© 2001 UMBCNeurological Management CCEMT-P SM 12/98 1 Intracranial Pressure

© 2001 UMBC Neurological Management CCEMT-P SM 12/98 1

Intracranial Pressure



• Definition– Pressure exerted by brain tissue, intracranial

blood, and cerebral spinal fluid (CSF) in a non-distended (closed) cavity


Normal Contents of the Skull

• Brain - 80%

• Blood - 10%

• CSF - 10%

• Monroe-Kellie Doctrine


Changes in Skull Contents

• Increased intracranial volume– Hyperemia– Bleeding, clots, bruises – Cerebral edema– Hydrocephalus– Foreign object– Tumor



• Cerebral edema (localized or generalized) can develop from any injury to the brain

• Swelling peaks in 3-5 days


Post-traumatic Hydrocephalia

• Communicating– CSF circulates but is not reabsorbed– Arachnoid villa are clogged

• Non-communicating– CSF circulation is obstructed– CSF can not reach the arachnoid villa to be

reabsorbed


Pressure - Volume Relationship

Compliance = change in volume change in pressure

Defines the relationship between pressure and volume within the skull


Pressure - Volume Relationship

• Three portions of the waveform curve– Flat– Curved– Vertical (inflection) point


ICP Waveforms

• Normal waveform resembles a set of stairs

• With increasing ICP, waveform loses shape

© 2001 UMBC Neurological Management CCEMT-P SM 12/98

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Brain Herniation

• Definition– Distortion and displacement of the brain from

one compartment to another caused by increased volume and pressure and decreased compliance


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Brain Herniation

• Three types– Central or transtentorial– Uncal or lateral transtentorial– Cingulate


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Mean Arterial Pressure (MAP)

• Calculate MAP– Subtracting diastolic pressure from systolic pressure– Divide by 3– And add diastolic pressure

140 - 100 = 40

3 = 13 + 100 = 113 MAP = 113


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Cerebral Perfusion Pressure (CPP)

• Pressure gradient driving blood flow and delivery of nutrients to the brain


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• Calculate CPP– Subtract ICP from MAP

Patient has an ICP of 80 and a MAP of 113 113 MAP

- 80 ICP 33 CPP


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CPP = MAP - ICP

Best if > 70 mmHg

< 60 mmHg = impaired blood flow to brain


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< 50 mmHg Mild cerebral ischemia

< 40 mmHg Cerebral blood flow down 25%

< 30 mmHg Irreversible cerebral ischemia

• If MAP = ICP – There is no blood flow to the brain

and brain death in imminent


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Increased ICP

• Neurological exam

• Motor function• Respiratory • Body temperature

• LOC • Pupil • Vision • Herniation


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Signs & Symptoms of ICP

• Vital signs changes - Cushing’s triad

• Widening pulse pressure

• Bradycardia

• Abnormal respiratory patterns


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Signs & Symptoms of ICP

• Respiratory changes– Cheyne-stokes– Central neurogenic hyperventilation– Biot’s– Kussmal


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ICP Monitoring


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ICP Monitoring

• Indications– Glasgow coma score <8 and positive CT– Paralytic and/or sedative medications are being

used


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Devices

• Interventricular cannula (IVC)

• Epidural catheter

• Subdural / subarachnoid monitoring devices

• Fiber optic transducer tipped probe


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Interventricular Cannula (IVC)

• Most commonly used monitor

• Placed within the ventricle

• Location of placement for some Caminos


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• Advantages– Drain CSF to lower

ICP

– Obtain CSF cultures

– Increased accuracy in ICP monitoring

– Accurate and reliable

• Disadvantages– Infection

– Injury to brain

– Clot formation

– Hemorrhage risk

– Collapsed ventricle

– Placement may be impossible


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• Transport considerations– System set-up – Charting ICP– Drainage orders – Movement – Pressure changes with air transport


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Epidural Catheter

• Lies beneath skull - above dura mater

• Advantages– Lesser rate of infection than IVC – Placement causes less injury to brain

• Disadvantages– Less accurate than IVC– Cannot be used to drain CSF


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Subdural / Subarachnoid Monitor

• Newer systems connect to fiber optics

• Called a “screw” or “bolt”

• Subdural - beneath dura and above pia

• Subarachnoid - placed beneath arachnoid and above pia


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Subdural / Subarachnoid Monitor

• Advantages– Not as invasive as

IVC or epidural

– Less rate of infection

– Less injury to brain

– Easier to place

• Disadvantages– Less accurate monitoring

– Cannot drain CSF

– Risk of bleeding and brain injury

– Higher rate of infection than epidural catheter

– Requires closed, intact skull


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Fiber Optic Transducer Tipped Probe

• Catheter with pressure sensing device placed into subdural space, brain parenchyma or ventricle

• Non fluid filled continuous intact system


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Fiber Optic Transducer Tipped Probe

• Advantages– Good waveform– Reliable and accurate pressure reading– No air bubble formation within catheter

• Disadvantages– Inability to access ICP unless IVC setup is used– Unit cannot be zeroed once placed


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Transport Considerations

• Avoid tension or kinking of cable

• Less problem with zeroing

• Maintain clean / intact dressing


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ICP Data

• Normal values 0-15 mmHg

• Normal waveforms first 3 waves– P1 - percussion

– P2 - tidal wave

– P3 - dicrotic wave

• Abnormal waveforms– C waves - think PACs

– B waves - think PVCs

– A waves - think V-fib


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Management of ICP

• Gas exchange– Optimize gas exchange to maintain ICP or

decrease ICP levels– Good pulmonary toilet– Ph changes– Hyperoxygenation– Hyperventilation– Positive end expiratory pressure (PEEP)


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Management of ICP

• Hyperventilation– Vasodilation occurs in brain tissue to increase

circulation and then increases ICP

• Goals of hyperventilation– Remove CO2 and cause vasoconstriction

– Cause - respiratory alkalosis– Effect - pace drops reducing cerebral blood

flow


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Hyperventilation Controversy

• What is optimal paco2 level?

– Old method - keep paco2 at 25 mmhg

– New method - paco2 range 28-32 mmhg


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Factors which Increase ICP

• Hip flexion (decreases venous return)

• Head and neck position• Changing level of height

of bed (especially flat)• External noxious stimuli

• Agitation• Pain• Coughing and

valsalva maneuver • Seizures


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Methods of Decreasing ICP

• Decrease external stimulation• Ensure a quiet environment• Pull slouching patients to the top of the bed• Use cervical collar with decreased neck

muscle tone• Shut off bright lights• Align head and neck• Surgical intervention


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• If IVC in place, open and drain

• If too much CSF is lost, the ventricle can collapse


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• Medications– Sedation – Paralytics– Diuretics – Steroids– Barbituate coma


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Medications

• Sedatives– Ventilator patients – Pentathol or fentanyl

• Paralytics– Decrease metabolism– Generally utilized with sedatives– ICP monitoring necessary for most medically

paralyzed patients


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Medications

• Diuretics – Mannitol and Lasix

• Steroids– Dexamethasone / methylprednisone– Controversial

• Some studies show no benefit, others show limited benefit if given within 8 hours of the injury


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Medications

• Barbiturate coma– Induced pharmacologically using barbiturates

• Barbiturate coma results– Neuro status - unresponsive with a GCS of 3– Respiratory - ventilator dependent– Cardiovascular - bradycardia and hypotensive


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Intracranial Pressure Monitoring

• Operative intervention– Surgical removal of blood clot or affected

portion of the brain


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Conclusion


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Neuromonitoring for Traumatic Brain Injury


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Intracranial Pressure Monitoring


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Jugular Venous Bulb Oximetry


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Transcranial Doppler Ultrasound


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Cerebral Function Monitoring


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Emerging Monitoring Technologies


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References

Documents

© 2001 UMBCNeurological Management CCEMT-P SM 12/98 1 Intracranial Pressure