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  • Increased Intracranial Pressure
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Key Formulas

  • CPP = MAP - ICP
  • MAP = ((2 x diastolic) + systolic)/3

Where:

  • CPP = Cerebral perfusion pressure
  • MAP = Mean arterial pressure
  • ICP = Intracranial pressure


Normal Values

Normal ICP is 5-15 cm H20.
Normal CPP is > 60 cm H2O


Herniation Syndromes

  • Cingulate herniation: Displacement of the cingulate gyrus under the falx cerebri with subsequent compression of the internal cerebral vein. Can compress the ipsilateral anterior cerebral artery producing subsequent vascular ischemia, edema, and progressive mass effect.
  • Central / transtentorial herniation: Downward displacement of the hemisphere with compression of the diencephalon and midbrain through the tentorium. Displacement of the diencephalon against the midbrain produces hemorrhage in the pretectal region and the thalamus. The medial perforating braches of the basilar artery rupture during derniation of the midbrain and pons.
  • Uncal herniation: Shift of the temporal lobe, uncus, and hippocampal gyrus toward the midline with compression of the adjacement midbrain. Ipsilateral third cranial nerve and PCA compressed by uncus and edge of the tentorium. Leads to a dilated ipsilateral pupil and occipital lobe ischemia. Further increased ICP from compression of the aqueduct. Expansion of the supratentorial volume can produce pressure necrosis of the para-hippocampal gyrus.
  • Cerebellar tonsillar herniation: Compression of teh medulla with respiratory compromise and death.
  • Upward cerebellar herniation: Causes hydrocephalus, coma. Caudal to rostral progression of dysfunction.


Treatment of increased ICP

  • Head of bed at >= 30 degrees.
  • Decrease stimulation.
  • No hypotonic fluids. If you need to treat hypernatremia, use enteral free water.
  • Hyperventilation to pCO2 of 25-30 has an immediate effect, but is short lived. Hypocapnia causes cerebral vasoconstriction.
  • Mannitol: 0.5 - 1 g/kg IV load over 10 minutes followed by 0.25 - 0.5 g/kg IV q4-6 hours. Check serum osmolality and aim for a goal of 310-320. Don't use longer than 5 days.
  • Steroids: Only useful for vasogenic edema (i.e. tumors, abscesses). Dexamethasone 4 mg or methylprednisolone 20mg. The is no indication for steroids for edema due to ischemic or hemorrhagic stroke.
  • Consult neurosurgery for consideration of ventriculostomy or decompression.
  • Consider pharmacological coma or hypothermia.



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