Acute Intracranial Problems Notes

Key Components of the Skull

• The skull contains three essential components:

  • Brain Tissue: 78% of total volume

  • Blood: 12% of total volume

  • Cerebrospinal fluid (CSF): 10% of total volume

Intracranial Pressure (ICP)

• Definition: The pressure within the skull influenced by the volume of blood, brain tissue, and CSF.

• Monro-Kellie Doctrine:

  • The total volume inside the skull is fixed. Increases in one component (blood, CSF, or brain tissue) must be compensated by a decrease in one of the others to maintain normal ICP.

  • Normal ICP ranges from 5 to 15 mm Hg. Sustained pressure above 20 mm Hg is considered abnormal.

• Factors Affecting ICP:

  • Arterial pressure

  • Venous pressure

  • Intra-abdominal and intrathoracic pressure

  • Posture, temperature, and blood gases (especially CO2 levels)

Compensatory Mechanisms for Increased ICP

• Changes in:

  • CSF Volume

  • Intracranial Blood Volume

  • Tissue Brain Volume

• Failure of compensatory mechanisms leads to increased ICP, decompensation, and ischemia.

Cerebral Blood Flow (CBF)

• Definition: The volume of blood passing through 100g of brain tissue per minute. Global CBF is approximately 50 mL/min/100 g.

• Autoregulation: Ability of cerebral vessels to maintain constant blood flow despite changes in systemic blood pressure (effective at MAP 70-150 mm Hg).

• Cerebral Perfusion Pressure (CPP):

  • Formula: CPP = MAP - ICP

  • Normal range: 60 - 100 mm Hg; less than 50 mm Hg indicates potential ischemia. Less than 30 mm Hg is incompatible with life.

Assessment and Diagnosis

• Clinical indications of increased ICP include:

  • Cushing’s Triad: Systolic hypertension, bradycardia, irregular respiration.

  • Changes in level of consciousness, vital signs, and body temperature.

• Diagnostic Studies for ICP Measurement:

  • Imaging: CT, MRI, PET

  • Monitoring devices for ICP: Ventriculostomy (standard), fiberoptic catheter, epidural, intraparenchymal, and subarachnoid placements.

Types of Cerebral Edema

1. Vasogenic: Disruption of blood-brain barrier, leading to fluid leakage.

2. Cytotoxic: Cellular injury causing fluid shift from extracellular to intracellular spaces.

3. Interstitial: Often due to hydrocephalus; causes ventricular enlargement.

Clinical Manifestations of Increased ICP

• Neurological Signs:

  • Altered LOC (flattening of affect to coma)

  • Changes in pupil response (dilated pupil indicates possible herniation)

  • Motor function decline (hemiparesis, posturing).

• Other Symptoms:

  • Persistent headaches, vomiting not preceded by nausea, and possible seizures.

Management of Increased ICP

• Goals include maintaining normal ICP, adequate oxygenation, and preventing secondary injuries.

• Interventions:

  • Optimize head positioning, avoid neck flexion, and control environmental stimuli.

  • Pharmacotherapy: Mannitol, hypertonic saline, corticosteroids, antiseizure medications.

  • Surgery may be required for mass lesions (like hematomas).

Nursing Assessment

• Use the Glasgow Coma Scale and assess:

  • Level of consciousness, pupil response, motor strength, vital signs, and respiratory patterns.

  • Monitor for signs of herniation and increased ICP.

Overall Nursing Goals

• Maintain adequate cerebral oxygenation and perfusion, control pain and discomfort, ensure normal body temperature, and keep the patient free from infection.

These notes summarize the critical aspects of acute intracranial problems, focusing on ICP, cerebral blood flow, and the management of head injuries, incorporating key definitions, pathophysiology, and clinical manifestations.