3. Physiology
        3.2. Cardiovascular
            3.2.5. Special circulations
                3.2.5.1. Cerebral blood flow
3.2.5.1.1. Cerebral perfusion

Cerebral perfusion

Cerebral perfusion

CBF = CPP/CVR
* CBR = Cerebral blood flow
* CPP = Cerebral perfusion pressure
* CVR = Cerebral vascular resistance

 

Factors affecting CBF via CVR

CVR affected by:

1. CBF vs CMRO2

CMRO2 = cerebral metabolic rate of oxygen consumption

2. CBF vs MABP

Between 50-60mmHg to 130-150mmHg

--> CBF stays constant
* i.e. curve is flat

Curve shifts to right

Due to:

Plateau moves up

Due to:

Neonate

3. CBF vs PaCO2

4. CBF vs PaO2

When PaO2>50-60 mmHg

--> No change in CBF with PaO2 changes
* because not much change in O2 content due to the shape of oxygen dissociation curve

When PaO2 <50-60 mmHg

--> CBF increase as PaO2 decreases
* because of the shape of ODC
* i.e.O2 content drops significantly and CBF increases to compensate

 

Factors affecting CBF via CPP

CPP = MABP - (ICP or JVP, whichever is higher)

However,

MABP is used as an index because

Thus,

Changes in MABP, ICP or JVP can affect CPP, and thus CBF

Role of sympathetic nervous system

e.g. carotid sinus baroreceptor reflex
--> Faster than pressure autoregulation of CBF via CVR

 

Other notes

Reduction in CBF may be beneficial because

 

 

 

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