Neurologic Diseases (Exam III) Flashcards
What vessels provide the blood flow to the brain?
- 80% via the carotid arteries
- 20% via the vertebral arteries
Name the pertinent vasculature of the circle of Willis.
This card is just to look at the picture on the other side.
What factors affect cerebral blood flow?
- CMR (cerebral metabolic rate)
- CPP (cerebral perfusion pressure)
- ICP
- PaCO₂
- PaO₂
How much O₂ is required by the brain per minute?
3 mlO₂ / 100g / min
What is the average cerebral blood blow?
50ml/100g/min
What drugs and/or metabolic states will decrease CMR?
- Hypothermia
- Anesthetic drugs (VAA, prop, etomidate, etc)
What drugs and/or metabolic states will increase CMR?
- Hyperthermia
- Seizures
- Ketamine
- N₂O
What temperature range do we generally want to keep our patients in?
36 - 38° C
This card previously said 42 which is 107.6F lol
When is hypothermia mediated EEG suppression achieved?
18 - 20° C
Hypothermia will cause a ___% decrease for every 1°C decrease.
7
What would a temperature of > 42°C do to the brain?
Denature proteins and destroy neurons (↓CBF)
This is a crazy high temp
At what cerebral blood flow rates would one expect irreversible brain damage?
≤ 10ml/100g/min
How is Cerebral Perfusion Pressure (CPP) calculated?
CPP = MAP - ICP
How is MAP calculated?
MAP = DBP + ⅓(SBP - DBP)
At what CPP and MAP does the brain exhibit autoregulation (myogenic response) ?
CPP of 50 - 150 mmHg
MAP of 60 - 160 mmHg
With what pathologies/drugs is a loss of CPP seen?
- Brain tumors
- Head trauma
- Volatile anesthetics
What can cause a rightward shift in the brain autoregulation curve?
- Chronic HTN
- SNS activation
What can cause a leftward shift in the brain autoregulation curve?
Volatile anesthetics
Name the three components of the brain that form the Monroe-Kellie Doctrine.
- Brain 80%
- Blood 12%
- CSF 8%
What is the Monroe Kellie Doctrine?
Any increase in one component of the intracranial space (blood, brain tissue, CSF) must be met with an equivalent decrease in another to prevent increased ICP.
What is the normal CPP range?
80 - 100 mmHg
An ICP > ____ mmHg will compromise CPP.
30
What pathologic processes or disease states are known to cause an increase in ICP?
- Tumors
- Hematomas
- Blood in CSF
- Infection
- Aqueductal Stenosis
At what CPPs would one expect to see EEG slowing?
What about irreversible brain damage?
- EEG slowing: < 50mmHg
- Brain damage: < 25 mmHg
What are the two types of hydrocephalus? Which is more common?
- Obstructive (most common)
- Communicating
What would occur from PaO₂ levels of < 50-60 mmHg in the brain?
- Vasodilation
- ↑CBF
Severe hypoxia will have what effect on cerebral blood flow?
↓O₂ = ↑CBF
PaO₂ exhibits an _______ mechanism in the brain similar to intracranial MAP.
autoregulation
What levels of PaCO₂ are maintained in the brain?
20 - 80 mmHg
PaCO₂ levels are directly proportional to ______ of the cerebral vasculature.
vasodilation
Ex. ↑PaCO₂ = ↑dilation
A PaCO₂ increase of 1mmHg will correspond to an increase in CBF by how much?
1mmHg PaCO₂ increase = 1-2mls/100g/min increase in CBF.
A patient’s PaCO₂ is increased by 10mmHg, how much would you expect CBF to increase if the patients brain was measured to weigh 250g?
10mmHg x 1-2mls x 2.5 =
25 - 50 mls/min increase in CBF.
Someone check my math and the question itself.
At what PaCO₂ levels does max cerebral vasodilation occur?
80 - 100 mmHg
At what PaCO₂ levels does max cerebral vasoconstriction occur?
20 - 25 mmHg
What does increased central venous pressure do to the brain?
- ↓ venous drainage
- ↑ cerebral blood volume
What things will increase cerebral venous pressure?
- Jugular compression (cervical collar, head rotation, etc.)
- ↑ intrathoracic pressure (coughing, PEEP)
- Vena Cava thrombus
What range is normal for ICP?
5 - 15 mmHg
What symptoms are seen with abnormally high ICP?
- Headache
- N/V
- Papilledema
- ↓LOC