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15 Cards in this Set
- Front
- Back
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How soon after an interruption in cerebral perfusion will unconsciousness occur?
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In < than 10 seconds as oxygen tension drop below 30 mm Hg
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How much CO & at what rate does the brain receive?
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Brain receives 15- 20% of CO or approx 50ml/100g/min
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Where does the brain’s blood supply originate?
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The anterior circulation receives blood from the carotid arteries & the posterior circulation from the vertebral arteries.
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Average CBF per minute in an adult =
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750ml/min
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What rate of CBF will the produce a flat EEG (isoelectric activity)?
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A CBF @ 15 – 20 ml/100g/min
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What is isoelectric neutrality?
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Isoelectric neutrality --> no AP, neurons need very little oxygen and this results in a flat EEG.
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Why would we produce a state of isoelectric neutrality?
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We want very little metabolic demand (thus less blood flow) in this area so the surgeon can operate on area. Deep anesthetics can achieve this.
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How is regulation of CBF achieved?
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By CPP, autoregulation &
extrinsic mechanisms. |
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What is the primary determinant of CPP
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MAP.
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Vessels in the brain like a tight pressure range. What is this range
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80-100 mm Hg
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How does the brain autoregulate CPP?
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By vasoconstriction and vasodilation.
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How does ICP correlate to RAP?
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ICP reflects the pressure in the head which is also reflected distally by the pressure in the RA.
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What is the most important extrinsic influence on CBF?
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PaCO2. CBF is directly proportionate to PaCO2 between 20 and 80 mm Hg
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In normal individuals CBF remains constant at what MAP range?
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When MAP is kept at 60 -160mm Hg. At MAPs > than 160, CBF slopes upward in direct proportion to increase in MAP (a right shift). Autoregulation of CBF stops at this point.
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How long will it take to deplete the brain's ATP stores causing irreversible brain injury?
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3-8 mins under most conditions
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