Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

6. Neurology (Med) > Clinical Aspects of Cerebral Perfusion and ICP > Flashcards

Clinical Aspects of Cerebral Perfusion and ICP Flashcards

1
Q

What percentage of cardiac output goes to the brain?

A

15%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the perfusion of the brain in ml/100g/min?

A

55-60ml/100g brain tissue per minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does grey matter and white matter blood flow differ?

A

Grey matter blood flow is 75ml/100g/min, white matter is around 45ml/100g/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

At what perfusion does ischaemia occur?

A

Ischaemia occurs at 20ml/100g/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

At what perfusion does permanent damage occur?

A

Permanent damage results when the blood flow drops below 10ml/100g/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the most significant factor that determines cerebral blood flow?

A

Most significant factor that determines cerebral blood flow at any given time is cerebral perfusion pressure (CPP):

  • Is the effective blood pressure gradient across the brain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does CPP stand for?

A

Cerebral perfusion pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What formula describes cerebral perfusion pressure?

A

CPP = MAP – ICP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does increased ICP impact CPP?

A

Increased ICP causes decreased CPP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are some factors that regulate cerebral blood flow under physiological conditions?

A
  • CPP
  • Concentration of arterial CO2
  • Arterial PO2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is cerebral autoregulation?

A

Ability to maintain constant blood flow to the brain over a wide range of CPP (50-150mmHg)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Over what range of mmHg does cerebral autoregulation work?

A

50-150mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens when CPP is low for cerebral autoregulation?

A
  • Cerebral arterioles dilate to allow adequate flow at the decreased pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens when CPP is high for cerebral autoregulation?

A
  • Cerebral arterioles constrict
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Under certain pathological conditions, cerebral blood flow cannot always be autoregulated. What are some examples?

A
  • Hypertension
    • If CPP exceeds 150mmHg such as in hypertensive crises the autoregulatory system fails
  • Exudation of fluid from the vascular system with resultant vasogenic oedema
  • Toxins such as CO2 can cause diffuse cerebrovascular dilation and inhibit proper autoregulation
  • During first 4 to 5 days of head trauma many patients experience a disruption in cerebral autoregulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Cerebral oedema is a prominent cause of what?

A

Subacute to chronic intracranial hypertension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is cerebral oedema?

A

State of increased brain volume as a result of an increase in water content

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are he different kinds of cerebral oedema?

A
  • Vasogenic oedema (extracellular oedema)
  • Cytotoxic oedema (intracellular oedema)
  • Interstitial oedema
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is vasogenic oedema also called?

A

Extracellular oedema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is cytotoxic oedema also called?

A

Intracellular oedema

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Compare and contrast the pathogenesis of each type of cerebral oedema?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Compare and contrast the location of each type of cerebral oedema?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Compare and contrast the composition of oedema fluid of each type of cerebral oedema?

A
24
Q

Compare and contrast the ECF (increasd/decreased) of each type of cerebral oedema?

A
25
Q

Compare and contrast the effect of steroids on each type of cerebral oedema?

A
26
Q

Compare and contrast the effect of mannitol on each type of cerebral oedema?

A
27
Q

What does BBB stand for?

A

Blood brain barrier

28
Q

What is the blood brain barrier?

A

A barrier composed of astrocytic foot process wrapping around a capillary endothelium composed of tight junctions

29
Q

Can all substances carried in the blood reach the neural tissue?

A

No, the blood brain barrier stops them

30
Q

What protects the brain from substances that can normally passively cross capillaries?

A

Endothelial tight junctions

31
Q

What are mechanisms by which materials may be transported naturally across the endothelial cells of the blood brain barrier?

A
  • Lipid soluble substances
    • Can usually penetrate all capillary endothelial cell membranes in a passive manner
  • Amino acids and sugars
    • Transported across the capillary endothelium by specific carrier-mediated mechanisms
32
Q

What is the total volume that makes up ICP and what is this composed of?

A
33
Q

Wha is the Monro-Kellie Doctrine?

A

Describes the relationship between the contents of the cranium and intracranial pressure, in non-pathological states 3 components exist in equilibrium to maintain normal intracranial pressure, the brain tissue, the blood and the cerebrospinal fluid

34
Q

What percentage of cranial volume is composed of brain tissue?

A

70%

35
Q

What are the contents of the cranium?

A

Brain tissue

BLood

Cerebrospinal fluid

36
Q

In line with Monro-Kellie Doctrine, what must happen when a new intracranial mass is introduced to the cranium?

A

Compensatory change in volume must occur through a reciprocal decrease in venous blood of CSF to keep the total intracranial volume constant

37
Q

What is compliance?

A

Change in volume for a given change in pressure

dV/dP

38
Q

What is elastance?

A

Inverse of compliance

Elastance = change in pressure for a given change in volume

dP/dV

Represents the accommodation to outward expansion of an intracranial mass

39
Q

Describe the homeostatic mechanisms that means initial changes in cranium volume produce small changes in pressure?

A

Venous system collapses easily and squeezes venous blood out through the jugular veins or through the emissary and scalp veins

CSF can be displaced from the ventricular system through the foramina of Luschka and Magendie into the spinal subarachnoid space

40
Q

What happens ones compensatory mechanism to keep cranium pressure change low with volume change have been exhausted?

A

Small changes in volume produce significant increases in pressure

41
Q

What are the 3 distinct peaks of ICP waveforms?

A
  • Percussion wave
  • Tidal wave
  • Dicrotic wave
42
Q

What is A?

A

Percussion wave

43
Q

What is B?

A

Tidal wave

44
Q

What is C?

A

Dicrotic wave

45
Q

What test is done to determine high or flow CSF?

A

ICP pressure monitoring

46
Q

What are Lundberg waves?

A

Repetitive changes in intracranial pressure occurring at frequencies of 0.5 to 2 waves/min

47
Q

What are the different kinds of ICP waveforms?

A

A waves:

  • Abrupt elevation in ICP for 5 to 20 minutes followed by rapid fall in pressure to resting levels
  • The amplitude may reach as high as 50 to 100mmHg

B waves:

  • Frequency of 0.5 to 2 waves per minutes, are related to rhythmic variations in breathing

C waves:

  • Rhythmic variations related to waves of systemic blood pressure and have small amplitude
48
Q

What are A waves?

A
  • Abrupt elevation in ICP for 5 to 20 minutes followed by rapid fall in pressure to resting levels
  • The amplitude may reach as high as 50 to 100mmHg
49
Q

What are B waves?

A
  • Frequency of 0.5 to 2 waves per minutes, are related to rhythmic variations in breathing
50
Q

What are C waves?

A
  • Rhythmic variations related to waves of systemic blood pressure and have small amplitude
51
Q

What is the frequency of B waves?

A

0.5 to 2 waves per minute

52
Q

What can the amplitude of A waves reach?

A

50 to 100mmHg

53
Q

What is Cushing’s reflex?

A

Physiological nervous system response to increased intracranial pressure that results in Cushing’s triad of increased blood pressure, irregular breathing and bradycardia

54
Q

What does Cushing’s reflex cause?

A
  • Compression of cerebral arterioles
  • Decreased CBF, activation of autonomic nervous system
  • Sympathetic response
    • Alpha-1 adrenergic receptors causing hypertension and tachycardia
  • Aortic baro-receptors stimulate vagus nerve causing bradycardia
  • Bradycardia is also due to mechanical distortion of medulla
55
Q

What is the management of increased ICP?

A

Head end elevation to facilitate venous return

Mannitol/hypertonic saline

Hyperventilation to decreased CBF (temporary measure)

Barbiturate coma to decrease cerebral metabolism and CBF

Surgical decompression

56
Q

What are some newer concepts for the investigation of ICP?

A

Brain tissue oxygenation monitoring:

  • Probe to monitor oxygenation of tissue
  • Detect and treat low oxygenation, increasing CPP

Micro-dialysis:

  • Investigate brain metabolism
  • Implantation of specially designed catheters
  • To collect small-molecular-weight substances to help measure and identify neurotransmitters, peptides and other substances

6. Neurology (Med) (47 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions