Increased Intracranial Pressure (IICP)

Intracranial Pressure (ICP)

• Force exerted within the skull, resulting from the combined volume of three key components.
• Normal ICP ranges between 8-15 mmHg.
• An equilibrium is maintained by the three components of ICP.
• In an intact cranium, expansion is not possible.
• The three essential components include:
• Cerebrospinal Fluid (CSF): 75ml
• Blood Volume: 75ml
• Central Nervous System (CNS) Tissue: 1400g

Monro-Kellie Hypothesis

• States that because the skull has limited space for expansion, an increase in any of its components forces a change in the volume of the others.
• An increase in one element requires balancing or compensation through proportional constriction of other components.

Increased Intracranial Pressure (IICP)

• A syndrome characterized by an increase in CNS tissue, CSF fluid, or blood, leading to an ICP greater than 15 mmHg.
• A marked elevation in ICP will be noted once it reaches around 25mmHg.

Pathophysiology of IICP

• An increase in Brain Tissue/CSF/Blood Volume means there's no room for expansion.
• Compliance is maintained through the Monro-Kellie Hypothesis.
• The displacement of CSF into the spinal cavity is limited to a certain point.
• Decreased blood flow in the brain can only be maintained for a period of time.
• The limit for CSF displacement is eventually reached, resulting in Acidotic Cerebral Metabolism, which will cause IICP.
• Acidotic cerebral metabolism leads to acidotic environment and causes cerebral swelling, and worsening cerebral hypoxia and Ischemia.
• Cerebral hypoxia and ischemia can result in brain herniation.
• Brain Herniation causes brainstem compression.
• Ultimately, IICP may lead to death.

Impact of Increased ICP

• Impedes circulation to the brain.
• Stimulates further swelling.
• Impedes the absorption of CSF.
• Affects nerve cell function.
• Can lead to brainstem compression and death.
• May cause brain tissue shift, resulting in herniation, a frequently fatal event.

Clinical Manifestations

• When the brain's ability to adjust to ICP reaches its limits, neural function is impaired, leading to changes in Level of Consciousness (LOC).
• Lethargy can be an early sign.
• Sudden changes in condition are a sign.
• The patient may become stuporous and react only to loud auditory or painful stimuli.
• Profound coma may present dilated and fixed pupils, impaired respirations and possible death.

Cushing's Triad

• Hypertension plus widening pulse pressure.
• Bradycardia.
• Bradypnea.

Assessments for IICP

• Headache
• Vomiting
• Diplopia, CN VI
• Body temperature may be elevated or subnormal
• Pupillary changes
• Papilledema, swelling of the optic nerve
• Lateralizing sign, a contralateral loss of motor function because of the decussation of motor fibers at the level of the medulla oblongata.
• Brainstem function impairment
• Doll’s eye phenomenon
• Decortication
• Decerebration

Pupillary Changes

• Pupillary changes can include:
• Ipsilateral Pupil Dilation (CN 3 Compression)
• Bilateral Pupil Dilations
• Can include anisocoria (unequal pupil size) and unilateral pupil dilation.
• Doll's eye phenomenon is abnormal when present and may occur as the client experiences a decrease in LOC.
  • Occurs when the client's head is moved from side to side & the eye remain in a fixed midline position

Diagnostics

• CT scan
• MRI
• Cerebral angiogram
• EEG
• Caloric test, oculovestibular response

ICP Monitoring Device

• Purpose:
• To identify increased pressure early on.
• To quantify the degree of elevation.
• To initiate appropriate treatment.
• To provide access to CSF for sampling and drainage.
• To evaluate the effectiveness of treatment.
• Ways to measure ICP:
• Intraventricular catheter is the most accurate.
• Subarachnoid/Subdural screw/bolt.
• Epidural Sensor.

Medical Management

• Increased ICP is a true emergency and must be treated promptly.
• Goals:
• Invasive monitoring of ICP.
• Decreasing cerebral edema.
• Lowering the volume of CSF.
• Decreasing cerebral blood volume while maintaining cerebral perfusion.
• Pharmacologic therapy.
• Patient requires care in the critical care unit.

Pharmacotherapy

• Diuretics, like Mannitol or Lasix.
• Anticonvulsants, like Valium, Dilantin, Phenobarbital, or Tegretol.
• Antipyretics.
• Muscle relaxants.
• BP medication.
• Corticosteroids, like Decadron (dexamethasone).
• Antacids/H2 receptors.
• Anticoagulants.
• Stool softener.
• Intravenous fluids.
• Electrolyte replacement.
• Opiates & sedatives are contraindicated to the client with IICP because they induce cerebral hypoxia and vasodilation.

Treatment and Collaborative Management

• Adequate oxygenation or maintenance of respiratory function
• Position in Low Fowler's, approximately 30 degrees.
• Protection from injury.
• Avoidance of factors that increase ICP like nausea & vomiting, sneezing & coughing, valsalva maneuver, over suctioning, restraints, rectal examination, enema, and flexion of waist, hip, or neck.
• Control fever.
• Monitor intake & output.
• Limit fluid intake to 1200 ml/day.

Surgical Interventions

• Ventriculoperitoneal Shunt: shunts CSF from the ventricles into the peritoneum.
• Craniotomy for space occupying lesions and cerebral hematoma.

Complications

• Herniation.
• Seizures.
• Cognitive deficits.
• Motor deficits.
• Sensory deficits.
• Coma.
• Death.