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NURS 487 EXAM 2 Questions And Accurate Answers A+ Graded
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NURS 487 EXAM 2 Questions And Accurate AnswersA+ Graded
3 Basic components of the cranial vault-ANSWER brain, blood, CSF; Total volume must
remain constant; if not increased ICP results
Monro-Kellie hypothesis-ANSWER hypothesis that because there is little room for
expansion within the skull, an increase in any one of the cranial contents-brain tissue,
blood or cerebrospinal fluid-causes the other 2 cranial conents to make room by
decreasing in volume
Blood Brain Barrier - ANSWER - Regulates brain volume-mainly water found
intracellularly-and contents through control of permeability
- Most drugs do not cross the BBB
- Disruption results in edema-increased brain volume
- Permeable to: water, oxygen, lipid-soluble compounds, and carbon dioxide [slightly to
electrolytes]
Cerebral Spinal Fluid - ANSWER - A clear fluid that circulates in subarachnoid spaces
and spinal cord and is reabsorbed into venous system
- 8% of intracranial volume (150 mL)
- Normal adult CSF pressure: 5-13 mmHg
- Too much production leads to hydrocephalus (need drain)
- Functions of CSF include providing a cushion and support for the brain and spinal
cord, maintaining a stable chemical environment for CNS, and excreting toxic wastes
carbon dioxide, lactate hydrogen ion
- Should not contain RBC or WBC and should not be cloudy
CSF-usually obtained by doing a lumbar puncture (needle inserted b/w 3rd and 4th
lumbar vertebrae, also done to measure pressure)
,Cerebral Perfusion: Arterial Circulation - ANSWER - Delivers blood to the brain which
contains oxygen, glucose, and substrates for energy
- Thin, delicate arteries (if HTN, increased risk of stroke or rupture bc of this)
- High-pressure, high-resistance system
- 2 major pairs: left and right internal carotids; left and right vertebral arteries
- The laregest are the middle cerebral arteries and are the most frequent arteries
involved in ischemic strokes
- Circle of Willis: primary collateral pathway; protective mechanism when major cerebral
vessels
are occluded (if blood clot, ciricle of willis helps provide blood flow to infarcted area)
Cerebral Perfusion: Venous Circulation - ANSWER - Low pressure system
-No valves so only drains by gravity positioning very important
-Venous pressures reflects intracranial pressure If there is an increase in CVP than
there will be an increase in ICP
Cerebral Blood Flow: Autoregulation -ANSWER- Compensatory mechanism
Cerebral arterioles alter blood flow to keep MAP within 60-130
Keeps CBF constant to maintain adequate cerebral perfusion pressure CPP
- Self-regulation-constriction/dilation of cerebral blood vessels, in response to changes
in: systemic arterial pressure (systemic BP), blood levels of carbon dioxide, blood levels
of O2
Cerebral blood volume-determined by what? - ANSWER - Systemic hypo-/hypertension
- Body metabolic rate
- Systemic acidosis/alkalosis
- Cerebral vasodilation/constriction
- Cardiac output
Conditions that result in reduced CBF - ANSWER - Reduction in metabolic rate of the
body decrease CNS activity: sedation, paralysis, hypothermia, hypocapnia
, - Cerebral edema
Low cardiac output
- Vasoconstriction
- Alkalosis causes cerebral vasoconstriction to decrease CBF
- Inadequate CBF can lead to cerebral hypoxia which leads to ischemia
Conditions resulting in increased CBF - ANSWER - Increased Metabolic Rate: high fever,
pain, seizures, posturing
- Acidosis (CO2 retention, Lactic Acidosis) causes cerebral vasodilation and increases
CBF and ICP
- Want to avoid this in pts with neurologcal injury and already increased ICP
If brain is deprived of its O2 and glucose then what happens with CBF? -ANSWER It does
not support the Aerobic metabolism, so the brain shifts to anaerobic metabolism, lactate
is produced and because of that it could not cross through the BBB, hence accumulated
and results in cerebral acidosis and cerebral vasodilation; this upsets the state of
equilibrium in cranial vault and increases CBF.
What if CBF is greater than metabolic needs? - ANSWER A state of hyperemia exists,
progressive vasodilation occurs, cerebral blood volume increases, and there is an
eventual loss of autoregulation which leads to increased ICP and cerebral ischemia
As a nurse caring for a patient with brain injury you must do your best to avoid situations
that will lead to. - ANSWER cerebral hypoxia or hypotension (makes ischemia worse)
Intracranial Pressure (ICP) - ANSWER - The pressure exerted by the CSF within the
brain ventricles
- Normal: 0-15 mm Hg (0-10 mm Hg in children)
- Fluctuates in response to: changes in respiratory rate, changes in body position,
coughing/sneezing
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