TRAUMATIC BRAIN INJURY Flashcards
A and P
-CNS(brain, spinal cord) vs PNS (cranial nerves and spinal nerves
- Brain
-Brainstem - reflexes , vital signs, non-concous stuff
midbrain, pons, medulla oblongata
- Cerebellum- muscle movement, balance, control
- cerebrum- largest part, 2 hemispheres, 4 lobes
-frontal- speech, higher level thinking , motor cortex
parietal- taste, reading, somatosensory area
temporal- smell, hearing
occipital- vision
MENINGES
- SKULL
- MENINIGES- protective connective tissue made out of three membranes
Dura mater
Arachnoid mater
Pia mater
-Cerebrospinal fluid- clear fluid in the subarachnoid space
cushions the brain
maintains chemical balance- has some nutrients (Mg,Na,Cl) and removes CO2 , lactate, and hydrogen
MENINGES 3 MEMBRANES
DURA MATER- outer layer lining skull
ARACHNOID MATER -contains blood vessels
SUBARACHNOID SPACE- filled with CSF
PIA MATER- COVERS BRAIN
WHAT IS TBI
- brain is in a closed system within the skull
- impacts to the head can cause the brain to impact against the skull
- bleeding within the skull can cause pressure which reduces blood flow to brain
- swelling to brain or surrounding tissues may do the same
INTRACRANIAL PRESSURE
- ICP is the pressure inside the skull( pressure on, and from CSF, blood, vasculature , brain, skull)
- maintained via balance of blood volume, brain tissue and CSF
MEASURING
- measured via the CSF in the ventricles of the brain
- normal is 5-15 in adults
- above 20 requires immediate intervention
- anything over 30 is life threatening
FACTORS AFFECTING ICP
- arterial / venous pressure
- intra abdominal / intra thoracic pressure
- posture
- temperature
- blood gasses , especially CO2
CO2 is a vasodilator , if CO2 is high , then increased cerebral blood flow , so increased ICP
MONROE KELLIE PRINCIPLE
if the volume of one component of the intracranial pressure increases it causes the displacement of another component , so the total intracranial volume wont change
the body tries to maintain equilibrium
ICP VOLUME CURVE
stage 1- compensation
stage 2- early reversible decompensation - increased risk for increased ICP
stage 3- late reversible decompensation - any small change causes huge increased ICP
stage 4- irreversible decompensation- lethal levels
CEREBRAL BLOOD FLOW
- amount of blood passing through 100g of brain tissue per min
- about 50mls/ min / 100g
- brain regulates its blood supply
- increase BP/ decreased =constriction
- decreased BP/ increased CO2= dilation
MEASURING CEREBRAL BLOOD FLOW
start with MAP= mean arterial pressure
MAP= ( SBP + 2DBP)/ 3
- PULSE PRESSURE MEASURES EXPANSION OF ARTERIES IN RESPONSE TO THE VOLUME OF BLOOD EJECTED DURING SYSTOLE
PP= SBP-DBP
CEREBRAL PERFUSION PRESSURE
CPP= MAP-ICP
pressure needed to ensure blood flow to brain
normal CPP is between 60-100
less than 50 is deadly
WHY DOES ICP INCREASE
- injury to brain occurs
- tissue edema = increase ICP
- edema compresses ventricles and blood vessels
- decreased cerebral blood flow
- decreased O2= death of brain cells
- edema around necrotic tissue
- increased CO2
- vasodilation to compensate
- increased ICP from increased blood volume leads to death
WHAT INJURIES CAUSE THIS
- tumors
- hematoma, hemorrhage, contusion
- surgery
- meningitis
- CVA, TIA
HOW DO WE MONITOR ICP
-invasive pressure tranducer placed in the ventricles, subarchnoid space, epidural space
- several varieties - best is the ventriculostomy
- some noninvasive options but not suitable for long monitoring and are generally not accurate
