Increased ICP Flashcards
Definition of increased intracranial pressure
Sustained increase of > 20 mmHg for at least 5 minutes
What is normal ICP range?
0-15 mmHg
What is the Monro-Kellie Hypothesis?
ICP is made up the pressure exerted by the combined volume of blood, brain, and CSF.
When the volume of any one of these increases, one or both of the other 2 must decrease to prevent ICP
What is CPP?
Cerebral perfusion pressure - estimate of cerebral blood flow
How to calculate CPP:
MAP-ICP
What is normal CPP?
Range: 70-100 mmHg
Average: 85 mmHg
CPP amt to prevent cerebral anoxia
Must be > 60 mmHg
Most important step for increased ICP
*Always alter ICP first if it’s high with *Mannitol
Then give fluids
Names of the compensatory mechanisms for increased ICP
Autoregulation
Accommodation
What is autoregulation
Compensatory mechanism for ICP
*A NORMAL bodily function
Ability of cerebral vessels to dilate or constrict in response to arterial pressure changes in the brain
How does autoregulation occur with hypertension?
Carotids constrict to decrease blood flow to the brain
How does autoregulation occur with hypotension?
The carotids dilate to increase blood flow to the brain
What is accommodation?
An ABNORMAL compensatory mechanism to ICP in which intercranial contents shift
What occurs during accommodation?
1st: CSF is reabsorbed or displaced to subarachnoid space
2nd: blood returned to venous sinuses and pushed down
3rd: shifting of brain tissue (starts the herniation process)
How does autoregulation try to compensate for hypercapnia?
High CO2 means decreased O2, so carotids dilate to increase blood flow which increases O2
How does autoregulation try to compensate for hypoxia?
Decreases O2 causes carotids to dilate to increase blood flow to brain, which increases amt of O2
Example of nursing intervention that could cause hypoxia
*Suctioning
How does autoregulation try to compensate for volume overload?
Increased BP causes carotids to constrict to decrease blood flow to brain
How does autoregulation try to compensate for an aneurysm?
Takes up more room in the head than there is, causing increased ICP
Carotids will constrict to decrease amt of blood flowing to the brain
How does autoregulation try to compensate for arteriovenous malformation?
Takes up more room in the head than there is, causing increased ICP
Carotids will constrict to decrease amt of blood flowing to the brain
Examples that could cause jugular drainage obstruction
Neck flexion, hyperextension (need to control with positioning)
Neck swelling (constricts carotids)
Tight tracheostomy (leave 2 finger with between tie and pt’s neck)
Coughing (ICP already increased, will increase it too much)
Vomiting
Valsalva’s maneuver (teach pt not to bear down)
Positive pressure ventilation/PEEP (constant pressure of vent to keep airway open makes neck tighter. Need to keep as low as possible)
Examples of situations that would cause increased oxygen (—> increased blood flow)
Seizure activity - anti-seizure drugs to prevent
Hyperthermia - causes increased energy demand
Shivering - usually in post op patients as reaction to anesthesia
Hyperactivity - increased movement causes increased brain waves (need to monitor and treat)
Pain - use drugs and positioning to help
Two types of cerebral edema
Cytotoxic ( most dangerous: life threatening event )
Vasogenic (usually from brain injury itself)
What causes Cytotoxic cerebral edema?
Hypoxia - ischemia from CVA, cardiac arrest, asphyxiation, severe SIADH (water intoxication)
What is vasogenic cerebral edema?
Breakdown in the blood brain barrier allowing proteins to penetrate, pulling water into cells
What causes vasogenic cerebral edema?
Head injuries
Brain tumors
Meningitis
Abscesses
Definition of herniation
Shifting of brain tissue resulting in neurological deficits and eventually death
Types of herniation
Supratentorial:
- cingulate
- central
- uncal
Infratentorial
- cerebellar tonsil