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Neuro (Wolfe 2024) > Cerebral hemodynamic, CBF, and ICP > Flashcards

Cerebral hemodynamic, CBF, and ICP Flashcards

1
Q

3 main components of the intracranial vault:

A

Cerebral spinal fluid 10-15%
Brain 80-85%
Blood 5-10%

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2
Q

CSF is produced by the _____ _____ in the ventricles.

A

Choroid plexus

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3
Q

CSF flow in the brain: Pneumonic

A

Lateral ventricles
Monroe (foramen)
3rd ventricle
Sylvia’s (aqueduct)
4th ventricle
Luschka
Magendie

“Love My 3 Silly 4 Lorn Magpies”

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4
Q

Properties of CSF: % of intracranial volume,
____cc produced per 24hrs
CSF volume = _____

A

10% of intracranial volume
500cc produced per 24hrs
CSF volume is ~ 150ml at any given time

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5
Q

Purpose of CSF:

A

“maintains an environment in which the brain can function by regulating pH and electrolytes, carrying away waste products, and delivering nutrients.”

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6
Q

Increases CSF volume:

A

Choroid Plexus Papilloma
Hyperthermia
Decreased serum osmolality
Increased CSF osmolality

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7
Q

Decrease CSF volume:

A

Hypothermia
Increased hydrostatic pressure
Diamox
Increased serum osmolality
Decreased CSF osmolality

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8
Q

Blood supply of Brain:___-___% of intracranial volume (__-___mL)

A

5-10%
60-80ml

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9
Q

Circle of Willis:
_______ arteries provide the _____ cerebral circulation
Bifurcates into the external and internal carotid arteries
The ______ branch enters the base of the skull
Arterial supply of the eye via the ______ _____.
Ultimately bifurcates into the _____ and ______ cerebral arteries.

A

Carotid
anterior
internal
ophthalmic artery
anterior and middle

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10
Q

The posterior circulation results from the ____ ______.

A

vertebral arteries

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11
Q

Largest artery in the brain?

A

-Middle cerebral artery

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12
Q

Venous blood drains into the _____ _____which lie between the layers of the _______ and drain into the ______ _____ _____.

A

venous sinuses
dura mater
internal jugular vein

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13
Q

Venous System: Sinuses are _______ and blood can flow…..
Pressure within them is _____ (_______ ______).
_______ influenced. (little influence of autonomic)

A

valveless
back and forth
negative (air embolism)
Chemically

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14
Q

BBB: junctions are _____.
Allows passage of _______ _____ substances but restricts the movement of _____ or _____ _____ _____ substances

A

tight
lipid soluble
ionized or large molecular weight

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15
Q

BBB: Water enters how?

A

By bulk flow

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16
Q

BBB disrupted by:

A

Severe HTN, Tumors, Trauma, Stroke, Infection
High PaCO2, Hypoxia, and sustained Seizures.

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17
Q

BBB: allows for passage/transport of-

A

small molecules (H2O, O2, CO2)
lipophilic molecules (EtOH, heroin)
passive transport of glucose
active transport of amino acids

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18
Q

BBB: prevents passage of:

A

large molecules (dopamine)
charged (ionized) molecules

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19
Q

Many factors affect CBF because of their effect on metabolism:
Stimulation, arousal, nociception, and mild hyperthermia _____cerebral metabolism and flow.

Sedative-hypnotic agents, and hypothermia _____ both metabolism and flow.

A

elevate
decrease

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20
Q

DANGEROUS CBF FLOWS:

Less than 30ml/100gm/min = ______
Less than 20ml/100gm/min =____ ____ ____
Less than 15ml/100gm/min = ______ ______

A

ISCHEMIA
ABNORMAL EEG (INFARCT)
IRREVERSIBLE DAMAGE

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21
Q

In general, increased _______ leads to increased CBF.

A

CMRO2

22
Q

CPP=……….

A

MAP-ICP or CVP (which ever is greater)

23
Q

Normal CPP range:
Cerebral Perfusion Pressure (CPP) determines ___.

A

70-100 mmHg
CBF

24
Q

Normal ICP= __-___ mmHg
significance of a raised ICP is two fold:
-it will _____ cerebral perfusion
-it will cause ____ and ____ of cerebral content

A

10-15
-decrease
-distortion and displacement

25
Q

CBF at __-__ (MAP) mmHg remains constant

A

60-150

26
Q

Loss of Autoregulation occurs with:

A

Acidosis
Hypoxia
Trauma
Volatile anesthetics (less so with Forane)

27
Q

3 types of compensation for ICP:

A
  1. CSF Regulation
  2. Cerebral Blood Flow-Auto Regulation
  3. Metabolic-Auto Regulation
28
Q

CSF regulation for ICP:

A

Compensation: ↓ CSF production or ↑ CSF absorption

29
Q

Monro-Kelly Doctrine:

A

ICP is stable as long as volume added is balanced by volume displaced

30
Q

Metabolic-Auto Regulation:
Compensation-

A

The balance of acid/base & oxygenation –
Vasoconstriction or vasodilation of cerebral vessels to ↓ or ↑ blood supply to brain in effort to rid the brain of waste products as needed

31
Q

Metabolic-Auto Regulation:
Decompensation-

A

Hypoxia (↓ oxygen) and Acidosis (↑ carbon dioxide) triggers vasodilation
Blood supply increases trying to “wash away“ the waste product of carbon dioxide BUT a compromised brain can’t handle the ↑ blood supply causing increased ICP and build up of lactic acid

32
Q

What is a potent cerebral vasodilator?

A

PaCO2

If you double PaCO2, you double CBF

33
Q

CBF changes by ~__%for each __mmHg change in Paco2

A

4%
1mmHg

Also- CBF changes 1-2 ml/100g/min per mmHg change in PaCO2

34
Q

Decreased pH →→→→ ________ CBF
(__________) (_________)

Increased pH →→→→ _________ CBF
(_________) (_____________)

A

Decreased pH →→→→ Increased CBF
(acidosis) (vasodilation)

Increased pH →→→→ Decreased CBF
(alkalosis) (vasoconstriction)

35
Q

The brain uses ____-____% of the O2 consumption of the body

A

15-20%

36
Q

An increase in CMRO2, such as with convulsions, increases………

A

CBF up to 50%

37
Q

_________ will decrease CMRO2

A

Anesthesia

38
Q

The primary substrate for the brain is ______.

A

glucose

39
Q

**Approximately ___-___% of glucose is obtained via an oxidative pathway
Without ___ no glucose is utilized

A

85-90%
O2

40
Q

There is a ________ in CBF with a decrease in body temperature.

A

decrease

41
Q

________ decreases both CBF and CMRO2

A

Hypothermia

42
Q

_______ increases both CBF and CMRO2.

A

Hyperthermia

43
Q

There is a___% decrease in CMRO2 with an __ºC temperature decrease. CVR _____ with cooling which will decrease your CBF.

A

50%
8
increases

44
Q

Other Control of CBF:
Age -

Trendelenberg -

Anemia -

Increased blood viscosity -

PEEP -

A

Age - decrease in brain mass and a decrease in CBF

Trendelenberg - increases CBF

Anemia - increases CBF

Increased blood viscosity - decreases CBF

PEEP - decreases CBF (Fine line between keeping alveoli open and CBF)

45
Q

IV Agents: Generally all ↓ CBF and CMRO2 except _______.

A

Ketamine

Ketamine ↑ CBF & CMRO2.
Prior administration of thiopental or benzodiazepines can blunt ketamine-induced increases in CBF. Blocks CSF absorption

46
Q

Minimal to no change in CBF, CMRO2, & ICP:

A

Narcotics

47
Q

…………do not appear to have clinically significant direct effects on CBF or CMRO2, provided MAP is not altered after administration.

A

Nondepolarizing neuromuscular relaxants

48
Q

Which paralytic can elevate ICP?

A

Succinylcholine

49
Q

__________ at 1 MAC depresses CSF production up to 40%

A

Sevoflurane

50
Q

Inverse Steal or Robin Hood Phenomenon:

A

A vasoconstriction caused by hypocapnia will cause a reduced blood flow to the normal responsive regions of the brain resulting into redistribution of blood to ischemic regions. This is called, “Robin Hood Phenomenon” or the “inverse- steal”.

The inverse steal redistributes more CBF to ischemic areas

TRAUMA PATIENTS!

Neuro (Wolfe 2024) (7 decks)

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