Cerebral hemodynamic, CBF, and ICP

Question 1

3 main components of the intracranial vault:

Answer 1

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

Question 2

CSF is produced by the _____ _____ in the ventricles.

Answer 2

Choroid plexus

Question 3

CSF flow in the brain: Pneumonic

Answer 3

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

“Love My 3 Silly 4 Lorn Magpies”

Question 4

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

Answer 4

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

Question 5

Purpose of CSF:

Answer 5

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

Question 6

Increases CSF volume:

Answer 6

Choroid Plexus Papilloma
Hyperthermia
Decreased serum osmolality
Increased CSF osmolality

Question 7

Decrease CSF volume:

Answer 7

Hypothermia
Increased hydrostatic pressure
Diamox
Increased serum osmolality
Decreased CSF osmolality

Question 8

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

Answer 8

5-10%
60-80ml

Question 9

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.

Answer 9

Carotid
anterior
internal
ophthalmic artery
anterior and middle

Question 10

The posterior circulation results from the ____ ______.

Answer 10

vertebral arteries

Question 11

Largest artery in the brain?

Answer 11

-Middle cerebral artery

Question 12

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

Answer 12

venous sinuses
dura mater
internal jugular vein

Question 13

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

Answer 13

valveless
back and forth
negative (air embolism)
Chemically

Question 14

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

Answer 14

tight
lipid soluble
ionized or large molecular weight

Question 15

BBB: Water enters how?

Answer 15

By bulk flow

Question 16

BBB disrupted by:

Answer 16

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

Question 17

BBB: allows for passage/transport of-

Answer 17

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

Question 18

BBB: prevents passage of:

Answer 18

large molecules (dopamine)
charged (ionized) molecules

Question 19

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.

Answer 19

elevate
decrease

Question 20

DANGEROUS CBF FLOWS:

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

Answer 20

ISCHEMIA
ABNORMAL EEG (INFARCT)
IRREVERSIBLE DAMAGE

Question 21

In general, increased _______ leads to increased CBF.

Answer 21

CMRO2

Question 22

CPP=……….

Answer 22

MAP-ICP or CVP (which ever is greater)

Question 23

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

Answer 23

70-100 mmHg
CBF

Question 24

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

Answer 24

10-15
-decrease
-distortion and displacement

Question 25

CBF at __-__ (MAP) mmHg remains constant

Answer 25

60-150

Question 26

Loss of Autoregulation occurs with:

Answer 26

Acidosis Hypoxia Trauma Volatile anesthetics (less so with Forane)

Question 27

3 types of compensation for ICP:

Answer 27

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

Question 28

CSF regulation for ICP:

Answer 28

Compensation: ↓ CSF production or ↑ CSF absorption

Question 29

Monro-Kelly Doctrine:

Answer 29

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

Question 30

Metabolic-Auto Regulation: Compensation-

Answer 30

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

Question 31

Metabolic-Auto Regulation: Decompensation-

Answer 31

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

Question 32

What is a potent cerebral vasodilator?

Answer 32

PaCO2 If you double PaCO2, you double CBF

Question 33

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

Answer 33

4% 1mmHg Also- CBF changes 1-2 ml/100g/min per mmHg change in PaCO2

Question 34

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

Answer 34

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

Question 35

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

Answer 35

15-20%

Question 36

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

Answer 36

CBF up to 50%

Question 37

_________ will decrease CMRO2

Answer 37

Anesthesia

Question 38

The primary substrate for the brain is ______.

Answer 38

glucose

Question 39

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

Answer 39

85-90% O2

Question 40

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

Answer 40

decrease

Question 41

________ decreases both CBF and CMRO2

Answer 41

Hypothermia

Question 42

_______ increases both CBF and CMRO2.

Answer 42

Hyperthermia

Question 43

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

Answer 43

50% 8 increases

Question 44

Other Control of CBF: Age - Trendelenberg - Anemia - Increased blood viscosity - PEEP -

Answer 44

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)

Question 45

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

Answer 45

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

Question 46

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

Answer 46

Narcotics

Question 47

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

Answer 47

Nondepolarizing neuromuscular relaxants

Question 48

Which paralytic can elevate ICP?

Answer 48

Succinylcholine

Question 49

__________ at 1 MAC depresses CSF production up to 40%

Answer 49

Sevoflurane

Question 50

Inverse Steal or Robin Hood Phenomenon:

Answer 50

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!