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130 Cards in this Set
- Front
- Back
The cranium is a rigid bony structure containing what?
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80% brain, water
12% blood 8% CSF |
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What artery supplies the vast majority of blood flow to the brain
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Internal carotid and basilar arteries (80%)
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Regional blood flow to the brain is how much?
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20-80ml/ 100g/min
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intercranial blood volume at any time is
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100-150 ml
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What is the amount of blood flow to the brain?
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40-50ml/ 100gm/min
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anterior circulation (80% of cerebral flow) is supplied by what?
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paired internal carotid arteries
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Posterior circulation (20%) of cerebral flow is supplied by what?
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vertebral arteries
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where do vertebral arteries arise?
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from subclavian arteries
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anastomotic circle of willis aries from
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carotid and vertebral arteries
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all major cerebral arteries are found where?
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subarachnoid space
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if your patient was showing hemiplegia on the contralateral side of the body, greater in the lower than the upper extremities, what arterial origin would you suspect?
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anterior cerebral artery
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if your patient was showing signs of aphasia in dominant hemisphere what arterial origin would you suspect.
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middle cerebral artery
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if your patient was showing signs of contralateral hemiplegia greater in the upper face and upper extremities than in the lower extremities, sensory loss, or visual loss what arterial origin would you expect
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Posterior cerebral artery
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What artery serves the basal ganglia, corpus callosum, medial surface of cerebral hemispheres, superior surface of frontal and parietal lobes
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anterior cerebral artery
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What artery serves the frontal lobe, parietal lobe, temporal lobe, (primarily the cortical surfaces)
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middle cerebral artery
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what artery supplies part of the diencephalon and temporal lobe, and occipital lobe
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posterior cerebral artery
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what lobe of the brain could be affected if you are having difficulty with abstract thinking? what artery supplies this area
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frontal lobe, anterior cerebral artery
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What lobe of the brian could be affected if you are having difficulty with somatic sensory things. What artery supplies this?
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Temporal lobe
Middle cerebral artery |
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What lobe of the brain may be affected if you are having problems with vision? What artery supplies this?
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occipital, posterior cerebral artery
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what are your main brain drains?
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internal jugular
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anytime you have a situation where the wound is higher than the heart and CVP goes down, what can occur?
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air can be entrained resulting in a venous air embolus
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What can a venous air embolus lead too?
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MI and Stroke
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your brian receives how much of your cardiac output?
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15%
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be able to label circle of Willis
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carotid, anterior cerebral, anterior communicating, posterior cerebral, posterior inferior cerebellar, middle cerebral, AICA, basilar, verterbrals, posterior comm.
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The circle of willis allows for what?
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collateral blood flow
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at any one time there is around how many ML of CSF
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150ml
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CSF is made at a rate of what?
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30ml/hr or 600-800 ml per day
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Explain the flow of CSF
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made it choroid plexus, secreted into the lateral ventricles, through the foramen of monroe, into the 3rd ventricle, down the aqueduct of sylvia, into the 4th ventricle, where is leaves though the 2 foramen of luscchka and 1 foramen of megendie into the subachnoid space by the spinal cord and brain.
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what absorbs CSF?
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arachnoidal villi
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the entire volume of CSF is exchanged how ofteN?
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3-4 hours
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hard, tough, non-stretchable membrane, outer dura periosteum of skull
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Dura Mater
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What is one space that DOES NOT contain CSF?
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subdural space
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Thin, avascular, membranous layer external to pia mater and connected to it by weblike trabeculations
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arachnoid
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Spinal anesthesia administered any where between ______ without cord damage.
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L1-S2
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Highly vascular membrane that closely approximates spinal cord. Continues beyond termination of spinal cord as FILUM TERMINALE which attaches to coccyx
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Pia Mater
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What contains blood supply to the spinal cord?
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Pia Mater
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which meninge membrane layer would cause the fastest bleed?
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Pia, slowest would be arachnoid
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describe the order of the meninge layers
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bone...epidural space....dura mater...subdural space (NO CSF)....arachnoid membrane...subarachnoid space (where CSF is)...pia mater (where blood supply is)
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CSF occurs mainly by secretion in
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choroid plexus
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what is the pressure of CSF
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12mmhg (same as ICp)
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What can occur if brain tumor , hemorrhage or infection block the aqueduct of sylvius?
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increased ICP that could lead to hydrocephalus.
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What is the difference between communicating and non-commnicating hydrocephalus?
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COmmunicating is a blockage of flow through the subarachnoid spaces or arachnoidal villi where non-communicating there is a block in the aqueduct of sylvius.
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How are cerebral capillaries different from capillaries that are found in all other parts of the body?
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they lack "pores" and form tight junctions with overlapping ends with endothelial cells creating an impervious seal.
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A continuous __________ surrounds the entire circumference of each cerebral capillary
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basement membrane
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85% of the outer surface of each capillary is surrounded by __________
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glial cells
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for a substance to get to a neuron it maybe have to pass through capillary cells and glial cells, what does this mean?
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slower arrival of the substance at the neuron
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what are the five areas outside the BBB
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pineal gland, neurohypophysis, area postrema, supraoptic crest and subfornical organ
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what is released by the neurohypophysis (posterior pituitary)
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ADH and oxytocin
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when is ADH released and what are its effects on the body?
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when osmolarity is up > 280...ADH acts on distal segments of the prox tubule and reabsorbs H2O.
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area postrem is associated with what?
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N/V
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what stabilizes the BBB
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cortisone
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What is the BBB like is premature babies
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immature
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BBB is made more permeable by what?
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tumors, trauma, hypoxia and severe changes in CO2
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what is the most important factor of getting IV amnesia drugs to the the GABA A receptors in the brain
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You want them to be lipid soluble because they will be highly permeable to the brain
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If an anesthetic drug is highly protein bound, will it cross the BBB?
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not as readily
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what is the cerebral metabolic rate of O2
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3-3.5/mg/100g/min
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what is the cerebral metabolic rate for glucose
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4.5/mg/100g/min
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what is the cerebral metabolic rate of lactate?
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2.3mM/100g/min
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What states that the cranial compartment is incompressible and the volume inside the brain is fixed
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Monroe Kellie Doctorine
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increased PaCO2 (hypoventilation) leads to what?
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cerebral dilation and perfusion due to increased H+ ions
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decreased PaCO2 (hyperventilation) leads to what?
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less H+ ions and cerebral vasoconstriction.
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If your PaO2 increases what happens to CBF?
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decreases
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If your PaO2 decrease what happens to your CBF
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increases
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CPP=
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MAP-ICP
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What is normal CPP
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100mm Hg
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CBF remains constant despite wide variations in CPP because of what?
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pressure autoregulation
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At what CPP do you start to notice EEG changes?
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50= slowing of EEG
25-40= Flat EEG <20=irreversibel tissue damage at normothermia |
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auto-regulation functions between what map?
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50-150
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what is the main factor affecting CPP in the normal brain?
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MAP
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During normal autoregulation of cerebral blood flow, what happens when the MAP is increase? MAP decreased?
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increased=vasoconstriction, decreasing CBF
decreased=vasodilation, increasing CBF |
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what are the two theories of autoregulation?
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Myogenic theory for autoregulation and metabolic theory for autoregulation
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This theory states that autoregulation is an intrinsic response of smooth muscle, stretching of smooth muscle produces vasoconstriction and reduction of BP leads to vasodilation.
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Myogenic theory for autoregulation
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Where is the only area in the body where the myogenic theory of autoregulation does not occur?
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lungs...(hypoxic pulmonary vasoconstriction)
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If a patient is chronically hypertensive which way will their auto regulation shift?
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right (keep pt 20% of baseline)
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This theory states that blood flow is regulated by metabolic activity. So when BP decreases it causes cerebral hypoxia, release of acid metabolites which cause vasodilation
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metabolic theory of autoregulation
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if you exceed the upper limit of autoregulation what will occur?
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autoregulation breakthrough, disruption of the BBB and cerebral edema
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what profoundly affects Cerebral Blood Flow
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PaCO2
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The new research suggest that the low limit for autoregulation should be 70-80 because with MAP of 50-80 why is seen?
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hypoperfusion of the brain
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What is the uncoupling effect?
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when cerebral vessels are dilated increasing CBF but a lower CRMO2 also occurs (anesthetic vapors do this)
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What causes the uncoupling effect?
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anesthetic vapors (increase CBF but decrease CMRO2)
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is the brain capable of anaerobic metabolism?
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no
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total lack of O2 to the brain can cause unconsciousness in
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5-10 seconds
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under normal conditions almost all of teh energy used by the brain cells is supplies by ______
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glucose derived from blood
(4.5mg/100g/min) |
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How will a BP taken in the lower extremity indicate the BP in the brain
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it will be much higher than what the brain BP is seeing
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for every one inch above or below the organ you are questioning the BP adjust your reading (MAP) by how much?
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1.85mmhg
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review effects of arterial blood gas on cerebral blood flow chart
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PaCO2 varies directly with CBF
PaO2 varies inversely |
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what is the critical level for PaO2?
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<50
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If your PaCO2 is 80 what effect does that have on your CBF
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doubles it
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if you hyperventilate your patient down to a CO2 of 25 what effect will that have on CBF?
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cuts CBF in half
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it is important to maintain constant levels of what ion to maintain neuronal activity
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H+
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CO2+H2O=__________ which dissociates into _____. THis leads to what?
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carbonicacid H+ leading to vasodilation increased CBF and ICP
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if you hypovevtilate someone this could lead to lactic acidosis....what other responses will you see
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increased CO2, which causes vasodilation and increased CBF and ICP. Also leads to decreased neuronal activity
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A patient with chronic hypercapnia will shift the CBF curve which way? what patients will you see this in?
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to the right.
COPD pts |
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an increase in CBF does not occur until the PaO2 is what?
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<50mmhg
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how does a change in HCT effect CBF?
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no change if HCT 30-50 (normal 45) if HCT is increased it leads to decreased CBF due to viscosity. If HCT is decreased it leads to increased CBF
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decreased body temp decreased CBF by ____ per degree centigrade drop
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5%
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What is the most effective way to protect the brain during both global and focal ischemia?
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hypothermia
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the brain uses O2 at a rate of what
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3,3.5/100g/min
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where is the metabolic rate the highest?
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cerebral cortex because that is where most of the neuronal activity is
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would you use dextrose containing solutions in a patient with transient ischemia?
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no, hyperglycemia causes greater neuronal damage
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surpatentorial CSF pressure or pressure in a lateral ventricle or SAS
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ICP
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what is the normal ICP
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10mmhg
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this position decreases CPP by 15% in the non anesthetizeed patient
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beach chair
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pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid, such that, the pressure ratio remains the same
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Pascals law
change in P=pg(change in h) |
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if a patients MAP is 60 in the arm what can you expect the MAP to be if patient raises there arm 10 in. from the heart
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10x1.85=18.5 60-18.5=42
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where can ICP be measured?
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SAS with a bolt
or in lateral ventricle with a ventriculostomy |
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brains ability to displace blood of CSF to maintain normal ICP
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buffering capacity
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label spatial compensation, spatial exhaustion and herniation on the intracranial compliance graft.
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see notes
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a tumor in posterior fossa usually produces some degree of brain edema because it obstructs what?
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Flow of CSF by compressing 4th ventricle
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If ICP >_____ vicious cycle begins
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30
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N2O is ____ time more diffusable than nitrogen. For every 1 N2 you get out ____ N2O go in thus expanding the air
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30, 32
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Iso, sevo, des, cause uncoupling effect. what does this mean?
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decreased CMRO2 but increases CBF and ICP. As blood flow goes up CMRO2 goes down
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it is important to keep you volatiles at what MAC?
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less than one (.4-.5)
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Is N2O a vasoconstrictor or vasodilator?
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vasodilator
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what is the anesthestic that causes the coupling effect?
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barbiturates ( thiopental )
decrease CMRO2 and decreases CBF and ICP |
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what is the number one goal of anesthetic management of neurosurgical patients?
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prevent hypoxemia
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it is important to position neuro surgery patients with slightly head up and head in a neutral position so you do no interfere with what?
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internal jugular drainage
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free amnesia with a GCS <
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8
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this artery supplies 80% of your anterior cord.
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artery of adamkiewicz
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used to evaluate the integrity of the spinal cord or nerves during procedures when blood supply to the cord or tissue of the cord is in danger of being damaged
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SSEP
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when using SSEP, what waveform would suggest damage in the neuro pathway being monitored?
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increased latency and decreased amplitude
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This type of neuro monitoring is least sensitive to anesthetic agents and evaluates CN VIII
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brainstem auditory evoked potentials
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this monitor monitors the integrity of CN II and is most sensitive to anesthetic agents
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visual evoked potential
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what can not be used with Motor evoked potential monitoring.
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muscle relaxants and volitiles must be low MAC
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nerve ______ is lost before cellular integrity is lost.
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function...this is why neurological monitoring is used.
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what are the 4A's of anesthesia
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amnesia, analgesia, akinesia, and autonomic stability
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what is the region responsible for amnesia
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cortex
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what is the region responsible for analgesia
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thalamus
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wat is the region responsible for akinesia
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cord reflex
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what is the region responsible for autonomic stability
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endocrine
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