INTRACRANIAL PRESSURE Dr. Akhmad Imron, SpBS Dept. of Neurosurgery

INTRODUCTION Our skull creates a hard casing in which our cranial contents rest and are protected from injury.  The cranial contents consist of three components.  Brain tissue or cells make up 80 –85% of the cranial contents.  Our cerebrospinal fluid averaged 8 – 12% and cerebral blood volume is 3 – 5%.  When there is an increase in one of the three components, it normally results in a decrease on one or both of the other.  This permits for stability of contents within the skull vault.

To maintain this stability the body has three compensatory mechanisms that are utilized.  The first is the autoregulation of the brain.  Autoregulation facilitates continual cerebral perfusion of brain tissue regardless of changes in systemic arterial blood pressure.  When a  person has a rise in blood pressure, the arterioles of the brain will constrict to maintain a constant amount of blood circulating within the tissue.  If the person has a drop in blood pressure, the arterioles will dilate to permit more blood flow into the cerebral circulation.

The second compensatory mechanism of the brain is cerebrospinal fluid regulation.  This is the slowest of the compensatory mechanisms.  It will regulate the production and re-absorption of the CSF with any changes in intra-cerebral volume.  If there is an increase in cerebral contents, this mechanism will decrease the production of CSF and call for an increase in re-absorption.  Ultimately it will cause a decrease in intracranial pressure.

The last compensatory mechanism of the brain to maintain stability is via metabolic regulation.  When there is a decrease in oxygen being fed to the brain tissue, there will be a subsequent increase in carbon dioxide.  These changes cause a vasodilatation within the brain permitting increased blood flow to the brain.  Hyperthermia causes an increased metabolic rate in the brain.  This increased metabolic rate increases oxygen and glucose consumption, the two major needs for proper brain functioning

INTRACRANIAL PRESSURE Intracranial pressure (ICP) is defined as the measure of cerebrospinal fluid pressure within the cranium.  Normal ICP ranges from 0 – 15 mm Hg.  A resting ICP value greater than 20 mm Hg is defined as intracranial hypertension and may be acute or chronic in nature.  Increased ICP can result in irreversible damage to the cranial contents by impairing blood flow and eventually cause death if left untreated.

INCREASED INTRACRANIAL PRESSURE Elevation in ICP can be graded as follows: Normal ICP                             0 – 15mm Hg Mile elevation                           16 – 20 mm Hg Moderate elevation                   21 – 30 mm Hg Sever elevation             31 – 40 mm Hg Very severe elevation                41 mm Hg and above  

ETIOLOGY OF INCREASED ICP Cerebral edema can be one of the causes for intracranial pressure to increase.  Other causes include: Blood clots or expanding lesions Abscess or infection Enlarged ventricles due to increased CSF volume Pneumocephalus Increased cerebral blood flow Increased thoracic pressure Impaired cerebral venous drainage

ICP MONITIRING Mean Arterial Pressure (MAP) – ICP = CPP   Mean Arterial Pressure is calculated as below: Systolic BP + (2 x Diastolic BP) ÷ 3 = MAP

SIGN AND SYMPTOM can be very subtle ,It may include: Restlessness       Agitation       Mild confusion       Personality changes       Decreasing Glascow Coma Score      Headache (usually early morning with noted vomiting)       Slowed or slurred speech

SIGN AND SYMPTOM Memory impairment Decreased hand grasp or paresis       Decreased response to touch or pinprick       Pupils will be delayed or sluggish to react to light.  Shape will become ovoid or they will become unequal.       Vision may become blurred with decreased visual acuity       Seizure activity may or may not be present       Vital signs are unchanged at this time  

HERNIATION SYNDROMES Increasing intracranial pressure if left untreated will lead to cerebral herniation of brain tissue.  Herniation is defined as the protrusion of a portion of the brain through an abnormal opening.  No matter what is causing the increasing pressure, it will cause brain tissue to shift from the area of high pressure to an area of low pressure.  There exists two categories of herniation, the supratentorial and the infratentorial

Supratentorial Herniation There are four types of supratentorial herniations: Cingulate herniation Central or Transtentorial herniation Uncal or Lateral Transtentorial herniation Transclavarial herniation

Infratentorial Herniation There are two forms of infratentorial herniation: Tonsillar or Downward Cerebellar herniation Upward transtentorial herniation

INTERVENTIONS FOR THE PATIENT WITH INCREASED ICP Nursing Management includes: Maintain the patients head midline to facilitate blood flow. Maintain the head of the bed at 30 – 45 degrees to facilitate venous drainage. Avoid activities that can increase ICP such as suctioning or gaging. Treat hyperthermia as it increases the metabolic needs of the brain. Decrease environmental stimuli which can increase ICP.

Maintain fluid balance via accurate I & O .      Maintain fluid balance via accurate I & O.  Overhydration will lead to cerebral edema. 7.      Monitor electrolytes as these patients are prone to hypernatremia, hypoglycemia, and hypokalemia with diuretic useage. 8.      Monitor hyperventilation to maintain CO2 levels at 25 – 35mm Hg to prevent vasodilation. 9.      Use of Lidocaine prior to suctioning to decrease gag reflex.  

Medical Management includes:     Anticonvulsant therapy for seizures.       Use of diuretics such as Mannitol, Urea, and Glycerol.       Barbiturate Coma Therapy to decrease the metabolic demands of the brain.       50% Dextrose solution if hypoglycemia is present and persistent.       Corticosteroid therapy witch remains controversial.       Intracranial pressure monitoring with drainage abilities. Surgical decompression -         considered life saving measure -         opening of the skull can lead to severe herniation  

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