27A Ischemic Stroke Flashcards
TIA symptoms occur within what time frame?
1 hr
Non-modifiable stroke risk factors:
- Age (doubles each year after 55)
- Gender (M 1.5x > than F)
- Rcae (AA = 2x)
- Family hx
Modifiable stroke risk factors:
HTN DM hyperlipidemia Smoking Carotid a stenosis Afib Obesity Phys inactivity
What modifiable risk factors have a high relative risk? Which are more prevalent?
Afib (RR = 5-17)
HTN (RR=3-5)
HTN»_space; smoking, hyperlip, inactivity
2 conditions which exacerbate brain injury:
- hyperglycemia (increased lactic acid)
2. hyperthermia (accelerates damage)
What is core ischemia?
central area of ischemia (no collateral flow); tissue dies in <1hr, permanent damage
What is penumbra?
peripheral areas of moderate ischemia; tissue dies in 4-6h, so CAN be salvaged with intervention
Why does acute stroke intervention have a 4-6h time frame?
time from of the evolving ischemic infarct ~4-6h
Cerebral blood flow is proportionally related to:
MAP/CVR
*cerebral vasc resistance
The relationship between CBF and MAP for the normal individual is a sigmoid curve with a plateau of CBF between MAPs of ___ and ___ mm Hg.
What does this demonstrate?
55 and 155 mmHg
in this range, CBF is pretty independent of MAP
How does CBF change with daily activities?
in normal individuals, it doesnt
this is because CBF is pretty independent of MAP when in the normal range
What happens when the MAP falls below 55 or climbs above 155 mm Hg?
CBF becomes proportionally related to MAP
- -> syncope (if below 55)
- -> hypertensive encephalopathy (if above 155)
How does chronic HTN affect the CBF?
shifts to the R
(The critical point at which CBF becomes proportionately related to MAP has been raised from 55 to approximately 75 mm Hg)
How does chronic HTN change the effects of a low-end of nml MAP?
decreased CBF
What happens when CBF drops below 20?
brain tissue will develop an infarction
**ischemic tissue loses all autoreg control
Anterior circulation strokes involve occlusion of:
internal carotid, middle cerebral, anterior cerebral arteries or any of their branches