Neuro Flashcards
(163 cards)
1
Q
What are the 2 tracts included in the Dorsal-Lemniscal System?
Are these sensory or motor tracts?
A
- Cuneatus
- Gracilis
*Sensory - touch, pressure, and vibration
Located in the posterior/dorsal cord (SAD)
2
Q
SSEP monitoring evaluates what tracts?
A
The Dorsal-Lemniscal System
- Cuneatus
- Gracilis
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
4
Q
What is the most “direct route” to the sensory cortex for touch, pressure, and vibration?
A
The Dorsal-Lemniscal System
- Cuneatus
- Gracilis
5
Q
The _________ serves as an “indirect route” by which sensory info reaches the cerebral cortex.
A
The Reticular Activating System
6
Q
What is the function of the Reticular Activating System?
A
Maintain the alert/awake state
7
Q
General anesthetics produce sedation and hypnosis by depressing the _____________.
A
Reticular Activating System
8
Q
Complete loss of RAS activity =
A
Coma
9
Q
Name 4 nerves that may be stimulated to elicit SSEPs.
Where are SSEPs recorded from?
A
- Tibial
- Median
- Ulnar
- Radial
SSEPs are recorded from the scalp
Stimulating electrode is placed peripherally
Detecting electrode is placed centrally
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
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
12
Q
What 2 characteristics are monitored by SSEPs?
A
- Latency - time it takes to arrive at the cerebral cortex
2. Amplitude - magnitude or size of the potential
13
Q
With SSEP monitoring, what 2 things would indicate damage is occurring in the neural pathway being monitored?
A
- Increase in latency
2. Decrease in amplitude
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!)
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!
- Temp - high or low
- BP - low, below cerebral auto-regulation levels
- PaCO2 - low d/t its affect on CBF
* Hyperventilation - vasoconstriction of vessels —Decrease ICP (good) BUT decrease BF (bad) - PaO2 - low
- Fluid balance - isovolemic hemodilution, Hct < 15%
Altered temp affects SEPs the most!
Hemodilution affects SEPs the least
16
Q
Brainstem auditory evoked potentials (BAEP) monitor the integrity of CN ________.
A
VIII - 8 - Vestibulocochlear
17
Q
Visual evoked potentials (VEP) monitor the integrity of CN _________.
A
II - 2 - Optic
* Useful for pituitary resections, transsphenoidal
18
Q
List the 3 types of evoked potentials in order from very sensitive to least sensitive.
A
- VEP - very
- SSEP - somewhat
- BAEP - barely
19
Q
EEG Waveforms
List the 4 waveform types along with their frequencies.
A
- Delta: 0-4 Hz *Lowest frequency, greatest amplitude
- Theta: 4-8 Hz
- Alpha: 8-12 Hz
- Beta: >12 Hz *Highest frequency, lowest amplitude
20
Q
EEG Waveforms
Describe the typical brain activities associated with the 4 types of waveforms.
A
- Delta - deep sleep
- Theta - THE lighter side
- Alpha - awake, but resting
- Beta - BE awake!
21
Q
What MAC correlates with an isoelectric EEG pattern?
A
1.5-2 MAC
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
23
Q
All anesthetic agents except ________ depress SSEPs to a varying degree.
A
Muscle relaxants
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
25
How does nitrous oxide affect SSEP?
Causes a decrease in amplitude WITHOUT an increase in latency
26
Flow through what spinal arterial vessels is monitored by SSEPs?
Posterior spinal arteries
*Arterial blood flow to spinal cord - 1 anterior, 2 posterior, segmental/radicular arteries
27
Why is the "wake-up" test performed?
To check spinal motor pathways - anterior/ventral spinal cord integrity (anterior spinal artery perfusion)
28
What agents will NOT alter BIS?
Opioids or analgesics
Nitrous oxide (alone)
Ketamine (may slightly increase BIS)
29
What 2 fibers conduct pain and temp?
1. A-delta
| 2. dC
30
Characteristics of A-delta Fibers
```
Myelinated
Larger diameter
"First" or "fast" pain
Discriminative
Sharp, stinging, pricking
Duration of pain coincides with duration of stimulus
Somatic
```
31
Characteristics of dC Fibers
```
Unmyelinated
Smaller diameter
"Second" or "slow" pain
Diffuse, persistent
Throbbing, burning, aching
Duration of pain > than duration of stimulus
Visceral
```
32
Where are the cell bodies of A-delta and dC fiber afferents found?
Dorsal root ganglion
33
Explain the pathway for fast-sharp pain.
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
34
Explain the pathway for slow-chronic pain.
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
35
What is the ascending sensory spinal cord tract carrying pain and temp?
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)
36
Substantia Gelatinosa = which Rexed's lamina?
II
| Or III ?
37
What is the major NT released from A-delta fibers?
| What receptor does this NT bind to on the postsynaptic membrane?
Glutamate
| AMPA & NMDA
38
What is the major NT released from dC fibers?
| What receptor does this NT bind to on the postsynaptic membrane?
Substance P
| Neurokinin-1
39
The Anterolateral System contains what 2 tracts?
| Are these tracts sensory or motor?
1. Lateral spinothalamic tract - ascending sensory tract
2. Ventral spinothalamic tract
These are sensory tracts!
40
What is the Dorsolateral Fasciculus/Funiculus/Tract?
A descending tract that modulates pain
41
What sensations are blocked in the lateral columns by epidural or spinal anesthesia?
Lateral columns - lateral spinothalamic tract - pain and temp
42
```
Dermatome Landmarks
Clavicle
Nipples
Xiphoid
Umbilicus
Tibia
Perineum
```
```
Clavicle - C4
Nipples - T4
Xiphoid - T6
Umbilicus - T10
Tibia - L4-5
Perineum - S2-S5
```
43
Which spinal nerve has no sensory component...it is purely motor?
C1
44
What is the site where pain impulses are attenuated?
Substantia gelatinosa (RL II, III)
45
What NT may be considered the "gate" in the gate control theory of pain?
Explain this.
Enkephalin
Enkephalin-releasing interneurons synapse on the substance P-releasing nerve terminal
This decreases the release of substance P = perception of pain is decreased
46
Describe spinal analgesia as a result of opioid administration in the intrathecal or epidural space.
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
47
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.
Alters the patient's perception of pain
Mu-1, Mu-2, kappa, delta
Dominant - Mu-2
Substantia gelatinosa
Periventricular/periaquaductal gray
48
Morphine is hydrophilic - water loving!
| What is the significance of this in regards to intrathecal and epidural placement?
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)
49
Fentanyl, Alfentanil, Sufentanil are lipophilic - lipid loving!
(Fentanyl loves Fat!)
What is the significance of this in regards to intrathecal and epidural placement?
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)
50
Ventilatory depression is most pronounced after intrathecal or epidural placement of opioid?
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
51
```
Supraspinal Analgesia
Describe.
What receptors?
Dominant receptor?
Results from the action of opioids in the _________ after IV administration.
```
Alters the patient's response to pain - "I don't care"
Mu-1, kappa, delta
Dominant - Mu-1
Limbic system, hypothalamus, thalamus
52
Describe spinal analgesia as a result of brain control of the substantia gelatinosa.
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
53
Opioids produce analgesia in 3 ways...
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
54
Where is the somatosensory cortex?
Postcentral gyrus
55
Responses to Opioid Receptor Stimulation
| Mu-1, Mu-2, Kappa, and Delta share what in common?
All produce spinal analgesia
| *Primary receptor for spinal analgesia - Mu-2
56
Responses to Opioid Receptor Stimulation
| All receptors EXCEPT ______ produce supraspinal analgesia.
Mu-2
| *Primary receptor for supraspinal analgesia - Mu-1
57
Responses to Opioid Receptor Stimulation
| What 2 receptors produce respiratory depression?
1. Mu-2 - mainly
2. Delta
* These 2 receptors also both have a high abuse/physical dependence risk
58
Responses to Opioid Receptor Stimulation
| What receptor causes bradycardia?
Mu
59
Responses to Opioid Receptor Stimulation
| What receptor causes euphoria? Dysphoria?
Euphoria - Mu-1
| Dysphoria - Kappa
60
Responses to Opioid Receptor Stimulation
| What 2 receptors have high abuse/physical dependence risk?
1. Mu-2
2. Delta
* These 2 receptors also both cause respiratory depression
61
Responses to Opioid Receptor Stimulation
| What receptor causes urinary retention? Diuresis?
Urinary retention - Mu-1
| Diuresis - Kappa
62
Responses to Opioid Receptor Stimulation
| What receptor causes constipation?
Mu-2
| minimal Delta
63
Responses to Opioid Receptor Stimulation
| What receptor causes pruritus?
Mu-1
64
Describe how opioid agonist-antagonist (Nalbuphine) work.
Antagonist or partial agonist - Mu
Agonist - Kappa (mainly) and Delta
*Analgesia withOUT severe respiratory depression
Can be used to reverse opioid-induced respiratory depression
65
The spinothalamic tract is severed at C2 on the right. What will happen?
Loss of pain and temp transmission on the left at all sensory dermatomes below C2
66
What are 2 types of nociceptive pain?
1. Somatic
| 2. Visceral
67
Define neuropathic pain.
Abnormal processing of painful stimuli
Initiated by a primary lesion or dysfunction in the nervous system
"Pathophysiological" pain
68
Which nerve fibers appear to be affected by epidural steroids?
Unmyelinated C fibers
69
Since s/s of complex regional pain syndrome type I and type II are identical, what differentiates CRPS type I from type II?
There is a documented nerve injury preceding CRPS type II
70
Epidural steroid injections
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
What is the major inhibitory NT of the CNS?
GABA
72
GABA opens channels to what ion?
Chloride
| *Causes hyperpolarization of neurons
73
How does a patient with acidosis change the properties of thiopental?
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
Why will thiopental have a pronounced effect in a patient with liver disease and hypoalbuminemia?
72-86% of thiopental is bound to albumin
| Larger portion of free/unbound/effective drug
75
How are the actions of general IV anesthetics terminated?
Redistribution
76
Things to know about barbiturates.
Methohexital
Thiopental
Thiamylal
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
Where dose Ketamine work?
NMDA-type glutamate receptors
78
Rank opioids from MOST to LEAST lipid soluble.
```
Sufentanil
Fentanyl
Alfentanil
Meperidine
Remifentanil
Morphine
```
79
The grey matter of the spinal cords is divided into...
10 lamina
Known as Rexed's laminae
Opioids work at lamina II (substantia gelationosa)
80
What opioid has a significant negative inotropic effect and a positive chronotropic effect?
Meperidine
81
How do opioids produce bradycardia?
Opioids stimulate the vagal nucleus in the medulla
| Increases vagal impulses to the heart
82
Do opioids increase or decrease the release of ADH?
Decrease
83
Your patient is complaining of angina pectoris. Disregarding a cardiac etiology, what else should you consider?
What is the treatment?
Opioid-induced spasm of the sphincter of Oddi
Naloxone, nitroglycerine, glucagon
84
What 3 things increase the possibility of skeletal muscle rigidity with opioids?
What receptors are at fault?
1. Large dose
2. Raid infusion
3. Concomitant use of nitrous oxide
Mu receptors
85
Which opioid has the smallest VD?
| What does this mean?
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
What 2 opioids release histamine?
1. Morphine
| 2. Meperidine
87
What is the most common side effect of intrathecal opioids?
Pruritus
Then urinary retention, N/V, and respiratory depression
88
Rank opioids from SHORTEST to LONGEST elimination half-life with continuous administration.
```
Remifentanil
Alfentanil
Morphine
Sufentanil
Meperidine
Fentanyl
*Fentanyl loves FAT! Meaning it is lipid soluble - large VD
```
89
Which has a shorter duration of action: morphine or fentanyl?
Fentanyl
| *Fentanyl has a longer elimination half-life than morphine d/t its large VD with a continuos infusion
90
Name an opioid competitive antagonist.
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
What is the duration of action of Naloxone?
60 min
92
Rank opioids from MOST to LEAST potent.
```
Sufentanil
Remifentanil
Fentanyl
Alfentanil
Morphine
Meperidine
```
93
Name 2 phenylpiperidine derivatives.
1. Meperidine
| 2. Fentanyl
94
What drug class should be avoided in a patient with heroin addiction taking methadone?
Opioid agonist-antagonist
95
During posterior fossa surgery, bradycardia and HTN suddenly occur. What nerve is being stimulated?
CN V - 5 - Trigeminal
| Pressure on the brainstem
96
During posterior fossa surgery, bradycardia and hypotension suddenly occur. What nerve is being stimulated?
CN IX - 9 - Glossopharyngeal
| OR CN X - 10 - Vagus
97
What is a concern with tumors or surgery around the glossopharyngeal or vagus nerve?
Impaired gag reflex
| Increased risk of aspiration
98
Name a common post-op complication following a transsphenoidal or transcranial procedure for tumor removal.
Diabetes insipidus
99
```
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?
```
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
Name 3 anesthetic goals for intracranial aneurysm surgery.
1. Avoid rupture with abrupt increases in BP
2. Maintain CPP
3. Provide "slack" brain (mannitol, lasix, hyperventilate)
101
What is transmural pressure?
| What is the significance in regards to a cerebral aneurysm?
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
What IV fluids should be avoided in neuro cases?
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
Cerebral blood flow remains constant/auto-regulated between what pressures?
50-150 mmHg
| Changing perfusion pressure does NOT normally alter CBF
104
What is the goal PaCO2 during a craniotomy - provide max intracranial decompression with minimal risk of cerebral ischemia?
25-30 mmHg
105
Why is controlled hypotension (MAP 50-70 mmHg) extremely useful for aneurysm surgery? Name 2 reasons.
1. Decreasing MAP reduces transmural pressure - rupture less likely
2. Decreases blood loss and improves visualization
106
What is the only volatile anesthetic recommended for production of deliberate hypotension?
Isoflurane
107
Describe intracerebral steal syndrome (aka luxury perfusion).
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
The spinal nerve root is connected to the paravertebral sympathetic ganglia by...
White and gray rami communicans
White rami carry myelinated preganglionic sympathetic neurons
Gray rami carry unmyelinated postganglionic sympathetic neurons (type sC fibers)
109
Where is the epidural space located in relation to the ligamentum flavum?
The epidural space is anterior to the ligamentum flavum.
110
Name the cranial nerves and their functions.
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
Explain the cerebrospinal fluid route.
```
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
Where is CSF formed?
Choroid plexuses of lateral, third, and fourth ventricles
113
Where is CSF reabsorbed?
Arachnoid villi
114
Name the major vessels supplying the circle of Willis.
Right and left internal carotids + Basilar artery (supplied by the right and left vertebral arteries)
115
Define stump pressure.
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
Effects of General Anesthetics on CBF & CMRO2
| Volatile Agents
Increases CBF - Halothane the most, Isoflurane the least
| Decreases CMRO2
117
Effects of General Anesthetics on CBF & CMRO2
| Nitrous Oxide
Increases CBF
| Increases CMRO2
118
Effects of General Anesthetics on CBF & CMRO2
| With the exception of Ketamine, IV general anesthetics...
Decrease CBF
| Decrease CMRO2
119
Effects of General Anesthetics on CBF & CMRO2
| Ketamine
Increases CBF
| Increases CMRO2
120
Blood supply to the spinal cord.
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
Artery of Adamkiewicz
| aka the great radicular artery (GRA)
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
The 2 posterior spinal arteries are formed from the anastomoses of the ________ and __________.
Posterior branch of the vertebral artery
Second posterior radicular artery
*Supplies 25% of the blood to the spinal cord
123
Decorticate vs. Decebrate Rigidity
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
What is normal ICP?
What is Cushing's triad?
At what ICP does focal ischemia occur? Global ischemia?
< 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
Where is the pituitary gland located?
Housed in the sella turcica
| Found in the sphenoid bone
126
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.
Single-orifice: 3 cm ABOVE the SVC-atrial junction
Multi-orifice: 2 cm BELOW the SVC-atrial junction
127
```
Time from birth until fontanelles close.
Anterior
Posterior
Anteolateral
Posterolateral
```
Anterior: 18 mo
Posterior: 2 mo
Anteolateral: 2 mo
Posterolateral: 2 years
128
Which cranial nerve controls motor activity of the larynx and pharynx?
CN X - 10 - Vagus
129
What is cerebral blood flow in mL/min?
| As a % of CO?
750 mL/min
15% of CO
Ischemia when CBF falls to about 50% of normal
130
What is the formula for cerebral blood flow?
CBF = CPP/CVR
131
What is the formula for cerebral perfusion pressure?
CPP = MAP - ICP (or RAP if it is higher than ICP)
132
Name 3 things that alter cerebral vascular resistance.
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
What is the single most important determinant of cerebral blood flow? In other words, the most potent vasodilator of the cerebral vascular system?
PaCO2
| CBF is proportional to PaCO2 when PaCO2 varies b/t 20 and 80 mmHg
134
What is the only IV anesthetic that dilates the cerebral vasculature and increases CBF by 50%?
Ketamine
135
Does metabolic acidosis or alkalosis alter CBF?
NO - ions do NOT cross the BBB
136
What % of the intracranial volume is occupied by brain, blood, and CSF?
Brain: 80%
Blood: 12%
CSF: 8%
137
What is papilledema?
Edema of the optic disk as a result of increased ICP
| Involves the CN II - 2 - Optic
138
What are the 3 ICP waveforms?
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
Name 3 potent cerebral vasoconstrictors.
1. Thiopental
2. Etomidate
3. Propofol
140
Rank the common therapies to reduce increased ICP from FASTEST to SLOWEST.
1. Hyperventilation (immediate)
2. Mannitol (15 min)
3. Lasix (30 min)
4. Dexamethasone
141
How does Mannitol decrease brain swelling?
Sugar similar to glucose
Cannot permeate the cerebral capillary
Exerts a high osmotic pressure across the cerebral capillary wall
142
What are some adverse effects of Mannitol?
Pulmonary edema if poor LV function
Rebound increase in ICP if BBB disrupted
Electrolyte abnormalities - hyper/hyponatremia
Does NOT alter serum glucose levels
143
What is the specific gravity of CSF?
What is the rate of formation of CSF?
What is the volume of CSF?
1.003-1.009
500-700 mL/day
150 mL (subarachnoid space = 25 mL)
144
What is the most common site of obstruction leading to hydrocephalus?
Aqueduct of Sylvius
145
Name 3 regions of the brain with NO BBB.
1. Chemoreceptor trigger zone
2. Capillaries of the choroid plexus
3. Posterior pituitary
146
Name the 2 tracts that transmit impulses from the motor cortex to the spinal cord.
1. Pyramidal Tract aka corticospinal tract
| 2. Extrapyramidal Tract (basal ganglia, cerebellum, and brainstem to spinal cord) - posture and involuntary movement
147
In acute spinal shock, what happens to BP, SVR, and HR?
Decreased BP & SVR
| Decreased HR
148
```
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?
```
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
Excessive brain dopamine is associated with what disease?
| Diminished brain dopamine is associate with what disease?
Excessive brain dopamine - Schizophrenia
| Diminished brain dopamine - Parkinson's
150
List 4 anesthetic concerns for patients with multiple sclerosis.
1. Anesthesia, esp. spinal, may exacerbate the disease
2. Avoid elevations in temp
3. Supplement with steroids
4. Sux may cause hyperkalemia
151
When the seizure threshold increases, is the patient more or less likely to have a seizure?
Seizure threshold increases = less likely to have a seizure
152
Does alkalosis increase or decrease the seizure threshold?
Decreases the seizure threshold = more likely to have a seizure
153
Name 2 metabolic factors and 4 electrolyte disorders that decrease the seizure threshold.
1. Hypoglycemia
2. Hypocapnia/hyperventilation
1. Hypocalcemia
2. Hypomagnesemia
3. Hyponatremia (TURP syndrome)
4. Hypernatremia
154
```
Venous Air Embolism
When is there a risk?
S/S
Treatment
Where should the Doppler be placed for detection?
```
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
What would you do if a cerebral aneurysm was to rupture intra-op?
```
Aggressive fluids/blood
Controlled hypotension (MAP 40-50 mmHg) - Nipride, labetalol, esmolol
```
156
What drugs are associated with increased resistance to NDMR?
What condition is associated with increased resistance to NDMR?
Antiepileptic drugs
Burns
157
What 4 drugs should be avoided in the patient with Parkinson's disease on L-DOPA?
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
What can be given to treat the droperidol-induced extrapyramidal reactions?
Diphenhydramine
159
What 4 drugs are prohibited in the patient taking an MAO-I?
| Isocarboxazid, Phenelzine, Pargyline, Tranylcypromine
1. TCA (imipramine)
2. Meperidine
3. Ephedrine
4. Fluoxetine
*Reversal of depression is produced by inhibition of MAO-A
160
List concerns with tricyclic antidepressants.
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
Why are sodium levels important in a patient taking lithium?
LOW sodium will decrease renal excretion of lithium...leading to toxicity
*Concurrent treatment with lithium and a diuretic can cause lithium toxicity
162
All eye muscles are innervated by Oculomotor CN 3 EXCEPT which 2 muscles?
1. Lateral rectus - Abducens CN 6
| 2. Superior oblique - Trochlear CN 4
163
What nerve stimulates the sneeze reflex?
Trigeminal CN 5
