Monitoring the Injured BrainMonitoring the Injured Brain

Barbara Stanley FRCABarbara Stanley FRCA

AimsAims

Identify the needIdentify the needUnderstand different methodsUnderstand different methodsWhat is the evidence-base fo monitoringWhat is the evidence-base fo monitoring

The need for monitoringThe need for monitoring

1 million annually in the US treated for TBI1 million annually in the US treated for TBI80,000 end up with disability80,000 end up with disabilityDeath rate - 30/100,000Death rate - 30/100,000

Source: Brain and SpinalCord.org. 2008Source: Brain and SpinalCord.org. 2008

Overview – why is it important?Overview – why is it important?

Unique physiology – complex organ in a Unique physiology – complex organ in a rigid boxrigid box

Consequences of increased pressure Consequences of increased pressure Secondary insults of hypoxia and Secondary insults of hypoxia and

ischaemia have a large influence on ischaemia have a large influence on outcomeoutcome

Restoration and preservation of adequate Restoration and preservation of adequate cerebral blood flow essentialcerebral blood flow essential

Risks of invasive monitoringRisks of invasive monitoring

Methods Methods

Functional – GCS and clinical neurological Functional – GCS and clinical neurological examinationexamination

Measurement ICP - CPPMeasurement ICP - CPPMeasurement metabolism-SJV02/ Pbr02/ Measurement metabolism-SJV02/ Pbr02/

MicrodialysisMicrodialysisMeasurement haemodynamics – TCDMeasurement haemodynamics – TCDElectrical activityElectrical activity ImagingImaging

ICP MeasurementICP Measurement

Catheters placed in ventricle, Catheters placed in ventricle, parenchyma, subdural or extraduralparenchyma, subdural or extradural

Commonly fluid filled external strain guage Commonly fluid filled external strain guage - often with a drain - External Ventricular - often with a drain - External Ventricular Drain’ EVDDrain’ EVD

Intraventricular is gold standard and more Intraventricular is gold standard and more reliable – CSF can be drained if ICP reliable – CSF can be drained if ICP elevated from intraventricular catheterelevated from intraventricular catheter

ICP monitors ICP monitors

Intra parenchymal –Intra parenchymal – Codman – resistance wires in Wheatstone bridge. Codman – resistance wires in Wheatstone bridge.

Pressure change at tip = change in resistance. No Pressure change at tip = change in resistance. No bolt required. Can be tunneledbolt required. Can be tunneled

Camino – Fibreoptic. Change in ICP=change in beam Camino – Fibreoptic. Change in ICP=change in beam reflected=alters resistance in catheters circuit. Bolt reflected=alters resistance in catheters circuit. Bolt requiredrequired

Fibreoptic – require calibration prior to insertionFibreoptic – require calibration prior to insertion Cannot be recalibrated once sitedCannot be recalibrated once sited Subdural and extadural placement give less Subdural and extadural placement give less

reliable readingsreliable readings

ICP Waveform InterpretationICP Waveform Interpretation

P1= ‘Percussive’ P1= ‘Percussive’ Transmission arterial Transmission arterial pulse from choroid pulse from choroid plexusplexus

P2= ‘Tidal’ brain P2= ‘Tidal’ brain compliancecompliance

P3= Dicrotic notch = P3= Dicrotic notch = closure Aortic valveclosure Aortic valve

EVDEVD

Pro’s and cons - EVDPro’s and cons - EVD

AdvantagesAdvantages Gold standardGold standard Recalibration in vivoRecalibration in vivo No driftNo drift Most accurateMost accurate Allows CSF drainageAllows CSF drainage

DisadvantagesDisadvantages Infection risk – 6-11% Infection risk – 6-11%

(Pahl 2007)(Pahl 2007) Consequences of Consequences of

misplacementmisplacement

Evidence for ICP monitoringEvidence for ICP monitoring

BTF – Level 2 in patients with GCS 3-8 BTF – Level 2 in patients with GCS 3-8 and abnormal CT who are salvageable – and abnormal CT who are salvageable – ICP should be monitoredICP should be monitored

Provides useful predictive information Provides useful predictive information regarding worsening intracranial pathologyregarding worsening intracranial pathology

Protocols with ICP monitoring show Protocols with ICP monitoring show improved outcomeimproved outcome

ICP > 20mmHg should be treatedICP > 20mmHg should be treated

Brain tissue OxygenationBrain tissue Oxygenation

Non-invasive – NIRS based Non-invasive – NIRS based InvasiveInvasive

SJV02SJV02Pbr02Pbr02

Pbr02 - NIRSPbr02 - NIRS

Non-Invasive skin Probes ‘INVOS’ Measures Non-Invasive skin Probes ‘INVOS’ Measures regional saturation of both hemispheresregional saturation of both hemispheres

Relies on differend light absorption spectra of Relies on differend light absorption spectra of oxygenated and de-oxygenated Hb at Infra red oxygenated and de-oxygenated Hb at Infra red spectrum – 700-1000nmspectrum – 700-1000nm

Concern over extracranial circulation contriutionConcern over extracranial circulation contriution Maintaining regional saturation (rS02) > 75% Maintaining regional saturation (rS02) > 75%

reduced strokes after bypass (Murkin et al,2004)reduced strokes after bypass (Murkin et al,2004) Correlation between low rS02 and low GCS Correlation between low rS02 and low GCS

(Dunham 2004)(Dunham 2004)

The Evidence for NIRSThe Evidence for NIRS

Pbt02 – SJV02Pbt02 – SJV02

SJV02 –Fibreoptic catheter measures venous SJV02 –Fibreoptic catheter measures venous saturation of presumed dominant drainge sidesaturation of presumed dominant drainge side

Placed in IJ – tip at level mastoid air cells = Jugular Placed in IJ – tip at level mastoid air cells = Jugular bulbbulb

The normal range of SjOThe normal range of SjO22, confirmed in a study of , confirmed in a study of

healthy young men, is 55%-71% (Feldman & healthy young men, is 55%-71% (Feldman & Robertson, 1997). Robertson, 1997).

Values below 55% reflects ischaemiaValues below 55% reflects ischaemia The ischemic threshold has been reported to be an The ischemic threshold has been reported to be an

SjOSjO22 of less than 50% for at least 10 minutes, with of less than 50% for at least 10 minutes, with

multiple episodes contributing to poor outcome multiple episodes contributing to poor outcome (Robertson et al., 1995). (Robertson et al., 1995).

Decreased SJV02 valuesDecreased SJV02 values

Decreased 02 Decreased 02 deliverydelivery Increased ICPIncreased ICP Excessive Excessive

HypocapnoeaHypocapnoea HypoxiaHypoxia HypotensionHypotension AnaemiaAnaemia SepsisSepsis

Increased 02 Increased 02 consumptionconsumption SeizuresSeizures HyperthermiaHyperthermia PainPain Insufficient sedationInsufficient sedation

Increased SJV02 ValuesIncreased SJV02 Values

Increased deliveryIncreased delivery Increased CPPIncreased CPP HypercapnoeaHypercapnoea HypertensionHypertension VasodilationVasodilation Increased arterial 02Increased arterial 02 A-V malformationA-V malformation

Decreased Decreased consumptionconsumption ComaComa Brain DeathBrain Death Deep sedationDeep sedation Cerebral InfarctionCerebral Infarction HypothermiaHypothermia Hyperaemic phase of Hyperaemic phase of

TBITBI

Evidence for SJV02Evidence for SJV02

Only level 3 evidence for SJV02 in BTF Only level 3 evidence for SJV02 in BTF guidelinesguidelines

Variable Values reported to represent Variable Values reported to represent ischaemia – 55-60%ischaemia – 55-60%

Prompt treatment required - 10 mins = Prompt treatment required - 10 mins = poor outcome poor outcome (Nemani & Manley, 2004) (Nemani & Manley, 2004)

Multiple episodes contribute to poor Multiple episodes contribute to poor outcome outcome (Robertson et al., 1995) (Robertson et al., 1995)

Evidence for SJV02Evidence for SJV02

A group of patients managed by targeting A group of patients managed by targeting optimal SjOoptimal SjO

22 levels and CPP enhancement levels and CPP enhancement

had better outcomes than a group of had better outcomes than a group of patients managed with CPP-targeted patients managed with CPP-targeted therapy alone (Cruz, 1998).therapy alone (Cruz, 1998).

However-up to half reported desat However-up to half reported desat episodes are false positives (Scheinberg episodes are false positives (Scheinberg 1992)1992)

Pbt02 - CathetersPbt02 - Catheters

Invasive – Pbt02 probes Invasive – Pbt02 probes LICOX – measures 02 and TemperatureLICOX – measures 02 and TemperatureCODMAN – measures 02, C02 and pHCODMAN – measures 02, C02 and pH

Accurate to only 15mm squared around Accurate to only 15mm squared around probe tipprobe tip

Optimum depth for placement is 25-35mm Optimum depth for placement is 25-35mm into brain. And placement in penumbra vs into brain. And placement in penumbra vs unaffected side of the brainunaffected side of the brain

According to Nemani and Manley (2004), According to Nemani and Manley (2004), placing the catheter in the contralateral placing the catheter in the contralateral hemisphere in a normal brain produces hemisphere in a normal brain produces values more reflective of global brain oxygen values more reflective of global brain oxygen even though it is still a regional even though it is still a regional measurement. measurement.

Nemani and Manley (2004) point out that true Nemani and Manley (2004) point out that true "normal" values have never been determined, "normal" values have never been determined, because the catheters have not been placed because the catheters have not been placed in healthy volunteers; in healthy volunteers;

The Pbr02 DataThe Pbr02 Data Critical threshold levels where poorer outcomes have been Critical threshold levels where poorer outcomes have been

identified differ between the two systems. identified differ between the two systems. In two studies using the In two studies using the Codman Codman system, vegetative state or system, vegetative state or

death resulted when PbtOdeath resulted when PbtO22 was less than 25 mm Hg or 31 mm was less than 25 mm Hg or 31 mm Hg, respectively (Doppenberg et al., 1998; Zauner et al., Hg, respectively (Doppenberg et al., 1998; Zauner et al., 1996).1996).

In studies using the LICOX system, critical thresholds where In studies using the LICOX system, critical thresholds where poor outcomes occurred varied. The PbtOpoor outcomes occurred varied. The PbtO22 threshold levels threshold levels identified were below 15 mm Hg, below 10 mm Hg, and any identified were below 15 mm Hg, below 10 mm Hg, and any occurrence below 6 mm Hg (van den Brink et al., 2000; Bardt occurrence below 6 mm Hg (van den Brink et al., 2000; Bardt et al., 1998; Valadka, Gopinath, Contant, Uzura, & Robertson, et al., 1998; Valadka, Gopinath, Contant, Uzura, & Robertson, 1998). The length of time under the particular threshold 1998). The length of time under the particular threshold measured also influenced poor outcomes. measured also influenced poor outcomes.

Evidence for Pbt02Evidence for Pbt02

1996 reduced 02 reactivity correlates with 1996 reduced 02 reactivity correlates with improved outcome, pbr02 of 5mmHg or improved outcome, pbr02 of 5mmHg or less 24hours after injury = poor outcomeless 24hours after injury = poor outcome

Cerebral hypoxic episodes more frequent Cerebral hypoxic episodes more frequent in those with worse outcomein those with worse outcome

Patients with Pbt02 monitoring as well as Patients with Pbt02 monitoring as well as ICP and CPP monitor had significantly ICP and CPP monitor had significantly less mortality vs ICP and CPP alone less mortality vs ICP and CPP alone (Steifel et al 2005)(Steifel et al 2005)

MicrodialysisMicrodialysis

Double-lumen probe with dialysis membrane at Double-lumen probe with dialysis membrane at tip. Perfused with isotonic fluidtip. Perfused with isotonic fluid

Sample brain tissue ECF and placed in Sample brain tissue ECF and placed in penumbra = most vulnerablepenumbra = most vulnerable

Cerebral hypoxia correlates with increased Cerebral hypoxia correlates with increased lactate/pyruvate ratio Normal = <25lactate/pyruvate ratio Normal = <25

Increased ratio = focal ischaemia BUT may Increased ratio = focal ischaemia BUT may represent failure utilisation of 02 by mitochondriarepresent failure utilisation of 02 by mitochondria

MicrodialysisMicrodialysis

Glycerol – componant of cell membranesGlycerol – componant of cell membranes Increased level = increased cell breakdownIncreased level = increased cell breakdownTypically high in first 24hrs – late peaks from Typically high in first 24hrs – late peaks from

seizures or ischaemiaseizures or ischaemiaGlucose – low levels = hyperglycolysis or Glucose – low levels = hyperglycolysis or

decreased supplydecreased supplyGlutamate – excitatory AAGlutamate – excitatory AA

Elevated earlyElevated earlyLate peaks due to secondary damageLate peaks due to secondary damage

Microdialysis - EvidenceMicrodialysis - Evidence

Not in BTF guidelinesNot in BTF guidelines Normal levels of cerebral chemicals include a Normal levels of cerebral chemicals include a

lactate - pyruvate ratio of 15-20, a glutamate lactate - pyruvate ratio of 15-20, a glutamate level of 10 mcm, and a glycerol level of 50-100 level of 10 mcm, and a glycerol level of 50-100 mcm with a 10-mm dialysis membrane mcm with a 10-mm dialysis membrane (Ungerstedt & Rostami, 2004) (Ungerstedt & Rostami, 2004)

Increased LPR and Glycerol may predict Increased LPR and Glycerol may predict delayed ischaemic deficit due to vasospasm 11-delayed ischaemic deficit due to vasospasm 11-23 hours before clinical appearance (Tisdall 23 hours before clinical appearance (Tisdall 2006)2006)

Largely research tool at presentLargely research tool at present

SummarySummary

ICP monitoring via EVD is gold standard ICP monitoring via EVD is gold standard and supported by level 2 evidenceand supported by level 2 evidence

SJV02 <50% is a level 3 recommended SJV02 <50% is a level 3 recommended treatment thresholdtreatment threshold

Other monitiring modalities of varying use Other monitiring modalities of varying use but have no recommendations from the but have no recommendations from the guidelinesguidelines

ReferencesReferences

‘‘Gizmos and Gadgets for the Neurointensive Care Unit’ Gizmos and Gadgets for the Neurointensive Care Unit’ MK Bader Medscape Critical Care. 2007MK Bader Medscape Critical Care. 2007

BTF Guidelines 2007 J Neurotrauma Vol 24 Suppl 1BTF Guidelines 2007 J Neurotrauma Vol 24 Suppl 1 Continuous Monitoring of Partial Pressure of Brain Continuous Monitoring of Partial Pressure of Brain

Tissue Oxygen in Patients with Severe Head InjuryTissue Oxygen in Patients with Severe Head Injury..van van Santbrink,Santbrink, Henk.; Maas, Andrew Avezaat, Cees J.J. Henk.; Maas, Andrew Avezaat, Cees J.J. Neurosurgery. 38(1):21-31, January 1996.Neurosurgery. 38(1):21-31, January 1996.

Traumatic Brain Injury: Management on the Traumatic Brain Injury: Management on the Neurointensive Care Unit Clemens Pahl FRCA DICM Neurointensive Care Unit Clemens Pahl FRCA DICM Consultant Intensivist King’s College HospitalConsultant Intensivist King’s College Hospital

ReferencesReferences

Monitoring the Injured Brain. Gupta AK. J Monitoring the Injured Brain. Gupta AK. J Postgraduate Med 2002:48;218-225Postgraduate Med 2002:48;218-225

Reduced Mortality Rate in patients severe Reduced Mortality Rate in patients severe traumatic brain injury treated with brain tissue traumatic brain injury treated with brain tissue oxygen monitoring. MF Stefel et al. J Neurosurg oxygen monitoring. MF Stefel et al. J Neurosurg 103:805-811;2005103:805-811;2005

Cerebral Microdialysis;research technique or Cerebral Microdialysis;research technique or clinical tool? BJA 2006:97;18-25clinical tool? BJA 2006:97;18-25

Neuromonitoring. M Smith. Anaesthesia and Neuromonitoring. M Smith. Anaesthesia and Intensive Care Medicine;9;5;2008Intensive Care Medicine;9;5;2008