NURS 505 Brain Injury Review
Questions and Correct Answers
Disorder of Brain Function ✅-Cerebral Edema
-ICP
-Hydrocephalus
-Traumatic Brain Injury
Intracranial Pressure ✅Cranial cavity consists of:
Blood: 10%
CSF 10%
Brain tissue 80%
-each of these volumes contributes to ICP- volume changes in 1 facilitate change in the
other.
Monro-Kellie Hypothesis ✅-reciprocal compensation occurs among the three
intracranial compartments- blood, CSF and brain tissue- each of these contributes to
ICP
-this is important because:
-tissue volume- brain tumor, edema
-blood volume- vasodilation of cerebral vessels or obstructed venous outflow
-CSF- excess production, decreased absorption of CSF
Compensations for Intracranial Pressure ✅-tissue least able to change
-CSF and blood volume are best at compensation
-initial increase in ICP-CSF Response--> shift into spinal space, increase reabsorption
of CSF
-increase in ICP- Blood Response.
Therefore, when there is a lot of intracranial pressure, it is hard for the tissue to change.
The CSF and the blood volume are the best to compensate because the CSF can shift
into the spinal space.
Blood Response for Increase in ICP ✅limited by small amount in cerebral circulation,
most of which is in the low pressure venous system. As volume buffering capacity
becomes exhausted, venous pressure increases and cerebral blood volume and ICP
rise
Autoregulation ✅effect on blood flow ability to compensate
-ischemia and elevated CO2 produce compensatory vasodilation (which increases
blood volume)
-decreased PCO2 has the opposite effect. Hyperventilation can be used in treatment of
ICP
, Cerebral Perfusion Pressure ✅Represents the pressure perfusing the brain. Mean
arterial blood pressure- intracranial pressure
-normal CPP= 70-100 mmhg
-ICP- 7-15 mm hg supine
-brain ischemia evidenced when the CPP falls below 44 mmhg
Compliance and Volume Pressure Curve ✅-curve indicates dramatic increase once
mechanisms fail
-A to B compensation of intracranial pressure & volume is adequate
-at A, ICP is still pretty normal, but compensation has reached its limits
-from C to D, compensation mechanisms are exceeded and ICP rises significantly
ICP Stage 1 ✅-phase of potential danger, increase in volume is compensated, with
reduction in CSF and blood volume- no rise in ICP
-clinical signs and symptoms stage 1, none. Normal blood pressure, pupillary response
and mentation
ICP Stage 2 ✅compensatory mechanisms exhausted: slow rise in ICP
-signs: drowsy, headache, decreased level of consciousness
ICP Stage 3 ✅Autoregulation Failure- widening pulse pressure (increase systolic,
decrease diastolic) and bradycardia
-Cushing Reflex
-pulse irregular
-cheyne stokes breathing
-pupils become small, sluggish, coma
Cushing Reflex ✅widening pulse pressure, hypertension, and bradycardia (ICP Stage
3)
-this is very bad- if something is not done immediately, their brain is going to herniate
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