Intracranial Pressure
Paula Ponder MSN, RN, CEN
(Relates to Chapter 62,63
Intracranial Pressure in the
textbook)
Learning objectives
• Discuss the physiologic mechanisms that maintain
normal intracranial pressure
• Identify the common clinical manifestations of the
patient with increased intracranial pressure.
• Describe the nursing management of the patient
with increased intracranial pressure.
Intracranial Pressure
• Skull has three essential components
– Brain tissue 78%
– Blood 12%
– Cerebrospinal fluid (CSF) 10%
Intracranial Pressure
• Factors that influence ICP
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Arterial pressure
Venous pressure
Intraabdominal and intrathoracic pressure
Posture
Temperature
Blood gases (CO2 levels)
– The brain has to be able to accommodate and change
all these things. Things change, like BP, we sneeze,
stand up, sit down, ect.
Intracranial Pressure
Regulation and Maintenance
• Normal intracranial pressure
– Pressure exerted by the total volume from the brain
tissue, blood, and CSF
– Modified Monro-Kellie doctrine: Describes relatively
constant volume within skull structure
• Your head is a rigid box and there is limited room for
expansion. An increase in any one of these components
(brain tissue, blood, and CSF) causes a decrease in volume of
the others. This is a mechanism to compensate. If things are
working normally, the brain can compensate just fine. The
easiest thing to decrease is the CSF, it’s also the first thing
that the head pushes out. Blood is next to be pushed out,
but vessels collapse, and then we get hypoxia, atrophy,
necrosis. If this goes on for long enough there will be brain
damage due to hypoxia
• Normal ICP is 0-15
Intracranial Pressure
Regulation and Maintenance
• Normal compensatory adaptations
– Displacement of CSF into spinal subarachnoid
space
• Ability to compensate is limited
– If volume increase continues, ICP rises
• Measuring ICP
– Ventricles, subarachnoid space, epidural space,
brain parenchymal tissue
Intracranial Pressure
Cerebral Blood Flow
• Definition
– The amount of blood in milliliters passing through
100 g of brain tissue in 1 minute
– About 50 ml/min per 100 g of brain tissue
• Autoregulation of cerebral blood flow
– Automatic alteration to maintain constant flow to
brain
Intracranial Pressure
Cerebral Blood Flow
• Cerebral perfusion pressure (CPP)
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Pressure needed to ensure blood flow to the brain
CPP = MAP – ICP
Normal is 70 to 100 mm Hg
<50 mm Hg is associated with ischemia and neuronal
death
• MAP greater than 150 we lose auto regulation. Vessels are
manually constricted, therefore they can’t constrict anymore
• If we get an ICP is equal to MAP cerebral circulation ceases
– We need a MAP of 60 to perfuse our brain and
kidneys and what not. We need CPP of 70 – 80
– MAP is 2x the diastolic plus the systolic divided by 3
Intracranial Pressure
Cerebral Blood Flow
• Pressure changes
– Compliance is the expandability of the brain
– Compliance = Volume/Pressure
– With low compliance, small changes in volumes
creates huge increases in pressure
Intracranial Pressure
Cerebral Blood Flow
• Pressure-volume curve represented by stages
– Stage 1: High compliance
• When we displace CSF
– Stage 2: Compliance ↓ , risk for ↑ ICP
– Stage 3: Any small addition in volume causes a great ↑
in ICP, loss of autoregulation
• When we see Cushing’s Triad
– Stage 4: ICP rises to lethal levels
Intracranial Volume
Pressure Curve
Intracranial Pressure
Cerebral Blood Flow
• Factors affecting cerebral blood flow
– Cardiac or respiratory arrest
– Trauma
– Tumor
– Cerebral hemorrhage, or stroke
– Treat shit with dopamine, but that gives them
tachycardia. May give them “pressers”
Increased Intracranial Pressure
Cerebral Edema
• Increased accumulation of fluid in the
extravascular spaces of brain tissue
• Three types of cerebral edema:
– Vasogenic
• Mainly in the white matter
– Cytotoxic
• Results from local disruption of the functional integrity of
cell membranes
– Interstitial
• Uncontrolled hydrocephalus
• Primarily in kids, can be communicating or non
communicating
Increased Intracranial Pressure
Mechanisms of Increased ICP
– Mass lesion
– Cerebral edema
– Head injury
– Brain inflammation
• Say from an abscess
– Metabolic insult
Increased Intracranial Pressure
Clinical Manifestations
• Headache
– Often continuous and worse in the morning
• Vomiting
– Not preceded by nausea
– Projectile (late sign)
Increased Intracranial Pressure
Clinical Manifestations
• Change in level of consciousness
• Change in vital signs
– Cushing’s triad
• Bradycardia, widened pulse pressure, and HTN
• With a widened pulse pressure, cerebral blood flow is
decreasing
• Will see Cheyne-Stokes
• Will lose brain stem reflexes, gag, corneal, and swallowing,
pupils
• Ocular signs
– Pupils won’t dialate
Increased Intracranial Pressure
Clinical Manifestations
• ↓ In motor function
– Decerebrate posturing (extensor)
• Indicates more serious damage
• Extension of all 4 extremities
– Decorticate posturing (flexor)
• “to the core” internal rotation and flexion of all 4
extremities
Increased Intracranial Pressure
Complications
• Two major complications of uncontrolled
increased ICP
– Inadequate cerebral perfusion
• Causes brain tissue hypoxia
– Cerebral herniation
• Tentorial herniation
• Uncal herniation
• Cingulate herniation
• Sustained increase in ICP results in brainstem
compression and herniation of brain from one
compartment to another
Increased Intracranial Pressure
Diagnostic Studies
• Aimed at identifying underlying cause
– MRI
– CT
– Cerebral angiography
– EEG
Increased Intracranial Pressure
Diagnostic Studies
• Aimed at identifying underlying cause
– ICP measurement
– Transcranial Doppler studies
– PET
– Brain tissue oxygenation measurement
Increased Intracranial Pressure
Measurement of ICP
• ICP monitoring used to guide clinical care
when at risk for increased ICP
– Those admitted with a Glasgow Coma Scale of 8 or
less
• Less than 8 are probably going to be intubated
– Those with abnormal CT scans or MRI
– History of neurological insult
Increased Intracranial Pressure
Measurement of ICP
• The gold standard for ICP
monitoring is the ventriculostomy
– Risk of infection, of course
• A wave
– Commonly associated with temporary change
neuro status
• B wave
– Respiratory changes
• C wave
– Clinically insignificant
Increased Intracranial Pressure
Measurement of ICP
• Inaccurate readings can be caused by
– CSF leaks
– Obstruction in catheter
– Differences in height of bolt/transducer
– Kinks in tubing
– Incorrect height of drainage system relative to
patient’s reference point
Increased Intracranial Pressure
Collaborative Care
• Adequate oxygenation
– ABG analysis guides the oxygen therapy
– May require mechanical ventilator
• Drug therapy
– Mannitol
– Corticosteroids
– Big doses of these guys!
Increased Intracranial Pressure
Collaborative Care
• Hyperventilation therapy
– Was the mainstay treatment
– Brief periods may be useful for refractory
intracranial hypertension
– Increases the risk for focal cerebral ischemia
• Nutritional therapy
– ↑ Need for glucose
– Keep patient normovolemic
• IV 0.9% NaCl
Increased Intracranial Pressure
Nursing Management
• Nursing assessment
– Glasgow Coma Scale
– Neurologic assessment
• Motor strength and response
• Vital signs
– BP, Pulse, Respiratory rate, Temperature
– O2 saturation
Increased Intracranial Pressure
Nursing Management
• Planning
– Overall goals
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Maintain a patent airway
ICP within normal limits
Normal fluid and electrolyte balance
No complications secondary to immobility and
decreased LOC
Increased Intracranial Pressure
Nursing Management
• Nursing implementation
– Respiratory function
– Fluid and electrolyte balance
– Monitoring of intracranial pressure
– Body position maintained in head-up position
– Protection from injury
– Psychologic considerations
Summary
• Maintain airway
– Semi fowlers is how they need to be laying
• Maintain adequate oxygenation
• Monitor neurological assessment for changes
• Document and Report any changes.