NUR 245 exam 2 UPDATED ACTUAL QUESTIONS AND CORRECT ANSWERS
intracranial regulation components 3 essential components
-Brain tissue (78%)
-Blood (12%)
-CSF (10%)
ICP primary injury at the initial time of the injury
-impact of car accident
-blunt force trauma
results in
-displacement bruising or damage to any of the components
ICP secondary injury resulting
-hypoxia, ischemia, hypotension, edema or increased ICP
follows primary injury
-can occur several hours to days after
intracranial pressure hydrostatic force measured in the brain CSF compartment
factors of ICP changes in
-arterial pressure
-venous pressure
-intra-abdominal and intrathoracic pressure
-temperature
-blood gases (CO2 levels)
to increase or decrease these depends on brains ability to adapt to change
Monroe-Kellie doctrine states: the 3 components must stay relatively close in the closed skull
-if 1 increases the volume from another component must decrease
will not happen in displaced skull fractures or craniotomy
ICP ranges can measure in ventricles, subarachnoid space subdural space, epidural space, or
brain tissue using a pressure transducer
Normal range- 5-15 mm Hg
increased ICP - pressure greater than 20 mm Hg (MUST BE TREATED)
Normal compensatory mechanisms ICP -changes in CSF volume (due to absorption or production/ displacing CSF into
the subarachnoid space)
-changes in blood volume (through collapse of cerebral veins/dural sinuses,
vasoconstriction/dilation or changes in venous return)
- changes in brain tissue volume (distention of dura or compression of brain tissue)
- limited ability to compensate for changes, ICP rises as volume increases and
decompression occurs, results in compression and ischemia
,Cerebral blood flow (CBF) amount of blood passing through 100 g of brain tissue a minute
-CBF is 50ml/ min passing through 100g of tissue
-brain requires constant supply of O2 and glucose
-uses 20% of body O2 and 25% of bodies glucose
Autoregulation of CBF brain regulates own blood flow; due to its metabolic needs
-automatic adjustment in diameter of blood vessels (Vasoconstricton or
vasodilator) ALLOWS CEREBRAL CIRCULATION
-ensures consistent CBF is provided for metabolic needs
Only effective is MAP is 70- 150
below 70- CBF decreases; ischemia, syncope/blurred vision occur
above 150- further vasoconstriction response is lost
cerebral perfusion pressure (CPP) pressure needed to ensure blood flow to the brain
-equal to MAP minus ICP ( CPP= MAP- ICP)
normal- 60-100
-decrease in CPP causes autregulation to fail and CBF to decrease
CPP less than 50= ischemia and neuronal death
CPP less than 30= ischemia and incompatible with life
(as we age weight size of 33 of neurons decreases)
-when cerebral vascular resistance is high, blood flow to brain tissue is impaired
(think high after load)
-Trascranial doppler monitors changes in cerebral vascular resistance
-higher CPP may be needed for patients to prevent tissue damage (stroke patient
may need higher BP, increased MAP/CPP)
Factors affecting CBF Co2, O2 and hydrogen concentration affect cerebral blood vessel tone (regulates
pressure)
increase in Co2/paCo2- relaxes smooth muscle, dilates vessels, decreases
cerebralvascular resistance and increases CBF
-decrease in PaCo2- constricts vessels, increases cerebral vascular resistance and
decreases CBF
O2 tension less than 50- cerebral vascular dilation - decreases cerebral vascular
resistance, increases CBF and increases O2 tension (causes lactic acid to
accumulate)
-lactic acid increases and hydrogen accumulates (causes acidic environment)
-acidic environment- further dilates (may cause autorgeulation to be lost)
calculations of cerebral perfusion pressure CPP= MAp-ICP
MAP= SBP+2 (DBP) divided by 3
factors affecting CBF -cardiac or respiratory arrest
-systemic hemorrhage
-diabetic comaterm-25
-encephalopathies
-infections
-toxicities
-trauma
-tumors
-stroke
, -changes in systemic BP, hypoxia, catecholamines
increased ICP -Life-threatening
-Increase in any of three components (risk for ischemia and infraction- cell death)
-Brain tissue
-Blood
-CSF
-↑ cerebral edema
results in
-brainstem compression and herniation (brain tissue forcibly shifted from a
compartment of greater pressure to lower pressure)
intracranial regulation components 3 essential components
-Brain tissue (78%)
-Blood (12%)
-CSF (10%)
ICP primary injury at the initial time of the injury
-impact of car accident
-blunt force trauma
results in
-displacement bruising or damage to any of the components
ICP secondary injury resulting
-hypoxia, ischemia, hypotension, edema or increased ICP
follows primary injury
-can occur several hours to days after
intracranial pressure hydrostatic force measured in the brain CSF compartment
factors of ICP changes in
-arterial pressure
-venous pressure
-intra-abdominal and intrathoracic pressure
-temperature
-blood gases (CO2 levels)
to increase or decrease these depends on brains ability to adapt to change
Monroe-Kellie doctrine states: the 3 components must stay relatively close in the closed skull
-if 1 increases the volume from another component must decrease
will not happen in displaced skull fractures or craniotomy
ICP ranges can measure in ventricles, subarachnoid space subdural space, epidural space, or
brain tissue using a pressure transducer
Normal range- 5-15 mm Hg
increased ICP - pressure greater than 20 mm Hg (MUST BE TREATED)
Normal compensatory mechanisms ICP -changes in CSF volume (due to absorption or production/ displacing CSF into
the subarachnoid space)
-changes in blood volume (through collapse of cerebral veins/dural sinuses,
vasoconstriction/dilation or changes in venous return)
- changes in brain tissue volume (distention of dura or compression of brain tissue)
- limited ability to compensate for changes, ICP rises as volume increases and
decompression occurs, results in compression and ischemia
,Cerebral blood flow (CBF) amount of blood passing through 100 g of brain tissue a minute
-CBF is 50ml/ min passing through 100g of tissue
-brain requires constant supply of O2 and glucose
-uses 20% of body O2 and 25% of bodies glucose
Autoregulation of CBF brain regulates own blood flow; due to its metabolic needs
-automatic adjustment in diameter of blood vessels (Vasoconstricton or
vasodilator) ALLOWS CEREBRAL CIRCULATION
-ensures consistent CBF is provided for metabolic needs
Only effective is MAP is 70- 150
below 70- CBF decreases; ischemia, syncope/blurred vision occur
above 150- further vasoconstriction response is lost
cerebral perfusion pressure (CPP) pressure needed to ensure blood flow to the brain
-equal to MAP minus ICP ( CPP= MAP- ICP)
normal- 60-100
-decrease in CPP causes autregulation to fail and CBF to decrease
CPP less than 50= ischemia and neuronal death
CPP less than 30= ischemia and incompatible with life
(as we age weight size of 33 of neurons decreases)
-when cerebral vascular resistance is high, blood flow to brain tissue is impaired
(think high after load)
-Trascranial doppler monitors changes in cerebral vascular resistance
-higher CPP may be needed for patients to prevent tissue damage (stroke patient
may need higher BP, increased MAP/CPP)
Factors affecting CBF Co2, O2 and hydrogen concentration affect cerebral blood vessel tone (regulates
pressure)
increase in Co2/paCo2- relaxes smooth muscle, dilates vessels, decreases
cerebralvascular resistance and increases CBF
-decrease in PaCo2- constricts vessels, increases cerebral vascular resistance and
decreases CBF
O2 tension less than 50- cerebral vascular dilation - decreases cerebral vascular
resistance, increases CBF and increases O2 tension (causes lactic acid to
accumulate)
-lactic acid increases and hydrogen accumulates (causes acidic environment)
-acidic environment- further dilates (may cause autorgeulation to be lost)
calculations of cerebral perfusion pressure CPP= MAp-ICP
MAP= SBP+2 (DBP) divided by 3
factors affecting CBF -cardiac or respiratory arrest
-systemic hemorrhage
-diabetic comaterm-25
-encephalopathies
-infections
-toxicities
-trauma
-tumors
-stroke
, -changes in systemic BP, hypoxia, catecholamines
increased ICP -Life-threatening
-Increase in any of three components (risk for ischemia and infraction- cell death)
-Brain tissue
-Blood
-CSF
-↑ cerebral edema
results in
-brainstem compression and herniation (brain tissue forcibly shifted from a
compartment of greater pressure to lower pressure)
