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.