Intracranial Pressure

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REPONSE OF BRAIN TISSUE
TO TRAUMA
INTRACRANIAL PRESSURE
Intracranial Pressure
• Response of brain tissue to trauma
occurs at the cellular level:
– Injury: massive vasodilation
– Cerebral edema: increase in size and volume
of brain
• Increased ICP:
– Increase in pressure exerted within the
cranial cavity
Intracranial Pressure
• Skull has three essential components:
- Brain tissue = 78%
- Blood = 12%
- Cerebrospinal fluid (CSF) = 10%
• Any increase in any of these tissues
causes increased ICP
Components of the Brain
Fig. 55-1
Intracranial Pressure
• Normal ICP = 4 -15 mmHg
• Factors that influence ICP
– Arterial pressure
– Venous pressure
– Intraabdominal and intrathoracic pressure
– Posture
– Temperature
– Blood gases (CO2 levels)
Intracranial Pressure
• The degree to which these factors  ICP
depends on the ability of the brain to
accommodate to the changes
Intracranial Pressure
Regulation and Maintenance
• Normal intracranial pressure
– The pressure exerted by the total volume
from the brain tissue, blood, and CSF
– If the volume in any one of the components
increases within the cranial vault and the
volume from another component is
displaced, the total intracranial volume will
not change
Intracranial Volume-Pressure Curve
Fig. 55-2
Intracranial Pressure
Regulation and Maintenance
• Normal compensatory adaptations
– Alteration of CSF absorption or
production
– Displacement of CSF into spinal
subarachnoid space
– Dispensability of the dura
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
Intracranial Pressure
Importance of ICP to BP and CPP
– Brain needs constant supply O2 and Glucose
– BP: heart delivers blood to brain at an average BP
of 120/80 (Mean BP = 100); this mean arterial
pressure (MAP) must be higher than ICP
– CPP (Cerebral Perfusion Pressure): is the pressure
needed to overcome ICP in order to deliver O2 &
nutrients
Intracranial Pressure
Importance of ICP to BP and CPP
– MAP is the DRIVING FORCE
– ICP is the RESISTENCE
– CPP = MAP – ICP
= 100 mmHg – 15 mmHg
= 85 mmHg (Normal)
CPP < 50 mmHg→ cerebral ischemia
CPP < 30 mmHg → brain death
Intracranial Pressure:
Regulatory Mechanisms of
Cerebral Blood Flow
• Autoregulation of cerebral blood flow
• Metabolic Regulation of cerebral blood
flow
Intracranial Pressure:
Regulatory Mechanisms of
Cerebral Blood Flow
• Autoregulation
– The automatic alteration in the
diameter of the cerebral blood vessels
to maintain a constant blood flow to
the brain
– Maintains CPP regardless of changes
in BP
Intracranial Pressure:
Regulatory Mechanisms of
Cerebral Blood Flow
• Problem: Autoregulation is limited
• If BP and/or ICP rises: Autoregulation
fails
• When autoregulation fails, blood flow to
brain increases or deceases → poor
perfusion and cellular ischemia or death
Intracranial Pressure:
Regulatory Mechanisms of
Cerebral Blood Flow
• Metabolic Regulation of cerebral
blood flow
Factors affecting cerebral blood flow
– PCO2
– PO2
– Acidosis
Increased Intracranial Pressure
Mechanisms of Increased ICP
• Causes
– Mass lesion
– Cerebral edema
– Head injury
– Brain inflammation
– Metabolic insult
Increased Intracranial Pressure
Mechanisms of Increased ICP
• Sustained increases in ICP result in
brainstem compression and herniation of
the brain from one compartment to
another
Increased Intracranial Pressure
Fig. 55-3
Herniation
Fig. 55-4
Increased Intracranial Pressure
Nursing Care: Assessment
• Change in level of consciousness
• Changes in vital signs (Cushing triad)
– Widening pulse pressure
– Tachy/Bradycardia
– Increased systolic BP
– Irregular respirations
Increased Intracranial Pressure
Nursing Care: Assessment
• Ocular signs
• Decrease in motor strength and function
– Assess movement
– Assess response to stimuli
– Assess:
• Decerebrate posturing (extensor)
– Indicates more serious damage
• Decorticate posturing (flexor)
Decorticate and Decerebrate Posturing
Fig. 55-6
Increased Intracranial Pressure
Nursing Care: Assessment
• Headache
– Often continuous and worse in the
morning
• Vomiting
– Not preceded by nausea
– Projectile
Increased Intracranial Pressure
Collaborative Care
• Hyperventilation therapy: suctioning →
hyperventilate with 100% oxygen
• Adequate oxygenation
– PaO2 maintenance at 100 mm Hg or
greater
– ABG analysis guides the oxygen therapy
– May require mechanical ventilator
Increased Intracranial Pressure
Collaborative Care
• Drug therapy
– Mannitol
– Loop diuretics
– Corticosteroids
– Barbiturates
– Antiseizure drugs
Increased Intracranial Pressure
Collaborative Care
• Nutritional therapy
– Patient is in hypermetabolic and
hypercatabolic state
–  Need for glucose
– Keep patient normovolemic
• IV 0.45% or 0.9% sodium chloride
Increased Intracranial Pressure
Nursing Management
Overall goals:
• ICP WNL
• Maintain patent airway
• Normal fluid and electrolyte balance
• No complications secondary to immobility
• Respiratory function
• Fluid and electrolyte balance
Increased Intracranial Pressure
Nursing Management
Overall goals (cont’d)
• Body position maintained in head-up
position: elevate HOB 30°
• Protection from injury: positioning/turning
• Pain control
• Psychologic considerations
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