Exam IV: Neuro Diseases Flashcards
CEREBRAL BLOOD FLOW(CBF):
*autoregulated—normally
*___mL/100g brain tissue when CPP ___-___ mmHG
*is about 750 ml/min (___-___% of cardiac output)
50
50-150
15-20%
CBF governed by:
Cerebral metabolic rate-CMRO2
Cerebral Perfusion Pressure-CPP
PaCo2 and O2 tension
Various medications
Intracranial abnormalities
Cerebral Metabolic Rate-CMR
Rate of O2 consumption-3.0-3.8mL O2/100 g brain tissue/min and consumes ____% of total body oxygen
20
Cerebral Metabolic Rate-CMR
Most used to generate ATP for ____ ____ activity
neuronal electrical
Cerebral Metabolic Rate-CMR
*High ____ _____ + low ____ _____ = unconsciousness in 10 sec if perfusion stopped
*If not restored in ___-___ min leads to ATP stores depleted causing cellular injury/death
O2 consumption
O2 reserve
3-8
Cerebral Metabolic Rate-CMR
Decreased by _____ temps, anesth agents
Increased by _____ temps, seizures
lower
higher
CPP =
MAP - ICP (or CVP, whichever is greater)
CPP is normally ___-___ mmHg
60-110
if ICP increases, MAP must _____ to maintain CPP
increase
if MAP falls below 60 mmHg, CPP _______________
cant be maintained
Even with normal MAP, if ICP is ______, CPP (thus CBF) can change
> 30
CPP less than 50 mmHg shows
slowing on EEG
CPP 25-50 mmHg shows
flat EEG
CPP less than 25 mmHg leads to
possible irreversible brain damage
Autoregulation b/t 50-150 mmHG (pressure dep beyond this)
Arterial constriction with ______ BP
Arterial dilation with ______ BP
increased
decreased
Normotensive, if CBF…
___mmHg - ischemia (nausea, dizziness)
___mmHG - vessels max constricted; fluid forced out of vessel causing cerebral edema
35
150
Hypertensive
Autoregulation curve shifted _____
Chronic HTN-lower limit shift _____
right
upward
Auto regulation lost or impaired with:
- intracranial tumors
- vessels around tumor are acidotic
- maximally dilated, now all pressure dependent
- head trauma
- volatile anesthetics
_____ is the most important extrinsic factor
PaCO2
change the PaCO2, change CBF, they are _____ _____
directly proportional
CBF changes approx ___-___ ml/100 g/min per mmHg change in PaCO2.
The change is _____
1-2
immediate
Thought to be b/c of changes in ____ of ____ around walls of arterioles, all compensated after ____-____ hours of hypo or hypercapnia
pH of CSF
24-48
Marked hyerventilation - PaCo2 < 20 shifts the curve to the ____, may have ____ changes
left
EEG
“The ability of hypocapnia to acutely decrease ____, ____, and _____ is fundamental to the practice of clinical neuroanesthesia.”
CBF, CBV, and ICP
CBF not significantly effected by decrease in PaCo2—–until threshold of ____
Below threshold, +cerebral vasodilation and CBF increase; +hyper_____ and +hypo_____ have synergistic effects
50
hypercarbia
hypoxemia
Hypocapnia= ____ _____ with RISKS
FINE LINE
Hypocapnia may be ____ ____ during craniotomy
Impact with TBI or intracranial hemorrhage ____
well tolerated
unclear
CBF changes ___-___% per 1°C
5-7
Hypothermia - decreases ____ & ____
CMR and CBF
Hyperthermia - increases _____ & _____
CMR and CBF
Lower Hct _____ viscosity, but also _____ O2 carrying capacity
decreases
decreases
Increased Hct increases viscosity, decreases _____
CBF
Studies suggest optimal Hct for cerebral O2 delivery = ___%
30
Blood Brain Barrier
unique vessels with junctions between endothelial cells that are nearly _____
fused
BBB is a _____ barrier for brain
lipid
lipid soluble (CO2, O2, H2O, and most anesthetics) move across BBB _____
easily
ionized/large molecular weight have _____ movement across BBB
restricted
BBB is disrupted by:
- severe HTN
- strokes
- trauma
- tumors
- infection
- hypercapnia
- hypoxia
- sustained seizures
(fluid movement now dependent on hydrostatic pressure not osmotic gradient)
CSF major fxn:
protect CNS against trauma
CSF formed by ____ _____ of cerebral ventricles (mostly _____)
choroid plexuses
lateral
CSF produced 2 ways
- ultrafiltration and secretion by the cells of the choroid plexus
- passage of water, electrolytes, and other things across the BBB
- CSF is produced by the ____ ____ in the ventricles
choroid plexuses
- CSF is produced by the choroid plexus in the ventricles
- CSF flows through the _____ _____ from the 3rd to the 4th ventricle
cerebral aqueduct
- CSF is produced by the choroid plexus in the ventricles
- CSF flows through the cerebral aqueduct from the 3rd to the 4th ventricle
- CSF flows into the subarachnoid space by the _____ and _____ _____ also into the spinal canal
lateral and medial aperatures
- CSF is produced by the choroid plexus in the ventricles
- CSF flows through the cerebral aqueduct from the 3rd to the 4th ventricle
- CSF flows into the subarachnoid space by the lateral and medial apertures also into the spinal canal
- CSF removes _____ and provides _____ from within subarachnoid space
waste
bouyancy
- CSF is produced by the choroid plexus in the ventricles
- CSF flows through the cerebral aqueduct from the 3rd to the 4th ventricle
- CSF flows into the subarachnoid space by the lateral and medial apertures also into the spinal canal
- CSF removes waste and provides buoyancy from within subarachnoid space
- Excess CSF will be ______ by the _____ ____ which will drain in tho the ____ _____ sinus
absorbed
arachnoid villi
superior sagittal
Adults: produce ___ mL/hr (500 ml/d) ____ mL is total CSF volume
21
150
LATERAL VENTRICLES
Intraventricular foramina of Monro
3rd Ventricle
Cerebral aqueduct of Sylvius
4th Ventricle
Foramen of Magendie &
Foramina of Luschka
Cisterna Magna
Subarachnoid space
Circulates around the brain & spinal cord
Absorbed into arachnoid granulations
cranial vault is _____
rigid
vault is made up of 3 things
brain - 80%
blood - 12%
CSF - 8%
if one thing in the cranial vault increases, another must ________
decrease
ICP usually ____ mmHg or less - measured in the ____ ventricles or over the cerebral _____
10
lateral
cortex
Monro-Kellie Doctrine:
Any increase in one compartment must be offset by an equal reduction in another to avoid increases in ICP
ICP reduction mechanisms:
- increased CSF absorption
- decreased CSF production
- decrease in total CBV (mostly venous)
- brain stem herniation
normal ICP
5-10 mmHg
mild increase in ICP
20-30 mmHg
moderate increase in ICP
30-40 mmHg
severe increase in ICP
> 40 mmHg
CBV increases ___ ml/100 g of brain per 1 mmHg ↑ PaCo2
.05
Blood pressure effects of CBV dependent on _______ of ______
autoregulation of CBF
if increase in ICP is sustained, can lead to ______
herniation
4 types of herniation
- cingulate gyrus under the falx cerebri (subfalcine herniation)
- uncinate gyrus through the tentorium cerebelli (transtentorial herniation)
- cerebellar tonsils through the foramen magnum
- transcalvarial - any area beneath a defect in the skull
subfalcine herniation leads to compression of anterior cerebral artery causing a _____ ____
midline shift
______ brainstem compression leads to altered consciousness, gaze defects, ocular reflex defect, hemodynamic and resp failure and then _____
transtentorial
death
*If _____ herniation (medial portion of temporal lobe), oculomotor nerve dysfun
uncal
S&S - pupil ______, ptosis, lat deviation of _____ eye and then death
dilatation
affected
S&S - indicates ______ dysfunction—cardio and resp dysfunction and leading to death
medullary
ICP
HA, nausea, vomiting, pupillary dilation, blurred vision (CNII)a, inability to adduct (____) or abduct (____)eye
Focal neurological deficits and unsteady gait
Decreased consciousness, seizures, coma
Cushing’s Triad: irregular _____, _____, _____
CNIII
CNVI
respiration, ↑ BP,↓HR
ICP Dx:
symptoms, CT or MRI, or direct measurement
_______ - helpful to measure, removal of CSF, and CSF sent to lab for analysis
Ventriculostomy
mean ICP should remain below _____
15 mmHg
dramatic increase in ICP leads to ______ and ______ change
hyperventilation and LOC
causes of increased ICP
- Tumor -Due to size, Indirectly b/c of edema in surrounding tissue, Causing obstruction of CSF flow out (tumor in 3rd vent)
- Intracranial hematomas (a lot like tumor)
- Blood in CSF (subarachnoid hemorrhage)
- Infection (meningitis, encephalitis)
- Aqueductal stenosis - congenital narrowing of cerebral aqueduct connecting 3rd and 4th ventricles
- Sz disorder seen in 1/3 of these patients
Decreasing ICP
elevate HOB ___-___ degrees above heart
15-30
Decreasing ICP
head neutral if possible, dont compress _____
jugulars
Decreasing ICP
hyperventilation - maintain PaCO2 ___-____ mmHg, effects diminish in 6-12 hours, rebound increases in ICP can be problematic
30-35
Decreasing ICP
drain _____
CSF
Decreasing ICP
hypo_____
thermia
Decreasing ICP
______ drugs - avoid sig hypovolemia, Mannitol 20% 0.25gm/kg, IV
hyperosmotic
Decreasing ICP
c_______
corticosteroids
