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Increased Intracranial Pressure


Increased intracranial pressure (ICP) is not a symptom; rather, intracranial hypertension is a pathologic state common to a variety of serious neurologic illnesses ( Table 13.1 ). All conditions that result in increased ICP are characterized by an increase in intracranial volume. Accordingly, all therapies for ICP (hyperventilation, mannitol, etc.) are directed toward reducing intracranial volume.

Table 13.1
Conditions Associated With Increased ICP
Intracranial Mass Lesions

  • Subdural hematoma

  • Epidural hematoma

  • Intracerebral hemorrhage

  • Brain tumor

  • Cerebral abscess

Increased CSF Volume (or Resistance to Outflow)

  • Hydrocephalus

  • Benign intracranial hypertension (pseudotumor cerebri)

Increased Brain Volume (Cytotoxic Cerebral Edema)

  • Cerebral infarction

  • Global hypoxia-ischemia

  • Reye syndrome

  • Acute hyponatremia

Increased Brain and Blood Volume (Vasogenic Cerebral Edema)

  • Head trauma

  • Meningitis

  • Encephalitis

  • Lead encephalopathy

  • Eclampsia

  • Hypertensive encephalopathy

  • Dural sinus thrombosis

  • Subarachnoid Hemorrhage

CSF, Cerebrospinal fluid; ICP, intracranial pressure.

Normal ICP is less than 20 cm H 2 O, or 15 mm Hg. Because elevations beyond these levels can rapidly lead to brain damage and death, prompt recognition and treatment are essential. This chapter will be most useful in cases in which the pathology is known, and increased ICP is the suspected cause of clinical deterioration.

Phone call

Questions

  • 1.

    What is the patient’s underlying neurologic problem?

  • 2.

    Why is increased ICP suspected?

  • 3.

    What is the patient’s current level of consciousness?

Bedside

Quick-Look Test

Does the patient have clinical signs of increased ICP?

Increased ICP should be suspected in patients with known or suspected intracranial pathology (e.g., stroke, trauma, neoplasm) who exhibit the following symptoms and signs.

Signs that are almost always present:

    • Depressed level of consciousness (lethargy, stupor, coma)

    • Hypertension, with or without bradycardia

Symptoms and signs that are sometimes present:

    • Headache

    • Vomiting

    • Papilledema

    • Cranial nerve (CN) 6 palsies

Remember, however, that these signs may be nonspecific. For this reason, the only way to confirm the diagnosis and properly treat increased ICP is to measure it.

Does the patient have clinical signs of herniation?

Clinical signs of herniation, listed here, result from brain stem compression:

    • Loss of pupillary reactivity

    • Impairment of eye movements

    • Hyperventilation

    • Motor posturing (flexion or extension)

When ICP is differentially increased across the tentorium (as is usually the case with hemispheric mass lesions), pressure gradients lead to downward displacement of brain tissue into the posterior fossa. Herniation is often rapidly fatal but can be reversed in some cases by treatments that reduce intracranial volume and ICP.

Management I

Emergency Measures for Reduction of Intracranial Pressure

If the clinical signs of potentially increased ICP are identified in a comatose patient, the emergency measures listed in Box 13.1 can “buy time” prior to computed tomography (CT) scan and a definitive neurosurgical procedure (craniotomy, ventriculostomy, or placement of an ICP monitor).

Box 13.1
IV, Intravenous; P co 2 , partial pressure of carbon dioxide.
Emergency Treatment for Elevated Intracranial Pressure in an Unmonitored Patient

  • 1.

    Elevate head of bed 30–45 degrees

  • 2.

    Intubate and hyperventilate (target P co 2 is 28–32 mm Hg)

  • 3.

    Insert a Foley catheter

  • 4.

    Administer mannitol (20%) 1 to 1.5 g/kg IV rapid infusion

  • 5.

    Administer normal saline (0.9%) at 100 mL/h (avoid hypotonic fluids)

  • 6.

    Consult the neurosurgery service

Placement of an Intracranial Pressure Monitor

Most clinicians would not treat a patient with suspected high blood pressure (BP) without measuring it. However, empirical therapy for increased ICP (i.e., repeated doses of mannitol) without monitoring is used all the time to the great disadvantage of the patient. This approach is unsatisfactory because most ICP treatments are effective for a short time only, lose their efficacy with prolonged use, and have side effects. Optimally, therapy should be given when ICP is high and should be withheld when it is normal. Only the use of an ICP monitor can make this possible.

Indications for ICP monitoring (all three conditions should be met):

  • 1.

    The patient is in a coma (Glasgow Coma Scale score of < 8).

  • 2.

    Brain imaging shows intracranial mass effect or global brain edema.

  • 3.

    The prognosis is such that aggressive treatment in the intensive care unit (ICU) is indicated.

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