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Increased Intracranial Pressure

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Background 

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  • Etiology:

    • trauma, CNS tumors, hydrocephalus, hepatic encephalopathy, impaired venous outflow

  • Normal ICP ≤ 15mmHg in adults

    • Increased ICP ≥ 20 mmHg

  • Intracranial components = 1400 - 1700mL total

    1. Brain parenchyma = 80%, usually fixed in adults

    2. CSF = 10%, can vary greatly,

    3. Blood 10%, can vary greatly

    4. Pathologic structures = masses, abscesses, hematomas etc.

  • Monro-Kellie doctrine:

    • Cranial compartment is a fixed volume

    • ∴ increased in one component (blood, brain, CSF) means:

      1. displacement of other components or;

      2. increased ICP or;

      3. both 1 & 2

  • Main compensatory mechanisms for rising ICP:

      1. Displacement of CSF into thecal sac

      2. Displacement of venous blood from cranial vault

  • Major causes of increased ICP:

    • Intracranial masses (i.e. tumor, hematoma)

    • Cerebral edema (i.e. severe infarcts, severe TBI)

    • Increased CSF production

    • Decreased CSF absorption

    • Obstructive hydrocephalus

    • Obstructed venous outflow

    • Idiopathic ICH

  • Signs:

    • CN VI palsies, papilledema

    • Decreasing GCS

    • Decorticate or decerebrate posturing

    • Cushing triad: bradycardia, respiratory depression, hypertension

    • Herniation syndromes

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Management 

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  • Search for underlying treatable cause, for example:

    • Evacuating blood clot

    • Resection of mass

    • CSF drainage

  • R/o alternate causes of decreased GCS

    • hypotension, hypothermia, intoxication

  • ABCs

    • A: secure airway to allow for sedation and monitoring/controlling respiration

    • B: aim for hypocapnia, avoid hypoxemia

    • C: avoid hypotension, goal CPP 60-120mmHg with ICP monitor in-situ

  • Determine urgent/emergent patients:

      • GCS < 8

      • Worrisome history (i.e. head trauma or sudden thunder-clap headache)

      • Worrisome physical exam: Dilated & fixed pupils, decorticate/decerebrate posturing

      • Cushing's triad

    • If true emergency patients (i.e. impending herniation):

      • Employ measures below before continuing with further work-up

        • Elevated HOB

        • Hyperventilate PCO2 26-30mmHg

        • IV mannitol (1-1.5 g/kg)

    • If not an emergency (increased ICP is suspected and no immediately treatable cause)

      • Use ICP monitoring

        • Goal ICP < 20mmHg

      • Proceed with general strategies to lower ICP as proximate cause is being investigated

  • General strategies to lower ICP:

    • Aim for euvolemia

    • Serum osmolality 295 to 305 mOsm/L

      • Avoid free water

      • Use 0.9% NaCl

    • Elevate Head of bed

    • Treat fevers with acetominophen

    • Consider neuromuscular blockade

    • Sedate with propofol

    • Consider cooling

    • Consider seizure prophylaxis

  • Specific therapies to lower ICP:

    • Hypertonic Saline (250mL of 7.5%)

    • Mannitol (1g/kg bolus, then 0.25-0.5mg/kg q6-8hrs)

    • Consider glucocorticoids if brain tumor or CNS infection

    • Hyperventilate to PaCO2 26-30 (lasts <24hrs)

    • Barbiturates (pentobard load 5-20 mg/kg bolus then 1-4 mg/kg/hr)

      • Need EEG monitoring to avoid burst suppression

    • Ventriculostomy if hydrocephalus is present

      • Remove CSF at 1-2 mL/minute for 2-3 mins at a time, aim for ICP <20mmHg

    • Decompressive craniectomy

 

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References 

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  • Schizodimos, T., Soulountsi, V., Iasonidou, C. et al. An overview of management of intracranial hypertension in the intensive care unit. J Anesth 34, 741–757 (2020). https://doi.org/10.1007/s00540-020-02795-7

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