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Neurologic Formulas and Parameters

INTRACRANIAL PRESSURE

  • Normal 0 to 20 mmHg

CEREBRAL PERFUSION PRESSURE (CPP)

Formula: CPP = Mean Arterial Pressure (MAP) − Intracranial Pressure (ICP)

  • Infants: 40 mmHg

  • Adults: 65 mmHg

    • Changes throughout development: parallels changes in systemic blood pressure (BP); increases gradually throughout development to adult levels.

    • Consider patient's baseline BP: Baseline MAP should be considered when considering therapeutic target for CPP in setting of acute neurologic injury. A patient with baseline hypertension will need blood pressure supported to a level that approximates their baseline physiology.

    • In adults poor outcomes are associated with sustained CPP <40 mmHg.

CEREBRAL BLOOD FLOW (CBF)

  • Infants: 40 mL/100 g/min

  • Children (4 years): 100 mL/100 g/min

  • Children (9 years): 50 to 70 mL/100 g/min

  • Adults: 50 mL/100 g/min

CEREBRAL METABOLIC RATE FOR OXYGEN (CMRO2)

  • Normal: 3.0 to 3.8 mL O2/100 g brain/min

CEREBROSPINAL FLUID (CSF)

Normal values:

  • White blood cell count (WBC): 0 to 5

  • Total protein: 22 to 38 mg/dL

  • Glucose: 60% to 80% of serum glucose

GLASGOW COMA SCALE (GCS)

TABLE 38-1

Glasgow Coma Scale

SUGGESTED READINGS

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Downard C, Hulka F, Mullins RJ,  et al. Relationship of cerebral perfusion pressure and survival in pediatric brain injured patients. J Trauma. 2000;49(4):654–658.  [PubMed: 11038082]
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Teasdale G, Jennett B. Assessment of coma and impaired consciousness. A practical scale. Lancet. 1974;304(7872):81–84.

Neurosurgical and Neurologic Emergencies

NEUROSURGICAL EMERGENCIES

MONRO KELLIE DOCTRINE

  • Physiology: Most cases of neurosurgical emergencies are related to the volume-occupying relationship between the brain matter, cerebral blood volume, and cerebrospinal fluid volume sharing space in the fixed-volume compartment of the skull (See Figure 39-1)

    • Changes in the relative volume of one of these components require compensatory change in the volume occupied by one or more of the other components

    • In the event that a change in the volume of one component overwhelms compensatory mechanisms, brain matter may move along the path of least resistance as it is pushed by pathologically elevated pressure within the calvarium

      • Cerebellar herniation via the foramen magnum

      • Transtentorial herniation across the falx cerebri

        ...

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