Neuro

Question 1

Between what PaCO2 pressures is CBF directly related?

Answer 1

20-80mmHg

Question 2

How much does CBF change per 1mmHg PaCO2?

Answer 2

1-2mL/100g/min

Question 3

How much does CBF change per degree celcius?

Answer 3

5-7%

Question 4

How cool is a patient kept during CPB?

Answer 4

30-32* C

Question 5

What kind of drugs can cross the BBB?

Answer 5

small, lipophilic, uncharged

Question 6

What causes rupture of cerebral aneurysm?

Answer 6

rapid changes in pressure (up or down)

Question 7

List contents and percentages of the cranial vault

Answer 7

brain 80%, blood 12%, CSF 8%

Question 8

What are two equations for CPP?

Answer 8

MAP - ICP (or CVP)

Question 9

What’s an ideal CPP?

Answer 9

60-70mmHg

Question 10

Which IV induction drugs increase CMRO2?

Answer 10

ketamine

Question 11

Which IV induction drugs increase CBF?

Answer 11

none

Question 12

Which volatile can cause isoelectric EEG?

Answer 12

isoflurane (think isoelectric)

Question 13

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

Answer 13

out of

Question 14

Describe the relationship between PaO2 and CBF

Answer 14

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

Question 15

What is total CSF volume?

Answer 15

~150cc

Question 16

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

Answer 16

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

Question 17

Severe hypoxemia would have what effect on CBF?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

Optimal cerebral O2 delivery occurs at a Hct of ___.

Answer 19

~30%

Question 20

Why does mannitol cause a transient increase in CBF?

Answer 20

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

Question 21

What are the advantages/disadvantages of mannitol vs lasix?

Answer 21

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)

Question 22

Which IV induction agents are capable of producing burst suppression?

Answer 22

barbs, etomidate, propofol

Question 23

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

Answer 23

barbs, etomidate, propofol

Question 24

Which volatile can produce burst suppression and at what MAC?

Answer 24

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

Question 25

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

Answer 25

anterior - MEP, posterior - SSEP

Question 26

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

Answer 26

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

Question 27

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

Answer 27

visual evoked potential

Question 28

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

Answer 28

brain stem auditory evoked potentials

Question 29

Opioids have what effect on EEG?

Answer 29

depression

Question 30

How do you treat cerebral vasospasm?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

they affect all areas of the brain equally

Question 33

The brain consumes what percent of total body O2?

Answer 33

20%

Question 34

At what CBF is cell function deranged?

Answer 34

<10ml/100g/min

Question 35

Vasopressors have what effect on CBF?

Answer 35

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

Question 36

Why is lidocaine used in neuro as an anesthetic adjunct?

Answer 36

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

Question 37

What are the effects of barbs on the CNS?

Answer 37

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

Question 38

When might a venous air embolism occur?

Answer 38

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

Question 39

CBF is autoregulated between what MAPs?

Answer 39

60-160mmHg

Question 40

What could be the effect of MAP above 160mmHg?

Answer 40

cerebral edema, hemorrhage

Question 41

What is a normal ICP?

Answer 41

10mmHg or less

Question 42

What is "luxury perfusion?" What is circulatory steal phenomenon?

Answer 42

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.

Question 43

Opioids have what effect on CMRO2 and ICP?

Answer 43

minimal, unless PaCO2 rises secondary to respiratory depression

Question 44

What is Cushing's Triad?

Answer 44

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

Question 45

What ICP would be considered elevated?

Answer 45

sustained P over 15

Question 46

What is the equation for CBF?

Answer 46

CBF = CPP/CVR

Question 47

Describe where you might find a cerebral aneurysm?

Answer 47

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

Question 48

What typically triggers a breath, hypoxia or hypercapnia?

Answer 48

Hypercapnia