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Cerebral monitoring
SAMIR EL ANSARY
ICU PROFESSOR
AIN SHAMS
CAIRO
The CNS can sometimes be insufficiently monitored leading to grave postoperative complications
Classification
• Cerebral perfusion monitoring .
• Cerebral metabolism monitoring .
• Cerebral function monitoring .
Cerebral perfusion monitoring
• Global cerebral perfusion monitoring :
Cerebral blood flow measurements.
Transcranial Doppler ultrasonography.
Near-infrared spectroscopy.
Jugular bulb oximetry.
• Regional cerebral perfusion monitoring :
Brain tissue partial oxygen tension
monitoring.
Global cerebral perfusion monitoring
Cerebral blood flow measurements :
-Methods :
-Kety-Schmidt Inert-gas Saturation Technique.
-(TCID) transcerebral double-indicator dilution technique.
TCID may become a feasible & clinically useful alternative method fore measurement of global cerebral blood flow.
Transcranial Doppler ultrasonography (TCD) :
Its noninvasive , used for the diagnosis of cerebral vasospasm by measurement of
blood flow velocity.
- <120 or >200 cm/s
Transcranial colour-coded sonography
Monitors of blood flow dynamicsTranscranial doppler
• Direct, noninvasive measurement of CBF
• Sound waves transmitted through
thin temporal bone contact blood,
are reflected, and detected
• Most easily monitor middle
cerebral artery
Near-infrared spectroscopy
(NIRS)
(brain oximetry)- continuous noninvasive monitoring of cerebral
oxygen saturation.
- measures arterial , venous & capillary blood oxygen saturation.
Accuracy (emitter-detector separation).
Jugular bulb oximetry (SjO2) :
- continuous invasive monitoring of jugular bulb oxygen saturation
- has been applied in neuroanesthesia & neurological intensive care management as an indirect measure of the adequacy
of cerebral perfusion.
Jugular venous oxygen saturation (SjVO2)
The jugular bulb is the dilated portion of the jugular vein just below the base of the skull which contain blood with little extra cerebral contamination.
Measurement of oxygen saturation of the jugular bulb provide information about the global oxygenation state of the brain.
Regional cerebral perfusion monitoring
Brain tissue partial oxygen tension monitoring (PbtO2) :
- invasive catheter measures oxygenation in very localized area of the brain
- catheter (probe) need guidance to help place into areas of brain by xenon computed tomography or
single-photon emission computed tomography.
- ischaemia threshold SjvO2 50% = PbtO2 8 mmHg.
Major differences :
1. SjvO2 more reduction during hyper ventilation.
2. PbtO2 was more affected by changes in arterial partial oxygen tension.
3. during global ischaemia
- PbtO2 decreas to 0 & remained at 0
- SjvO2 initially decreased, but then increased again as cerebral blood flow ceased, & the only blood in
the jugular bulb was of extracerebral origin.
Cerebral Oximetry (Near infrared spectroscopy)
• determine cerebral saturation
• uses a similar principle to pulse oximetryby using multiple wave lengths of near infrared light , the absorption of this light by oxygenated and deoxygenated
haemoglobin determines
the overall saturation
of the blood present within
the brain tissues.
Cerebral metabolism monitoring
Cerebral microdialysis :
- Molecules in the extracellular space extracted & measured.
- catheters inserted into the temporal & subfrontalcortex at the end of cerebral aneurysm surgery .
- samples extracted & analyzed by microdialysisapparatus (which can analyze glucose, lactate,
glutamate, glycerol & urea concentrations within minutes of collection.
Revealed that lactate & glutamate appeared to be sensitive markers of
impending ischaemia
Whereas increased glycerol levels were associated with sever
ischaemic deficits.
Cerebral function monitoring
• Bispectral index (BIS).
• Approximate entropy.
• Auditory evoked potential (AEP).
Bispectral index BIS
Is a processed
electroencephalographic parameter that is obtained by discriminate analysis of a set of
electroencephalographic features.
Is known to have a high correlation with clinical signs of anaesthesia & with the
concentrations of most hypnotic agents.
Bispectral index BIS
- is a dimensionless scale from 0 (complete EEG suppression) to 100 (awake).
- BIS values of 65-85 have been recommended fore sedation
- BIS values of 40-65 have been recommended fore GA
- BIS values lower than 40, cortical suppression becomes discernible in raw EEG as a burst
suppression pattern.
Approximate entropy :
BIS + EMG (facial muscle).
as a measure of anaestheticdepth.
Auditory evoked potential (AEP).
Used for measuring hypnotic drug effects.
Is better discriminatory power in describing the transition from the
conscious to the unconscious state in the individual patient.
Ancillary Testing
• IN BRAIN DEATH
Ancillary Testing
• Nuclear Flow Study (Cerebral Scintigraphy)
– Injection of radionuclide tracers are used to
establish flow or lack of flow to the brain
– “Hollow Skull” sign { IN BRAIN DEATH }
TCD
• Transcranial Dopplar– Ultrasound used to establish cerebral circulatory
arrest
– Pros: inexpensive, portable
– Cons: requires an experienced operator and
interpreter. 10-20% of patients have inadequate bone
windows with which to examine the brain’s circulatory
system
Eeg: Electroencephalogram
EEG
• Brain tracing of activity, much like the EKG
for the heart. Routinely used in Neurology
for diagnosing/localizing seizure disorders,
sleep disorders
• No brain activity (flat waves) is diagnostic
of brain death
Cerebral Angiography
BRAIN DEATH
Cerebral Angiography
• Contrast dye study to determine blood flow to the brain
• Dye is injected into the vessels of the brain by a small
catheter
• Presence of dye = blood flow.
Absence of dye = brain death
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Wellcome in our new group ..... Dr.SAMIR EL ANSARY
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