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Clinical Decisions Final > Neuro > Flashcards

Neuro Flashcards

1
Q

Between what PaCO2 pressures is CBF directly related?

A

20-80mmHg

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2
Q

How much does CBF change per 1mmHg PaCO2?

A

1-2mL/100g/min

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3
Q

How much does CBF change per degree celcius?

A

5-7%

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4
Q

How cool is a patient kept during CPB?

A

30-32* C

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5
Q

What kind of drugs can cross the BBB?

A

small, lipophilic, uncharged

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6
Q

What causes rupture of cerebral aneurysm?

A

rapid changes in pressure (up or down)

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7
Q

List contents and percentages of the cranial vault

A

brain 80%, blood 12%, CSF 8%

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8
Q

What are two equations for CPP?

A

MAP - ICP (or CVP)

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9
Q

What’s an ideal CPP?

A

60-70mmHg

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10
Q

Which IV induction drugs increase CMRO2?

A

ketamine

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11
Q

Which IV induction drugs increase CBF?

A

none

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12
Q

Which volatile can cause isoelectric EEG?

A

isoflurane (think isoelectric)

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13
Q

Hypertonicity of blood causes movement of H2O into/out of brain

A

out of

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14
Q

Describe the relationship between PaO2 and CBF

A

CBF is 50ml/100g/min for all PaO2 values above 50mmHg

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15
Q

What is total CSF volume?

A

~150cc

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16
Q

How long does hypercapnia/hypocapnia effect the brain? Why?

A

~24hr; CO2 crosses the BBB and HCO3- does not until about 24hr

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17
Q

Severe hypoxemia would have what effect on CBF?

A

hypoxemia causes a drastic increase in CBF after PaO2 drops below 50mmHg

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18
Q

What is the most important determinant of blood viscosity? how does it affect CBF?

A

hematocrit; decreased viscosity increases CBF (though decreases ability to deliver oxygen to cells)

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19
Q

Optimal cerebral O2 delivery occurs at a Hct of ___.

A

~30%

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20
Q

Why does mannitol cause a transient increase in CBF?

A

It causes an increase in circulating blood volume from other cells of the body

21
Q

What are the advantages/disadvantages of mannitol vs lasix?

A

mannitol decreases brain water volume (lasix does not); mannitol causes a transient increase in ICP as water from other cells enters the systemic circulation (lasix does not)

22
Q

Which IV induction agents are capable of producing burst suppression?

A

barbs, etomidate, propofol

23
Q

Which IV induction agents can cause EEG electrical silence at high doses?

A

barbs, etomidate, propofol

24
Q

Which volatile can produce burst suppression and at what MAC?

A

des (>1.2MAC), sevo (>1.5MAC)

25
Q

Which test assesses which part of the spinal cord: anterior/posterior, SSEP/MEP

A

anterior - MEP, posterior - SSEP

26
Q

Spinal cord perfusion is best assessed with which test? why?

A

MEP; because it assesses the anterior portion of the spinal cord (where the supplying arteries are located)

27
Q

Which type of evoked potential is most affected by anesthetic agents?

A

visual evoked potential

28
Q

Which type of evoked potential is not affected by anesthetic agents?

A

brain stem auditory evoked potentials

29
Q

Opioids have what effect on EEG?

A

depression

30
Q

How do you treat cerebral vasospasm?

A

“triple H” - hemodilute ~30% Hct, HTN 160-180mmHg systolic, hypervolume 12-14 CVP

31
Q

What is the advantage of electric silence in the brain? what is the limitation?

A

electrical silence eliminates the metabolic cost of electrical activity (~60% of overall O2 consumption), however it has no effect on basal energy requirements

32
Q

Among the drugs that cause electrical silence, why are barbs preferred?

A

they affect all areas of the brain equally

33
Q

The brain consumes what percent of total body O2?

A

20%

34
Q

At what CBF is cell function deranged?

A

<10ml/100g/min

35
Q

Vasopressors have what effect on CBF?

A

none, unless MAP was below 50-60mmHg or above 150-160mmHg

36
Q

Why is lidocaine used in neuro as an anesthetic adjunct?

A

it decreases CBF (by increasing CVR) without any other significant hemodynamic effects

37
Q

What are the effects of barbs on the CNS?

A

sedation, depression of CMRO2, reduction of CBF (due to increased CVR), anticonvulsant activity

38
Q

When might a venous air embolism occur?

A

whenever the wound is above the heart (pressure in vein is sub-atmospheric)

39
Q

CBF is autoregulated between what MAPs?

A

60-160mmHg

40
Q

What could be the effect of MAP above 160mmHg?

A

cerebral edema, hemorrhage

41
Q

What is a normal ICP?

A

10mmHg or less

42
Q

What is “luxury perfusion?” What is circulatory steal phenomenon?

A

Luxury perfusion is the decreased CMRO2 combined with increased CBF (O2 supply) seen with volatiles. Circulatory steal is when vasodilation only effects non-ischemic areas (ischemic areas are already maximally dilated), and results in a redistribution of blood flow to non-ischemic areas.

43
Q

Opioids have what effect on CMRO2 and ICP?

A

minimal, unless PaCO2 rises secondary to respiratory depression

44
Q

What is Cushing’s Triad?

A

Hypertension, bradycardia, irregular breathing (signs of dangerously high ICP)

45
Q

What ICP would be considered elevated?

A

sustained P over 15

46
Q

What is the equation for CBF?

A

CBF = CPP/CVR

47
Q

Describe where you might find a cerebral aneurysm?

A

usually seen around the circle of Willis, most commonly at bifurcations (anterior communicating 30%, posterior communicating 25%, middle cerebral 20%)

48
Q

What typically triggers a breath, hypoxia or hypercapnia?

A

Hypercapnia

Clinical Decisions Final (4 decks)

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