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AP Summer > Anesthesia for Neurosurgery > Flashcards

Anesthesia for Neurosurgery Flashcards

1
Q

During all neurosurgery cases, how will the head be in relation to anesthesia?

A

90* away from you

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2
Q

How many fingers should you leave between the mandible and sternum and/or clavicle to ensure proper venous drainage?

A

2 fingers to avoid kinking of jugular veins

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3
Q

Generally speaking, the tube goes too deep or becomes too shallow after positioning?

A

Too deep

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4
Q

With C spine flexion, where does the tip of ETT migrate to?

A

Caudally, or towards carina

causes endobronchial intubation

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5
Q

With C spine extension and/or rotation, where does the tip of ETT migrate to?

A

Cranially

closer to the vocal chords so could extubate

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6
Q

What are some of the rules concerning blood loss in neurosurgery?

A
    • Blood loss difficult to estimate

- - Can lose lots of blood during closing

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7
Q

With IV fluids in neurosurgery, what must be taken into account?

A
  • -Minimal third spacing
    • Minimal evaporation
    • Only give enough to maintain cardiac stability
    • Avoid hyperglycemia
    • Avoid hyper/hypo natremia
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8
Q

What are the two main diuretics that are used to decrease the brain’s water content?

A

Mannitol

Lasix

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9
Q

Of the hyper and hypo natremia (which are things to avoid during neurosurgery) which is the detrimental to the patient?

A

Hyponatremia
(water movement in/out of the brain is controlled by Na shifts, hyponatremia causes large amounts to enter, thus resulting in brain edema)

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10
Q

The brain looks at what aspect of IV fluids to determine effect?

A

Osmolarity

brain does not care about the oncotic pressure of fluids

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11
Q

What is the normal value for osmolarity of human plasma?

A

295 mOsm / L

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12
Q

What is the IV fluid we give that is 273 mOsm / L ?

A

Lactated ringers

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13
Q

Normal saline has what osmolarity?

A

308 mOsm / L

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14
Q

20% mannitol has what osmolarity?

A

1098 mOsm / L

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15
Q

What is the IV fluid we give that is 290 mOsm / L ?

A

Albumin

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16
Q

Is brain tissue sensitive to pain?

A

NO

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17
Q

Because brain tissue is not sensitive to pain, when are the only times that anesthesia needs to be deep?

A

Opening and closing

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18
Q

Ideally, the patient needs to be fully awake and full consciousness how long after closing of tissue?

A

20-30 min

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19
Q

What is CBF?

A

Cerebral blood flow

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20
Q

CBF accounts for how much of CO?

A

20%

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21
Q

How much does average human brain weigh?

A

1500 grams

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22
Q

What is the average CBF of an adult?

A

40-50 ml/100gram/minute

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23
Q

What is known as critical CBF?

A

18 mL / 100 gm

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24
Q

What percentage of CBF does grey matter receive?

White matter?

A

G M: 80%

W M: 20%

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25
Q

What is the new target for EtCO2 ?

A

Low 30’s

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26
Q

Between what MAP values ensures the brain is adequately perfused?

A

50 - 150 mmHg

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27
Q

For the normal autoregulatory curve associated with MAP and CBF, what causes a right shift?

A

Choric hypertension

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28
Q

For the normal autoregulatory curve associated with MAP and CBF, what causes a left shift?

A

Vasodilators such as inhaled anesthetics

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29
Q

What 2 types of ischemia can occur in brain?

A

Global

Focal

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30
Q

What is known to cause global ischemia?

A
    • Cardiac arrest
    • Severe hypotension
    • Hypoxia (normal BP but without O2
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31
Q

How is focal ischemia defined or described?

A
    • Temporary or permanent

- - Partial or complete arterial obstruction

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32
Q

A stroke is a kind of what focal ischemia?

A

Permanent

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33
Q

A TIA is a kind of what focal ischemia?

A

Temporary

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34
Q

What is known to cause focal ischemia?

A
    • Stenosis
    • Vasospasm
    • Embolus
    • Clip
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35
Q

What is the best inhaled anesthetic because it decreases CMRO2 while not affecting CBF?

A

Isoflurane

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36
Q

Halothane used to be used as an inhaled anesthetic until it was found to have what effect?

A

Large increase in CBF that caused brain to become congested and full

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37
Q

What is the only IV drug given that decreases CMRO2 but increases CBF?

A

Ketamine

so do use this drug during brain surgery

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38
Q

When treating a hypertensive patient during neurosurgery, what is best drug to use?

A

Labetolol

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39
Q

When treating a hypertensive patient during neurosurgery, what 2 drugs do you not want to use?

A

Nitroglycerine
Nitroprusside
Both increase ICP - CBF ratio

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40
Q

What is ICP?

A

Intracranial pressure

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41
Q

What is a normal ICP?

A

10 - 15 mmHg

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42
Q

What is the reference point for measurement of ICP?

A

Tragus of ear

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43
Q

Moderately increased ICP is what?

A

20-40 mmHg

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44
Q

What is any ICP that is > 40 mmHg?

A

Severely increased ICP

45
Q

What is the most aggressive and invasive way to measure ICP?

A

Ventriculostomy

46
Q

What is the least aggressive means to measure ICP and is used with patients with coagulopathic disorders?

A

Subdural bolt

47
Q

What to mechanisms regulate ICP?

A
    • Shift of CSF from cranium to spinal cord

- - Shift of blood from cranium to spinal canal

48
Q

What risks does an elevated ICP present?

A
    • Decrease in CPP
    • Herniation of brain tissue
    • Inadequate exposure
    • Retractor’s Ischemia
49
Q

What is CPP?

A

Cerebral perfusion pressure

50
Q

How is CPP determined?

A

CPP = MAP - ICP

51
Q

Of the 4 most common sites for herniation, what is the most often occurring?

A

– number 4

herniation out of opened skull either from trauma or surgical removal

52
Q

Of the 4 most common sites for herniation, what is the most deadly?

A

– number 3

Herniation of cerebellum

53
Q

What is the main goal of ICP management?

A

Prevention of further increases in ICP

54
Q

What is brain tissue called?

A

Parenchyma

55
Q

What is brain tissue?

A

Parenchyma

56
Q

What does parenchyma consist of?

A
    • Brain cells and myelin
    • Intracellular fluid
    • Extracellular fluid
57
Q

Which component of parenchyma responds well to steroids?

A

Extracellular fluid

58
Q

What are the three main components of intracranial contents?

A
    • Parenchyma
    • Blood
    • CSF
59
Q

What are the 2 types of components of intracranial contents that respond and compensate to changes in pressure very quickly?

A
    • Blood

- - CSF

60
Q

An increase in intracellular fluids is due to what?

A
    • Acute hyponatremia

- - Physical cellular damage

61
Q

An increase in interstitial water (extracellular fluid) is due to what?

A
    • Venous engorgement
    • Hypertension
    • Hypervolemia
62
Q

What causes both intra and extra cellular fluid decreases?

A
    • Diuretics (mannitol)
    • Encouragement of venous drainage
    • Decadron (only for tumors)
63
Q

How does mannitol increase urine output?

A

Mannitol stays in the vasculature and is filtered by the kidneys so has no reuptake. This causes an increase in urine because filtered mannitol takes large volumes of fluid with it

64
Q

T OR F? Cerebral blood flow and cerebral blood volume are not the same

A

TRUE

65
Q

What is CBV?

A

Cerebral blood volume

66
Q

What is normal CBV?

A

150 mL

75% of which is in venous system

67
Q

What helps determine amount of venous drainage from the head?

A
    • Gravity
    • Head position
    • Intra-thoracic pressure
68
Q

Will ICP increase or decrease with jugular compression?

A

Increase

69
Q

If you have a venous obstruction, what will happen in the acute setting?

A

An increase the CBV and subsequently will increase ICP (monitor closely)

70
Q

If you have a venous obstruction, what will happen long term?

A

Increase edema which will lead to a decrease in CSF absorption to decrease ICP

71
Q

What is the normal CSF?

A

75 - 100 mL

72
Q

What are the basic principles concerning drugs used during neuroanesthesia?

A
    • Want prompt recovery
    • Minimal barbiturates
    • Propofol good
    • Short acting narcotics
    • Moderate concentrations of inhalational anesthetics
    • Avoid Succyinycholine in patients with hyperkalemia and recent strokes (because succ will increase ICP)
73
Q

What are the other basic principles to follow besides drugs in neuroanesthesia?

A
    • Proper positioning to encourage venous drainage
    • Clear airway
    • Proper use of muscle relaxants
    • Proper IV Fluids
74
Q

What is the cutoff to treat hyperglycemia?

A

nothing over 180

75
Q

What are the goals for emergence ?

A
    • No coughing
    • No hypertension
    • Prompt recovery and awakening
    • Minimal hypercarbia
76
Q

What would be some reasons for a neurosurgical patient to not wake up?

A
    • SUrgical problems such as hemorrhage, tension pnemocephalus, seizures, strokes
    • Hypercarbia ( Anything over 70)
77
Q

What patients are not expected to wake up quickly?

A
    • Acute subdural hematoma
    • Closed head injury
    • Surgery on frontal lobe
    • Surgery around brain stem
78
Q

Intracranial Aneurysms are what and occur most often where?

A

– Dilation of the blood vessel that tends to be located around bifurcation of arteries

– Are in 2% of population

79
Q

What is SAH?

A

Sub arachnoid hemorrhage

when the aneurysm ruptures

80
Q

What 2 detrimental outcomes are brought on by a SAH?

A
    • Rebleeding

- - Vasospasm’s

81
Q

What are optimal days you can operate on a SAH patient?

A
    • 1 to 3 days after initial hemorrhage
    • > 14 days after hemorrhage

(because of vasospasm likelihood, you cannot operate between 3-14 days)

82
Q

What grading scale is used for classifying neurological status?

A

Hunt grading scale
1 = good
5 = Very bad

83
Q

What hunt grades can you extubate the patient?

A

Hunt scales 1-2

84
Q

What hunt grades are not extubatable?

A

Grades 4-5

85
Q

What hunt grade allows practitioner to use judgement and clinical signs as to whether to extubate the patient or not?

A

Grade 3

86
Q

What are some important pre-anesthetic evaluation things to remember for aneurysms?

A
    • Hunt grade
    • Number of aneurysms
    • Vasospasms or not
    • Hydrocephalus
    • Serum sodium levels
87
Q

There are 2 types of hyponatremia that could present, what are they?

A

– SIADH

– Cerebral Salt Wasting Syndrome

88
Q

What is SIADH?

A

Hyponatremic state in which patient is making too much ADH which causes patient to retain fluid and dilute Na.

–Goal is to restrict fluids

89
Q

What is Cerebral Salt Wasting Syndrome?

A

Hyponatremic state in which patient is secreting too much water and thus secreting Na.

– Goal is to give fluids

90
Q

What type of monitors are needed for aneurysm clippings?

A

–ASA std
– 2 16g IVs
– A line
– CVP or SG catheter
(double lumen is better for giving fluids because has 2 14 gauges compared to the triple lumen which has 1 16g and 2 18g)
– Intra-op angiography

91
Q

What is the one main thing you want to avoid in patients presenting for aneurysm repair?

A

HYPERTENSION

92
Q

How much will a 1*C drop equate to loss in CBF?

A

5-7%

93
Q

Focal ischemia will always occur during what clipping phase?

A

Placement of temporary clips

94
Q

What do you want to give/do during a temporary clip placement?

A
    • Hypertension
    • CNS depressant
    • Mild hypocarbia
95
Q

Aneurysm ruptures occur in how many cases?

A

15-20%

96
Q

What is the goal when an aneurysm ruptures?

A
    • Keep up with blood loss
    • Controlled hypotension
    • Barbiturates (particularly propofol)
    • Adenosine (to stop heart if surgeon cannot control bleeding and needs no flow for short period of time)
97
Q

What things can we do to decrease O2 consumption of the brain to protect it?

A
    • Induced hypothermia (~34*C)

- - Drugs (Isoflurane, Propofol)

98
Q

What things can we do to increase focal blood flow of the brain to protect it?

A
    • Hypertension

- - Hypocarbia

99
Q

What is the 2nd leading cause of morbidity and mortality and has an incidence of 30 - 45%?

A

Vasospasm

100
Q

What drugs are given to treat cerebral vasospasm?

A
    • Nimodipine (Ca blocker)
    • Mg. Sulfate
    • Hypervolemia, Hypertension, Heamodilution after clipping
101
Q

What is an alternative approach to aneurysm repair that is much less invasive and is done in Interventional radiology?

A

Thrombogenic wire placement

Coiling

102
Q

Who are not candidates for the coiling procedure?

A
    • Pt with wide neck aneurysm

- - Pt who has no access to neck of aneurysm

103
Q

What is an AVM?

A

Arterio-venous malformation

104
Q

Where are most AVM’s found?

A

90 % supratentorial

mostly in the cortex

105
Q

What is AVM?

A

Where the arteries and veins are directly connected without having capillaries and capillary beds between them

106
Q

What are some signs and symptoms of AVM?

A
    • Headaches (number 1 symptom)
    • Seizures
    • Bleeding
    • Focal ischemia
107
Q

What are the courses of treatment for AVM?

A
    • Embolization to make less bloody
    • Followed by resection

– Gamma knife used for unresectable locations (uses targeted focused radiation to knock out AVM)

108
Q

What are some general assumptions for AVM?

A
    • Protracted and massive blood loss
    • No vasospasm
    • Bleeding occurs into parenchyma
    • Hyperperfusion (b/c body must compensate for lack of area around resected AVM)
    • Want to keep Blood pressure low post -op
    • Want to have normal blood volume post -op
109
Q

What are some general assumptions for aneurysms?

A
    • Blood loss minimal unless rupture
    • High incidence of vasospasm
    • Bleeding occurs into sub arachnoid space
    • No incidence of hyperperfusion
    • Want to keep blood pressure high post -op
    • Want to keep blood volume high post -op

AP Summer (24 decks)

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