ICP%20

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ICP Head Trauma

• Sophia R. Smith, MD
• WRAMC
• November 2, 2005

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Introduction

• Head injuries are one of the most common causes
  of disability and death in children.
• The Centers for Disease Control and Prevention
  (CDC) estimates that more than 10,000 children
  become disabled from a brain injury each year.
• Head injuries can be defined as mild as a bump to
  severe in nature.

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Prevalence of Pediatric Trauma

• Trauma is the leading cause of death in infants
  and children
• Trauma is the cause of 50 of deaths in people
  between 5 and 34 years of age
• Motor vehicle related accidents account for 50
  of pediatric trauma cases
• 16 billion is spent annually caring for injuries
  to children less than 16 years of age

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Traumatic Brain Injury

• Primary Brain Injury
• Results from what has occurred to the brain at
  the time of the injury

• Secondary Brain Injury
• Physiologic and biochemical events which follow
  the primary injury

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Examples of Primary Brain Injuries
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Factors that Effect Secondary Brain Injuries

• Blood Pressure
• Oxygenation
• Temperature
• Control of Blood Glucose
• Fluid Volume Status
• Increased Intracranial Pressure

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SOME of the SECONDARY EVENTS IN TRAUMATIC BRAIN
INJURY
diffuse axonal injury
inflammation
BBB disruption
apoptosis
necrosis
Brain trauma
edema formation
ischemia
energy failure
cytokines
Eicosanoids endocannabinoids
Calcium
polyamines
ROS
Acetyl Choline
Shohami, 2000
Green pathophysiological processes Yellow
various mediators
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Anatomy of the cranium

• There are various brain contents that are
  localized within a rigid structure.
• Cranium
• The cranial vault contents include
• The brain
• The cerebral spinal fluid
• The cerebral blood

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Cerebral Spinal Fluid

• CSF
• 150 cc in adults at all times
• Children slightly less
• Produced by choroid plexus 20 cc/hr
• CSF is absorbed into venous system at the
  subarachnoid villi

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Cerebral blood and brain

• Cerebral blood
• Sum of blood in capillaries, veins, and arteries
• Brain
• 80 of the total intracranial volume
• All of these contents are maintained _at_ a balanced
  pressure referred to as intracranial pressure
  (ICP)

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Monro-Kellie Doctrine

• The ICP within the skull is directly related to
  the volume of the contents.
• Defined as the Monro-Kellie Doctrine
• This doctrine states that any increase in volume
  of the contents within the brain must be met with
  a decrease in the other cranial contents.

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Monro-Kellie Doctrine

• Vintracranial vaultVbrainVblood Vcsf

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Increased Intracranial Pressure
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Cerebral Blood Flow

• CBF is directly linked to the metabolic
  requirements of the brain.
• As the brain metabolic activity increases, CBF
  increases
• Vasodilatation of cerebral vessels
• Increase in cerebral blood volume
• Consequent increase in ICP

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Cerebral blood flow

• CBF maintained when MAP range is 50mmHg to
  150mmHg
• Cerebral auto regulation
• As BP increase? baroreceptors sense event and
  cerebral arteries vasoconstrict ?CBF maintained
  with a CBV decrease
• As BP decrease ? cerebral arteries dilate to
  increase flow ? CBV increase

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Auto regulation

• This process is lost in pathological states
• Esp. Head trauma
• CBF decreases linearly to MAP below range
• Results is ischemia (strokes) to brain regions
• CBF increases linearly to MAP above auto
  regulation range
• HTN encephalopathy as CBV and ICP increase

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Mediators of CBF

• Local and global mediators of CBF and metabolism
  are important.
• Hypoxia and pH are most important
• As local paO2 decreases, CBF increases
• CBF is affected by pH (and its surrogate pCO2)

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Blood Cerebral Blood Flow

• The brain has the ability to control its blood
  supply to match its metabolic requirements
• Chemical or metabolic byproducts of cerebral
  metabolism can alter blood vessel caliber and
  behavior

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Studies of hyperventilation ICP

• This relationship has been well studied as a
  therapeutic option in particular intentional
  hyperventilation to lower cerebral blood flow and
  thus intracranial pressure.
• No longer a practice
• Modest hyperventilation

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On call

• So, you are in the ER on your first night of call
  and the next thing you know you get your very
  first trauma patient.
• How do you evaluate?

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Trauma
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Traumatic Brain Injury
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Glascow Coma Scale Eye Opening     Spontaneous  
                   4     To Voice               
             3     To Pain                      
         2     None                              
    1Best Verbal     Oriented                  
           5     Confused                       
     4     Inappropriate Words           3     I
ncomprehensible Sounds  2     None               
                    1Best Motor     Obeys
Commands              6     Localizes
Pain                     5     Withdraws to
Pain               4     Flexion to
Pain                    3      Extension to
Pain                2     None                   
                1
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Severe TBI

• Indications for Intubation
• GCSlt 8
• Fall in GCS of 3
• Unequal pupils
• Inadequate respiratory effort or significant
  lung/chest injury
• Loss of gag
• apnea

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Treatment

• Intubation.
• Pretreatment with lidocaine 1 mg/kg IV may
  prevent rise in intracranial pressure (ICP).

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Treatment

• Hyperventilation
• to maintain PO2 gt90 torrs, PCO2 30 to 32 torrs.
• Hyperventilation may actually increase ischemia
  in at risk brain tissue if PCO2 lt25 torr by
  causing excessive vasoconstriction and has fallen
  out of favor. Prophylactic hyperventilation for
  those without increased ICP is contraindicated
  and worsens outcomes.
• PEEP relatively contraindicated because reduces
  cerebral blood flow.

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Maintain normal cardiac output.

• If hypotensive from other cause such as
  multi-trauma, treat shock as usual.
• Normal saline is preferred over LR since LR is
  slightly hypotonic.
• Hypertonic saline (3 or 7.5) can be used.
  Especially if you see ICP changes.

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Maintain normal cardiac output.

• If markedly hypertensive, consider labetalol or
  nitroprusside.
• Avoid lowering the blood pressure unless
  diastolic blood pressure is gt120 mm Hg.

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Diuresis

• Mannitol 1 g/kg IV over 20 minutes induces
  osmotic diuresis.
• Avoid if hypotensive or have CHF/renal failure.
• Some suggest furosemide (Lasix and others).
• Avoid if hypotensive.

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ICP Precautions

• Elevate head of bed 30 degrees.
• Seizure prophylaxis Phenytoin will reduce
  seizures in the first week after injury but does
  not change the overall outcome.
• Steroids are ineffective in controlling ICP in
  the trauma setting.

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Positioning II
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Manipulation of CPP
CPP MAP - ICP

• Maintain adequate intravascular volume
• CVP
• Increase MAP
• Utilize alpha agonist--dopamine, phenylephrine,
  norepinephrine
• What is appropriate goal for children?

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CPP for children

• Aim for a CPP of gt60 mmHg
• by maintaining an adequate MAP and control of ICP
• MAP ICP CPP
• Minimizing the morbidity of TBI in children

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Additional therapies

• Prevent hyperglycemia exacerbates ischemic
  cerebral damage
• Attention to electrolyte status. These patients
  are prone to electrolyte abnormalities due to
  osmotic diuresis, cerebral salt losing states,
  SIADH and diabetes insipidus

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Manipulation of ICP
Blood

• Decrease cerebral metabolic demand
• sedation, analgesia, barbiturates
• avoid hyperthermia
• avoid seizures
• Hyperventilation
• decreases blood flow to brain
• only acutely for impending herniation
• Mannitol

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Manipulation of ICP
Brain

• Mannitol
• dehydrate the brain, not the patient!
• monitor osmolality
• Hypertonic saline
• Decompressive craniectomy

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ICP Monitoring

• ICU patients who have sustained head trauma,
  brain hemorrhage, brain surgery, or conditions in
  which the brain may swell might require
  intracranial pressure monitoring.
• The purpose of ICP monitoring is to continuously
  measure the pressure surrounding the brain.

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Why Monitor?

• Detect events
• Manage intracranial pressure
• Manage cerebral perfusion pressure

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How?

• Ventriculostomy
• Intraparenchymal fiberoptic catheter
• Subarachnoid monitor
• Useful adjuncts
• Arterial line
• Central venous line
• Foley catheter

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Manipulation of ICP
CSF

• External drainage
• therapeutic as well as diagnostic
• technical issues
• infectious issues

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What to do with the information...

• Goal adequate oxygen delivery to maintain the
  metabolic needs of the brain.
• Intracranial pressure lt20
• Cerebral perfusion pressure gt50-70 mm Hg
  CPPMAP-ICP

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Indications for ICP monitoring

• Glasgow coma scale lt8
• Clinical or radiographic evidence of increased
  ICP
• Post-surgical removal of intracranial hematoma
• Less severe brain injury in the setting which
  requires deep sedation or anesthesia

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Other monitoring devices

• CT Scan
• MRI
• PET Scan
• Jugular Venous Oxygen Saturation

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Near-infrared Spectroscopy

• Uses absorption characteristics of oxy Hgb, deoxy
  Hgb, and o cyt aa3
• Uses the ability to penetrate the superficial
  brain
• Therefore the state of oxygenation can be
  determined.
• Good assessment of cerebral oxygenation

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Transcranial Doppler US

• TCD is a noninvasive technique used to determine
  cerebral blood velocity in large intracranial
  arteries.
• Assessment of
• Brain death
• Reperfusion injury
• Identify regions S/P TBI that are adversely
  effected

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Cerebral Microdialysis

• Measuring the partial pressure of oxygen of brain
  parenchyma and metabolites using microdialysis
• Electrode in vulnerable brain region measures O2
  concentration
• Measures also local brain metabolism