1. Lateral rectus - Abducens CN 6

2. Superior oblique - Trochlear CN 4

163
Q

What nerve stimulates the sneeze reflex?

A

Trigeminal CN 5

The BIG Test (21 decks)

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