ICP

ICP & Head TraumaICP & Head Trauma

Sophia R. Smith, MDSophia R. Smith, MD

WRAMCWRAMC

November 2, 2005November 2, 2005

IntroductionIntroduction

• Head injuries are one of the most common Head injuries are one of the most common causes of disability and death in children.causes of disability and death in children.

• The Centers for Disease Control and The Centers for Disease Control and Prevention (CDC) estimates that more Prevention (CDC) estimates that more than 10,000 children become disabled than 10,000 children become disabled from a brain injury each year. from a brain injury each year.

• Head injuries can be defined as mild as a Head injuries can be defined as mild as a bump to severe in nature.bump to severe in nature.

Prevalence of Pediatric TraumaPrevalence of Pediatric Trauma

• Trauma is the leading cause of death in infants Trauma is the leading cause of death in infants and childrenand children

• Trauma is the cause of 50% of deaths in people Trauma is the cause of 50% of deaths in people between 5 and 34 years of agebetween 5 and 34 years of age

• Motor vehicle related accidents account for 50% Motor vehicle related accidents account for 50% of pediatric trauma casesof pediatric trauma cases

• $16 billion is spent annually caring for injuries to $16 billion is spent annually caring for injuries to children less than 16 years of agechildren less than 16 years of age

Traumatic Brain InjuryTraumatic Brain Injury

Primary Brain InjuryPrimary Brain Injury

Results from what Results from what has occurred to the has occurred to the brain at the time of brain at the time of the injurythe injury

Secondary Brain Secondary Brain InjuryInjury

• Physiologic and Physiologic and biochemical events biochemical events which follow the which follow the primary injuryprimary injury

Examples of Primary Brain Injuries

Factors that Effect Secondary Factors that Effect Secondary Brain InjuriesBrain Injuries

• Blood PressureBlood Pressure

• OxygenationOxygenation

• TemperatureTemperature

• Control of Blood GlucoseControl of Blood Glucose

• Fluid Volume StatusFluid Volume Status

• Increased Intracranial PressureIncreased Intracranial Pressure

Brain trauma

BBB disruption

diffuse axonal injury

edema formation

Eicosanoidsendocannabinoids

necrosis

energy failure

cytokines

SOME of the SECONDARY EVENTS IN TRAUMATIC BRAIN INJURY

apoptosis

inflammation

ROS polyamines CalciumAcetylCholine

ischemia

Shohami, 2000Green – pathophysiological processes; Yellow – various mediators

Anatomy of the craniumAnatomy of the cranium

• There are various brain contents that are There are various brain contents that are localized within a rigid structure.localized within a rigid structure.– CraniumCranium

• The cranial vault contents include:The cranial vault contents include:– The The brainbrain– The The cerebral spinal fluidcerebral spinal fluid– The The cerebral bloodcerebral blood

Cerebral Spinal FluidCerebral Spinal Fluid

• CSFCSF

– 150 cc in adults at all times150 cc in adults at all times

• Children slightly lessChildren slightly less

– Produced by choroid plexus – 20 cc/hr Produced by choroid plexus – 20 cc/hr

– CSF is absorbed into venous system at CSF is absorbed into venous system at the subarachnoid villi the subarachnoid villi

Cerebral blood and brainCerebral blood and brain

• Cerebral bloodCerebral blood– Sum of blood in capillaries, veins, and arteriesSum of blood in capillaries, veins, and arteries

• BrainBrain– 80% of the total intracranial volume80% of the total intracranial volume

• All of these contents are maintained @ a All of these contents are maintained @ a balanced pressure referred to as intracranial balanced pressure referred to as intracranial pressure (ICP)pressure (ICP)

Monro-KellieMonro-Kellie DoctrineDoctrine

• The ICP within the skull is directly related The ICP within the skull is directly related to the volume of the contents.to the volume of the contents.– Defined as the Defined as the Monro-Kellie DoctrineMonro-Kellie Doctrine

– This doctrine states that any increase in This doctrine states that any increase in volume of the contents within the brain must volume of the contents within the brain must be met with a decrease in the other cranial be met with a decrease in the other cranial contents.contents.

Monro-Kellie Doctrine

Vintracranial vault=Vbrain+Vblood +Vcsf

Increased Intracranial Pressure

Cerebral Blood FlowCerebral Blood Flow

• CBF is directly linked to the metabolic CBF is directly linked to the metabolic requirements of the brain.requirements of the brain.

• As the brain metabolic activity increases,As the brain metabolic activity increases, CBF increases CBF increases – Vasodilatation of cerebral vesselsVasodilatation of cerebral vessels– Increase in cerebral blood volumeIncrease in cerebral blood volume– Consequent increase in ICPConsequent increase in ICP

Cerebral blood flowCerebral blood flow

• CBF maintained when MAP range is CBF maintained when MAP range is 50mmHg to 150mmHg50mmHg to 150mmHg– Cerebral auto regulationCerebral auto regulation

• As BP increaseAs BP increase baroreceptors sense baroreceptors sense event and cerebral arteries vasoconstrict event and cerebral arteries vasoconstrict CBF maintained with a CBV decreaseCBF maintained with a CBV decrease

• As BP decrease As BP decrease cerebral arteries dilate cerebral arteries dilate to increase flow to increase flow CBV increase CBV increase

Auto regulationAuto regulation

• This process is lost in pathological statesThis process is lost in pathological states– Esp. Head traumaEsp. Head trauma– CBF decreases linearly to MAP below rangeCBF decreases linearly to MAP below range

• Results is ischemia (strokes) to brain regionsResults is ischemia (strokes) to brain regions

– CBF increases linearly to MAP above auto CBF increases linearly to MAP above auto regulation rangeregulation range• HTN encephalopathy as CBV and ICP increase HTN encephalopathy as CBV and ICP increase

Mediators of CBFMediators of CBF

• Local and global mediators of CBF and Local and global mediators of CBF and metabolism are important.metabolism are important.– Hypoxia and pHHypoxia and pH are most importantare most important

– As local paO2 decreases, CBF increasesAs local paO2 decreases, CBF increases– CBF is affected by pH (and its surrogate CBF is affected by pH (and its surrogate

pCO2)pCO2)

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

Blood: Cerebral Blood Flow

Studies of hyperventilation & ICPStudies of hyperventilation & ICP

• This relationship has been well studied as This relationship has been well studied as a therapeutic option in particular a therapeutic option in particular intentional hyperventilation to lower intentional hyperventilation to lower cerebral blood flow and thus intracranial cerebral blood flow and thus intracranial pressure.pressure.

• No longer a practiceNo longer a practice– Modest hyperventilationModest hyperventilation

On callOn call

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

• How do you evaluate?How do you evaluate?

Trauma

Traumatic Brain Injury

Glascow Coma Scale

Eye Opening Spontaneous 4 To Voice 3 To Pain 2 None 1Best Verbal Oriented 5 Confused 4 Inappropriate Words 3 Incomprehensible 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

Severe TBISevere TBI

• Indications for IntubationIndications for Intubation– GCSGCS<< 8 8– Fall in GCS of 3Fall in GCS of 3– Unequal pupilsUnequal pupils– Inadequate respiratory effort or Inadequate respiratory effort or

significant lung/chest injurysignificant lung/chest injury– Loss of gagLoss of gag– apneaapnea

TreatmentTreatment

• IntubationIntubation..

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

TreatmentTreatment

• HyperventilationHyperventilation– to maintain PO2 >90 torrs, PCO2 30 to 32 torrs. to maintain PO2 >90 torrs, PCO2 30 to 32 torrs. – Hyperventilation may actually increase ischemia Hyperventilation may actually increase ischemia

in at risk brain tissue if PCO2 <25 torr by causing in at risk brain tissue if PCO2 <25 torr by causing excessive vasoconstriction and has fallen out of excessive vasoconstriction and has fallen out of favorfavor. Prophylactic hyperventilation for those without . Prophylactic hyperventilation for those without increased ICP is contraindicated and worsens increased ICP is contraindicated and worsens outcomes.outcomes.

• PEEP relatively contraindicated because PEEP relatively contraindicated because reduces cerebral blood flow. reduces cerebral blood flow.

Maintain normal cardiac outputMaintain normal cardiac output. .

• If hypotensive from other cause such as If hypotensive from other cause such as multi-trauma, treat shock as usual. multi-trauma, treat shock as usual.

• Normal saline is preferred over LR since Normal saline is preferred over LR since LR is slightly hypotonic. LR is slightly hypotonic.

• Hypertonic saline (3% or 7.5%) can be Hypertonic saline (3% or 7.5%) can be used. Especially if you see ICP changes.used. Especially if you see ICP changes.

Maintain normal cardiac outputMaintain normal cardiac output..

• If markedly hypertensive, consider If markedly hypertensive, consider labetalol or nitroprusside. labetalol or nitroprusside.

• Avoid lowering the blood pressure unless Avoid lowering the blood pressure unless diastolic blood pressure is >120 mm Hg. diastolic blood pressure is >120 mm Hg.

DiuresisDiuresis

• Mannitol 1 g/kgMannitol 1 g/kg IV over 20 minutes IV over 20 minutes induces osmotic diuresis. induces osmotic diuresis. – Avoid if hypotensive or have CHF/renal Avoid if hypotensive or have CHF/renal

failure. failure.

• Some suggest Some suggest furosemidefurosemide (Lasix and (Lasix and others). others). – Avoid if hypotensive. Avoid if hypotensive.

ICP PrecautionsICP Precautions

• Elevate head of bed 30 degreesElevate head of bed 30 degrees..

• Seizure prophylaxisSeizure prophylaxis: Phenytoin will : Phenytoin will reduce seizures in the first week after reduce seizures in the first week after injury but does not change the overall injury but does not change the overall outcome. outcome.

• SteroidsSteroids are ineffective in controlling ICP are ineffective in controlling ICP in the trauma setting. in the trauma setting.

Positioning II

Manipulation of CPPManipulation of CPP

• Maintain adequate intravascular volumeMaintain adequate intravascular volume– CVPCVP

• Increase MAP Increase MAP – Utilize alpha agonist--dopamine, Utilize alpha agonist--dopamine,

phenylephrine, norepinephrinephenylephrine, norepinephrine

• What is appropriate goal for children?What is appropriate goal for children?

CPP = MAP - ICPCPP = MAP - ICP

CPP for childrenCPP for children

• Aim for a CPP of >60 mmHgAim for a CPP of >60 mmHg – by maintaining an adequate MAP and control by maintaining an adequate MAP and control

of ICPof ICP• MAP – ICP = CPPMAP – ICP = CPP

– Minimizing the morbidity of TBI in childrenMinimizing the morbidity of TBI in children

Additional therapiesAdditional therapies

• Prevent hyperglycemiaPrevent hyperglycemia: exacerbates : exacerbates ischemic cerebral damage ischemic cerebral damage

• Attention to electrolyte statusAttention to electrolyte status. These . These patients are prone to electrolyte patients are prone to electrolyte abnormalities due to osmotic diuresis, abnormalities due to osmotic diuresis, cerebral salt losing states, SIADH and cerebral salt losing states, SIADH and diabetes insipidus diabetes insipidus

Manipulation of ICPManipulation of ICP

• Decrease cerebral metabolic demandDecrease cerebral metabolic demand

– sedation, analgesia, barbituratessedation, analgesia, barbiturates

– avoid hyperthermiaavoid hyperthermia

– avoid seizuresavoid seizures

• HyperventilationHyperventilation

– decreases blood flow to braindecreases blood flow to brain

– only acutely for impending herniationonly acutely for impending herniation

• MannitolMannitol

Blood


• MannitolMannitol– dehydrate the brain, not the patient!dehydrate the brain, not the patient!– monitor osmolalitymonitor osmolality

• Hypertonic salineHypertonic saline

• Decompressive craniectomyDecompressive craniectomy

Brain

ICP MonitoringICP Monitoring

• ICU patients who have sustained head ICU patients who have sustained head trauma, brain hemorrhage, brain surgery, trauma, brain hemorrhage, brain surgery, or conditions in which the brain may swell or conditions in which the brain may swell might require intracranial pressure might require intracranial pressure monitoring. monitoring.

• The purpose of ICP monitoring is to The purpose of ICP monitoring is to continuously measure the pressure continuously measure the pressure surrounding the brain.surrounding the brain.

Why Monitor?Why Monitor?

• Detect “events”Detect “events”

• Manage intracranial pressureManage intracranial pressure

• Manage cerebral perfusion pressureManage cerebral perfusion pressure

How?How?

• VentriculostomyVentriculostomy

• Intraparenchymal fiberoptic catheterIntraparenchymal fiberoptic catheter

• Subarachnoid monitorSubarachnoid monitor

• Useful adjuncts:Useful adjuncts:– Arterial lineArterial line– Central venous lineCentral venous line– Foley catheterFoley catheter


• External drainageExternal drainage– therapeutic as well as diagnostictherapeutic as well as diagnostic– technical issuestechnical issues– infectious issuesinfectious issues

CSF

What to do with the What to do with the information...information...

• Goal: adequate oxygen delivery to maintain Goal: adequate oxygen delivery to maintain the metabolic needs of the brain.the metabolic needs of the brain.

• Intracranial pressure <20Intracranial pressure <20

• Cerebral perfusion pressure >50-70 mm Hg Cerebral perfusion pressure >50-70 mm Hg CPP=MAP-ICPCPP=MAP-ICP

Indications for ICP monitoringIndications for ICP monitoring

• Glasgow coma scale Glasgow coma scale <<88

• Clinical or radiographic evidence of Clinical or radiographic evidence of increased ICPincreased ICP

• Post-surgical removal of intracranial Post-surgical removal of intracranial hematomahematoma

• Less severe brain injury in the setting which Less severe brain injury in the setting which requires deep sedation or anesthesiarequires deep sedation or anesthesia

Other monitoring devicesOther monitoring devices

• CT ScanCT Scan

• MRIMRI

• PET ScanPET Scan

• Jugular Venous Oxygen SaturationJugular Venous Oxygen Saturation

Near-infrared SpectroscopyNear-infrared Spectroscopy

• Uses absorption characteristics of oxy Uses absorption characteristics of oxy Hgb, deoxy Hgb, and [o] cyt aa3Hgb, deoxy Hgb, and [o] cyt aa3

• Uses the ability to penetrate the Uses the ability to penetrate the superficial brainsuperficial brain

• Therefore the state of oxygenation Therefore the state of oxygenation can be determined.can be determined.

• Good assessment of cerebral Good assessment of cerebral oxygenationoxygenation

Transcranial Doppler USTranscranial Doppler US

• TCD is a noninvasive technique used TCD is a noninvasive technique used to determine cerebral blood velocity to determine cerebral blood velocity in large intracranial arteries.in large intracranial arteries.

• Assessment ofAssessment of– Brain deathBrain death– Reperfusion injuryReperfusion injury– Identify regions S/P TBI that are Identify regions S/P TBI that are

adversely effectedadversely effected

Cerebral MicrodialysisCerebral Microdialysis

• Measuring the partial pressure of Measuring the partial pressure of oxygen of brain parenchyma and oxygen of brain parenchyma and metabolites using microdialysismetabolites using microdialysis

• Electrode in vulnerable brain region Electrode in vulnerable brain region measures O2 concentrationmeasures O2 concentration

• Measures also local brain metabolismMeasures also local brain metabolism

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