Lab

Intracranial Pressure

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Intracranial Pressure, CSF Pressure, CSF Opening Pressure, Cerebral Perfusion Pressure

  • See Also
  • Background
  1. Not affected by systemic Blood Pressure
  2. Sensitive to blood pCO2
    1. Hyperventilation lowers Intracranial Pressure
  • Technique
  1. Counsel patient to try to relax
    1. Avoid Hyperventilation (lowers pressure)
    2. Avoid straining (raises pressure)
  2. Patient lies in lateral decubitus position
    1. Legs and neck should be in neutral position
    2. Opening pressure not accurate in sitting position
  • Interpretation
  1. Normal
    1. Children <8 years: 10 to 100 mm H2O
    2. Children >8 years: 60 to 200 mm H2O
    3. Adults: 60 to 200 mm H2O
    4. Obesity: 60 to 250 mm H2O
    5. Fluctuation
      1. With pulse: 2 to 5 mm H2O
      2. With respirations: 4 to 10 mm H2O
  2. Decreased: Intracranial Hypotension (uncommon)
    1. Trauma with secondary cerebrospinal fluid leak
    2. Recent Lumbar Puncture (Spinal Headache)
    3. Idiopathic Intracranial Hypotension
  3. Increased: Intracranial Hypertension
    1. See Increased Intracranial Pressure Causes
  • Calculation
  • Cerebral Perfusion Pressure (CPP)
  1. Cerebral Perfusion Pressure (CPP) = Mean Arterial Pressure (MAP) - Intracranial Pressure (ICP)
    1. Critical to maintain in Increased Intracranial Pressure in Trauma
    2. If continuous ICP monitoring, Arterial Line transducer should zeroed at the ear (kept at same height of head)
    3. Decreased Cerebral Perfusion Pressure risks brain ischemia
  • References
  1. Kooiker in Roberts (1998) Procedures in ER, p. 1067-75
  2. Ravel (1995) Lab Medicine, Mosby, p. 294-9
  3. Tunkel in Mandell (2000) Infectious Disease, p. 974-8
  4. Seehusen (2003) Am Fam Physician 68:1103-8 [PubMed]