Syafruddin Gaus

Pertemuan Ilmiah Berkala PERDATIN 2014

Grand Clarion Hotel and Convention-Makassar

Dept. of Anesthesiology, Intensive Care, and Pain Management

Faculty of Medicine, Hasanuddin University

Introduction

Patients with neurologic disease undergoing

surgical procedures have increased risk of

ischemic / hypoxic damage to the CNS

Risk may be related to hemodynamic /

embolic events associated with:

* non-neurosurgical operation (CPB)

* neurosurgical procedure (temporary

clipping during cerebral aneurysm surgery

Introduction

Intraoperative neurophysiologic monitoring

may improve patient outcome by:

allowing early diagnosis of ischemia/hypoxia

before irreversible damage occurs

enabling surgeons to provide optimal operative

treatment as indicated by the monitoring

parameter.

The brain can be monitored in terms of:

function

cerebral blood flow (CBF) & intracranial

pressure (ICP)

brain oxygenation and metabolism

Introduction

Monitoring of Function Electroencephalograms (EEG)

Raw EEG

Computerized Processed EEG: Compressed spectral array, Density spectral array, Aperiodicanalysis, Bispectral analysis (BIS)

Evoked Potential Sensory EP:

○ Somatosensory EP

○ Visual EP

○ Brain stem auditory EP

Motor EP:

- Transcranial magnetic MEP

- Transcranial electric MEP

- Direct spinal cord stimulation

EMG- Cranial nerve function (V, VII, IX, X, XI, XII)

EEG

Result of excitatory postsynaptic potential

EEG Waves : Beta: high freq, low amp (awake state)

Alpha: med freq, high amp (eyes closed while awake)

Theta: Low freq (not predominant)

Delta: very low freq hugh amp (depressed functions/deep coma)

EEG waves reflects state of arousal and metabolism depends on energy substrates supply blood flow

EEG

Sudden development of delta waves

coincident with surgical manuver

injury warning

In penumbra region, EEG poorly predict

brain damage

Anesthetics & hypothermia causes EEG

changes multifactorial interpretation

EEG

Indication:

Surgery that place the brain at risk

(difficulties: restricted access)

Anesthesia induced metabolic suppresion

Seizure monitoring in ICU

Indication for EEG

Monitoring Carotid endarterectomy

Cerebral aneurysm surgery when temporary clipping is used.

Cardiopulmonary bypass procedure

Extracranial-intracranial bypass procedure

Deliberate metabolic supression for cerebral protection.

Newfield P, Cottrell JE. Handbook ofNeuroanesthesia;2012

Bispectral Index

Bispectral analysis (BIS)

Monitor degree of hypnosis (40-60

adequate hypnosis)

Doesn’t detect ischemia

Evoked Potential Monitoring

Sensory Evoked Potential (SEP)

Time-locked, event related, pathway specific

EEG in respones of peripheral stimulus

Resistant to IV anesthetics, recordable in

inhalation anesthetics (dose related)

Monitor integrity of the pathway from

periphery to the cortex

Evoked Potential Monitoring

• Somatosensory Evoked Potential (SSEP)

○ Electrical stimulator placed at median, ulnar, or

posterior tibial nerves.

○ Used in spinal column surgery to asses potential

risk to the spinal cord

• Visual Evoked Potential (VEP)

○ Using LED goggles to create stimulus

○ Difficult to perform

• Brainstem Auditory Evoked Potential (BAEP)

○ Repetitive clicks delivered to the ear

○ Reflects the VIII nerve & brainstem “well-being”

Indication for SEP Monitoring

SSEP Monitoring:

Spinal column surgery

Carotid endarterectomy

Cerebral aneurysm

surgery

BAEP Monitoring:

Acoustic neurinoma

Vertebral-basilar

aneurysm

Other posterior fossa

procedure.

SSEP: somatosensory evoked potential

BAEP: brain stem auditory evoked potential

Evoked Potential Monitoring

Motor Evoked Potential (MEP)

Monitors motoric pathway as a

complement of SSEP

Basically an electromyographic using train

of four stimuli

Instant feedback

Can’t be recorded if muscle relaxant used

Monitoring of CBF and ICP

Absolute CBF.

Nitrous oxide wash in (jugular bulb

cannulation) invasive

Xenon clearance non invasive

Relative CBF

Laser Doppler Flowmeter (LDF) measure

flow quantitatively (1 mm brain tissue).

Requires a burr hole.

Monitoring of CBF and ICP Transcranial Doppler (TCD) –overview-

Measure CBF velocity in the Circle of Willisnoninvasively and continuously

Intraoperative middle cerebral artery measured by placing probe over zygomatic arch

Qualitative assesment tools for ICP

Detects air / particulate emboli

Monitoring of CBF and ICP

Transcranial Doppler (TCD) –principles- Flow can be measured if the vessel diameter

remain constant Basal Cerebral Arteries

The diameter remain constant as the vascular resistance changes or during administration of IV or inhaled anesthetics

The diameter only constricts during vasospasm in subarachnoid hemorhage

Once confirmed by angiography, TCD can track patient’s response to therapy of the vasospasm

Changes in flow velocity correlates with CBF

Monitoring of CBF and ICP Transcranial Doppler (TCD) –clinical app-

Carotid endarterectomy:○ Detection of ischemia if 60% Vmca decrease from

baseline

○ Detection of microemboli

○ Diagnosis of postoperative hyperperfusion syndrome

○ Diagnosis of postoperative intimal flap or thrombosis

Cardiac Surgery (cognitive dysfunction 30-70%):○ Cerebral emboli during cardiopulmonary bypass

○ Cerebrl perfusion during cardiopulmonary bypass

Closed Head Injury:○ Assess autoregulation, diagnose hyperemia,

vasospasm, and intracranial circulatory arrest

Diagnosis of brain death

Monitoring of CBF and ICP

ICP monitoring:

Optimizes Cerebral Perfusion Pressure

(CPP)

Prevents possible herniation

Methods: ventriculostomy, subarachnoid

bolt, epidural sensor, fiberoptic

intraparenchymal monitor (commonly used)

Can be incorporated with LDF, brain

temperature, PaO2, PaCO2, and pH

monitoring

Monitoring of Cerebral

Oxygenation and Metabolism

Invasive monitoring:

Brain tissue oxygenation

Jugular bulb venous oximetry monitoring

Microdialysis catheter

Non-Invasive monitoring:

Near Infrared Spectroscopy (NIRS)

Monitoring of Cerebral

Oxygenation and Metabolism

Brain tissue oxygenation (Po2)

Po2 monitor is useful to assess O2 demand and

supply

The tissue Po2 monitor is placed intraparenchymal-

ly in conjunction with ICP monitor.

Reveals regional or local O2 levels

O2 tension 10 mmHg: threshold for brain hypoxia

Monitoring of Cerebral

Oxygenation and Metabolism

Brain tissue oxygenation (Po2)

Po2 : increasing supply O2 (supplemental O2,

raising CPP, treating anemia)

Po2 : decreasing demand (propofol or barbiturate

therapy)

Loss of cerebral autoregulation: may demonstrate

hyperoxia that could occur with cerebral hyperemia

Monitor placement ? Normal brain parenchyma or

adjacent to the injured brain

Monitoring of Cerebral

Oxygenation and Metabolism

Jugular bulb venous oximetry monitoring

Provide GLOBAL cerebral oxygen

demand and supply

Relative CBF estimated by calculation of

arteriovenous oxygen content

difference reflects oxygen balance

Intraoperative cerebral ischemia can be

diagnosed readily

Limitation: unable to detect focal

ischemia

Monitoring of Cerebral

Oxygenation and Metabolism

Interpretation of jugular venous oxygen saturation (SjvO2) Increased values: >90% indicates absolute/relative

hyperemia○ Reduced metabolic need comatose/brain death

○ Excessive flove sever hypercapnia

○ AVM

Normal Values: 60-70% focal ischemia?

Decreased Values: <50% increased O2 extraction,indicates a potential risk of ischemia injury○ Increased demand: seizure / fever

○ Decreased supply: decreased flow, decreased hematocrit

As ischemiaprogress to infarction: O2 consumption decreases

Monitoring of Cerebral

Oxygenation and Metabolism Microdialysis catheters

Small catheter inserted with ICP/tissue PO2 monitor

Artificial cerebrospinal fluidequilibrates with extracellular fluid chemical composition analysis

Markers:○ Lactate/pyruvate ratio onset of ischemia

○ High level glycerol inadequate energy to maintain cellular integrity membrane breakdown

○ Glutamate neuronal injury and a factor in its exacerbation

Catheter placement is important small coverage

Monitoring of Cerebral

Oxygenation and Metabolism

Near-infrared Spectroscopy (NIRS)

Transcranial oximetry

Measure cerebral regional O2 reflected by the chromophobes in the brain

Limits:

○ Intersubject variability

○ Potential contamination from extracranial blood

○ Lack definable threshold

Might be promising in neonate & infant due to thin skull & scalp

Summary

Neurophysiologic monitoring not universally adopted but in many centers has become routine monitor for some surgical procedures

Ideal neurophysiologic monitoring in the neurosurgical procedure should be: non-invasive (v.s invasive), high sensitivity & specificity, cost effective, easy to use, simple instrumentation, and real time or continousmonitoring.