Intracranial pressure

Revision as of 03:59, 27 August 2020 by SAI (talk | contribs) (→‎Risk Factors)
Jump to navigation Jump to search
Intracranial pressure
Severely high ICP can cause herniation.

WikiDoc Resources for Intracranial pressure

Articles

Most recent articles on Intracranial pressure

Most cited articles on Intracranial pressure

Review articles on Intracranial pressure

Articles on Intracranial pressure in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Intracranial pressure

Images of Intracranial pressure

Photos of Intracranial pressure

Podcasts & MP3s on Intracranial pressure

Videos on Intracranial pressure

Evidence Based Medicine

Cochrane Collaboration on Intracranial pressure

Bandolier on Intracranial pressure

TRIP on Intracranial pressure

Clinical Trials

Ongoing Trials on Intracranial pressure at Clinical Trials.gov

Trial results on Intracranial pressure

Clinical Trials on Intracranial pressure at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Intracranial pressure

NICE Guidance on Intracranial pressure

NHS PRODIGY Guidance

FDA on Intracranial pressure

CDC on Intracranial pressure

Books

Books on Intracranial pressure

News

Intracranial pressure in the news

Be alerted to news on Intracranial pressure

News trends on Intracranial pressure

Commentary

Blogs on Intracranial pressure

Definitions

Definitions of Intracranial pressure

Patient Resources / Community

Patient resources on Intracranial pressure

Discussion groups on Intracranial pressure

Patient Handouts on Intracranial pressure

Directions to Hospitals Treating Intracranial pressure

Risk calculators and risk factors for Intracranial pressure

Healthcare Provider Resources

Symptoms of Intracranial pressure

Causes & Risk Factors for Intracranial pressure

Diagnostic studies for Intracranial pressure

Treatment of Intracranial pressure

Continuing Medical Education (CME)

CME Programs on Intracranial pressure

International

Intracranial pressure en Espanol

Intracranial pressure en Francais

Business

Intracranial pressure in the Marketplace

Patents on Intracranial pressure

Experimental / Informatics

List of terms related to Intracranial pressure

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Luke Rusowicz-Orazem, B.S., Sabeeh Islam, MBBS[2]

Overview

Intracranial pressure, (ICP), is the pressure exerted by three structures inside the cranium; brain parenchyma, CSF and blood. The norma ICP is 10-15 mmHg and is usually maintained by equilibrium of the intracranial contents. Intracranial hypertension ( IH), is elevation of the pressure in the cranium. It typically occurs when the ICP is >20 mmHg.

Historical Perspective

  • In 1950s, therapeutic hypothermia (goal core temperature of 32-34C) was first introduced as a treatment for brain injury.

Classification[edit | edit source]

  • Elevated intracranial pressure or Intracranial hypertension may be classified into two subtypes/groups:
  • Acute
  • Chronic
  • Intracranial hypertension may also be classified as various stages:
    • Stage 1: Minimal increases in ICP due to compensatory mechanisms
    • Stage 2:
      • Any change in volume greater than 100–120 mL
      • Exhaustion of compensatory mechanisms
      • Compromise of neuronal oxygenation and systemic arteriolar vasoconstriction to increase MAP and CP
    • Stage 3:
      • Sustained increased ICP
      • Dramatic changes in ICP with small changes in volume
      • The ICP approaches the MAP,

Increased ICP:

Intracranial pressure, (ICP), is the pressure exerted by three structures inside the cranium; brain parenchyma, CSF and blood. The norma ICP is 10-15 mmHg and is usually maintained by equilibrium of the intracranial contents.

Intracranial Hypertension:

Intracranial hypertension ( IH), is elevation of the pressure in the cranium. It typically occurs when the ICP is >20 mmHg.

Pathophysiology

Intracranial components and their proportions:

  • Brain parenchyma volume: 1400 ml (80%)
  • CSF volume: 10 ml (10%)
  • Blood volume: 10 ml (10%)

The Monro-Kellie Hypothesis:

  • The Monro-Kellie hypothesis explains the relationship between the contents of the cranium and intracranial pressure. It explains the underlying pathophysiology of elevated intracranial pressure or intracranial hypertension
  • In normal physiological state, intracranial contents (the brain tissue, the blood, and the cerebrospinal fluid) maintain an equilibrium state and keep the ICP within normal range by acting as compensatory mechanisms for small volume changes
  • Compensatory mechanisms are being exhausted by large volume changes, eventually causing significantly elevated intracranial pressures and potential herniation

Intracranial compliance:

  • There is an inverse relationship between intracranial components and the compliance.
  • Generally the normal compliance is maintained by compensatory mechanisms such as
    • Increased CSF reabsorption via thecal sac
    • Increased venoconstriction to decrease cerebral venous flow
    • Decreased cerebral venous flow via increased extracranial drainage

Cerebral Blood Flow (Ohm's Law):

  • Cerebral blood flow is generally assessed by subtracting jugular venous pressure from carotid arterial pressure and dividing by cerebrovascular resistance, as follows:
    • CBF = (CAP - JVP) ÷ CVR
    • Cerebral perfusion is assessed by cerebral perfusion pressure (CPP). CPP is calculated by subtracting ICP from mean arterial pressure, as follows:
    • CPP = MAP - ICP
    • In normal physiological states, ICP and CPP is maintained by autoregulation.

Several pathophysiologic mechanisms are thought to be involved in the pathogenesis of Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH). All mechanisms eventually lead to brain injury from brain stem compression and decreased cerebral blood supply or ischemia. These mechanisms are as follows:

    • Mass effect
      • It can occur secondary to brain tumor, contusions, subdural or epidural hematoma, or abscess
    • Cerebral edema or Generalized brain swelling
      • It can occur secondary to ischemic-anoxia states, hypertensive encephalopathy, pseudotumor cerebri, hypercarbia, and hepatocerebral syndrome.
      • These conditions tend to decrease the cerebral perfusion pressure but with minimal tissue shifts.
    • Increase in venous pressure
      • Secondary to venous sinus thrombosis, heart failure, neck surgery or obstruction of superior mediastinal or jugular veins.
    • Obstruction to CSF flow
      • Secondary to hydrocephalus, extensive meningeal disease (e.g., infectious, carcinomatous, granulomatous, or hemorrhagic), or obstruction in cerebral convexities and superior sagittal sinus (decreased absorption).
    • Increased CSF production
      • Meningitis, subarachnoid hemorrhage, or choroid plexus tumor.
    • Increased cerebral blood flow (CBF)
      • Increased CBF is generally seen in conditions associated with hypercapnia and hypoxia
    • Drugs
    • Idiopathic
      • Pseudotumor cerebri


Causes

Common Causes

Differential Diagnosis of Increased Intracranial Pressure (ICP)

Epidemiology and Demographics

  • The prevalence of intracranial hypertension is approximately 1.0 per 100,000 individuals worldwide.

Gender

  • Idiopathic ICH is more prevalent among women of childbearing age.

Risk Factors

  • Common risk factors in the development of Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH) include underlying pathologies such as; mass lesions, abscesses, and hematomas.
  • Other risk factors include
    • Obesity
    • Chronic hypertension
    • Women of childbearing age

Natural History, Complications and Prognosis

  • Early clinical features include nausea, vomiting, and confusion.
  • If left untreated, patients may progress to have severe neurologic consequences such as brain herniation, brain death, respiratory depression, coma and death.
  • Common complications of intracranial hypertension include brain herniation and neurologic deficits.

Diagnosis

Diagnostic Criteria

  • The diagnosis of Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH) is made when ICP is >20 mmHg.

History and Symptoms

  • Symptoms of elevated intracranial pressure may include the following:

Physical Examination

  • Physical examination may be remarkable for

Laboratory Findings

  • There are no specific laboratory findings associated with Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH).

Electrocardiogram

  • There are no ECG findings associated with Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH).

X-ray

  • There are no x-ray findings associated with Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH).

CT scan

  • CT scan may be helpful in the diagnosis of Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH).
  • Findings on CT scan suggestive of Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH) include presence of mass lesions, midline shift or hemorrhage
  • CT scan is particularly helpful for people with acute rise in ICP

MRI

  • MR venography (MRV) is preferred over MRI for the diagnosis of cerebral venous thrombosis
  • MRI has a greater sensitivity to detect subtle intracranial masses (eg, gliomatosis cerebri) and meningeal-based pathologies and should be done if no contraindications (eg, pacemakers, metallic clips in head, metallic foreign bodies) present

Other Diagnostic Studies

Other diagnostic studies for Increased Intracaranial pressure (ICP) or Intracranial hypertension (ICH) include invasive and non-invasive ICP monitoring, particularly preferred in patients with no CT or MRI findings, at risk of developing increased ICP, and comatosed.

  • Invasive ICP monitoring usually involves 4 anatomic sites
    • Intraventricular
    • Intraparenchymal
    • Subarachnoid
    • Epidural
  • Noninvasive devices still need further large randomized trials to prove their clinical efficacy. They are not used in clinical practice but are still under investigation and include
    • Transcranial Doppler (TCD)
    • Tissue resonance analysis (TRA)
    • Ocular sonography
    • Intraocular pressure
    • Tympanic membrane displacement

Treatment

Medical Therapy

  • The management of intracranial hypertension is generally directed towards treating the cause/etiology of the raised intracranial pressure.
  • Intracranial hypertension is considered a medical emergency and the management includes emergent resuscitative as well as specific treatment.

Resuscitation:

General principles for resuscitation include

  • Maintain oxygen
  • Head elevation
  • Hyperventilation to achieve a PaCO2 of 26-30 mmHg
  • Osmotic diuresis with intravenous mannitol and Lasix
  • Appropriate sedation, if patient requires intubation. Propofol is considered to be the preferred agent.
  • Therapeutic hypothermia to achieve a low metabolic state
  • Appropriate choice of fluids to achieve euvolemic state. Avoid hypotonic agents
  • Allow permissive hypertension. Treat hypertension only when CPP >120 mmHg and ICP >20 mmHg
  • Seizure prophylaxis with anticonvulsant therapy.


Other therapies for intracranial hypertension:

  • Osmotic diuresis can be achieved by hypertonic saline bolus or mannitol. Hypertonic saline is usually considered to be more effective compared to mannitol for acute ICP reduction.

Mannitol can be given as a bolus of 1 g/kg when prepared as 20% solution. The dose is usually repeated every 6-8 hours. It should be used cautiously in patients with renal insufficiency. Intravenous Lasix (0.5 to 1 mg/kg) is usually given with mannitol.

  • Glucocorticoids are usually preferred when the underlying etiologies brain tumor are underlying CNS infection. Their use is contraindicated in head injury, cerebral infarction and intracranial hemorrhage.
  • Phenobarbital is considered to have a neuroprotective effect by decreasing brain metabolism. It is given as a loading dose of 5 to 20 mg/kg, followed by 1 to 4 mg/kg per hour. EEG monitoring is used to guide therapy. A burst suppression seen on EEG indicates maximal dosing.

Surgery

Surgical options for persistent intracranial hypertension include

  • Surgical evacuation
  • CSF drainage via ventriculostomy
    • CSF is usually drained at a rate of 1 to 2 mL/minute for 2 to 3 minutes. The procedure is repeated after every 2 to 3 minutes, until ICP is less than 20mmHg
  • Decompressive craniectomy

Prevention

  • Effective measures for the primary prevention of intracranial hypertension include early detection of underlying intracranial etiology such as tumor or congenital deformities.
  • Once diagnosed and successfully treated, patients with intracranial hypertension are followed up every 6 months to 1 year with a head CT scan to prevent secondary complications.

References

Additional Resources

  • Monroe A. Observations on the structure and function of the nervous system, Edinburgh: Creech & Johnson; 1783.
  • Kelly G. An account of the appearances observed in the dikssection of two of three individuals presumed to have perished in the storm of the 3rd, and whose bodies were deiscovered in the vicinity of the Leith on the morning of the 4th of November 1821, with some reflections on the pathology of the brain, Trans Med Chir Sci Edinb 1824;1:84–169.

External links


Template:WikiDoc Sources