Intracranial Pressure And Brain Herniation

Intracranial Pressure And Brain Herniation Intracranial Pressure And Brain Herniation Portion Of Exam
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Factors influencing ability to compensate for increased ICP
 
1. Location of lesion 2. Rate of expansion 3. Impaired CSF drainage/displacement 4. Intracranial compliance
3 components of intracranial space
 
Brain - 80% blood - 10% CSF - 10%
THypothesis that states that the skull (rigid compartment) is filled to capacity with essentially non-compressible contents
 
Monroe-Kellie hypothesis
Defined as the pressure exerted by the intracranial volumes of brain mass, blood, and CSF
 
ICP
The only major organ that is fully encased in bone.
 
Brain
There is approximately _________ ml of tissue and fluid in the skull
 
1700 ml
A Severe increase: in ICP is considered to be _________
 
>40mmHg
Causes cerebral vasodilation which would increase cerebral blood flow
 
Hypercarbia (increases pCO2—is too high)
The pressure at which brain cells are being perfused
 
Cerebral perfusion pressure
Normal ICP pressure is_________
 
0- 10 or 15mmHg
Decreases sodium transport in brain and somewhat inhibits CSF production
 
Lasix
Used to decrease ICP and reduce extracellular fluid volume in the brain and throughout the body
 
Hyperosmolar agent such as manitol
Late sign, see more often if ICP rises gradually
 
Papilledema
Formula for determining ICP
 
MAP – ICP = CPP
Primary CNS tumors or metastatic tumors
 
Neoplasms
Shifting of brain tissue from 1 compartment to another, brain is displaced either within the head or through normal or artificial opening
 
Brain herniation
Most frequent type of herniation; is a unilateral expanding mass lesion usually of temporal lobe
 
Uncal
Occurs when expanding mass displaces hemispheres, basal ganglia and diencephalon downward
 
Central Herniation
An expanding lesion of 1 hemisphere shifts laterally
 
Cingulate herniation
Type of herniation where brain tissue comes through the cranium
 
Transcalvarial
If head is out of neutral position ______venous return and causes an increase in ICP
 
decreased
Caused by lack of drainage, absorption, deficient or over secretion of CSF
 
Hydrocephalus
Mechanism by which cerebral blood flow is maintained at a constant rate over a wide range of BP’s
 
Pressure autoregulation
Anything that causes a hematoma, hemorrhage, or edema in the head can cause increased ICP
 
Craniocerebral trauma
Usually level transducer at ____________ for ICP pressure monitoring
 
foramen of Monroe (lateral to the outer canthus of the eye or top of the ear)
Examples of metabolic causes for increased ICP
 
SIADH or water intoxication, alcohol poisoning, lead poisoning, acidosis or hypoxia
Most compensatory mechanisms for accommodating a volume increase
 
CSF
put a burr hole into epidural space. Can’t drain with them, but easy and versatile, Now seeing this used more often for monitoring ICP
 
Fiber optic epidural screw
A way to monitor ICP includes a drill hole into subarachnoid space on non-dominate hemisphere
 
Subarachnoid screw
1st device that was ever used for monitoring intracranial pressure; is very reliable and accurate
 
Intraventricular catheter
Examples of vascular causes for increased ICP
 
Stroke (embolic or hemorrhagic), DIC
Examples of infectious processes/toxic states causing increased ICP
 
Meningitis, encephalitis, abscesses, Reye’s Syndrome (kids aspirin)
Typicall motor function changes in ICP
 
Contralateral (opposite side) due to pressure on motor tracts
Normal osmolarity is
 
275-295
Will decrease cerebral metabolic oxygen demand and blood flow and therefore decrease ICP
 
Hypothermia
May see this used in drastic cases; inducing a coma is an effect of this type of therapy
 
Barbituates
Draining too fast in cases of ICP can cause
 
ventricular collapse
Typically, if HA is due to increase in ICP, will be more severe when pt. _________
 
wakes up in morning
Due to tissue shifts that compress the oculomotor nerve; whenever you have papillary changes, usually means that your ICP is _______
 
>28
________ used most commonly if is a tumor
 
Solumedrol
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