Increased Intracranial Pressure (Intracranial Hypertension)

Physiology

Cranial Vault

  • Cranial Vault Volume: 1400-1700 mL (this volume is fixed in an individual)
  • Intracranial Components
    • 80%: Brain
    • 10%: Cerebrospinal Fluid (CSF)
    • 10%: Blood
  • Monro-Kellie Doctrine: intracranial pressure is a function of the compliance of each component of the intracranial compartment
    • Based on Rigid Structure of the Skull and Inability of Cranial Vault Volume to Change: increased volume in any of the three intracranial components may result in intracranial hypertension
    • Relationship Between Intracranial Volume and Intracranial Pressure is Exponential: with initial increase in volume, pressure rises only slightly, but when the buffering capacity of the system is exceeded, intracanial pressure rises rapidly -> this explains the rapid clinical deterioration that may occur in the setting of a traumatic intracranial hematoma
  • Normal Intracranial Pressure (Adult): <15 mm Hg
    • Intracranial Pressure Fluctuates with Cardiac and Respiratory Cycles
    • Transient Increases in ICP May Occur During Coughing/Sneezing
    • Pathologically Increased ICP is Defined as Sustained ICP >20 mm Hg
    • ICP is Normally Lower in Children (and May Be Subatmospheric in Newborns)

Cerebral Blood Flow

  • Hypercapnia and Hypoxia Increase Cerebral Blood Flow

Cerebral Perfusion Pressure (CPP)

  • Cerebral Perfusion Pressure = MAP-ICP

Cerebrospinal Fluid (CSF) Dynamics

  • Cerebrospinal Fluid is Produced in the Choroid Plexus and Other Locations Within the Central Nervous System: CSF is produced at a rate of 20 mL/hr
  • Cerebrospinal Fluid is Normally Absorbed by the Arachnoid Granulations into the Venous System

Etiology of Increased Intracranial Pressure (by Predominant Mechanism)

Cerebral Edema

  • Anoxic/Ischemic Encephalopathy (see Hypoxic-Ischemic Brain Injury, [[Hypoxic-Ischemic Brain Injury]])
    • Physiology
      • Cerebral Edema
  • Cerebral Venous Thrombosis
    • Physiology
      • Altered Cerebrospinal Fluid Circulation
      • Cerebral Edema
  • During the Course of Therapy for Diabetic Ketoacidosis/Hyperosmolar Hyperglycemic State (see Diabetic Ketoacidosis and Hyperosmolar Hyperglycemic State, [[Diabetic Ketoacidosis and Hyperosmolar Hyperglycemic State]])
    • Physiology
      • Cerebral Edema
  • Fulminant Hepatic Failure (FHF) (see Fulminant Hepatic Failure, [[Fulminant Hepatic Failure]])
    • Etiology
    • Physiology
      • Cerebral Edema
      • Cerebral Vasodilation
  • High-Altitude Cerebral Edema (HACE) (see High-Altitude Cerebral Edema, [[High-Altitude Cerebral Edema]])
    • Physiology
      • Cerebral Edema
  • Hypertensive Encephalopathy (see Hypertension, [[Hypertension]])
    • Physiology
      • Cerebral Edema
  • Hyponatremia (see Hyponatremia, [[Hyponatremia]])
    • Physiology
      • Cerebral Edema
  • Large Intracerebral Hemorrhage (see Intracerebral Hemorrhage, [[Intracerebral Hemorrhage]])
    • Physiology
      • Cerebral Edema
      • Mass Effect
  • Large Ischemic Cerebrovascular Accident (CVA) (see Ischemic Cerebrovascular Accident, [[Ischemic Cerebrovascular Accident]])
    • Physiology
      • Cerebral Edema
  • Malaria (see Malaria, [[Malaria]])
    • Physiology
      • Cerebral Edema
  • Meningitis (see Meningitis, [[Meningitis]])
    • Physiology
      • Cerebral Edema
  • Subarachnoid Hemorrhage (SAH) (see Subarachnoid Hemorrhage, [[Subarachnoid Hemorrhage]])
    • Physiology
      • Altered Cerebrospinal Fluid Circulation
      • Cerebral Edema
      • Mass Effect
  • Traumatic Brain Injury (TBI) (see Traumatic Brain Injury, [[Traumatic Brain Injury]])
    • Physiology
      • Cerebral Edema
      • Mass Effect
      • Cerebral Vasodilation

Cerebral Vasodilation

  • Fever (see Fever, [[Fever]])
    • Physiology
      • Cerebral Vasodilation
  • Hypoxemia (see Hypoxemia, [[Hypoxemia]])
    • Physiology
      • Cerebral Vasodilation
  • Hypercapnia (see Hypercapnia, [[Hypercapnia]]): hypercapnia causes cerebral vasodilation
    • Physiology
      • Cerebral Vasodilation
  • Hypotension (see Hypotension, [[Hypotension]])
    • Physiology
      • Cerebral Vasodilation
  • Seizures (see Seizures, [[Seizures]])
    • Physiology
      • Cerebral Vasodilation

Intracranial Mass Lesion

  • Brain Abscess (see Brain Abscess, [[Brain Abscess]])
    • Physiology
      • Cerebral Edema
      • Mass Effect
  • Brain Tumor
    • Physiology
      • Cerebral Edema
      • Mass Effect

Decreased Cerebrospinal Fluid (CSF) Absorption

  • Post-Bacterial Meningitis Arachnoid Granulation Adhesions (see Meningitis, [[Meningitis]])

Increased Cerebrospinal Fluid (CSF) Production

  • Choroid Plexus Papilloma

Obstructive Hydrocephalus (see Hydrocephalus, [[Hydrocephalus]])

  • xxxx

Increased Arterial Blood Pressure/Hypertension

  • Bladder Distention
  • Pain

Obstruction of Venous Outflow from Brain

  • Abdominal Compartment Syndrome (see Abdominal Compartment Syndrome, [[Abdominal Compartment Syndrome]])
    • Physiology: increased venous pressure
  • Jugular Vein Compression
    • Physiology
      • Neck Position
      • Restrictive Neck Dressing
  • Neck Surgery
  • Pneumothorax (see Pneumothorax, [[Pneumothorax]])
    • Physiology: increased venous pressure
  • Sagittal Sinus Thrombosis (see Cerebral Venous Thrombosis, [[Cerebral Venous Thrombosis]])
  • Other Venous Sinus Thrombosis
  • Patient-Ventilator Dyssynchrony
    • Physiology: increased venous pressure

Idiopathic Intracranial Hypertension (Pseudotumor Cerebri) (see Pseudotumor Cerebri, [[Pseudotumor Cerebri]])

  • Physiology
    • Altered Cerebrospinal Fluid Circulation: probable mechanism

Transiently Increased Intracranial Pressure

Other

  • Craniosynostosis
    • Physiology: inadequate skull growth
  • Reye’s Syndrome
    • Physiology: vasodilation
  • Succinylcholine (see Succinylcholine, [[Succinylcholine]])
    • Physiology: xxx

Diagnosis

Head CT (see Head Computed Tomography, [[Head Computed Tomography]])

  • xxx

Brain MRI (see Brain Magnetic Resonance Imaging, [[Brain Magnetic Resonance Imaging]])

  • xxx

External Ventricular Drain (EVD) (see External Ventricular Drain, [[External Ventricular Drain]])

  • Indications for Monitoring in the Setting of Traumatic Brain Injury (Guidelines for the Management of Severe Traumatic Brain Injury, 2007) [MEDLINE]
    • All Salvageable Patients with Severe TBI, GCS 3-8 After Resuscitation, and an Abnormal CT Scan (Hematoma, Contusion, Edema, Herniation, Compressed Basal Cisterns) (Level II Recommendation)
    • Severe TBI with Normal CT Scan with Two or More Criteria at Admission: Age >40 y/o, Unilateral or Bilateral Motor Posturing, SBP <90 mm Hg (Level III Recommendation)
  • Contraindications
    • Coagulopathy (see Coagulopathy, [[Coagulopathy]]): relative contraindication
    • Thrombocytopenia with Platelets <100k (see Thrombocytopenia, [[Thrombocytopenia]]): relative contraindication
  • Adverse Effects/Complications
    • Intracerebral Hemorrhage: rate of hemorrhage with ventricular catheter is 1-7%
      • Rate of Hemorrhage for Intraparenchymal Monitor is Less Than That of Ventricular Catheter
      • Hemorrhages Rarely Require Surgical Evacuation
    • Infection/Ventriculitis (see Central Nervous System Device Infection, [[Central Nervous System Device Infection]])
      • Culture of Tip of External Ventricular Drains May Demonstrate Bacterial Colonization: however, the rate of invasive infection is lower
      • Risk of Infection is Higher with Ventricular Catheter (1-27%) Than with Parenchymal Monitor
      • Risk Factors for Infection
        • Leakage Around the Ventriculostomy Site
        • Longer Duration of Catheter Placement
        • Presence of Open Skull Fracture with Leakage of Cerebrospinal Fluid

Clinical Manifestations

Neurologic Manifestations

Coma (see Obtundation-Coma, [[Obtundation-Coma]])

  • xxx

Brain Herniation

  • Routes of Brain Herniation
    • Hemisphere is Displaced Medially Against the Falx, Resulting in Falcine Herniation
    • Unilateral Pressure Gradient Pushes the Medial Edge of the Temporal Lobe (Uncus) Through the Tentorial Foramen, Resulting in Uncal Herniation
      • Third Cranial Nerve and Posterior Cerebral Artery are Compressed -> Unilateral Pupillary Dilation, Lack of Response to Light, and Infarction
      • Brainstem is Distorted and Compressed with Early Impairment of Consciousness
    • Bilateral Homogeneous Increase in Intracranial Pressure in the Supratentorial SPace Displaces the Brain Downward Through the Tentorial Foramen, Resulting in Transtentorial Herniation
      • Brainstem is Compressed and Displaced Downward without Signs of Lateralization -> Bilateral Pupillary Abnormalities

Other Manifestations

  • xxx

Management of Increased Intracranial Pressure (ICP)

General Measures

  • Avoid Increases in ICP >20-25 cm H2O
  • Body Position: keep head at 30 degree elevation

Sedation

Barbiturates (see Barbiturates, [[Barbiturates]])

  • Pharmacology

    • Decrease Cerebral Blood Flow: decreasing intracranial pressure
    • Decrease Cerebral Metabolism

      Propofol (Diprivan) (see Propofol, [[Propofol]])

  • Pharmacology

    • Onset: rapid
    • Half-Life (with Infusion): 30-60 min
      • Longer Half-Life is Observed After Prolonged Infusion, Due to Redistribution from Fat Stores
      • However, the Duration of the Clinical Effect is Typically Minutes, as Propofol is Rapidly Distributed into Peripheral Tissues
  • Properties
    • Amnestic Effect (see Amnesia, [[Amnesia]])
    • Anti-Emetic Effect
    • Anxiolytic Effect
    • Decreases Intracranial Pressure (see Increased Intracranial Pressure, [[Increased Intracranial Pressure]])
    • Increases Seizure Threshold
    • Sedative Effect
    • No Analgesic Effect
    • Large Lipid Load: requiring adjustment of enteral/parenteral nutritional support
  • Administration
    • Dose: 10-60 μg/kg/min
    • Decrease Dose in Elderly by 20%
    • Slow Administration in Elderly

Other Pharmacologic Interventions

Mannitol (see Mannitol, [[Mannitol]]): indicated for

  • Indications
    • xxxx
  • Pharmacology: osmotic diuretic
  • Adverse Effects
    • xxxx

Hyperosmolar Fluids

Corticosteroids (see Corticosteroids, [[Corticosteroids]])

  • Indications
    • xxxx

Respiratory Support

  • Mechanical Ventilation (see General Ventilator Management, [[General Ventilator Management]])
    • Avoid Hypoxemia (see Hypoxemia, [[Hypoxemia]]): hypoxemia causes cerebral vasodilation
    • Avoid Hypercapnia (see Hypercapnia, [[Hypercapnia]]): hypercapnia causes cerebral vasodilation
    • Avoid Patient-Ventilator Dyssynchrony
  • Treat Airway Obstruction: airway clearance, intubation, etc

Treatment of Cerebral Vasodilation

  • Treat Fever (see Fever, [[Fever]])
    • Rationale: fever causes cerebral vasodilation
    • Standard Therapy
  • Treat Hypotension (see Hypotension, [[Hypotension]])
    • Standard Therapy
  • Treat Seizures (see Seizures, [[Seizures]])
    • Rationale: seizures result in cerebral vasodilation
    • Agents

Treatment of Increased Arterial Blood Pressure/Hypertension (see Hypertension, [[Hypertension]])

  • Treat Bladder Distention
  • Treat Pain
    • Analgesics

Treatment Increased Venous Pressure

  • Neck Repositioning/Removal of Restrictive Neck Dressings
  • Treat Abdominal Compartment Syndrome (see Abdominal Compartment Syndrome, [[Abdominal Compartment Syndrome]])
    • Exploratory Laparotomy with Decompression
  • Treat Abdominal Distention/Ileus
  • Treat Pneumothorax (see Pneumothorax, [[Pneumothorax]])

Treatment of Hydrocephalus/Disturbance in Cerebrospinal Fluid Flow (see Hydrocephalus, [[Hydrocephalus]])

Treatment of Hyponatremia (see Hyponatremia, [[Hyponatremia]])

  • Rationale: hyponatremia causes cerebral edema
  • Standard Therapy

Renal Management

  • Choice of Intermittent Hemodialysis vs Continuous Venovenous Hemodialysis (CVVHD)
    • If Hemodialysis is Required, CVVHD is Preferred Over Intermittent HD, Due to Rapid Solute Changes and Potential for Hypotension with Intermittent HD (Which May Exacerbate Cerebral Ischemia) (see Hemodialysis, [[Hemodialysis]])

Decompressive Craniectomy (see Decompressive Craniectomy, [[Decompressive Craniectomy]])


References

  • Hypertonic saline solutions in brain injury. Curr Opin Crit Care. 2004;10:126-131
  • A comparision of albumin and saline for fluid resuscitation in the intensive care unit. N Engl J Med. 2004;350:2247-2256
  • Injury to the cranium. In: Moore EE, Feliciano DV, Mattox KL, eds. Trauma. 5th ed. New York, NY: McGraw-Hill; 2004:385-404
  • Effects of 23.4% sodium chloride solution in reducing intracranial pressure in patients with traumatic brain injury: a preliminary study. Neurosurgery. 2005;57(4):727 [MEDLINE]
  • The use of hypertonic saline for treating intracranial hypertension after traumatic brain injury. Anesth Analg. 2006;102:1836-1846
  • Guidelines for the management of severe traumatic brain injury. J Neurotrauma. 2007;24 Suppl 1:S1-106 [MEDLINE]
  • Refractory intracranial hypertension and “second-tier” therapies in traumatic brain injury. Intensive Care Med. 2008;34:461–467 [MEDLINE]
  • Sedation for critically ill adults with severe traumatic brain injury: a systematic review of randomized controlled trials. Crit Care Med. 2011 Dec;39(12):2743-51 [MEDLINE]
  • Decompressive craniectomy in diffuse traumatic brain injury. N Engl J Med. 2011;364(16):1493 [MEDLINE]
  • Hyperosmolar therapy for raised intracranial pressure. N Engl J Med. 2012;367:746–752 [MEDLINE]
  • Traumatic intracranial hypertension. N Engl J Med. 2014;370:2121–2130. doi: 10.1056/NEJMra1208708 [MEDLINE]